Supplementary Material for: Head-Shaking Aids in the Diagnosis of Acute Audiovestibular Loss due to Anterior Inferior Cerebellar Artery Infarction

Objective: To determine the patterns and diagnostic value of head-shaking nystagmus (HSN) in patients with acute audiovestibular loss. Method: Eighteen patients underwent evaluation of spontaneous nystagmus, gaze-evoked nystagmus, HSN, head impulse test, ocular tilt reaction, subjective visual vertical, bithermal caloric tests, and pure-tone audiogram. The findings were compared with those of 21 patients with labyrinthitis. Results: Fifteen patients (83%) exhibited HSN, and the horizontal HSN usually beat contralesionally (10/14, 71%). However, 9 (50%) patients also showed patterns of central HSN that included perverted HSN (n = 7), HSN in the opposite direction of spontaneous nystagmus (n = 4), and HSN beating towards unilateral canal paresis or abnormal head impulse testing (n = 3). Overall, central HSN, gaze-evoked nystagmus, and normal head impulse testing were specific for anterior inferior cerebellar artery (AICA) infarction. Moreover, central HSN was the only sign that indicated stroke in 1 of our patients with isolated audiovestibular syndrome. Lesion subtraction analyses revealed that damage to the flocculus was relatively frequent in patients with perverted HSN. Conclusions: In AICA infarction, HSN was common with both peripheral and central patterns. Careful evaluation of HSN may provide clues for AICA infarction in patients with acute audiovestibular loss.