The transmastoid partial labyrinthectomy approach to medial skull base lesions.
BACKGROUND
It has long been thought that surgical disruption of the membranous labyrinth invariably results in sensorineural hearing loss and balance dysfunction. Recent evidence suggests that the inner ear can withstand such manipulation without loss of function. The technique of transmastoid partial labyrinthectomy has recently been described as a means of providing access to lesions of the medial skull base by removing part of the labyrinth and at the same time attempting to preserve hearing and vestibular function of the lateral semicircular canal (LSCC) and otolithic organs.


METHODS
An extended cortical mastoidectomy is performed and the posterior and middle cranial fossa dura are exposed widely. The posterior and superior semicircular canals are occluded at their ampullated ends and at the crus commune, and then resected. The LSCC and vestibule are left undisturbed. The petrous apex is removed and the medial end of the internal auditory canal is exposed. Posterior cranial fossa dural flaps are raised allowing access to the brainstem, petro-clival area and cerebellopontine angle. Temporal and suboccipital craniotomies can be performed, as required.


RESULTS
Four patients underwent this procedure by a joint Otolaryngological-Neurosurgical team for access to the following lesions: three intra-axial pontine cavernomas and a basilar artery aneurysm. The preliminary hearing and balance results are discussed.


CONCLUSIONS
The partial labyrinthectomy approach provides improved access to certain lesions of the medial skull base and requires less brain retraction compared with the retrolabyrinthine approach. It also has the potential to preserve serviceable hearing.
Walsh
R M
RM
University Health Network, Toronto General Hospital, Ontario, Canada.
Tymianski
M
M
Wallace
M C
MC
Bath
A P
AP
Bance
M L
ML
Rutka
J A
JA
D000328:Adult; D001488:Basilar Artery / Q000000981:diagnostic imaging / Q000473:pathology; D002528:Cerebellar Neoplasms / Q000175:diagnosis / Q000601:surgery; D002530:Cerebellopontine Angle / Q000473:pathology / Q000601:surgery; D002533:Cerebral Angiography; D007758:Ear, Inner / Q000601:surgery*; D006392:Hemangioma, Cavernous / Q000175:diagnosis / Q000601:surgery; D006801:Humans; D002532:Intracranial Aneurysm / Q000175:diagnosis / Q000601:surgery; D008279:Magnetic Resonance Imaging; D008416:Mastoid / Q000601:surgery*; D019635:Neurosurgical Procedures / Q000379:methods*; D011183:Postoperative Complications; D019292:Skull Base Neoplasms / Q000175:diagnosis / Q000601:surgery*