Functional head impulse testing for detection and quantification of vestibular dysfunction in multiple sclerosis

Background Multiple sclerosis (MS) is the most prevalent cause of non-traumatic neurological disability in young adults. Vestibular dysfunction (VD) is frequently observed in MS patients and may considerably impair their daily activities. Early diagnosis of VD is pivotal for optimizing treatment. Methods A total of 36 patients (29 females; mean age: 45.5 +/- 10.6 years) with relapsing-remitting MS (RRMS) were enrolled. The presence of VD was investigated, and patients were identified as positive for VD (VD-RRMS; 19 patients; 18 females; mean age: 44.9 +/- 11.4) and asymptomatic (A-RRMS; 17 patients; 11 females; mean age: 46.2 +/- 9.9). VD was assessed using a Vestibular Symptoms Classification (VSC), assigning one point each for the presence of vertigo, postural instability, and nystagmus (0-3). The functional head impulse test (fHIT) was administered with rightward and leftward passive horizontal head rotation in all patients, and the test performance was quantified as the percentage of correctly identified Landolt C optotypes during head rotations. Lesion load was quantified via semiautomated lesion segmentation at Magnetic Resonance Imaging, extracting total lesion number/volume and regional lesion counts. Results ANOVA indicated a significant main effect of VD factor on leftward and rightward fHIT performance, with a lower percentage of correct responses in the VD-RRMS group compared to A-RRMS group (p < 0.05). A negative correlation was identified between VSC and fHIT performance (p < 0.05). Finally, higher lesion burden predicted poorer fHIT performance, with total and periventricular lesion counts emerging as significant negative predictors. Conclusions The fHIT is a safe, noninvasive and rapid test to assess the VD presence and correlate the performance with the VSC in RRMS patients. The fHIT might be investigated longitudinally to monitor VD worsening and develop a more effective therapeutic strategy.