THE LABYRINTH AND THE EIGHTH NERVE 397
however, the eighth nerve signs are usually less evident than the other neuro-
1. Syphilitic neurolabyrinthitis should be diagnosed by the history of
syphilitic infection and the serological reactions of the blood and cerebro-
2. Neuritis due to toxaemia may be eliminated by a careful history of the
cases and thorough physical examination. Such cases do not show complete
deafness and loss of vestibular reaction.
3. Haemorrhage into the labyrinth in the bleeding diseases should be
excluded by an examination of the blood.
Fig. 212. Myeloencephalograph demonstrating filling defect in the internal acoustic meatus due to
neuron1 broma. (By courtesy of Dr E. Samuel.)
4. Senile or arteriosclerotic nerve deafness is bilateral. The low tones are
retained, along with the vestibular reactions.
5. Unilateral congenital deafness is rare. The vestibular reaction is present
in such cases.
6. Circumscribed labyrinthitis is associated with otitis media and
7. Otosclerosis is occasionally associated with giddiness, but audiometric
examination should demonstrate the conductive deafness.
8. Serous meningitis in the lateral cistern is as a rule associated with a
history of otitis media and a well-marked pointing error, which is not usually
found in acoustic tumour.
TREATMENT. Acoustic tumours should be dealt with by surgical removal as
early as they can be diagnosed; and this signifies in the 'otological stage' of
diagnosis. Four types of surgical approach are employed: (1) By way of the
middle cranial fossa, for removal of tumours confined to the internal acoustic
meatus and to save the hearing and the facial nerve; (2) Translabyrinthine;
(3) Suboccipital; and (4) Combined suboccipital-petrosal. Small tumours may
be removed by a middle cranial fossa or translabyrinthine approach with