Vestibular function tests

1.    Head thrust test (HTT): used to assess the angular vestibulo-ocular reflex (VOR). During the HTT, the patient is asked to focus the eyes on the nose of the doctor. Next, the patient's head is gently grasped, and a small amplitude (5-10º) but high acceleration thrust is applied by the examiner. Once the head stops moving, the eyes are observed for a corrective saccade. The corrective saccade is a rapid eye motion that returns the eyes toward the target and indicates a decreased gain of the VOR. Individuals with normal vestibular function do not use corrective saccades after HTT (the eyes stay fixed on the target). Patients with vestibular hypofunction may use a corrective saccade after the head is thrust toward the side of the hypofunction. The specificity of the test is high (95-100%), the sensitivity is variable. In case of complete unilateral vestibular hypofunction due to nerve section both are 100%.

2.     The nystagmus (horizontal or torsional, never vertical) is typically away from and Romberg sign positive towards the side of the lesion. The nystagmus is fatigable and inhibited by visual fixation. The nystagmus also increases in the direction of the pathological ear.

3.     Caloric responses are usually decreased.

4.     Post-head-shaking nystagmus at 2-3 Hz for 10-20 sec can induce horizontal nystagmus in central and unilateral peripheral vestibular lesions. In unilateral peripheral vestibular lesions, this post-head shaking nystagmus is usually contralesional (away from the affected side). In Wallenberg syndrome this post-head shaking nystagmus is ipsilesional for middle and rostral medullary lesions and contralesional for caudal lesions.

Auditory bedside testing

AC: air conduction

BC: bone conduction