Chronic encephalopathy (progressive dementia plus syndrome)
Toxic leucoencephalopathy: A variety of drugs can be associated with leucoencephalopathy e.g. immunosuppressive agents like cyclosporin.
One form is called Multifocal inflammatory leucoencephalopathy (MFILE) and is an idiosyncratic reaction following chemotherapy (e.g. 5-fluorouracil, levamisole). The symptoms start between 1-19 weeks after chemotherapy with subacute confusion, focal neurological symptoms, seizures and progress for 1-2 months after discontinuation of the drugs. Recovery is often incomplete. Steroids may be helpful in the management.
Multi-infarct dementia (MID): MID is characterized by sudden deficits, asymmetric reflexes, focal neurological signs associated with strokes. The distribution of deficits is multifocal distribution and a stepwise deteriorating course. Visual hallucinations are common and need to be differentiated from those appearing in AD and LBD.
Binswanger disease: This type of dementia can be associated with parkinsonism but MRI shows extensive white matter lesions.
Alzheimer disease (AD): 50-80% of all dementias are due to AD. About 120 people per 100,000 population is affected by AD annually. The onset of symptoms usually begins after the age of 65 years. Familial AD is autosomal dominant and is the most common form of early onset (presenile) familial dementia. Early signs are deficits in attention, concentration, orientation, abstract reasoning, progressive amnesia (often periodic loss of recent memory e.g. delayed verbal recall rather than remote memory). As the disease advances problems with language (impaired naming, progress to fluent aphasia, and mutism), calculations, topographical memory and visuospatial functions (difficulty driving, getting lost, difficulty copying figures) and praxis (constructional dyspraxia) become increasingly apparent. Parietal signs typically appear after memory loss. Behavioral alterations (depression, agitation, delusions, anxiety and hallucinations) may become evident at any time during the course of illness, but are often precipitated by events such as admission. In contrast to FTLD, language and social functioning are generally preserved until late in the course. Seizures (generalized onset) occur in less than 15% of patients. Extrapyramidal signs occurs in 25% of AD patients. Other manifestations include gait disturbances, frontal signs and myoclonus (more common in familial forms). The Addenbrooke Cognitive Examination (Neurology 2000;55:1613) is a brief and reliable bedside instrument for early detection of AD, and offers a simple objective index to differentiate AD and FTLD in mildly demented patients. Diagnosis of AD is confirmed at autopsy! Autopsy-confirmation of clinically diagnosed series of probable AD patients is less than 85%. The alpha rhythm on the EEG gradually disappears. Brain MRI shows early atrophy of the hippocampus which correlates with the degree of impaired memory function. APOE e4 allele (chromosome 19) which is more prevalent among AD patients than among the general population, is a risk factor for developing AD and lowers the age of onset of the disease, particularly it makes the late-onset form of AD occur earlier. APOE e4 is found in familial (80%) and sporadic forms (64%) of AD, compared with 31% of controls. Conversely, bearing an APOE e2 allele is associated with a reduced risk for developing AD. The positive predictive value of APOE e4 genotype increases the clinical accuracy 0f 60-70% to almost 100%. In familial forms mutations in presenilin-1 (mapped to chromosome 14q24.3), presenilin-2 (mapped to chromosome 1q31-42) and amyloid precursor protein genes (mapped to chromosome 21q21.1) have been identified.
Mild cognitive impairment (MCI): About 40% of people aged > 65 have age-associated memory impairment and 10% suffer from MCI. Nearly 15% of them will develop AD. MCI is defined as important memory loss without functional impairments. MCI can be defined as MMS of >22 or word delayed recall list test (WDRL) < 5. Evaluation should be done as for dementia including APOe-4 genotyping.
Frontotemporal degeneration (FTD): FTD accounts for 20% of early-onset dementia and has prevalence of around 0.15 in the age group below 65 years. The average age of onset is often between 40-65 years (average 53 years) with striking male preponderance (>4:1). Three subtypes can be identified: familial chromosome 17-linked frontal lobe dementia (FTDP-17), progressive nonfluent aphasia (PNFA) and semantic dementia (SD). Pick disease refers only to those cases in which microscopic examination shows Pick bodies. The clinical characteristics of FTD include PNFA, socially disruptive behaviors, or both. Early and prominent disturbances in language (aspontaneity, phonemic paraphasias, or anomia and agrammatism), hyperorality, alterations in diet (sweet tooth), akinesia and behavior (desinhibition, social misconduct, mental rigidity, emotional blunting and apathy) combined with absence of declarative (episodic) memory and perceptual difficulties, and affected executive functions such as abstract reasoning, judgment, and problem solving differentiate these disorders from AD. Early retirement is often a consequence. The onset is insidious and progression gradual. Although FTD is usually sporadic, autosomal dominant forms occur and are often associated with parkinsonism and linkage to chromosome 17 (FTDP-17). Patients with SD have difficulties in word retrieval, and word and object meaning such as verbal output, although fluent, is progressively devoid of content words. In addition, social and personal misconduct impaired insight, narrowed preoccupations may differentiate them from PNFA. Other cognitive functions such as episodic memory are preserved in the early stages of the SD. Brain MRI shows anterior left temporal atrophy. In progressive nonfluent aphasia, nonfluent verbal output with syntactic errors and word-finding difficulties remains the only symptom for at least 2 years. Supportive diagnostic speech and language features include stuttering or oral apraxia, impaired repetition, and alexia with agraphia. Alpha rhythm is preserved on EEG. Brain MRI shows left perisylvian atrophy. In FTD, CSF levels of tau are elevated and Ab42 levels are decreased (both together sensitivity of 85% at a specificity of 85% vs. AD). MRI and CT scan shows frontal/temporal lobe atrophy. PET scan may show hypometabolism in a frontotemporal distribution. These types of dementias need to be differentiated from CBGD, and MND-inclusion dementia, and even PSP-like forms.
Cerebral autosomal recessive arteriopathy with subcortical infarcts and leukoencephalopathy (CARASIL): This form is associated with osseous manifestations e.g. spinal deformities in addition to MRI findings of leucoencephalopathy and lacunar infarcts.
Cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL): Recurrent stroke (cerebral infarcts) (70-80%) and progressive cognitive impairment (subcortical dementia with pseudobulbar palsy and urinary incontinence) (30-50%) are the main clinical manifestations of CADASIL. Additional manifestations include migraine with aura (20-40%), ischemic manifestations of the optic nerve and mood disturbance (30%). MRI reveals leukoaraiosis consisting of extensive cerebral white matter lesions and subcortical infarcts. Anterior temporal lobe and external capsula-insula hyperintensity (sometimes patchy) is a radiologic marker of CADASIL. The disorder is autosomal dominant and is caused by mutations in the Notch3 gene on chromosome 19q13 (at least 23 exons should be screened). The presence of a clear family history in the context of typical clinical and radiologic findings makes the diagnosis straightforward. Skin biopsy (or muscle and nerve biopsy) with ultrastructural examination of small blood vessels may be diagnostic.
The neuroacanthosis exists of three major groups: 1) the core
neuroacanthosis syndromes with neurodegeneration of the basal ganglia,
comprising autosomal recessive chorea-acanthosis due to mutation of VPS13A
(chromosome 9q21) and the X-linked McLeod phenotype (indistinguishable
phenotypes) due to mutation of XK gene, 2) conditions with decreased
lipoproteins (abetalipoproteinemia and hypobetalipoproteinemia) consisting of
peripheral neuropathy and ataxia without movement disorders, 3) associated forms
such as HSD (PANK2) and HD (HDL2).
The core neuroacanthosis affects men twice as common as women.
Symptoms usually start in the 3rd to 5th
decade (mean 32 years) and consist of
limb chorea, especially affecting the legs, along
with parkinsonism, oro-facial dyskinesias, self-mutilation, and dementia. 50%
of cases have seizures, areflexia (chronic axonal motor
polyneuropathy: small SNAPs; normal CMAPs)
with distal symmetric wasting.
Elevated serum CK levels and acanthocytes on a fresh wet blood film facilitate
the diagnosis. The latter usually precedes the neurologic features. Needs to be
differentiated from abetalipoproteinemia (abnormal serum lipoprotein profile)
and McLeod syndrome (reduced expression of Kell blood group on RBC and Kx
surface antigen (100%)).
Brain MRI may show caudate atrophy. Acanthocytes are seen in the peripheral
blood smears of some of the asymptomatic family members. Average life span is
approximately 14 years from onset of illness.
Homocystinuria (type III): This autosomal recessive disorder is caused by deficiency of 5,10-methylenetetrahydrofolate reductase (MTHFR). It is the most common inborn error of folate metabolism. The disease develops usually in the 2nd or 3rd decades of life and is characterized by progressive premature atherosclerosis and recurrent thromboembolic complications with a variety of neurological manifestations (cerebellar ataxia, spastic paraplegia, paresthesia, seizures, and mental dysfunction). Asymptomatic forms have been described. NCVs may be slowed. MRI demonstrated abnormalities characteristic of leukodystrophy. The diagnosis is based on raised plasma total homocysteine (normal <15 micromol/L) and methionine (normal <37 micromol/L) levels. MTHFR activity is low in lymphocytes, leukocytes and cultured fibroblasts. The gene is mapped to chromosome 14q24.
Cerebrotendinous xanthomatosis: This a rare autosomal recessive disorder caused by mutation of the sterol 27-hydroxylase (CYP27) gene and resulting in defective bile acid synthesis. The adult form is almost invariably characterized by juvenile cataract (97%), progressive neurological dysfunction (spastic paraplegia (often very prominent) (81%), low intelligence (poor attention, memory impairment) (66%) and cerebellar ataxia (56%)), chronic intractable diarrhea (since childhood) (50%) and bilateral Achilles tendon xanthomas (41%). Less frequently, seizures, sensorimotor demyelinating peripheral neuropathy and premature cardiovascular disease may occur. Serum cholesterol levels are reduced and cholestanol levels are increased (normal 0.2 + 0.2 mg/dl). Brain MRI scan reveals consistently bilateral signal hyperintensities in the dentate nuclei on FLAIR. Proton MR spectroscopy appears to be a useful measure of disease outcome. Treatment chenodeoxycholic acid can reverse neurological syndrome.
Niemann-Pick disease type C (NPC): This autosomal recessive disorder is almost invariably characterized by two major features: psychomotor retardation and supranuclear downgaze paresis. In addition, ataxia, extrapyramidal features (dystonia) and seizures occur. In late-onset cases progressive dementia or psychosis may be the major presenting manifestation besides supranuclear downgaze paresis, extrapyramidal features and seizures. Unlike in early-onset cases visceromegaly is usually mild. The diagnosis is based on the triad of vertical gaze paresis, organomegaly and foam cells (sea blue histiocytes) in the bone marrow. A confirmatory test is the determination of the rate of cholesterol esterification in cultured skin fibroblasts. The NPCI gene is located on chromosome 18q11-12. Brain MRI is usually normal or may show demyelination. Death usually occurs from aspiration and intercurrent pulmonary infection.
Lesch-Nyhan syndrome: X-linked disorder characterized by uric acid overproduction and variable neurologic impairment. Males are usually affected. Hypoxanthine-guanine phosphoribosyltransferase deficiency (HGPRT) may have two clinical forms: that of the Lesch-Nyhan syndrome (complete HGPRT deficiency) and that of Kelley-Seegmiller syndrome (partial HGPRT deficiency). Lesch-Nyhan syndrome presents with a triad of choreoathetosis with spasticity, mental retardation and the unique feature of self mutilation, while the neurologic manifestations of the patients with the Kelley-Seegmiller syndrome are very heterogeneous: psychomotor retardation with spastic movement, mentally retarded with generalized dystonia or adult onset gout with no neurologic manifestations. Plasma urate and urine urate are increased. The definitive diagnosis requires an enzymatic analysis of HRPT activity in erythrocytes or cultured skin fibroblasts. Affected males and carriers can also be identified by DNA analysis. The gene for HGPRT is mapped to chromosome Xq26. Allopurinol does not seem to affect the CNS symptoms.
Panthotenate kinase-associated neurodegeneration or Hallervorden-Spatz disease (HSD): The adult onset form of this autosomal recessive disorder presents in early adulthood with atypical parkinsonism (initially affecting the legs or bulbar musculature), ataxia, myoclonus, dystonia (tongue or blepharospasm), chorea or dementia. Most patients also develop pyramidal syndrome and seizures (20%). T2 weighted brain MRI shows an eye of the tiger sign corresponding to pallidal hypointensity with a high signal center. Very low signal intensity is also seen in the red nucleus, and substantia nigra, consistent with increased iron deposition in these structures. Bone marrow contains sea blue histiocytes. The gene locus (PANK2) has been identified on chromosome 20. Treatment of patients with HSD is largely symptomatic. Many patients, especially in the early stages of the disease, may respond modestly to levodopa treatment. Variants have been reported such as HARP syndrome (hypoprebetalipoproteinemia [very low VLDL], acanthocytosis, retinitis pigmentosa, and pallidal degeneration). The dystonia affects cranial musculature and MRI findings are those of HSD. HSD needs to be differentiated from WD, juvenile HD, SNE, PD, DRD, Fahr disease, Lafora body disease (EPM2A gene), MS, DRPLA, Kufs disease, gangliosidoses and APBD.
pressure hydrocephalus (NPH):
Frontal lobe dementia, urinary incontinence and frontal ataxia (triad of Hakim-Adams)
are the clinical characteristics of NPH. Gait disturbance and urinary
incontinence usually occurs before dementia develops. The gait disorder is
similar to that seen in vascular parkinsonism. A spinal tap can often be
diagnostic and therapeutic: 40 - 50 ml of CSF is tapped, and walking and mental
function is measured before and after the lumbar puncture. Alternatively, the
Katzman test can be used. The Diamox test is not useful. The finding of more
than 50% B-waves on intracranial pressure measurement is suggestive of NPH. MRI
may show flow void over the aquaduct. High concentrations of sulphatide have
also been supportive for the diagnosis. Causes of NPH are SAH, resolved
acute or chronic meningitis, Paget disease of the skull base and
Aceruloplasminemia: This autosomal recessive disorder presents in the 4th to 5th decade of life and is caused by a mutation in the ceruloplasmin gene and affects iron metabolism. A triad of cerebellar ataxia, retinal degeneration and diabetes mellitus in a middle-aged person typically characterizes the disorder. Involuntary movements (late-onset blepharospasm) and dementia may occur in later stages of the disease. Heterozygotes are asymptomatic. Serum ceruloplasmin is low, plasma ferroxidase activity is reduced with 60%, while serum iron and transferrin saturation are normal. Plasma copper and ferritin may be increased. CSF analysis reveals threefold increase in iron concentration. Urinary copper may be increased. MRI shows cerebellar atrophy and T2 weighted studies are remarkable for the presence of iron deposition (increased signal intensity in the basal ganglia and thalamus, and dentate nuclei). PET scan shows cortical glucose hypometabolism.
Glutaric acidemia type I: This progressive neurodegenerative autosomal recessive disorder of lysine, hydroxylysine, and tryptophan metabolism is caused by deficiency of the mitochondrial enzyme glutaryl CoA dehydrogenase (GCDH) (chromosome locus 19p13.2) and results in the accumulation and excretion of increased urinary concentrations of glutaric, glutaconic and 3-hydroxyglutaric acids. Adult-onset glutaric aciduria type I is clinically characterized by acute-onset and atypical recurrent, nystagmus, upward gaze palsy, hyperactive tendon reflexes, dyskinesia and dystonia, seizures and mild mental deterioration. Urinary organic acids (glutaric acid (normal value <10 mmol/mol creatinine) and 3-hydroxyglutaric acid (normal value <10 mmol/mol creatinine) are increased. Serum carnitine may be low (normal value 15 - 79 micromol/L) and glutarylcarnitine increased (normal value <11 micromol/L). Serum lactate and pyruvate levels may be increased. Brain MRI reveals leucoencephalopathy: increased signal intensity on T2 weighted images in the supratentorial white matter with sparing of the U-fibres). The diagnosis is confirmed by determination of GCDH enzyme activity in fibroblasts. Measurement of urinary glutarylcarnitine levels by tandem mass spectrometry can serve as a diagnostic tool for identifying individuals with glutaric acidemia type I. Treatment includes administration of L-carnitine and restriction of protein intake. Differential diagnosis should include CADASIL, Alexander disease, leucokodystrophies and Canavan disease.
Kuru: The disease is prevalent in ritual cannibalistic New guinea and presents clinically with progressive cerebellar ataxia, abnormalities of extraocular eye movements, weakness and incontinence. Death occurs in 3 to 6 months of onset. Brain MRI reveals abnormalities in thalamus and limbic system.
Subacute sclerosing panencephalitis (SSPE): SSPE is a neurodegenerative disease due to persistent rubeola (measles) infection that affects children and young adults. Onset of the disease is insidious and often only recognized after significant neurologic deficits occur. The diagnosis of SSPE can be made if three of the following five criteria are fulfilled: 1) typical clinical presentation with progressive cognitive decline and stereotypical myoclonus (sustained myoclonus), 2) characteristic EEG changes, 3) elevated cerebrospinal fluid globulin levels without pleocytosis, 4) elevated CSF measles antibody titers, and 5) typical histopathologic findings in a brain biopsy or autopsy. Affected individuals progress through four loosely defined clinical stages at differing rates. Stage I is characterized by subtle behavioral changes, cognitive decline, emotional lability, lethargy, and nonspecific neurologic symptoms. This stage may last for weeks to months. Stage II includes continued intellectual decline, myoclonus, focal seizures with secondary generalization, choreoathetosis, apraxia, and visual changes with optic atrophy, dysarthria, and tremors. A wide variety of visual disorders have been associated with SSPE, including papilledema, retinitis, chorioretinitis, optic nerve pallor, homonymous visual field deficits, and cortical blindness. This stage may last three months or less. Neurologic decline persists in stage III (decreased level of consciousness, autonomic instability (with a variable heart rate and widely fluctuating temperatures and blood pressures), dystonia and rigidity, decorticate/decerebrate posturing), but the pace slows down, and symptoms may stabilize for one to two years. Features of stage IV include active startle reflex, flexor limb positioning, quadraparesis, akinetic mutism, wandering eye movements and coma. At this time, myoclonus, seizures, and rigidity are less frequent than in prior stages. CSF reveals markedly elevated intrathecal IgG synthesis rate and multiple oligoclonal bands in the gamma region on high-resolution electrophoresis, without a cellular reaction. Serum and CSF rubeola IgG titers are elevated with normal IgM titers. The EEG exhibits periodic complexes with generalized bilateral, usually synchronous and symmetrical sharp and slow wave complexes of high amplitude (greater than 500 uV), classically occurring every 5-10 seconds. Early in the course of the disease these periodic discharges may occur on a normal background but later the background becomes increasingly slower and disrupted. These periodic complexes are usually associated with clinically evident myoclonic or dystonic activity. MRI may be normal or may show early changes of increased signal on T2-weighted sequences, frequently involving the periventricular or subcortical white matter in the frontal, temporal, and occipital white matter; late changes include significant white matter loss, approximately 30% of patients show basal ganglia changes, while 25% have cortical changes. Fifty percent of patients who develop SSPE had measles (rubeola) before two years of age, and 80% before age four years. Five percent of patients survive three months or less and 20% survive four or more years, with a mean survival of only 18 months. Death occurs in stage IV, often the result of intercurrent illnesses such as pneumonia. MS (visual changes, oligoclonal bands) is often considered in the differential diagnosis of SSPE. Treatment is disappointing. The most promising results to date have used a combination of inosiplex, an antiviral agent, and intraventricular or intrathecal alpha-interferon as an immunomodulator, with stabilization or improvement in some patients. Early childhood measles vaccinations remain critical in limiting the incidence of SSPE.
Brain abscess: Common risk factors for brain abscesses include suppurative pulmonary infections, ENT infections, bacterial endocarditis, left-to-right shunt, odontogenic infections, AIDS and other conditions associated with immunosuppression. In about 10-20% of all cases of brain abscesses the infectious source cannot be identified and justifies diagnostic surgical exploration. The most common organisms causing brain abscess, especially in association with cranial sinuses or dental infections are Streptococcus viridans, less commonly Proteus, Pseudomonas, Pneumococcus, Meningococcus and Haemophilus and Staphylococcus (penetrating trauma and neurosurgery). The most common cause of brain abscess in AIDS is toxoplasmosis and cryptococcosis. Nocardia and toxoplasmosis are common organisms at the background of hematologic tumors (leukemia and lymphoma). The triad of headache, fever and focal neurological deficit should suspect brain abscess. Brain abscesses usually occur at the interface grey/white matter. Brain MRI shows a ring enhancement with surrounding edema (differential diagnoses should include toxoplasmosis, TB, cysticercosis, necrotic fungal infection, glioblastoma and lymphoma, demyelinating lesions, vascular lesions (thrombosed giant aneurysm, hematoma and resolving infarction), radiation necrosis). However it may be difficult to exclude subdural empyema, cerebritis, brain infarction, HSE, and AHLE on the basis of the appearances of the lesions on imaging studies. Monthly neuroimaging should be performed to document resolution of the abscess. Therapy should initially consist of ceftriaxone, vancomycin, metronidazole, phenytoin and dexamethasone. Antibiotherpy should last for 6 weeks.
Adult polyglucosan body disease (APBD): APBD is an autosomal recessive disorder. The disease is more common in a subgroup of patients of Ashkenazi Jewish origin. It represents an allelic variant of glycogen storage disease type IV and Lafora body disease (EPM2A gene), and contrary to infantile cases (Andersen disease or type IV glycogenosis or amylopectinosis) is usually not associated with a significant deficiency of the branching enzyme. The disease is caused by mutations of the gene coding for the glycogen-branching enzyme (GBE gene), which is essential for branching of polyglucose chains in the normal glycogen molecule. The age of onset is mostly between 40 - 60 years and its course is slowly progressive. This disorder is recognized by sensory loss in the lower extremities with peripheral neuropathy, chorea, atypical progressive upper and lower motor neuron disease, spastic tetraparesis, parkinsonism unresponsive to dopaminergic therapy, frontal dementia, and bowel and bladder dysfunction. Sural nerve biopsy reveals diagnostic intra-axonal polyglucosan bodies. Similarly the diagnosis of APBD can be confirmed by a skin biopsy from axillary dermal sweat glands showing inclusions in myoepithelial cells of apocrine glands. Decreased glycogen-branching enzyme (GBE) activity in leukocytes can be found. Brain MRI findings reveal cortical atrophy, extensive white matter signal changes on T2-weighted images and/or marked atrophy of the entire spinal cord, without signal abnormalities on long TR images. The disease is often misdiagnosed as adrenoleukodystrophy.
Friedreich ataxia (FA): This form of ataxia is the most common hereditary form (autosomal recessive with variable phenotype) with a frequency of 1/50,000 in the population. Essential diagnostic criteria include its onset before the age of 25 years and <5 years after onset the development of the following: progressive gait ataxia, early areflexia in lower limbs, vibration and joint position sensory deficits, extensor plantar responses, and motor nerve conduction velocity >40 m/s in upper limbs with small or absent SNAPs consistent with axonal sensory neuropathy. Other features are scoliosis, club feet, cardiomyopathy (>50%), diabetes or impaired glucose tolerance (10%) and dementia. Optic neuropathy and deafness occurs in less than 25% of cases. Life expectancy of FA is on average 35 years, death occurring from heart failure. The locus is mapped to chromosome 9q13-q21.1 (frataxin). Frataxin results in intramitochondrial iron accumulation, which explains why FA is now considered a mitochondrial disorder. Abnormal ECG and echocardiography are seen in approximately 60% of cases. CSF is normal. The condition most frequently confused with FA is HSMN I. This demyelinating form of HSMN, is essentially characterized by autosomal dominant inheritance with slow conduction velocities (always <40 m/s). Late-onset FA (after the age of 25 years) (LOFA) is characterized with a slower progression and lower incidence of skeletal deformity. Investigations should include brain MRI, serum vitamin E and B12 levels, and a-fetoprotein levels and DNA analysis to detect GAA trinucleotide expansion.
Chronic meningoencephalitis: Unexplained progressive headache associated with cognitive or behavioral changes and neurologic deficits or seizures should prompt the search for TB, Blastomyces, Cryptococcus neoformans and histoplasmosis. But also include Lyme disease, HIV, CJD and nvCJD, Whipple disease, neurosyphilis, brucellosis, toxoplasmosis and cysticercosis. CSF antibodies of fungi can be false positive or serve as witness of the past. Go by culture in that case!
Cryptococcal meningitis: This fungal infection is ubiquitous and occurs most commonly in patients who are immunosuppressed (HIV-1, reticuloendothelial malignancies, sarcoidosis, organ transplantation, collagen vascular disease, diabetes mellitus, chronic hepatic failure, chronic renal failure and patients on corticosteroids). Despite this up to 30% of cases of cryptococcosis are reported in patients with no known predisposing condition. 5-10% of AIDS patients develop cryptococcal meningitis. In non-AIDS patients, cryptococcal meningitis is typically a subacute process (days or weeks) consisting of headache, fever, meningismus, and personality change. Ocular abnormalities and cranial nerve palsies are common. In AIDS patients, the presentation is more subtle sometimes presenting with only headache, fever and lethargy, in the absence of meningeal signs. Overt meningeal symptoms and signs like nuchal rigidity are less common, occurring in about one third of patients. The CSF opening pressure is usually >200 mm H2O. Most non-AIDS patients have lymphocytic pleocytosis (20-500 cells/mm3). CSF protein is usually increased and glucose normal or subnormal. In AIDS patients CSF may be normal. CSF India ink examination remains a rapid, effective test that is positive in 50-75% of cases. Latex agglutination test is both sensitive and specific and titers of 1/8 are considered diagnostic. The yield of CSF cultures is very high (96%) but requires long time. Alternatively serum and CSF antigen (90% sensitive) detection can be used. The detection of serum antigen is felt to be more sensitive than CSF antigen and is generally reported positive in 99% of cases. False-negative antigen results are reported in a small number of immunocompetent patients early in the course of the disease, with chronic low grade infections, or after treatment. Brain MRI may show multiple nonenhancing cystic periventricular masses in the basal ganglia but is often normal. Without treatment (6 week course of amphotericin B along with flucytosine is the treatment of choice unless patients are immunosuppressed followed by long-term maintenance therapy with oral fluconazole), cryptococcal meningitis is almost always fatal. Overall, following acute treatment, it is important to repeat a LP to document decreasing opening pressure, cell counts, glucose, and cryptococcal load. Features associated with high mortality include an abnormal mental status at presentation, and an initial CSF antigen titer of greater than 1:1,024. Likewise, initial CSF parameters including an elevated opening pressure, a positive India ink stain, glucose less than 20 mg/100 ml, and less than 20 WBC/mm3 indicated a poor prognosis when patients who were cured were compared to patients who died. The only predictor of failure to respond to treatment is CSF glucose remaining low for more than 4 weeks.
Coccidioidomycosis meninigitis: Most commonly seen in the southwestern US, northern Mexico, and Argentina. C. immitis rarely disseminated to CNS. Predisposing factors for dissemination are old age, pregnancy, corticosteroids therapy, antitumoral chemotherapy, immunosuppression and HIV infection. The meningitis is usually subacute or chronic with patients complaining of headache, low-grade fever, weight loss, and mental status changes. Signs of meningismus are usually absent. CSF findings are typical for fungal meningitis and can be sometimes normal. The diagnosis depends upon the demonstration of elevated serum concentrations of complement-fixing antibodies (titers >1/32 to 1/64 suggest dissemination). Occasionally CSF may reveal prominent eosinophilia. CSF cultures are positive in 25-50% of patients with meningitis.
Histoplasmosis meningitis: Histoplasmosis is common in the Mississippi and Ohio river valleys. H. capsulatum may develop without evidence of systemic infection and even in immunocompetent patients. Meningitis occurs in 10-20% of patients with disseminated histoplasmosis. The symptoms are headache and fever and occasionally focal neurologic deficits. Mental status abnormalities may occur. Pulmonary lesions may be mild, resolving or asymptomatic. Repeated LP may be required. CSF may show signs of chronic meningitis (raised protein, decreased glucose and lymphocytic pleocytosis). CSF and blood cultures may be negative. Immunological studies include yeast phase and mycelial phase. CSF, serum and urinary histoplasma antigen may provide the diagnosis in cases of dissemination. Brain MRI may show hydrocephalus and meningeal enhancement after gadolinium injection. Brain and meningeal biopsy may be required.
Candida meninigitis: Candida species are ubiquitous but infections commonly occurs in patients receiving corticosteroids, braod-spectrum antimicrobial therapy; in patients with malignancies, neutropenia, sarcoidosis, collagen vascular disease, diabetes mellitus, and in patients with central venous catheters. Candidal meningitis is nonspecific. The onset can be either abrupt or insidious and the clinical manifestations can be differentiated from other forms of fungal meningitis. CSF reveals pleocytosis (600 cells/mm3) lymphocytes or neutrophils. Yeast is detected in 50% of cases on direct microscopy of CSF. A single positive culture from a patient with risk factors or symptoms is considered significant when CSF indices are compatible and the fungus is isolated in pure culture.
Aspergilosis meningitis: The lungs are the usual site of primary infection or alternatively direct extension from an area anatomically adjacent to the brain (paranasal sinuses). In most cases patients are neutropenic with underlying hematologic malignancy, iv drug users, HIV-1 infection, sarcoidosis, organ transplantation, diabetes mellitus, chronic hepatic failure and patients on corticosteroids. However some patients do not have any risk factor at all. Brain abscess is the most common clinical manifestation with stroke-like presentation. Headache, encephalopathy, fever and seizures (sometimes as part of CVT) may also occur. Meningeal irritation is rare. CSF is usually abnormal but nonspecific. Neuroimaging shows often signs of infarction which later develop into abscesses (often frontal or temporal and cerebellum). Biopsy is diagnostic. Any patient with cerebral infarct and risk factors for invasive aspergillosis should be suspected for aspergillosis.
Rhinocerebral mucormycosis: This fungal infection is one of the most acute, fulminant fungal infections known. Predisposing conditions are diabetes mellitus often in association with ketoacidosis, academia from profound systemic illness (sepsis, severe dehydration and chronic renal failure), hematologic malignancies, organ transplantation, injection drug use, and deferoxamine use. However < 5% of patients do not have any risk factor at all. Patients with rhinocerebral mucormycosis may initially present with ophthalmologic (diplopia, proptosis) or ENT manifestations. Cranial nerve abnormalities are common. Thrombosis is a striking feature of this infection hence focal neurologic deficits are very common suggesting far-advanced disease. Involvement of the carotid arteries is common in this infection. Brain MRI may show sinus opacification, erosion of bone, cavernous sinus involvement, and obliteration of deep fascial planes. In iv drug users basal ganglia are the most common site of CNS disease (bilateral infarction). Biopsy is diagnostic. Treatment with intravenous amphotericin B is essential.
Actinomycetes, Nocardia, and pseudallescheria occurs almost exclusively in immunocompromised patients (Hodgkin and non-Hodgkin disease, multiple myeloma, solid tumors, long-term use of steroids, chronic obstructive pulmonary disease, alveolar proteinosis, SLE, vasculitis, Cushing disease, chronic liver disease, hemochromatosis, RA, sarcoidosis, TB, diabetes, alcoholism, chronic granulomatous disease, solid organ or bone marrow transplantation and AIDS). Pseuodallescheria boydii presents as brain abscess and occasionally as meningitis. The infection becomes manifest 2-3 weeks after an episode of near drowning. Biopsy is diagnostic. Nocardia results in 70% from lung infections. In the presence of nocardia meningitis (CSF show pleocytosis (83%), reduced glucose (64%) and protein >100 (61%)) brain abscesses may result in 20-40% of cases.
Blastomycosis disseminated in late stage of advanced disease. Blastomycosis is common in Africa, the Middle East, and India.
Subacute combined degeneration of the spinal cord (SACD): Vitamin B12 deficiency leads to SACD. High-risk groups for the deficiency syndrome include the elderly, defective intrinsic factor production by gastric parietal cells (pernicious anemia), patients taking ulcer medications over long periods, heavy abuse of nitrous oxide, patients with AIDS, vegetarians, patients who have undergone stomach resection or small bowel resection, or both, and patients with dementia. The onset of symptoms is usually insidious, with paresthesias in the hands and feet present in the majority of patients. Sensory peripheral neuropathy can be the sole manifestation of B12 deficiency. Paresthesias in the feet and distal loss of all modalities of sensation with loss of ankle jerks are observed. Symptoms improve after therapy with B12. The next most common complaints include weakness and unsteadiness of gait. Cerebral symptoms may occur and can include confusion, delusions, hallucinations, mental slowing, and depression. Loss of position or vibration sense is the most common abnormality. Motor impairment may range from only mild clumsiness to a spastic paraplegia. Visual impairment can be seen; ophthalmological exam may show bilateral visual loss, optic atrophy, and centrocecal scotomata. Brainstem or cerebellar signs or even reversible coma may occur. Hematological abnormalities, including hypersegmentation of polymorphonuclear cells and a macrocytic anemia, can be seen; however, they may be completely absent at the time of neurological presentation. Current state-of-the-art testing uses serum cobalamin levels as a screening test, and the Schilling test, serum or urine methylmalonic acid and homocysteine determinations as confirmatory tests. A Schilling test detecting impaired intestinal absorption of vitamin B12, should be performed if there is enough clinical suspicion for the disease, and may reveal low vitamin B12 absorption even when the serum level is normal. The presence of circulating antibodies to parietal cells in many of these patients suggests an underlying autoimmune disorder. MRI reveals confluent leukoencephalopathy, even in the absence of anemia or myelopathy. VEP and SEP are frequently abnormal. SNAPs are absent or reduced in about 80% of patients and motor NCVs show axonal and demyelinating features. A typical regimen consists of intramuscular vitamin B12 injections of 1 mg twice weekly for 2 weeks, followed by monthly injections of 1 mg. For patients whose Schilling test demonstrates malabsorption of vitamin B12, monthly 1 mg injections should be continued on a lifelong basis. There is no evidence that overdosing can speed neurologic recovery; adverse reaction to high doses of vitamin B12 is unknown.
Inflammatory disease: SLE, Hashimoto encephalitis, mitochondrial encephalopathies, neurosarcoidosis, lymphomatoid granulomatosis, Churg-Strauss syndrome (asthma, eosinophilia), Wegener granulomatosis and PAN.
SLE: Systemic lupus erythematosus (SLE): Nervous system dysfunction occurs in 50 - 90% of patients with SLE. Neurologic involvement is more common in patients with APLS. SLE-related nervous system involvement encompasses a wide spectrum of overt neurologic and psychiatric features ranging from subtle cognitive abnormalities (such as attention, memory, visuospatial abnormalities) to dementia (80%), headaches (including migraine and benign intracranial hypertension) (54%), seizure disorders (42%), visual failure (32%), mood disorders and psychosis (44%), cerebrovascular disease, demyelinating disease, movement disorders, myelopathy, (9%), acute confusional states (7%), cranial neuropathy (7%), cognitive dysfunction, anxiety disorders (13%), mood disorders and psychosis, stroke (15%), acute aseptic meningitis (2%), chorea, demyelinating syndrome and myelopathy are all recognized as common manifestations of CNS lupus. Peripheral nervous system involvement includes mild (or even asymptomatic) symmetric distal sensory or sensorimotor polyneuropathy (including mononeuritis multiplex, GBS-like, CIDP, CTS or chronic sensorimotor axonal neuropathy)(28%), and, rarely, MG. Presentation with neurologic features at onset of disease is rare and occurs in only 3%. Arthralgias, pulmonary involvement, proteinuria, hypertension, DVT, Raynaud's phenomenon, skin rash are the most common systemic manifestations preceding neurological SLE. Smith antibodies are very specific but are only found in 30% of patients. CSF findings are often non-specific. A modest protein elevation and pleocytosis are seen in the CSF of 25-60% of patients with CNS lupus. Damage to the blood-brain barrier is present in about 30% of CNS lupus patients, as evidenced by elevated Q-albumin. An elevated IgG index, indicating the presence of intrathecal IgG production, is present in 25-60% of these patients, and an elevated IgM index is even more common. Oligoclonal banding is present in 20-80% of CNS lupus patients indicating that only a few B-cell clones may be responsible for CNS IgG production. The presence of anticardiolipin antibodies and the lupus anticoagulant have also been suggested as risk factors for CNS involvement in SLE. Additional evidence can be episodic polyarthralgias, anemia of chronic disease, transient skin rash, and recurrent pneumonitis, elevated erythrocyte sedimentation rate (50%), depressed complement levels and laboratory reports of high-titer antinuclear antibodies (85%) and antibodies to double-stranded DNA. MRI may be normal in up to 36% of patients, while abnormalities are seen in 15 to 78% of patients with active neuropsychiatric SLE. Many different neuroimaging presentations of CNS lupus can occur. These can include atrophy, infarct, discrete gray matter lesions, diffuse gray matter hyperintensities, focal, diffuse or periventricular white matter hyperintensities, and cerebral edema. MRI may show extensive bilateral white matter abnormalities suggestive of edema in the cerebral hemispheres, the brain stem, in the cerebellum, which may be associated with hypertension, benign intracranial hypertension, immunosuppression or other signs of active CNS lupus. CNS involvement in SLE is often reversible. Recovery from the CNS symptoms is observed in 70-85% of episodes. Treatment for CNS lupus involves high-dose steroids and cytotoxic agents such as cyclophosphamide, as is usually the case in patients with renal glomerular disease or other significant organ system involvement. The prognosis for 5-year survival is >90%. Primary angiitis of the CNS (PACNS): The mode of onset ranges from acute to insidious, but there is often a prodromal period of > 6 months. Characteristically, the course is chronic and fluctuating with recurring episodes of severe headache (64%), confusion (56%), a wide range of neurologic deficits such as transient ischemic attacks, strokes, paraparesis, cranial neuropathies, ataxia, seizures and myelopathy (5%), and mostly thoracic, on the background of a progressive dementia. ESR is raised in 2/3 and leucocytosis in 50% of patients. The CSF findings usually include a modest pleocytosis, elevated protein, and normal glucose. It is extremely important that the CSF be cultured, since PACNS has been reported in association with numerous infections involving bacteria, fungi, parasites, spirochetes, mycobacteria, and viruses. Brain MRI may reveal small multiple infarcts and cerebral angiogram (normal in 40% of cases) may show abrupt changes in the caliber of small cerebral arteries. Cerebral angiography demonstrates several areas of segmental arterial narrowing. Although the gold standard for diagnosis is brain or leptomeningeal biopsy, nearly one in four biopsy procedures may result in a false-negative outcome. CNS vasculitis may also develop in the course of infections (bacterial, viral (HSV), fungal, syphilis, borreliosis, rickettsiosis), lymphoproliferative disorders, and connective tissue diseases, or may be associated with drugs (amphetamines, cocaine, heroin, ephedrine, phenylpropanolamine). Since the differential diagnosis with HSV may be difficult PCR test of CSF is crucial. The diagnosis of PACNS is based on the clinical scenario of multiple strokes in different vascular territories, headaches, memory difficulties, behavioral changes, and CSF pleocytosis with absence of systemic signs and symptoms (fever, weight loss, joint or muscle pains, skin rash or ulcers; and serologic evidence of inflammation and autoantibodies). The clinical course, as well as the CSF protein and WBC, should be monitored to determine response to treatment (standard therapy has been a combination of corticosteroids and cyclophosphamide continued for 6-12 months) and also to help regulate the duration of treatment and the dose of oral prednisone. NeuroBehçet disease: Men are affected more commonly, and when there is any serious organ involvement (including the CNS), this gender predilection is further pronounced; among cases with neurologic involvement, the male to female ratio is nearly 4:1.The diagnostic criteria for Behçet disease require recurrent oral aphthae plus any 2 of the following: genital ulcers or scars; uveitis or retinal vasculitis; skin lesions such as folliculitis, acneiform lesions, or erythema nodosa; and hyperreactivity of skin to nonspecific physical insult such as pinprick (skin pathergy test). Other organ systems also may be involved, including the gastrointestinal tract, blood vessels (mainly the venous side), and lungs. There is CNS involvement in about 5% of cases. In the majority of these, there is a meningoencephalitis involving mainly the brainstem and diencephalon. In a smaller group, occlusion of the major cerebral dural sinuses may lead to intracranial hypertension without any meningoencephalitic involvement. Headache in Behçet disease may be due to either migraine, ETTH, sinus venous thrombosis or meningoencephalitis. When there is CNS involvement, treatment of Behçet syndrome consists of high-dose steroids and other immunosuppressants such as azathioprine or cyclophosphamide. If there is no CNS involvement or any other serious organ involvement, immunosuppression is not indicated. Since Behçet syndrome is a chronic disease with a predilection for inducing vascular occlusion, the use of triptans is risky in those patients with migraines.
Hashimoto encephalopathy: This type of encephalopathy may present with subacute or acute encephalopathic process with generalized or focal seizures and stroke-like episodes, temporary neurological deficits, a variety of psychiatric disturbances (ranging from sleep disturbance, dementia to psychosis) often associated with myoclonus and tremulousness and occasionally myelopathy. Patients are usually euthyroid or TSH can be increased with reduced T4. Independently, serum and CSF antithyroglobulin and antithyroperoxidase antibody titers are increased and no raised protein or oligoclonal bands are found in the CSF. Other antibodies (antineuronal and antinuclear) may be increased. CSF is normal or nonspecific. EEG may reveal diffuse slowing w or w/o intermittent runs of high-amplitude delta rhythm or synchronous sharp waves. Brain MRI may normal or show diffuse or focal reversible white matter abnormalities and generalized atrophy. Spontaneous recovery may occur however dramatic improvement may also be observed after a 5-day course of methylprednisolone 500 mg/day.
Metachromatic leucodystrophy (MLD): This slow progressive autosomal recessive disorder presents in its adult form typically with psychiatric manifestations; behavioral problems and slowly progressive dementia (frontal or subcortical in nature). Motor disturbance (spasticity) and cerebellar dysfunction may not occur until one decade after the onset of psychiatric manifestations. NCVs reveal substantially impaired motor nerve conduction (segmental demyelination) even in the absence of clinical features of polyneuropathy. CSF reveals raised protein levels. Some patients may develop abdominal symptoms related to sulphatide gallbladder stones. Brain MRI shows periventricular leukodystrophy (with frontal predilection) or can be normal. A convenient way to demonstrate MLD is the sulphatide excess in urinary sediment. The laboratory diagnostic tests show marked decrease or absence of arylsulphatase A activity in the urine and white blood cells or cultured skin fibroblasts. Sural biopsy reveals accumulation of metachromatic material. Important to know is that 1/50 to 1/100 of the normal population are homozygous for a common pseudodeficiency mutation in the arylsulphatase A gene (P426L, chromosome 22q). The work up for MLD deserves attention in any atypical MS-like syndrome or peripheral neuropathy of unknown origin. The course is prolonged and survival into 5th and 6th decade is possible.
Polycystic lipomembranous osteodysplasia with sclerosing leucoencephalopathy (PLOSL or Nasu-Hakola disease): This autosomal recessive disorder is characterized by the unique combination of progressive presenile dementia with sclerosing leucoencephalopathy, and systemic bone cysts. Ankle and wrist pain after strain are the initial symptoms during the 3rd decade, followed by fractures due to cystic bone lesions. Frontal lobe dementia (with prominent memory impairment, upper motor neuron involvement and incontinence) and seizures develop by the age of 30. The disease leads to death at the age of 40. Brain MRI reveals abnormally high and progressively increasing bicaudate ratios and calcifications in the basal ganglia and white matter even before the onset of neurologic syndrome. X-ray of ankles and wrists show cystic lesions. The defective gene (DAP12) has been mapped to chromosome 19q13.1. It is important to differential this disorder from FTD, CADASIL and X-AMN.
Brain tumors: Metastasis from sites outside the CNS (e.g. lung, breast, colon etc.) accounts for the majority of CNS neoplasms in adults. Metastasis are typically located at the junction grey/white matter. During the course of their disease, about 20% of patients with cancer will develop metastatic disease to the CNS. Of the primary CNS tumors 40% are gliomas and the majority of these are of astrocytic origin (75-90%). Other glial tumors include oligodendrogliomas, ependymomas, and primitive neuroectodermal tumors (PNET). The World Health Organization (WHO) classification is the most widely used, and separates astrocytomas into 4 main types: 1) grade 1 - pilocytic astrocytomas, 2) grade 2 - low grade astrocytomas, 3) grade 3 - anaplastic astrocytoma and 4) grade 4 - glioblastoma multiforme. The clinical features result from the destruction of underlying normal brain tissue, and can be extremely variable depending upon the location of the tumor and the specific structures that are compromised. Findings may vary from, focal findings in a patient with headaches to subacute dementia (due to a predilection for traveling across white matter). The white matter spread is called gliomatosis cerebri and could be mistaken for PMFLE, MS etc. Gliomas also can spread via the CSF leading to leptomeningeal gliomatosis. These patients may present with cranial neuropathies, obstructive hydrocephalus, compressive myelopathies, radiculopathies etc. Spread outside the CNS is extremely rare, but may spread to the peritoneal cavity in patients with shunts. Diagnosis is based on neuroimaging and confirmed by biopsy. High grade glioma are often heterogeneous, with ill-defined edges and surrounded by edema (T1). In addition they are enhancing after contrast (increasing contrast enhancement meaning dedifferentiation to high grade malignancy). Calcification may be present in about 15% of astrocytes and can help in differentiation. Glioblastoma multiforme characteristically demonstrate a heterogeneous appearance. These tumors have no distinct wall, a large amount of associated edema, and cystic areas which can be seen on imaging studies. They may cross to the other cerebral hemisphere, giving rise to the characteristic "butterfly tumor". Final diagnosis is usually made by stereotactic biopsy. A diagnosis can be made in 92-98% of cases, and the morbidity and mortality for biopsy is low (0-3%). Loss of the short arm of chromosome 17 is seen in about 30% of astrocytomas and are seen in much higher frequency in higher grade astrocytomas. Gliomatosis cerebri: This disorder is usually considered a disease of young adults but it can occur at any age. Reflecting the infiltrative nature of the tumor involvement, personality and mental status changes (1-2 years) (44%) are the most common initial manifestations, followed by headache, ataxia (33%), hemiparesis (58%), seizures, nausea, vomiting, and brainstem signs, in descending order of frequency. CSF analysis is usually normal: protein level is normal in 75% of cases and only slightly decreased in the remainder, glucose levels and cell count are generally normal. EEG shows typically poorly organized focal or diffuse theta and delta slowing, more pronounced late in the course of the illness. MRI signal hyperintensity in thalamus, midbrain, temporal lobe, gyral cerebral cortex and affects commonly the corpus callosum. CT scan is negative. Carcinomatous meningitis: Meninges are involved in 5-15% of all patients with solid or hematological tumors: (leukemia (40%), breast (34%), lymphoma (30%), lung (26%), melanoma (25%) and gastrointestinal (9%). About one third of patients with meningeal carcinomatosis have cranial nerve involvement, but less than 50% of patients have nuchal rigidity, headache or vomiting. MRI reveals diffuse dural meningeal enhancement (50-90%) and CSF in over 50% of cases elevated protein and reveals aseptic meningitis. CSF cytology is positive in only 50% of cases. Useful tumor makers in CSF are CEA (breast, lung, gastrointestinal tumors), epithelial membrane antigen, β-glucuronidase, β-2-microglobulin, and lactate dehydrogenase.
Mitochondrial encephalopathy lactatic acidosis syndrome (MELAS): The frequency of MELAS in the adult population averages 16/100,000. The disorder can onset in adulthood and may remain unrecognized until precipitated by metabolic stress. Epileptic seizures (particularly partial seizures, photoparoxysmal EEG responses and focal or multifocal EEG epileptiform activities) are the first recognized symptom in adults and can occur at any age. In contrast to KSS, MELAS and MERRF are often familial. Mitochondrial DNA is transmitted only from females to their offspring but a single female can bear offspring who harbour different levels of mutant mitochondrial DNA and have a variable phenotype. Clinical features are short stature (with normal milestones), sensorineural hearing impairment in late childhood (clinically obvious in 94%), exercise intolerance, in 4th and 5th decades diabetes mellitus (or impaired glucose intolerance), migraine-like headaches, epilepsy, recurrent stroke-like episodes commonly involving the posterior part of the cerebrum (occipital brain infarct resulting in hemianopia/cortical blindness)(10% of occipital strokes between the age of 18- 45 years are due to MELAS), ophthalmoplegia, pigmentary retinal degeneration (usually asymptomatic and best detected by retinal photography), cerebral white-matter disease, basal ganglia calcifications (54%), hypertrophic cardiomyopathy, syncopal attacks due to complete atrioventricular block, neuropathy (predominately axonal form), dementia or psychiatric manifestations or ataxia. The diagnosis of a mitochondrial myopathy can be confirmed by increased CSF lactate level, muscle biopsy (enzymatical assay) and molecular-genetic investigations on muscle specimen (in 80% of patients mtDNA point mutation at A3243G in the tRNA gene of mtDNA). MtDNA analysis on hair follicles is as sensitive as muscle in detecting this mutation. Analysis using blood samples appears not as sensitive, particularly in older subjects. Diffusion weighted MR findings support the metabolic rather than the ischemic pathophysiological hypothesis for stroke-like episodes occurring in MELAS. Normal or increased apparent diffusion coefficient values within 48 hours of a neurological deficit of abrupt onset should raise the possibility of MELAS, especially if conventional MR images show infarct-like lesions (cortico-subcortical posterior temporal and parieto-occipital). Brain MRI reveals leukoencephalopathy. Regional cerebral blood flow (rCBF) in patients with MELAS, using [123I]N-isopropyl-p-iodoamphetamine or 99mTc-hexamethyl propyleneamine oxime SPECT shows focal hypoperfusion in the parietal and/or occipital lobes. In vivo lactate determination in brain by 1H NMR spectroscopy can be helpful in evaluating prognosis. Early death (cardiopulmonary failure, status epilepticus and pulmonary embolism) has been reported in MELAS (mean age of 34 years). Hypertrophic cardiomyopathy advancing to dilated cardiomyopathy. There is evidence for maternal inheritance, and the mutation is always present in oligosymptomatic maternal relatives and most asymptomatic maternal relatives. The encephalopathy is often mistaken for HSE and CADASIL. Sodium valproate causes reduction of serum carnitine, inhibition of β-oxidation and oxidative phosphorylation and may therefore be contraindicated.
X-linked adrenomyeloneuropathy (X-AMN): The adult form of this X-linked recessive peroxisomal disorder starts on average at the age of 28 years and is predominantly confined to the spinal cord (adrenomyeloneuropathy). Cerebral involvement is observed in half of the cases. X-AMN is often misdiagnosed as familial MS. Slowly progressive spastic paraparesis with sensory deficit (predominantly reduced vibratory sensation), bladder dysfunction and mild distal mixed axonal demyelinating polyneuropathy are common features. These clinical symptoms are often preceded or followed by behavioral disturbances or frontal dementia (mania, psychosis and cognitive impairment) and are often misdiagnosed as brain tumor. Both neuroleptic and anticholinergic medications may result in significant side effects with little resolution of the underlying psychiatric symptoms. Adrenal insufficiency (Addison syndrome) develops in 70% of the patients before, during or after the onset of the neurological syndrome, and does not correlate with the severity of the neurological disease. 20% of heterozygous female patients may develop a late middle age syndrome, which resembles adrenomyeloneuropathy (spastic paraparesis, loss of vibration, long tract signs and peripheral neuropathy), but are unlikely to develop adrenal dysfunction. Other phenotypes are pure adrenal insufficiency or simply asymptomatic carriers. The diagnosis is confirmed by the presence of increased levels of saturated VLCFA in plasma (15% false negative in female heterozygotes) and cultured skin fibroblasts or white blood cells. CSF reveals increased intrathecal IgG. NCVs in patients with X-AMN are often abnormal and suggest a mixture of axonal loss and multifocal demyelination. Although MRI can be normal in up to 50% of patients, high signal intensities in the periventricular parieto-occiptal white matter (often asymmetric and mimicking brain tumor) have been reported in cerebral forms. However in 15%, the initial lesions may be frontal. Brain MRI findings may often provide the first clue to the diagnosis. A decreased N-acetylaspartate/choline ratio is found on MR spectroscopy. BAEP reveals prolonged latencies of III-V. The defective ALDP gene encodes for ATP-binding cassette transporter involved in transport of VLCFA into peroxisomes and has been mapped to Xq28.
Krabbe leukodystrophy (KLD): Three adult forms of this slowly progressive autosomal recessive disorder have been reported: (1) familial spastic paraplegia or tetraplegia, (2) an asymmetric pyramidal syndrome and (3) an asymptomatic form. Later on features such as frontal dementia, seizures, cerebellar ataxia, optic atrophy and demyelinating sensorimotor peripheral polyneuropathy appear. Motor nerve conduction is substantially reduced (NCVs may however be normal). CSF protein levels may be normal. Brain MRI may be normal but most often reveals increased signal intensity on T2 in the spinal pyramidal tracts, bilateral in the white matter of the cerebrum and brainstem. Proton MR spectroscopy shows increased choline and myoinositol in affected white matter. The diagnosis is based on the presence of low lysosomal galactocerebrosidase activity (<5% of normal) in white blood cells or cultured dermal fibroblasts. Some healthy individuals may have low enzyme activity. The gene maps to 14q25-31.
Propionic academia: This autosomal recessive disorder presents in adulthood with chorea, dementia, seizures and episodes of recurrent vomiting. Plasma, urine and CSF propionic acid levels (organic acids screening) are elevated and excretion of metabolites, including methylcitrate are typical. Propionic acidemia is due to propionyl CoA carboxylase deficiency (chromosome 3q13.3-22).
Antiphospholipid syndrome (APLS): This syndrome can masquerade vasculitis. The syndrome is part of the coagulopathies and results clinically in migraine, recurrent ischemic strokes or TIAs, livedo reticularis, acrocyanosis, ulceration, Raynaud's phenomenon, and purpuric macular lesions, thrombocytopenia, recurrent miscarriages (up to 30%), and thickening of the mitral valve. Age is significantly associated with coagulopathy with anticardiolipin IgG antibodies titer. The current diagnostic criteria for neurologic diagnosis of probable APLS are: (a) age < 55 years; (b) episodes of brain infarction, TIA, amaurosis fugax, retinal infarction, myelopathy, vascular dementia, or abnormal movements such as chorea; and (c) the presence of antiphospholipid antibodies of which there are at least two types: lupus anticoagulant and anticardiolipin antibody: high levels of IgG anticardiolipin antibodies (titer>16 on at least 2 occassions, 2 to 3 months apart), presence of lupus anticoagulant (abnormal aPTT, Kaolin clotting time test), or both. These antibodies are present in about 25% of patients with APLS and are associated with an increased risk for thrombosis; anticardiolipin antibodies resulting predominantly in venous thrombosis, while lupus anticoagulant is associated with both venous and arterial thrombosis (including coronary, cerebral, retinal and lower limbs). 8-10% of all patients with venous thrombosis have antiphospholipid antibodies. In patients with SLE these circulating procoagulant antibodies are found in 7-58% of patients. 23-58% of patients with lupus anticoagulant develop thrombosis, often recurrent. Sneddon syndrome (antiphospholipid antibodies, stroke and livedo reticularis in the absence of other systemic disease).
PMFLE: PMFLE is caused by either a primary infection or reactivation of infection by JC virus (polyoma virus). JC stands for the initials of the patient from which the virus has been discovered. PMFLE develops in association with immunodepression such as hematologic tumors (lymphoma, leukemia, multiple myeloma), sarcoidosis, TB, AIDS, carcinoma, connective tissue diseases treated with immunosuppressive drugs, after bone marrow and renal transplants. Patients typically develop cognitive deficits, memory problems, or behavioral and personality changes, which eventually progress to dementia and coma. Focal neurological deficits (hemiplegia, hemianopsia, dysarthria, dysphagia, cranial nerve palsies, vertigo, seizures, or gait abnormalities) are common. Asymptomatic infections by JC virus are common and more than 75% of population develop antibodies against the JC virus in adulthood. The CD4 count tends to be below 200 cells/mm3 (mean CD4 count at the time of diagnosis being approximately 85). The CSF is typically normal or shows few than 20 cells/mm3 and elevated protein (< 200 mg/dL). CSF examination with PCR for JC virus provides a sensitivity of over 90% (and hence often alleviates the need for brain biopsy). Brain MRI shows extensive, multifocal areas of increased signal on T2 images in the periventricular white matter. Asymmetric involvement is the rule, with a predilection for the white matter of the parietal and occipital lobes. Brain biopsy with positive immunocytochemical stain with anti-JC virus antigen antibody will confirm the diagnosis. The prognosis is infaust with a survival rate rarely exceeding a few months (median survival of PMFLE complicating AIDS is 6 months). PMFLE presenting as the initial manifestation of AIDS, CD4 counts >300 cells/mm3, and contrast enhancement on radiographic imaging have been associated with prolonged survival. Only highly aggressive antiretroviral therapy has been shown to improve both neurologic conditions and survival of individuals with AIDS-associated PMFLE. Toxoplasmosis, AIDS-dementia complex, cryptococcal meningitis, atypical lymphoma, CMV, herpes and VZV encephalitis, metastatic Kaposi sarcoma, acute stroke, and TB or fungal abscesses should be included in the differential diagnosis.
Stroke (Trousseau syndrome): Small strokes due to hypercoagulability or nonbacterial thrombotic endocarditis develop early in the course of cancer and need to be differentiated from vasculitis.
Dementia pugulistica: 87% of boxers develop neurological impairment. 50% of them develop changes on neuroimaging, EEG or neuropsychological testing. Traumatic encephalopathy begins near the end of a fighters career or shortly after retirement. It evolves over a period of a few years. Association with MND is possible. Apolipoprotein e4 allel is often positive.
Systemic diseases: Endogenous disorders causes are responsible for 5% of dementias. They include: liver, kidney or heart failure, hypoxia or carbon dioxide, severe anemia, excess or deficiency of thyroid, pituitary, adrenal or parathyroid hormone, electrolyte, acid-base, and metabolic disturbances (glucose, ketones, vitamins).
Idiopathic hypertrophic cranial pachymeningitis (IHCPM): This chronic disease is characterized by headache, ataxia and cranial nerve palsies (particularly VIIIth cranial nerve). Obstructive hydrocephalus may occur. Some patients have concomitant systemic fibrosis including: myocarditis, episcleritis and sclerosing cholangitis. There are no pulmonary abnormalities and ESR is raised. Steroids may result in complete resolution of pachymeningeal inflammation. Differential diagnosis of pachymeningeal lesions include infectious disease (TB, Lyme disease, syphilis, cat-scratch fever, candidiasis, aspergillosis and epidural abscess), noninfectious inflammatory disorders (neurosarcoidosis, autoimmune disorders (RA and Wegener granulomatosis), intracranial hypotension, neoplastic disease (benign or malignant forms), polyclonal plasma cell hyperplasia, plasmacytoma, meningeal carcinomatosis and metastatic (lung and breast carcinoma, lymphoma, leukemia, melanoma and colorectal cancer).
Thalamic dementia: The syndrome of thalamic amnesia is associated with lesions involving the anterior, dorsomedial and paramedian nuclei of the thalamus. It is characterized by severe anterograde memory loss with preservation of motor learning. Cognitive abilities such as language, visuospatial abilities and the ability to solve complex arithmetic problems are remain preserved. Some patients also develop retrograde memory loss with a temporal gradient. The amnesia produced is material-specific, with left-sided lesions producing a verbal memory deficit, and right-sided lesions producing visual memory impairment. Bilateral lesions involving the anterior thalamus have been shown to produce a lasting global amnesia.
Progressive encephalopathy with rigidity and reflex myoclonus (PERM): This syndrome of may also be considered in patients presenting with acquired axial rigidity and spasms, presenting with mental deterioration and myoclonus.
Chronic focal encephalitis (Rasmussen encephalitis): This slowly progressive (sometimes more than 25 years) disorder with onset in the 1st decade of life. The disorder is characterized by drug refractory unilateral focal seizures (epilepsia partialis continua, SPS and CPS, status epilepticus), slowly progressive aphasia, hemiparesis, and intellectual impairment (encephalopathy) with progressive atrophy of one cerebral hemisphere (neuroimaging). Within 4 months of onset all patients have refractory focal seizures with a predominant motor component, slow focal activity on EEG contralateral to the motor manifestations, and focal contralateral white matter hyperintensity with insular cortical atrophy on MRI. Serum anti-GluR3 antibody (ELISA), CSF oligoclonal bands may contribute to the diagnosis. Follow up may be over 25 years. AEDs fail to control the disease or halt progression.
Kufs B type