Oculomotor and Caloric Test Findings in 122 Patients With Unilateral Vestibular Schwannoma

Introduction Vestibular schwannoma (VS), a benign neoplasm of the eighth cranial nerve, can disrupt both peripheral vestibular function and central oculomotor pathways. The caloric test evaluates the vestibulo-ocular reflex (VOR) pathway, while oculomotor testing assesses central neural mechanisms. In this study, caloric and oculomotor assessments were performed in patients with unilateral VS to examine peripheral and central pathway integrity. Materials and methods The study recruited 122 patients (aged 18-55 years) with unilateral VS. It encompassed 60 patients with right-sided VS (Rt-VS) and 62 with left-sided VS (Lt-VS). It also included 120 age- and gender-matched healthy controls. Participants underwent bi-thermal caloric and oculomotor testing, and relevant metrics were recorded. Between-group differences were assessed using the Mann-Whitney U test, and associations between tumor volume and test metrics were examined using Spearman's correlation. Results The patient groups (Rt-VS and Lt-VS) revealed significant differences (p<0.05) in caloric and oculomotor tests compared to controls. In the caloric test, patient groups demonstrated significantly reduced lesion-side responses and exhibited unilateral weakness. Oculomotor assessment showed significant (p<0.05) abnormalities in saccadic, smooth pursuit, and optokinetic functions in patient groups. Saccade and optokinetic parameters were significantly affected bilaterally and in both horizontal and vertical directions. In smooth pursuit, though horizontal was reduced in both groups, vertical deficits were observed only in the Rt-VS group. Overall findings indicate central oculomotor dysfunction, along with vestibular impairment in unilateral VS.  Conclusion The study findings confirm that VS could compromise both peripheral and central functions. Caloric test results indicate significant peripheral vestibular dysfunction, whereas oculomotor abnormalities suggest central involvement. Large tumor size could mask the benefit of the compensatory mechanisms. Together, these findings underscore the importance of combining vestibular and oculomotor assessments to achieve a more comprehensive evaluation of functional impairment in individuals with VS.