THE LABYRINTH AND THE EIGHTH NERVE
The Vestibular Apparatus. Spontaneous nystagmus is usually present to
both sides. It generally appears first towards the unaffected side and is
followed, as the tumour progresses, by nystagmus to the side of the lesion.
Positional nystagmus (non-fatiguable) has been observed in more than 50
per cent of cases. In advanced cases there is, as a rule, vertical nystagmus.
Fig. 209. Horizontal section of right ear in a case of neurofibroma of the eighth nerve. 1, Head of
stapes with stapedius; 2, Facial nerve; 3, Posterior canal with haemorrhage in perilymph space; 4,
Tumour; 5, Lower part of utricle; 6, Dilated internal meatus with tumour. ( x 3.)
Fig. 210. Tumour of the eighth nerve. Axial section through right cochlea. 1, Dilated cochlear canal,
basal coil; 2, Capsule of tumour; 3, Tumour tissue; 4, Cochlear nerve, which is compressed by tumour
tissue; 5, Central canal of modiolus. Note the infiltration of the scala vestibuli and scala tympani by
delicate connective tissue.
The pointing reaction is usually normal. On Romberg's test the patient
usually tends to fall to the side of the lesion. The caloric tests are abnormal—
and indeed are absent on the affected side—in the large majority of cases.
When the cold and hot method of caloric testing is employed, abnormal
results are reported to occur in all cases, by far the commonest finding being
complete canal paralysis on the affected side.