Gamma Knife Radiosurgery (GKRS) in the Management of Trigeminal Neuralgia: Long-term Follow-up Report of 511 Cases

Abstract

Gamma knife radiosurgery (GKRS) has been used successfully in the treatment of trigeminal neuralgia (TN). Results have compared favorably to surgical procedures with respect to pain relief and complications. We report our updated long-term results with GKRS in the treatment of TN. Between 1991 and 2007, 511 patients with medically-refractory typical TN were treated with GKRS, and have not been lost to follow-up. Prior neurosurgical intervention had been performed in 30.1% of the patients (158/511), with a total of 356 procedures. All patients had typical TN. The GKRS was given to the cranial nerve V entry root zone into the brainstem. Targeting was defined by CT and MRI scans, and inversion recovery MRI, utilizing axial, coronal, and sagittal images. Treatment planning was accomplished through the Leksell Treatment Planning System. The prescribed doses ranged from 70 to 90 Gy prescribed to Dm, in one shot using the 4 mm collimator, with the 20% isodose line just touching the brainstem. Response to treatment was defined as excellent (no pain, off analgesics), good (no pain, with analgesics), and poor (continued pain despite analgesics). Response to treatment was recorded in interviews conducted by a gamma knife nurse. With a median follow-up of 10 years (range, 5–16 years), 54.2% (277/511) of patients reported an excellent result, and 23.1% (118/511) a good result after GKRS. There was a dose response, with 55.7% (68/122) of patients reporting an excellent or good response after 70 Gy, compared to 82.4% (183/222) at 80 Gy, and 86.2% (144/167) at 90 Gy (p < 0.01). Temporary ipsilateral facial numbness occurred in 18.8% (96/511), and permanent facial numbness in 5.1% (26/511). Loss of corneal reflex occurred in 1.4% (7/511), and painful dysesthesias in 2.7% (14/511). There have been 2 cases of anesthesia dolorosa. There was a dose-response in facial numbness, with temporary numbness occurring in 6.5% (8/122) at 70 Gy, 17.1% (38/222) at 80 Gy, and 29.3% (49/167) at 90 Gy (p < 0.01). Permanent numbness occurred in 2.5% (3/122) at 70 Gy, 3.2% (7/222) at 80 Gy, and 9.0% (15/167) at 90 Gy (p < 0.01). The GKRS offers favorable results, both in pain relief and complications, compared to surgery in the management of medically refractory TN. In view of these long-term good pain relief and low complication risks, GKRS should be considered as a primary initial treatment option in medically-refractory TN. The optimal dose with maximum pain relief and minimal complications, appears to be 80 Gy.