Bilateral Vestibular Loss With Gaze-Evoked Nystagmus and Saccadic Visually Enhanced VOR

This is 55-year-old man with the subacute onset of head movement-induced oscillopsia and dizziness. He had a history of psoriatic arthritis. He had not used medications known to be vestibulo-toxic such as gentamicin. ; Salient findings on his examination included 1) bilateral vestibular loss (BVL) demonstrated by bilaterally abnormal head impulse test (HIT, with corrective saccades and low gains seen bilaterally with bedside and video HIT), as well as 2) cerebellopathy demonstrated by gaze-evoked nystagmus and saccadic smooth pursuit. His vestibulo-ocular reflex suppression (VORS) was nearly normal appearing because there was no VOR to suppress (given his BVL). As expected given his bilateral VOR hypofunction and saccadic pursuit, his (slow) visually-enhanced VOR (vVOR) was saccadic. If VOR is impaired but pursuit is normal, vVOR will be normal. If pursuit is impaired but VOR is normal, vVOR will be normal. However, if VOR and pursuit are impaired - as in cerebellar ataxia, neuropathy, areflexia syndrome (CANVAS, which this patient did not have, mainly given the subacute onset) - then the vVOR will be saccadic or choppy. Patients with vestibulopathy and cerebellopathy will have significant imbalance. MRI was unrevealing and further investigation for infectious, inflammatory, autoimmune, neoplastic, nutritional etiologies is ongoing.