Bilateral posterior semicircular canal dysfunction: a new finding with video head impulse test.

Development of the video head impulse test (vHIT) assessing all three semicircular canals in both labyrinths has uncovered the existence of new vestibular failure patterns and made bilateral posterior canal dysfunction detection possible. We conducted a retrospective analysis of 41 patients with bilateral posterior semicircular canal failure and compared results to 37 controls, with normal posterior semicircular canal function. Mean calculated gain showed significant difference between patients and controls in right [0.54 (SD 0.016)] and left [0.57 (SD 0.014)] posterior semicircular canals. There was a peak in prevalence between 71 and 80 years. Presentation was chronic in 78% of patients, and gait instability was the most common complaint. Sixty eight percent of cases were classified as idiopathic. Significant difference between groups was seen regarding the presence of Meniere's disease, presbycusis, and positional down-beat nystagmus (posDBN). This new vHIT pattern is most often seen in elderly patients, mainly of idiopathic etiology and presents together with sensorineural hearing loss and posDBN. Our findings suggest idiopathic cases may well contribute to the so-called "presbyastasis".