Gamma Knife surgery for recurrent or residual trigeminal neuralgia after a failed initial procedure.
OBJECTIVE
The purpose of this study was to assess outcomes of Gamma Knife surgery (GKS) as a second treatment for recurrent or residual trigeminal neuralgia (TN) after failure of 3 initial procedures: microvascular decompression (MVD), GKS, and percutaneous radiofrequency rhizotomy (PRR).


METHODS
Between 1999 and 2008, 65 patients (31 men [48%] and 34 women [52%]) with recurrent TN were treated with GKS. All 65 patients had undergone previous medical procedures that failed to achieve sufficient pain relief: 27 patients (42%) had undergone MVD, 8 (12%) had undergone PRR, and 30 (46%) had undergone GKS as the initial treatment. The entry zone of the trigeminal nerve was targeted using a 4-mm collimator and treated with 35-90 Gy. The isocenter was positioned so that the brainstem surface was usually irradiated at an isodose no greater than 20% (59 patients) to 30% (6 patients). The median duration of TN symptoms in these patients was 39 months (range 1-192 months).


RESULTS
At the clinical evaluation, 42 patients (65%) with idiopathic TN reported successful pain control at a median follow-up point of 64 months (range 18-132 months). Of these patients, 33 (51%) were no longer using medication. At the 1-, 2-, and 3-year follow-up examinations, 74%, 71%, and 66% of patients experienced successful pain control, respectively. There was no significant difference in pain relief in the initial MVD group compared with the initial GKS and initial PRR groups (74% vs 59% and 50%, respectively; p = 0.342). Recurrence of pain was noted in 23 patients. Twelve of these 23 patients underwent another GKS, resulting in pain control in 8 patients (67%); 8 other patients underwent MVD, resulting in pain relief in 7 patients (87.5%). The median time from GKS to pain recurrence was 7 months (range 3-48 months). There was no significant difference in new facial numbness among the 3 groups (p = 0.24); however, in the initial GKS group, facial numbness was significantly associated with freedom from pain (p = 0.0012). There was a significant correlation between the total radiation dose and facial numbness. The cutoff value for facial numbness ranged from 115 to 120 Gy (p = 0.037).


CONCLUSIONS
Gamma Knife surgery as a second treatment achieved acceptable levels of pain control in 65% of patients with residual or recurrent TN after long-term follow-up. Initial treatment was not a factor that affected pain control, but salvage surgery may be considered separately for each group.
Gamma Knife Center, Chung-Shan Medical University Hospital and School of Medicine, Chung-Shan Medical University, Taichung, Taiwan. gk@csh.org.tw
Chuan-Fu
CF
Huang
Shyh-Ying
SY
Chiou
Ming-Fang
MF
Wu
Hsien-Tang
HT
Tu
Wen-Shan
WS
Liu
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D016009:Chi-Square Distribution; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D010147:Pain Measurement; D016634:Radiosurgery / Q000295:instrumentation*; D011879:Radiotherapy Dosage; D012086:Reoperation; D016896:Treatment Outcome; D014276:Trigeminal Nerve / Q000601:surgery*; D014277:Trigeminal Neuralgia / Q000601:surgery*