Diseases Of The Nose Throat And Ear

396

THE EAR

DIFFERENTIAL DIAGNOSIS. If tumours of the eighth nerve are to be diagnosed
at the early 'otological' stage, otologists must thoroughly examine all cases of
unilateral nerve deafness. Radiographic examination of both temporal bones
(Figs. 211, 212), including tomography, may show dilatation of the internal
acoustic meatus and, less frequently, erosion of the apex of the petrous bone
on the affected side. An air encephalogram is probably more informative

A»

view showing enlargement of the right internal acoustic meatus due to
nerve. B, Stenver's position, right side. (By courtesy of Dr E. Samuel.)

+- Vew

of the eighth nerve

than a ventriculogram. The intrathecal introduction of a positive contrast
medium (v&ntopa.que)~myeloencephalography—by outlining a filling defect
in the internal acoustic meatus (fig. 212), is of considerable value in the
presence of doubtful small tumours. The protein content of the cerebrospinal
fluid is nearly always raised (100-300 mg per cent).

The clinical features of an acoustic neurofibroma are in large degree also
characteristic of other lesions in the cerebellopontine angle. In the latter,