Malte Erik Wigand

Department of O.R.L., University of Erlangen-

Nuremberg, D-91054 Erlangen, Germany

Microsurgery of the ear related skull base, refined during recent decades, has reduced mortality to almost zero, facial paralysis and other neurological deficits to acceptable complication rates. Preservation of hearing has become a next goal with acoustic tumor removal. The enlarged middle cranial fossa approach (E.M.F.A.) provides excellent results for neurinomas smaller than two centimeters in the c.p.a.. Its great advantages are the extradural dissection of the temporal bone and the good exposure of the meatal fundus. The retrosigmoid approach offers a better visualization of larger tumors, but is compromised by 1) difficulties to expose the lateral end of the i.a.c., and 2) by the concealment of the facial and the cochlear nerves by the overlying tumor. Hearing preservation rates are by these facts lowered.

The E.M.F.A. opens a gate of 2-3 centimeters diameter into the c.p.a. from above by resecting the bone anterior and posterior to the i.a.c.. The facial nerve, overiying the tumor can initially be identified and separated from the tumor under direct inspection between the Fallopian canal and the brain stem. After having evulsed the lateral tumor pole, the cochlear nerve can be bluntly dissected. With the support of an auditory monitoring hearing preservation can thus be achieved in about 70 % of the smaller, and in 32 % of the larger tumors. The indication for this procedure should include ears with marked hearing loss for the benefits of a preserved directional hearing.