Neurovascular compression syndrome of the eighth cranial nerve. What are the most reliable diagnostic signs?

Forty-three surgical cases were retrospectively analyzed to establish diagnostic criteria and operative indications for vertigo and tinnitus due to neurovascular compression (NVC) of the eighth cranial nerve (8th N). Many NVC syndromes were mistakenly diagnosed as Ménière's disease or benign paroxysmal positional vertigo. NVC was confirmed in 31 of the 43 patients. Neurovascular decompression (NVD) resulted in complete recovery or marked improvement of subjective symptoms in all 19 cases with vertigo (100%), and in 19 of 29 patients with tinnitus (65.5%). Multiple factor analysis revealed that abnormal caloric responses have high diagnostic value for vertigo due to NVC. Vertigo due to NVC is of short duration (a few sec to a few min.) in the early phase of the disease, which becomes longer and hearing becomes impaired as the history of NVC lengthens. Low pitch pulsatile and high pitch continuous tinnitus are probably due to NVC and are cured by NVD if hearing is still preserved. Tinnitus associated with hemifacial spasm is strongly indicative of NVD. Decompression of the 8th N should be performed in the early phase of disease, since cochlear and vestibular functions are irreversibly impaired if NVC continues for a long period of time.