Horizontal VOR function shows frequency dynamics in vestibular schwannoma

The objective of this retrospective study was to investigate the horizontal vestibulo-ocular reflex (hVOR) pathway with caloric test (low-frequency hVOR) and video head impulse test (vHIT) (high-frequency hVOR) in patients with sporadic vestibular schwannoma (69 patients, 27–86 years, mean age 58.1 years) and to compare both test methods in terms of their sensitivity and specificity to detect a retrocochlear lesion. Test results with a unilateral weakness (UW_Caloric) >25 % (caloric test) or a Mean-Gain_vHIT <0.79/asymmetry ratio of Gain (AR-Gain_vHIT) >8.5 % and accompanied refixation saccades (vHIT) were considered abnormal. The overall sensitivity of the caloric test was 72 %. The evaluation of AR-Gain_vHIT detected more abnormal cases than did Mean-Gain_vHIT (44 vs. 36 %). In up to 4 %, a normal caloric test result was related to an abnormal vHIT. There was only a moderate correlation of UW_Caloric and AR-Gain_vHIT (r = 0.54, p < 0.05) with a linear regression line intercept/slope of 32.2/0.9 (p < 0.05). Receiver operating characteristics curve analysis exhibited at a UW_Caloric of 50 % a vHIT sensitivity/specificity/positive predictive value/negative predictive value of 0.45/0.9/0.94/0.42. Vestibular testing at varying frequencies provides deeper insights into hVOR function and is helpful in detecting a cerebello-pontine lesion. Whereas caloric test yields a high sensitivity for nerve dysfunction, vHIT test reveals a remaining function of hVOR in the high-frequency range.