gms | German Medical Science

The translabyrinthine approach has been established as a reliable technique in removing vestibular schwannoma in the cerebellopontine angle and in the internal auditory canal maintaining good facial function. The posterior labyrinth is however destroyed in the process and anacusia is therefore inevitable.

In 1991 McElveen et al. [Ref. 4] modified the traditional translabyrintine approach by sealing the vestibule with bone wax which allowed the hearing function to be preserved in one patient. Other Authors have not however managed to obtain the same results with this modification and therefore prefer partial removal of the labyrinth to total labyrinthectomy in order to reach the fundus of the internal auditory canal.

The present study aimed specifically at evaluating the effectiveness of the modified translabyrintine technique in preserving hearing function in a group of patients with vestibular schwannoma that involved the internal auditory canal. The outcomes and the possible disadvantages of the method are discussed.

Our group of study consisted of 18 patients with vestibular schwannoma.

Our selection criteria was that the schwannoma, including the intracanalicular segment, was smaller than 2 cm in size in all the patients who had surgery. The size of the schwannoma was calculated according to the axial and coronal scans shown on the last preoperative MR. The measurements were taken calculating the canalicular part and the part outside the acoustic porus of the cerebellopontine angle separately.

The patients accepted for the study were required to have preserved hearing function. The preoperative hearing of all the patient was graded as class A (12 patients), B (3 patients) or C (3 patients) according to Sanna classification.

The whole group had an excellent final facial functionality (grade I or II according to the House-Brackmann scale).

Surgical technique: The patient is placed in a supine position with his/her head rotated 60°–75° towards the affected side. The cutaneous incision is similar to that used in the traditional translabyrintine approach. A total mastoidectomy is performed. The three semicircular canals are identified and the horizontal canal can then be used as a starting point. The next step involves resection of the semicircular canals, taking great care to avoid the violation of the membranous labyrinth. It is our practice to use bone wax and bone dust to seal the labyrinth once it is identified after taking away the covering bone with a diamond burr.

During the removal of the labyrinth bone it is highly important to keep the dissection area as wet as possible and to carefully avoid suctioning the fluid around the labyrinth. The removal of the posterior bony labyrinth is then completed by occluding the labyrinth compartment of the posterior, horizontal and upper semicircular canals with bone wax and bone dust. Particular care must be taken to close off completely the access to vestibule maintaining it anatomically intact and isolating it completely. Bone between the jugular bulb and the resected semicircular canals must be removed. The internal auditory canal should be exposed as far as possible towards its lateral end. The tumor is then removed following the conventional method. Once the tumour has been removed, an endoscopy is performed to ensure that no tumoral residue had been left in the inner auditory canal.

The schwannoma was totally removed in all the patients and none have shown signs of persistence or tumoral relapse on the postoperative MRI. Our patients did not have any of the possible complications or consequences of cerebellopontine surgery (CSF leak, aseptic meningitis, postoperative headache, brainstem or cerebellar lesions etc). The whole group had an excellent final facial functionality (grade I or II according to the House-Brackmann scale).

The last follow-up after surgery showed that 8 patients had maintained their hearing function (1 class A, 3 class B and 4 class C according to Sanna classification) (Table 1 [Tab. 1]).

The comparison between CT scan and MRI stressed the importance to maintain the integrity of the membranous vestibule that is considered the key point in preserving hearing function.

The treatment of vestibular schwannoma reaching the fundus of the inner auditory canal is a much discussed matter. With retrosigmoid and middle cranial fossa approaches there’s a blind area and the fundus of the internal auditory canal is not completely under control. Partial labyrinthectomy enlarges the approach , but still remains a blind area. Total labyrinthecthomy further reduces it, but does not eliminate completely the blind area.

The hearing preservation with translabyrinthine approach is reproducible. The essential points are preservation of the blood vessels and the integrity and complete isolation of the vestibule.

There are still doubts as to the consequences of removing the endolymphatic duct regarding the possibility of endolymphatic hydrops development.

This series is to small to establish if the hearing has a long-term preservation. Larger series and longer follow-up will answer this question.