Unilateral Peripheral Vestibular Dysfunction Confounded by Central Inhibition
PD is a pleasant 39-year-old male with a 6-year history of occasional vertigo as well as imbalance with fast head or body turns. He had sought several medical opinions in the past and had been diagnosed with bilateral peripheral vestibular loss, bilateral perilymphatic fistulae, as well as benign positional vertigo. Past medical treatments included a repositioning maneuver for benign positional vertigo, sequential middle ear explorations, and subsequent packing for a suspected perilymphatic fistula. He then presented at our audiology clinic for further evaluation.
PD was seen by a neurotologist for his symptoms of persistent imbalance and vertigo. He stated that the world “jiggled” when he chewed or used handheld power tools that vibrated, and he indicated difficulty walking in the dark. Medical examination revealed intact tympanic membranes; normal nasal, oral, laryngeal, and neck exam; absence of spontaneous nystagmus; absence of gaze-evoked nystagmus; normal saccades and smooth pursuit; and negative Dix-Hallpike testing. He revealed a positive head impulse sign during head impulse testing (HIT) in the right horizontal plane. This meant that when the examiner moved PD’s head quickly to the right in the horizontal plane, PD was unable to maintain fixation on the target and a refixation saccade was visible to the examiner. Dynamic visual acuity testing (DVAT) revealed markedly reduced results with performance diminishing more than seven lines on the Snellen eye chart. The DVAT test looked at the difference in visual acuity between PD’s static visual acuity and when the examiner shook his head side to side. A decrease of greater than two lines on the chart is considered abnormal. Increased sway was noted while he stood with eyes closed. Also, he fell with delayed posture response when standing on 3-inch foam with his eyes closed. Magnetic resonance imaging (MRI) and computed tomographic (CT) scans were unremarkable. The medical impression was suspected bilateral vestibular dysfunction with idiopathic etiology. PD’s physician ordered bithermal caloric irrigation, ice water caloric irrigation, cervical vestibular-evoked myogenic potentials (cVEMPs), and rotational chair (RC) studies.