Pathologic significance of Meniere's symptom complex. A histopathologic and electron microscopic study.

Histologic and ultrastructural findings in the temporal bones of a patient clinically diagnosed as having unilateral Meniere's disease are presented. The patient underwent two endolymphatic subarachnoid shunt operations that failed to relieve symptoms and a middle fossa vestibular nerve section that completely relieved episodic vertigo and stabilized hearing in the ear operated upon. Histopathologic examination of the temporal bones showed no endolymphatic hydrops in either ear. The maculae and cristae on the side operated upon showed severe degenerative changes attributed to vestibular neurectomy. The cochleograms of the operated and contralateral ears showed degeneration of the sensorineural structures in the basal two turns of the cochlea. No apparent cause for the fluctuant hearing loss was found in the cochlea or the cochlear nerve of the involved ear. Light and electron microscopic studies of the vestibular nerve excised at the time of vestibular neurectomy showed that most of the nerve fibers and ganglion cells were essentially normal. Collagen tissue deposition was increased in some areas of the endoneurial space. Most myelinated nerve fibers in these areas had degenerated. Although these changes may be partly due to artifacts and partly due to aging, they probably are the result of a pathologic process affecting the vestibular nerve. These findings suggest that a revised approach to the etiology, pathogenesis, and treatment of Meniere's symptom complex is indicated.