Pathologic correlates of electronystagmographic tracings.

Electronystagmographic tracings were correlated with the histopathologic findings in the peripheral vestibular system of 66 temporal bones of 34 patients who complained of dizziness. Although some findings (e.g., spontaneous nystagmus, unilaterally reduced caloric response, and directional preponderance) seemed to have doubtful value in localizing vestibular system disease, other findings indicated a peripheral site of the vestibular lesions. Bilaterally reduced or bilaterally absent caloric responses were consistently associated with pathologic changes in the peripheral vestibular system. Similarly, a unilaterally absent caloric response consistently indicated peripheral disease. On the other hand, positional nystagmus and bilaterally equal caloric responses seemed to indicate the absence of a peripheral site of disease in the vestibular system. Although there is no reliable way to differentiate end organ from vestibular nerve lesions, the latter were more commonly associated with positional nystagmus and absence of a caloric response. The direction of nystagmus beating correlated with the side of the diseased peripheral site in two of four patients with spontaneous nystagmus, in five of seven with positional nystagmus, and in all with unilateral reductions in or absence of caloric responses. Electronystagmographic findings in the present study seemed to reflect diffuse rather than localized pathologic changes in the peripheral vestibular system.