Acute confusion with episodic muscle rigidity
Strychnine poisoning: Strychnine is rapidly absorbed from the gastrointestinal tract, with symptoms developing within 10 to 20 minutes after ingestion. Acute encephalopathy (confusion) in association with episodes of muscle rigidity resulting in rhabdomyolysis are typical for strychnine poisoning. The initial symptoms of poisoning include nervousness, a hyperalert state, and acute confusion. Stiffness is first noted in the face and neck. Contraction of the facial muscles may cause risus sardonicus. The initial symptoms are soon followed by episodes of overwhelming muscle rigidity throughout the body in response to even minimal stimuli. Myokymia can be observed. Opisthotonos may be so severe that only the head and the heels touch the bed, with all voluntary muscles in full contraction resulting in rhabdomyolysis. The patient is fully conscious during the episodes, confirming the noncortical origin of the convulsions. In between the spasms, which last from 30 seconds to 2 minutes, the muscles become completely relaxed. During severe convulsions, there is respiratory arrest, and the combination of sustained muscle contraction and hypoventilation may result in rhabdomyolysis, myoglobinuria, and severe lactic acidosis. Without treatment, the patient usually dies from asphyxia and cardiac arrest after two to five such episodes. Most patients are treated with gastric lavage and instillation of charcoal at the first sign of poisoning. The spasms are usually treated effectively with benzodiazepines, phenobarbital, or pentobarbital. Occasionally, it is necessary to induce paralysis with pancuronium. Prophylactic endotracheal intubation and mechanical ventilation should be considered in cases of severe poisoning. Aggressive treatment with intravenous fluids may diminish the deleterious effects of myoglobinuria on the kidneys and improve the lactic acidosis. A variety of traditional remedies still exist, including coin rubbing, moxibustion, and the use of traditional herbs, aromatic oils, and teas. Strychnine, in the form of the nut of the Strychnos nux-vomica plant, is a traditional remedy in Cambodian. EEG is normal and EMG is not able to differentiate between generalized tetanus and strychnine poisoning. The diagnostic procedure is a test of the urine, gastric contents, or blood for strychnine.
Tetanus: Tetanus is caused by tetanospasmin, the exotoxin elaborated by Clostridium tetani, an anaerobic, spore-forming rod usually detected in infected wounds. The spores are commonly found in samples of soil but have also been isolated from other sources such as house dust and cultured surfaces in operating rooms. The interval between the wound and the onset of symptoms of tetanus is typically 4 to 20 days, but much longer intervals have been reported. In most cases, the patient is either unimmunized or incompletely immunized. Generalized tetanus begins with restlessness and irritability. Lockjaw, neck stiffness or dysphagia are the common initial signs. Spatula sign (trigger of mouth clenching following palatal touch) is diagnostic. Overactivity of the facial muscles gives rise to the classic appearance of risus sardonicus (sardonic smile). As the disease progresses, sudden tonic contractions of the muscles cause dramatic, painful episodes of opisthotonos, flexion of the elbows, clenching of the fists, and hyperextension of the legs, during which the patient remains fully conscious. Paroxysmal tonic contractions with preserved consciousness to external stimuli look like convulsions. Accompanying glottal and laryngeal spasms can lead to cyanosis, asphyxia, and death. The spasms may result in fractures of the spine or long bones. Autonomic dysfunction is also common, often manifested by tachycardia and labile hypertension. Patients may die from sudden cardiac causes; complications of management in the intensive care unit may also result in death. Interneuron-mediated inhibition can be demonstrated by EMG. After a stretch reflex, there is a brief pause in EMG activity, reflecting the inhibition mediated by these interneurons. Agents that block this inhibition, such as tetanus toxin, shorten or abolish the normal brief pause in EMG activity, a phenomenon best observed in the masseter muscle. There are no other distinctive laboratory findings in tetanus, although the level of creatine kinase may be elevated as a result of rhabdomyolysis. History of a suspicious wound is suggestive, but the absence of such a history does not necessarily rule out tetanus. Rapid onset of symptoms consisting of episodes of stiffening with prominent confusion are against the diagnosis of tetanus and rather indicate strychnine poisoning. Antitetanus immunoglobulin should be given (100-500 IU/kg i.v. together with tetanus vaccination in previously non-immune patients and a second dose 6 weeks later). Alternatively, the following therpeutic strategy can be followed when available: antitetanus immunoglobulin i.m. (3,000 IU) with or without intrathecal immunoglobulin (1,000 IU lyophilized human immunoglobulin free of preservative diluted to volume of 4 ml with distilled water and injected lumbar or suboccitpital after removing an equal amount of CSF). The latter gives 20% better clinical progression. Antibiotic therapy should consist of 10-day course of penicillin (1.2 million units of procaine penicillin/day) in combination with metronidazole (500 mg q6h i.v.). Wound treatment is imperative. Diazepam (or more expensive, midazolam) should be given ad libitum till complete muscle relaxation is achieved (e.g. diazepam 15 mg/h i.v.), and if required in combination with baclofen (p.o. or intrathecal 20 mgram/h with max. of 2 mg). Botox can be used for local spasm (e.g. trismus). The objective of the whole therapy is to suppress spasm and keep the patient arousable. Failure to achieve proper muscle spasm control requires the use of neuromuscular blocking agents (e.g. pancuronium). Mortality is overall 50%. Prognostic factors are the length of the incubation time (≤ 7 days results in 75% mortality), presence of fever and tachycardia. ICU admission (dark room) requiring tracheostomy and continuous monitoring is essential for survival.
Rabies: Rabies may be associated with confusion and episodes of muscle stiffening. Rabies usually enters the body through the bite of an infected animal, traveling by retrograde axoplasmic flow toward the spinal cord at a rate of 8 to 20 mm per day. After an incubation period of 30 to 90 days, a nonspecific prodrome consisting of low-grade fever, malaise, nausea or vomiting, cough, and headache develops and typically lasts 1 to 4 days. In many patients, pain and paresthesias develop near the bite wound. Two clinical forms of infection have been described. The "dumb," or paralytic, form, which occurs in less than 20 percent of cases, resembles the GBS, with ascending paralysis and loss of the deep-tendon reflexes. A characteristic symptom of the "furious" form of rabies infection, which is more common, is hydrophobia, with inspiratory spasms involving the pharynx and larynx when the patient attempts to swallow liquid. These 5-to-15-second spasms may be associated with facial grimacing and extension of the neck and back, which may evolve to opisthotonos. Some patients become agitated and disoriented and have hallucinations; others remain calm and oriented. Examination reveals a waxing-and-waning pattern of muscle contractions, with facial grimacing, hyperreflexia, muscle twitching, and other involuntary movements. Brainstem involvement, with multiple cranial nerve abnormalities, is a hallmark of rabies infection. The viral strain varies according to the animal species, and in patients who report no history of an animal bite, the strains carried by bats are implicated most often.
Neuroleptic malignant syndrome
Herpes simplex encephalitis