Purpose: The efficacy of radiosurgery in cases of mesiotemporal tumours associated with long standing epilepsy has not clearly been documented up to now. The authors present a retrospective analysis of 19 cases treated by Gamma-Knife radiosurgery (GKRS) for mesiotemporal tumour epilepsy.
Methods: Between 1992 and 1997 19 patients (12 male and 7 female) with a mean age of 31 years (5-72) and mesiotemporal tumour-induced epilepsy of a mean duration of 8.6 years (0.9-28) were treated by GKRS. All tumours were within the mesiotemporal structures and the pathohistology proven by biopsy or resective procedure revealed 15 (79%) low grade astrocytomas, 3 (16%) gangliogliomas and 1 (5%) cavernoma. Beside tumour control, the main aim of GKRS was alleviation of epilepsy by irradiating the presumed epileptic foci outside the tumour volume. The 50% isodose volumes surrounding the tumours measured a mean of 6.2 ccm (1.1-18 ccm). Doses given at marginal isodoses ranged from 12 to 30 Gy (mean 17.3 Gy). The outcome with respect to epileptic seizures was evaluated by the Engel classification.
Results: After a follow-up (FU) of 1.7 to 9.7 years (mean 6.5 years) 11 patients (57.9%) were significantly ameliorated (Engel I and Engel II), 7 patients (36.8%) worthwhile improved (Engel III) and 1 patient (5.3%) unchanged. In 11 patients (58%) radiosurgically induced image changes were seen on MRI.
Interpretation: Although microsurgical approach guided by electrocorticography (EcoG) is the state of art for treatment of mesiotemporal tumour epilepsy, GKRS can be used as a non-invasive, safe and effective alternative to resective surgery for selected cases.