Improved trigeminal and facial nerve tolerance following fractionated stereotactic radiotherapy for large acoustic neuromas

The purpose of this study was to demonstrate improved cranial nerve toleran ce following fractionated stereotactic radiotherapy for large acoustic neur omas, defined as tumours with pons-petrous distance (A) >1 cm and midporous transverse diameter (A+Y) >2 cm. Of 28 patients with acoustic neuromas tre ated with fractionated stereotactic radiotherapy, 19 had large tumours at h igh risk for radiosurgery-induced cranial neuropathy. Six patients received 36 Gy in six, weekly, fractions and 13 patients received 30 Gy in six, wee kly, fractions. 15 patients had evaluable trigeminal nerve function and 16 had evaluable facial nerve function. At a median follow-up of 4.5 years, tu mour shrinkage was seen in 10 patients and tumour size was stable in nine. None of the patients developed any evidence of transient, or permanent, tri geminal or facial neuropathy at any time during their follow-up period. Fra ctionated stereotactic radiotherapy may offer a superior therapeutic ratio to single fraction stereotactic radiosurgery in the management of large aco ustic neuromas, as evidenced by the absence of post-treatment trigeminal an d facial neuropathy.