If the operation has been limited to the external semicircular canal, and the hearing power still exists, the after-treatment should be carried out as already described in the complete mastoid operation. If, on the other hand, the cochlea has been interfered with, or if it be certain that there is no longer any hearing power, then there is no object in trying to preserve the patency of the tympanic cavity, which in this case may be allowed to granulate up from its depth like an ordinary surgical wound.
The immediate anxiety of the surgeon after the operation is the possible onset of meningitis or the presence of a cerebellar abscess, which will necessitate further operation unless otherwise contra-indicated (see [p. 460]).
Comparison of the operations. Opening of the vestibule above the facial nerve is limited to those cases in which the lesion is situated within the semicircular canals and to the posterior portion of the vestibule; that is, either in non-suppurative cases in which the operation is performed in the hope of curing vertigo, or in suppurative cases in which the function of hearing still exists.
Opening of the vestibule below the facial nerve is to be preferred as a rule, especially if the function of hearing is already destroyed, because it permits of drainage from the inferior part of the vestibule; in addition, by working forwards, the outer wall of the cochlea can be removed and any disease within it can be tracked out to its limits.
If there be suppuration within the cochlea, sufficient drainage will not be obtained by merely opening the vestibule through the semicircular canals, but the cochlea itself must be opened. Again, if the lower portion of the vestibule and cochlea be first explored and found filled with purulent secretion, it is wiser to complete the operation by also opening the vestibule from above,—that is, to completely extirpate the labyrinth, which is now functionally useless and almost certain to be infected throughout its whole extent.
Intracranial complications. If, in addition to the labyrinthine suppuration, intracranial suppuration be suspected, the labyrinth should be explored first; but when possible the operation should be arrested at this point to see if the symptoms subside. If they continue, the exploration of the intracranial cavity can then take place through the internal ear, after a delay of twenty-four hours or more.
Of the intracranial complications, meningitis is most frequent, and next in order cerebellar abscess. In addition, thrombosis of the bulb of the jugular vein may take place from infection through one of the smaller tributary veins; or a localized extra-dural abscess may be found situated along the posterior portion of the petrous bone in consequence of direct extension of the infection through the internal auditory meatus, or as a result of empyema of the endolymphatic sac. This latter condition is almost impossible to diagnose, but may be discovered accidentally if the vestibule is opened by the posterior route according to Neumann’s method.
Difficulties. The chief difficulties are anatomical, and the inability to obtain a clear view owing to general oozing of blood.
The first is generally due to insufficient removal of bone; the second can usually be controlled by means of good assistants and the frequent employment of hydrogen peroxide or of adrenalin solution.
Dangers. Injury to the facial nerve. This, as might be expected, is not infrequent. If a burr be used, the nerve may be completely torn across and permanent paralysis may result. If, however, the gouge and mallet be employed, complete recovery usually takes place, as the injury seldom consists in complete destruction of the nerve.