Is cochlear implantation possible after acoustic tumor removal?

HYPOTHESIS: This study aimed to assess the possibility of hearing restoration after acoustic tumor removal.

BACKGROUND

Hearing restoration surgery may be indicated after surgery of bilateral acoustic tumors or surgery of acoustic tumor in the only hearing ear. The choice is between cochlear implantation and brainstem implantation.

METHODS

From the temporal bone collection at the House Ear Institute, Los Angeles, the author histologically examined eight temporal bones from seven patients who had undergone acoustic tumor removal during their lifetime. Special emphasis was put on examining the patency of the cochlear turns and on survival of the spiral ganglion cells and cochlear nerve.

RESULTS

This study showed that after translabyrinthine acoustic tumor removal, there is progressive osteoneogenesis of the cochlea associated with almost complete degeneration of the spiral ganglion cells and cochlear nerve. Similar findings were noticed after middle fossa removal of acoustic tumor with unsuccessful hearing preservation.

CONCLUSIONS

The histologic changes described in the cochlea and cochlear nerve represent the effects of ischemia resulting from inadvertent cutting of the blood supply during acoustic tumor removal. It is possible to do cochlear implantation after acoustic tumor removal provided that the result of promontory electrical stimulation test is positive (the cochlear nerve is intact) and that implantation is done at the time of acoustic tumor removal or shortly thereafter, before cochlear ossification is complete.