In such cases it is first essential to make certain that the attacks of vertigo originate from some lesion within the semicircular canals. For this reason the other forms of vertigo must be excluded, and, in addition, there should be evidence of definite involvement of the labyrinth, such as falling over of the patient to the affected side, internal-ear deafness, or post-suppurative changes within the middle ear, suggestive that the internal ear has also become affected. It must, however, be remembered that it is possible, though extremely rare, for a lesion, limited to the semicircular canals, to produce marked vertigo without any deafness being present, in which case the operation will be limited to extirpation of the semicircular canals.
(b) To relieve tinnitus. If the tinnitus be unbearable and all other measures have failed to cure it, the question of extirpation of the cochlea, in order to destroy the nerve-terminals, may be discussed. This operation, so far, has not been completely successful, and therefore it cannot be recommended.
In this connexion it may be mentioned that, instead of attacking the cochlea, it has been proposed to divide the auditory nerve before it enters the internal meatus. Charles Ballance has recently described such a case.
The difficulty of this latter operation and the very slight chance of cure which it offers, owing to the tinnitus probably being central, are sufficient to raise the question as to whether such an operation is really justifiable.
(ii) In suppurative labyrinthitis. The object of the operation is to remove the infective focus and, by permitting drainage, to prevent further complications, such as meningitis or intracranial suppuration.
Before deciding the question of operation every means available should be used to determine: (1) whether the symptoms are merely the result of disturbance of the labyrinthine function in consequence of suppuration still limited to the tympanic and mastoid cavities; (2) whether the labyrinthine lesion is localized or general; (3) whether the labyrinthine suppuration is associated with some intracranial complication, more especially meningitis or cerebellar abscess.
Suggestive of labyrinthine suppuration are vertigo, vomiting, spontaneous nystagmus, and disturbances of the equilibrium. In the more acute cases there may be loud tinnitus, pyrexia, rapid onset of deafness (with inability to hear high tuning-forks and loss of bone conduction), facial paralysis, and deep-seated pain.
In addition much information may be gained by determining the character of the spontaneous nystagmus, if present, or whether nystagmus can be elicited by Bárány’s caloric tests.
(a) If the ear be normal, there is no spontaneous nystagmus.
If, however, the ear be syringed with water above or below the body temperature, a rotatory nystagmus will be obtained if the patient’s head is kept in the erect position, or a horizontal nystagmus if the patient is lying in the horizontal position with the face upwards.