Peripheral Vestibular System Disease in Vestibular Schwannomas: A Human Temporal Bone Study

INTRODUCTION:Dizziness is a common symptom in patients with vestibulo-cochlear schwannoma (VS), and several recent studies have identified this symptom as the single most important concerning the quality of life. Clinical and histological observations regarding hearing loss have suggested that this may be caused by both cochlear and retrocochlear mechanisms. Multiple mechanisms may also be at play in the case of dizziness, which may broaden perspectives of therapeutic approach. This study presents a systematic and detailed assessment of vestibular histopathology in temporal bones from patients with VS. METHODS:Retrospective analysis of vestibular system histopathology in temporal bones from 17 patients with unilateral VS. The material was obtained from The Copenhagen Temporal Bone Collection. RESULTS:Vestibular schwannomas were associated with atrophy of the vestibular ganglion, loss of fiber density of the peripheral vestibular nerve branches, and atrophy of the neuroepithelium of the vestibular end organs. In cases with small tumors, peripheral disease occurred only in the tissue structures innervated by the specific nerve from which the tumor originated. CONCLUSION:Vestibular schwannomas are associated with distinctive disease of the peripheral vestibular tissue structures, suggesting anterograde degeneration and that dizziness in these patients may be caused by deficient peripheral vestibular nerve fibers, neurons, and end organs. In smaller tumors, a highly localized disease occurs, which opens perspectives of differentiated clinical assessment and subsequent, targeted therapy.