Objective: To determine why dynamic visual acuity (DVA) improves after vestibular rehabilitation in people with vestibular hypofunction.
Design: Combined descriptive and intervention study.
Setting: Outpatient department in an academic medical institution.
Participants: Five patients (age, 42-66 y) and 4 age-matched controls (age, 39-67 y) were studied. Patients had vestibular hypofunction (mean duration, 177+/-188 d) identified by clinical (positive head thrust test, abnormal DVA), physiologic (reduced angular vestibulo-ocular reflex [aVOR] gain during passive head thrust testing), and imaging examinations (absence of tumor in the internal auditory canals or cerebellopontine angle).
Intervention: Vestibular rehabilitation focused on gaze and gait stabilization (mean, 5.0+/-1.4 visits; mean, 66+/-24 d). The control group did not receive any intervention.
Main outcome measures: aVOR gain (eye velocity/head velocity) during DVA testing (active head rotation) and horizontal head thrust testing (passive head rotation) to control for spontaneous recovery.
Results: For all patients, DVA improved (mean, 51%+/-25%; range, 21%-81%). aVOR gain during the active DVA test increased in each of the patients (mean range, 0.7+/-0.2 to 0.9+/-0.2 [35%]). aVOR gain during passive head thrust did not improve in 3 patients and improved only partially in the other 2. For control subjects, aVOR gain during DVA was near 1.
Conclusions: Our data suggest that vestibular rehabilitation increases aVOR gain during active head rotation independent of peripheral aVOR gain recovery.