Isolated perverted head-shaking nystagmus in focal cerebellar infarction

Head-shaking nystagmus (HSN) refers to the nystagmus induced by head oscillation, and usually beats to the healthy side in unilateral peripheral vestibulopathy.1 It may occur from velocity storage mechanism and Ewald second law.1,2 In perverted HSN (pHSN), the nystagmus develops in the plane other than that being stimulated, i.e., downbeat or upbeat after horizontal head oscillation. pHSN has been reported in diffuse cerebellar degeneration or medullary lesion,3,4 and signifies central vestibular lesion. However, isolated pHSN from focal cerebellar lesions has not been described. A 59-year-old man reported recurrent dizziness that most often occurred from exposure to heat or after taking a hot bath and lasted several minutes without other neurologic symptoms. On initial examination, he had blood pressure of 155/95 mm Hg and fasting blood glucose of 206 mg/dL. Other physical, neurotologic, and routine laboratory examinations were normal. In view of hypertension, diabetes, and duration of the dizzy spells, he was suspected to have vertigo of vascular origin and was scheduled for brain MRI. Five days later, while …