Abstract
Purpose::
Patients with otolith dysfunction often present with a variety of symptoms, including diplopia, oscillopsia, visual tilt perceptions, false sensations of linear or tilting motion (either of self or the environment), lateropulsion, falling sensations or drop attacks. The purpose of this study is to investigate whether testing of the translational vestibulo-ocular reflex (tVOR) with transient, high-acceleration interaural head translations (head-heave) could aid in the diagnosis and localization of utricular lesions.
Methods::
Thirteen patients presenting with symptoms suggestive of otolith diseases and 10 healthy age-matched controls were recruited. All patients underwent a complete clinical otoneurological examination, as well as standard laboratory vestibular evaluation, including audiometry, electronystagmography with bithermal caloric, high-frequency/acceleration head thrust test with search coils (Halmagyi-Curthoys test), and vestibular evoked myogenic potential test. All subjects underwent subjective visual vertical (SVV) test and head-heave test at mean peak acceleration of 0.62g while viewing an earth-fixed target at 15 cm. Velocity gain of the tVOR, defined as the ratio of actual to ideal peak eye velocities, was calculated for the response within the first 100 msec after onset of head movement.
Results::
Five of the 13 patients recruited (38%) showed no abnormality in any of the tests. Of the remaining 8 patients, three (3/8 i.e. 38%) had a reduced tVOR gain (z-test, p<0.05), while one (1/8 i.e. 13%) had abnormal SVV. The gain was symmetrically reduced in both directions in 2 of these 3 patients, who had symptoms for 8 and 24 months. The third patient also had bilateral reduction of tVOR gain, but gain was more severely reduced during leftward head translation than during rightward translation. This third patient, who had symptoms for 7 weeks, was the only patient with abnormal SVV, showing a significant deviation to the left.
Conclusions::
Both the head-heave and SVV tests were able to detect asymmetric otolith disease in the acute stage. The SVV test relies on imbalance of utricular tone, and may not detect bilateral symmetric otolith dysfunction, or partial otolith disease with central compensation. Measuring the translational vestibulo-ocular reflex in a higher and more physiologic range of frequencies serves as useful adjunct to detect acute and chronic otolith dysfunction, and is superior to SVV in detecting bilateral symmetric or asymmetric otolith disease.
Keywords: eye movements • ocular motor control