GREEN PEACE

The auditory nerve has two components, the cochlear nerve which is concerned with hearing and the vestibular nerve which is concerned with the appreciation of the position of the head and its movement in space. It is impossible without special tests to differentiate lesions involving these nerves from lesion confined to their end organs in the inner ear. Irrigative lesions of the inner ear or of the cochlear nerve cause tinnitus, and destructive lesions deafness. Thus tinnitus may be an early symptom of a neuroma of eighth nerve (acoustic neuroma) but it is often due to aural cause. The most important destructive lesion of the eighth nerve is an acoustic neuroma, but the nerve may also be damaged in meningitis and by the toxic effect of dihydrostreptomucin. Irrigative lesions of the vestibular part of the eighth nerve cause vertigo.