Long-term evolution of subjective visual vertical after vestibular neurectomy and labyrinthectomy

Subjective visual vertical (SVV) tilt, observed after vestibular neurectomy and labyrinthectomy, is considered to be due to the deafferentation of the otolithic organs. The aim of this study was to determine the long-term evolution of the SVV up to 4 years after surgery. Between 1993 and 1998 the SVV was measured in 35 patients (18 men, 17 women) aged from 21 to 71 years (mean 36 years). Vestibular neurectomy was performed in 30 patients and labyrinthectomy in 6. SVV was measured with a binocular test (vertical frame) and a monocular test (Maddox rod). Immediately after operation, the SVV showed a 10-30 degrees tilt toward the operated ear with the vertical frame (normal 0 +/- 2 degrees) and a 5-22 degrees tilt with the Maddox rod (normal 0 +/- 4 degrees). After labyrinthectomy, SVV returned to normal values after 1 year in all patients. SVV also returned to normal within 1 year after vestibular neurectomy in 20 patients; in the other 10 patients SVV was still slightly tilted 1-4 years after neurectomy: > 2 degrees with the vertical frame and > 4 degrees with the Maddox rod, particularly on the eye ipsilateral to the operated ear. Some of these 10 patients also had persisting disequilibrium.