Transtemporal, translabyrinthal (or transmastoid) and suboccipital (also retrosigmoidal) are the anxiety provoking names that characterise which way the surgeon will approach the tumour in the intracranium.
Transtemporal = through the temporal bone area.
Translabyrinthal = through the labyrinth of the inner ear.
Suboccipital = via the posterior cranial fossa.
The patient cannot choose between these. These three access ways are selected by the surgeons performing the operation depending on the size and position of the acoustic neuroma. Only if they decide for the translabyrinthal way is an agreement between the doctor and patient required, as this approach leads to a forced total loss of hearing on one side.
Opening the skull to begin the acoustic neuroma operation – left: transtemporal, middle: translabyrinthal, right: suboccipital.
(Simplified drawing, the head of hair remains largely unchanged)
This approach via the temporal region is preferred by ENT surgeons. The acoustic neuroma should not be too big and show be positioned exclusively or mainly in the bony ear canal. Both the facial nerve and the auditory nerve can be preserved in this case, therefore this approach is recommended for patients with hearing ability on the side affected by the tumour. The operation is performed with the patient lying down. The head is stretched far back and underneath (see image).
At the front, above the ear an incision is made into the scalp, a piece of bone is drilled from the temporal bone, the meninges and the so-called temporal lobe of the brain is lifted with a special instrument to gain access to the petrous bone.
Then the upper bone of the inner ear canal in the petrous bone is drilled so that the upper balance archway and the inner ear canal are open. This presents a good overview of the facial and auditory nerves. At this point the facial nerve can be freely dissected, the meninges opened and the tumour cut and made smaller, one piece at a time. This is essential to be able to remove the shell completely from the nerve skin by the completion of the operation.
The balance nerve is severed during this procedure. Lastly, the remaining hole is filled with tissue from the patient's body, such as body fat or muscles from the temples and bone flap is reset. Then the wound is sewn.
This approach is a typical path chosen by ENT surgeons and for acoustic neuroma situated further back in the ear canal.
It is a very safe way through the ear (labyrinth) and is chosen unanimously if the hearing ability has already been destroyed by the tumour. The patient is not weighed down, which for older patients can be significant. During the operation almost no cranial structures are compromised. Another advantage lies in the fact that the facial nerve can be exposed early and almost always, therefore almost no facial paralysis is caused by the operation. However, the hearing on the affected side is gone in every case and any remaining hearing ability is lost.
With this approach the an incision is made behind the ear, a hole drilled in the so-called mastoid and then the whole inner ear labyrinth is removed. The facial nerve can already be seen in the middle ear and can easily be tracked to the inner ear. Subsequently, the tumour can be removed step by step. In this case the remaining holes will also be filled with body tissue.
This approach is typical for neurosurgeons and is preferred for medium and large-sized acoustic neuroma. For tumours that have grown far into the posterior cranial fossa and cerebullum and/or press hard on the brainstem, it is compulsory. Even here the preservation of hearing ability is possible, along with preventing facial paralysis.
Hereby, an incision is made in the skin at the back of the head, behind the ear (see image). The bone cover is removed from the so-called squama occipitalis and the hard meninges is cut. With the patient lying on his/her side, the cerebullum moves far enough back that the ear canal is exposed. If the patient is perpendicular, the cerebullum must be carefully moved to the side, to expose and identify the acoustic neuroma in the posterior cranial fossa. The operation mainly occurs in a (half) sitting position, which allows for a particularly good view of the sensitive nerve structure and cleaning of the operation area.
Blood vessels, that supply parts of the brain, may lie nearby the tumour and can be preserved.
First of all, the tumour is by all means made smaller from within, as generally they are dealing with larger tumours.
The tumour parts in the cranial fossa are the first to be removed. After that the inner ear canal is bored and the parts within are removed.
Through teamwork of neuro and ENT surgeons, the ENT surgeons take the lead on the boring of the ear canal.
The bored out bone piece is reset by many surgeons, although many close the opening "only" with bone adhesive. The hard, inner meninges and the thick external, muscular scalp are themselves sufficient protection for the intracranium.