Head-Jolting Nystagmus: Occlusion of the Horizontal Semicircular Canal Induced by Vigorous Head Shaking.

IMPORTANCE: We report a new syndrome, which we are calling head-jolting nystagmus, that expands the differential diagnosis of head movement-induced paroxysmal vertigo. OBSERVATIONS: Two male patients (65 and 58 years old) described rotational vertigo after violent and brief (1- to 2-second) oscillations of the head (head jolting) that triggered intense horizontal nystagmus lasting 45 seconds. Accelerations of the head required to induce these episodes could only be achieved by the patients themselves. In case 1, the episodes gradually disappeared over a 6-year period. In case 2, magnetic resonance imaging (3-T) suggested a filling defect within the left horizontal semicircular canal. He underwent surgical canal plugging in March 2013 that resolved the symptoms. CONCLUSIONS AND RELEVANCE: We attribute head-jolting nystagmus to dislodged material within the horizontal semicircular canal and provide a mechanistic model to explain its origin.