CHAPTER VII

OPERATIONS UPON THE LABYRINTH

GENERAL CONSIDERATIONS

Labyrinthine suppuration usually occurs in the course of a chronic middle-ear suppuration; more rarely, as the result of tuberculous disease of the temporal bone, or in consequence of an acute middle-ear suppuration. In the latter case, however, it is a matter of experience that, although symptoms of labyrinthine suppuration may be present, they almost invariably subside as a result of drainage of the middle ear and mastoid. This is an important point which should be remembered, as otherwise the labyrinth may be explored unnecessarily at a considerable risk to the patient’s life.

The most frequent paths of extension of the pyogenic infection from the middle ear to the internal ear are through the external semicircular canal, the promontory, and the fenestra ovalis, the result of cholesteatomatous erosion, caries, or necrosis. Hinsburg, in 198 cases of labyrinthine suppuration, traced the infection in 61 cases. In 27 cases the infection had entered through the external semicircular canal, in 17 through the fenestra ovalis, in 7 through a fistula of the promontory, in 5 through the fenestra rotunda and ovalis, and in 5 through a fistula in the posterior or superior semicircular canal (_Archives of Otology_, 1902, vol. xxxi, p. 116).

Although operations on the labyrinth are practically limited to suppurative disease, yet under certain conditions they are justifiable when no suppuration is present.

These operations may consist in partial or complete opening of the semicircular canals, or of the vestibule, or in removal of the cochlea, or complete extirpation of the labyrinth.

INDICATIONS FOR OPERATION

(i) =In non-suppurative labyrinthitis.=

(_a_) _To relieve vertigo._ This operation is only justifiable if the condition cannot be cured by other methods, and is so distressing as to render the patient’s life unendurable.

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.

Syringing with hot water causes a nystagmus directed _towards_ the ear syringed; syringing with cold water, _away from_ the ear.

(_b_) If there be a localized labyrinthine lesion, and the function of the labyrinth is still maintained, the same results will be obtained on syringing. Care, however, must be taken that the syringing is not forcible, otherwise the caloric tests will be unreliable, as in these cases nystagmus may be produced on even slight increase of pressure within the external auditory canal, and with this there may be a sensation of giddiness and nausea.

Spontaneous nystagmus, however, will probably be present, and will be directed towards the affected side. This spontaneous nystagmus is greatly modified by the caloric tests, being strongly exaggerated on syringing with hot water, and weakened or arrested on syringing with cold water.

(_c_) If the function of the labyrinth be destroyed, as in suppurative labyrinthitis, nystagmus will not be produced as a result of the caloric tests, but the spontaneous nystagmus, if present, will be directed towards the opposite, the normal side.

These various tests must be taken in combination with the symptoms, and frequently are of extreme value in deciding whether operation is indicated or not.

The chief difficulty is to exclude the possible existence of a cerebellar abscess (see p. 460). In favour of labyrinthine inflammation is complete internal-ear deafness, although this in itself does not exclude an accompanying intracranial lesion.

1. _Immediate exploration of the labyrinth is indicated_ (provided there is internal-ear deafness):--

(_a_) If symptoms of _acute_ labyrinthine suppuration occur in the course of a middle-ear suppuration, even although at the time of opening of the mastoid no definite fistula of the labyrinthine wall can be discovered.

(_b_) If symptoms of involvement of the labyrinth be present and a definite fistula is found on operation.

(_c_) If symptoms of a cerebellar abscess or of meningeal irritation be present in addition to those suggestive of a labyrinthine affection.

2. _Opening of the labyrinth should be delayed_ if Bárány’s and other tests show that the labyrinth is not yet destroyed:--

(_a_) If, in spite of clinical symptoms pointing to involvement of the labyrinth, pus be found under tension within the tympanic cavity or the mastoid process.

(_b_) If the symptoms before operation consist only of attacks of vertigo and nystagmus, and on operation merely an erosion of the outer wall of the labyrinth (usually the external semicircular canal) is discovered.

In the above cases, if the symptoms be due to irritation of the labyrinth, a rapid recovery is to be expected as a result of the mastoid operation. If, however, they continue or become progressively worse, then the wound cavity must be reopened and the labyrinthine wall carefully examined and further operation undertaken.

The reader may again be reminded that although exploration of the labyrinth is indicated when it is certain that a suppurative lesion exists, yet it is a very serious mistake to open up a labyrinth not yet infected.

Although a great advance has been made in the last few years with regard to operations on the labyrinth, yet there is still much to be learnt, not only with regard to the indications for operation but the result obtained by operation. Now that operations on the labyrinth have become universal, the general tendency is to operate on the immediate occurrence of symptoms of labyrinthine irritation without waiting to see whether simple opening of the mastoid process will not be sufficient--a matter much to be regretted.

=Surgical Anatomy.= The facial canal, it will be remembered, extends horizontally backwards above the promontory, and passes downwards superficially to the inferior portion of the vestibule which lies between the fenestra ovalis below and ampullary ends of the external and superior semicircular canals above. The nerve then extends directly downwards towards the stylo-mastoid foramen, being situated deeply within the posterior meatal wall.

Of the semicircular canals the external is the most prominent, and the only one visible during the performance of the ordinary mastoid operation; its outer border forms the inner and lower boundary of the aditus, and can usually be recognized as a white eminence. The superior semicircular canal can only be seen on careful removal of the overlying bone; its ampullary end is found lying just above that of the external canal. It forms the highest point of the labyrinth, becoming fused with the innermost portion of the tegmen tympani, and is in such close relationship with the upper surface of the petrous bone as to cause a smooth elevation on its surface. It is at this point in the operation of removal of the semicircular canal that the greatest risk is encountered of breaking through the petrous bone and of injuring the dura mater.

The posterior semicircular canal lies at right angles to the external canal, and is best exposed by careful removal of bone just posterior to the latter (see Fig. 240).

The outer half of the first whorl of the cochlea is formed by the promontory. Anteriorly it is in close relationship with the carotid canal, whilst below it lies the dome of the jugular fossa. Medially the modiolus is only separated from the internal auditory meatus by a very fine rim of brittle bone, which can easily be broken; a mishap which may permit of escape of the cerebro-spinal fluid, and also of possible infection of the meninges through the internal meatus.

METHODS OF OPERATING

These operations may be divided into: (1) simple curetting away of a localized lesion of the labyrinthine wall; (2) opening up of the vestibule with removal of the semicircular canals; (3) opening of the cochlea; (4) a combination of these methods--extirpation of the labyrinth.

=Curetting away of a localized lesion of the labyrinthine wall.= It has been already stated that, provided the labyrinth be not yet destroyed, it is not justifiable to explore it on the mere discovery of an erosion of the semicircular canal. At the same time, if a definite fistula from which granulations protrude is present, a small fragment of bone may be chipped away, the granulations being afterwards removed by the curette. Unless pus is found to exude from the labyrinth, it is not necessary to do anything further at the present moment. If, however, at a later period, symptoms of labyrinthine infection occur, then it is necessary to further explore the semicircular canal and vestibule, the extent of the operation depending on what is discovered at the time of the operation.

Sometimes an examination of the tympanic cavity may be prevented before operation owing to the auditory canal being filled with polypi or granulations. On performing the complete mastoid operation and curetting away these granulations and polypi, a fistula may be found in the promontory, and carious bone may be felt on probing. Not infrequently these cases are tuberculous in origin and are accompanied by facial paralysis. Provided there be no labyrinthine symptoms, it is sufficient to curette out the granulations, but only gently. Violent curetting may break through the barrier between the infected area and the internal meatus and so lead to meningitis. It is wiser to curette too little than too much.

A further condition which may be met with is necrosis of a portion of the promontory, or of the walls of the vestibule, or of the semicircular canals. If the sequestrum be not quite loose at the time of operation, it should be left _in situ_, provided there be no intracranial symptoms. In fact, there is less danger in leaving the sequestrum than in attempting to remove it. After the operation, the wound cavity is kept open, so that the sequestrum can be removed at a later date after it has separated from the living bone.

=Opening the vestibule= (with partial or complete removal of the semicircular canals). This may be performed by one of the following methods:--

_Above and behind the facial nerve through the semicircular canals._ The complete mastoid operation is performed first. The chief difficulty is to expose the field of operation so as to obtain sufficient room for the necessary manipulations. To do this the following steps should be carried out: The tip of the mastoid process and the remains of the posterior wall of the auditory canal are removed to their extreme limit without injury to the underlying facial nerve. The floor of the auditory canal is also chiselled away until the lower level of the tympanic cavity is brought freely into view, the amount of bone removed depending on the anatomical condition found. To expose the anterior portion of the tympanic cavity, the skin incision is extended slightly forwards, but not far enough to wound the temporal artery, the soft tissues being then separated from the bone and the auricle pulled still further forwards and downwards.

Skin meatal flaps are now fashioned--either the Y-shaped flap or Stacke’s flap (see p. 403)--and are afterwards kept in position by means of sutures. Good illumination is necessary, and for this reason a head-light should be used. One assistant is employed to retract the soft tissues from the wound, another to keep it as dry as possible.

The exposed portion of the external semicircular canal is first identified. If the bone be soft, the arches of the semicircular canal should be defined (Fig. 240). The posterior canal will be discovered by gouging away the bone just posterior to the arch of the external semicircular canal, and the superior, by working inwards and upwards towards the roof of the attic. If the outline of the canals can be made out, the further steps of the operation are rendered very much easier. Unfortunately, the bone is sclerosed in the majority of cases, rendering anatomical exposure of the canals an impossibility.

The next step is to remove the eminence of the horizontal semicircular canal. This is best done by means of a small gouge and mallet. Some prefer a burr, specially constructed to cut vertically; others a chisel. I prefer a fine gouge. As the facial canal runs along the lower anterior portion of the external semicircular canal, the gouge should be directed in a backward direction in removal of the outer wall of the latter, so as to cut away from the facial canal.

The surgeon should be content to remove the bone piecemeal, as, owing to its brittleness, it is very apt to splinter, or the point of the gouge itself may slip and so injure the facial nerve.

After an opening has been made into the canal, it should be enlarged by following the canal forward until its ampulla is reached. After this has been done, a fine probe, bent at a right angle (Schwartze’s seeker will do very well), is passed into the opening, and the limits of the vestibule made out as far as possible. The bone is then removed in an upward direction until the ampulla of the superior canal is reached. The opening may then be extended backwards so as to remove the outer wall of the vestibule, that is, the portion of bone which lies between the ampullæ of the superior and external canals.

If the bone be sclerosed, so that it is impossible to find the superior and posterior canals, then, after opening the exposed portion of the external semicircular canal, the bone should be chiselled away at the area marked out in Fig. 240. By this means the vestibule will certainly be reached, and from this point its opening can be extended in any given direction. A sufficient opening should be made so that the inner portion of the vestibule can be seen (Fig. 241). During each step of the operation a clear view must be obtained.

Not infrequently the facial nerve is exposed or pressed upon in chipping away the outer wall of the external semicircular canal, as will be shown by sudden twitchings of the face. If the surgeon be careful, and works in a direction away from the nerve, it should not be injured. If possible, the outer margin of the horizontal semicircular canal, together with the Fallopian canal, should be left intact as a bridge crossing the vestibule. If necessary, the external and superior canals can be removed in their entirety. A fine probe is inserted into the lumen of the canal so as to tell its direction, and its outer wall is then burred away. For this particular purpose a burr should be used as soon as the surgeon has got beyond the region of the facial nerve. After a view of the interior of the vestibule has been obtained, the ampullary nerves may be destroyed by means of the curette or with pure carbolic acid at the end of a probe. Removal of the posterior canal is best effected by opening it just behind the external semicircular canal and following it out in an upward direction until it meets the superior, and then downwards until it enters the vestibule. This extensive operation is one of extreme difficulty and seldom necessary.

_Posterior to the semicircular canals: Neumann’s method._ Neumann enters the vestibule posteriorly. The bone forming the inner wall of the antrum is removed by means of bone forceps or gouge and mallet until the posterior semicircular canal is opened. By this means the posterior surface of the petrous bone can be exposed as far inwards as the internal auditory meatus.

_Below and anterior to the facial nerve through the promontory._ The preliminary steps of the operation having been performed and the field of operation freely exposed, the stapes, if still present, is extracted by means of a small hook passed between its crura. The bridge of bone between the fenestra ovalis and fenestra rotunda is then cut through by light taps on a very fine gouge. The bone is removed by attacking the lower limit of the fenestra ovalis, and working downwards until the fenestra rotunda is reached. With a fine curette or scoop the loosened fragments of bone are removed. Care must be taken not to work above the region of the fenestra ovalis or the facial nerve will probably be injured. After a sufficient opening has been made, a bent probe can be passed through the opening in the promontory in an upward and backward direction behind the facial nerve into the inferior and anterior portion of the vestibule (Fig. 241).

=Removal of the cochlea.= If necessary, the first turn of the cochlea can now be removed by gouging away the promontory from behind forwards. If the anterior wall of the external auditory canal interferes with this being done, it may be partially removed by means of the gouge and mallet. After the first half-turn of the cochlea has been opened, its contents may be curetted out, care, however, being taken to avoid the carotid canal, which lies in close relationship with its anterior inferior portion. If the bone be carious only gentle curetting is necessary. If, however, this be not the case, simple curetting may not be sufficient, and the gouge and mallet may have to be used. To destroy the cochlear nerve, the whole of the cochlea should be removed. This is sometimes a difficult matter to determine. If the operation be done for the relief of tinnitus, then, after as much as possible of the cochlea has been removed, the interior may be swabbed out with strong carbolic acid solution, which should set up sufficient inflammatory reaction to destroy the nerve-terminals.

=Extirpation of the labyrinth.= This consists in the removal of the semicircular canals, and opening of the vestibule and cochlea, the steps of which have already been described in the above operations.

Before the operation is completed, the inner wall of the vestibule and the cochlea should be carefully examined for fistulæ, and in order to see if any pus enters these cavities from within. If this be the case it means that, in addition to labyrinthine suppuration, there is presumably an extra-dural abscess of the posterior intracranial fossa, drainage of which is essential in order to obtain a recovery.

After the operation has been completed, the cavity should be filled with hydrogen peroxide, then gently syringed out with weak biniodide solution, and finally dried and lightly packed with sterilized gauze.

Even although the operation may have been performed in a non-suppurative case, it is wiser to leave the posterior wound open for the first few days in order to permit of free drainage.

=After-treatment.= If the suppuration has been limited to the internal ear, a successful result may be expected if the symptoms subside rapidly as a result of the operation. If there be complete destruction of the labyrinth before operation its performance should give rise to no symptoms of shock nor further disturbance of equilibrium.

In the majority of cases, however, owing to the nerve-terminals being still in a state of activity, the irritation set up as a result of the operation may cause increased attacks of nystagmus, vertigo, and vomiting. The vomiting is the first symptom to disappear, and then the nystagmus; but complete recovery of equilibrium may not occur for a considerable period, during which time the patient, though otherwise well, may still have a slightly staggering gait.

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.

_Opening up of the internal meatus._ This may be accompanied by a gush of cerebro-spinal fluid. There is nothing to be done except to try and keep the part as clean as possible and see that there is free drainage. Undoubtedly, as a result of this mishap, death has afterwards occurred in consequence of septic meningitis.

_Injury to the internal carotid or bulb of the jugular vein._ These are possibilities which, however, should not occur if ordinary care is taken.

=Prognosis.= The prognosis of labyrinthine suppuration is always grave, owing to the frequency of intracranial complications.

The most favourable cases are those in which the disease is localized and is of chronic duration. The most unfavourable are those in which acute suppurative labyrinthitis is accompanied by extensive bone disease.

According to statistics, the mortality is about 50% in cases not operated upon. As a result of operation, this has been reduced to less than 20%, and in the majority of these cases the ultimate fatal result cannot be put down to the operation itself. The patient is frequently seen too late, that is, after intracranial complications have already occurred. There is no doubt that the death-rate will diminish proportionately according as the necessity of operating early becomes more and more recognized.

With regard to hearing, extensive operations upon the labyrinth lead to complete deafness; nor, indeed, can recovery of hearing be expected except in those cases in which the disease and operations have been limited to the semicircular canals and to the posterior portion of the vestibule, and even then recovery of hearing is exceptional.