Does increased nerve length within the treatment volume improve trigeminal neuralgia radiosurgery? A prospective double-blind, randomized study.

PURPOSE: To test the hypothesis that increasing the nerve length within the treatment volume for trigeminal neuralgia radiosurgery would improve pain relief. METHODS AND MATERIALS: Eighty-seven patients with typical trigeminal neuralgia were randomized to undergo retrogasserian gamma knife radiosurgery (75 Gy maximal dose with 4-mm diameter collimators) using either one (n = 44) or two (n = 43) isocenters. The median follow-up was 26 months (range 1-36). RESULTS: Pain relief was complete in 57 patients (45 without medication and 12 with low-dose medication), partial in 15, and minimal in another 15 patients. The actuarial rate of obtaining complete pain relief (with or without medication) was 67.7% +/- 5.1%. The pain relief was identical for one- and two-isocenter radiosurgery. Pain relapsed in 30 of 72 responding patients. Facial numbness and mild and severe paresthesias developed in 8, 5, and 1 two-isocenter patients vs. 3, 4, and 0 one-isocenter patients, respectively (p = 0.23). Improved pain relief correlated with younger age (p = 0.025) and fewer prior procedures (p = 0.039) and complications (numbness or paresthesias) correlated with the nerve length irradiated (p = 0.018). CONCLUSIONS: Increasing the treatment volume to include a longer nerve length for trigeminal neuralgia radiosurgery does not significantly improve pain relief but may increase complications.

Development of a model to predict permanent symptomatic postradiosurgery injury for arteriovenous malformation patients. Arteriovenous Malformation Radiosurgery Study Group.

PURPOSE: To better predict permanent complications from arteriovenous malformation (AVM) radiosurgery. METHODS AND MATERIALS: Data from 85 AVM patients who developed symptomatic complications following gamma knife radiosurgery and 337 control patients with no complications were evaluated as part of a multi-institutional study. Of the 85 patients with complications, 38 patients were classified as having permanent symptomatic sequelae (necrosis). AVM marginal doses varied from 10-35 Gy and treatment volumes from 0.26-47.9 cc. Median follow-up for patients without complications was 45 months (range: 24-92). RESULTS: Multivariate analysis of the effects of AVM location and the volume of tissue receiving 12 Gy or more (12-Gy-Volume) allowed construction of a significant postradiosurgery injury expression (SPIE) score. AVM locations in order of increasing risk and SPIE score (from 0-10) were: frontal, temporal, intraventricular, parietal, cerebellar, corpus callosum, occipital, medulla, thalamus, basal ganglia, and pons/midbrain. The final statistical model predicts risks of permanent symptomatic sequelae from SPIE scores and 12-Gy-Volumes. Prior hemorrhage, marginal dose, and Marginal-12-Gy-Volume (target volume excluded) did not significantly improve the risk-prediction model for permanent sequelae (p >/= 0.39). CONCLUSION: The risks of developing permanent symptomatic sequelae from AVM radiosurgery vary dramatically with location and, to a lesser extent, volume. These risks can be predicted according to the SPIE location-risk score and the 12-Gy-Volume.

Spinal epidural hematoma and high thromboembolic risk: between Scylla and Charybdis.

OBJECTIVE: To determine the optimal time for reinstitution of anticoagulant therapy after evacuation of spinal epidural hematoma in patients who have a high risk for cardiogenic embolization. MATERIAL AND METHODS: The clinical histories of all patients with a spinal epidural hematoma encountered at Mayo Clinic Rochester between 1975 and 1996 were reviewed. We present three cases of spontaneous spinal epidural hematoma and the management of anticoagulation in each case. RESULTS: Of the 17 patients identified, 3 received anticoagulant therapy at the onset of the hematoma and were at high risk for cardiogenic embolization. In two patients with a metallic heart valve and one patient with long-standing atrial fibrillation, anticoagulant therapy was discontinued for 5, 13, and 18 days, respectively, after decompressive laminectomy. Systemic embolization occurred in one patient with a previous history of embolization to the femoral artery. No systemic embolization occurred in the two patients with a metallic valve. CONCLUSION: Early resumption of warfarin therapy is indicated after a spinal surgical procedure; however, discontinuation of anticoagulation for several days seems safe while postoperative hemostasis is monitored.

High-dose trigeminal neuralgia radiosurgery associated with increased risk of trigeminal nerve dysfunction.

OBJECTIVE: Stereotactic radiosurgery is being used with more frequency in the management of patients with trigeminal neuralgia. To improve facial pain outcomes, many centers have increased the prescribed radiation dose to the trigeminal nerve. METHODS: Between April 1997 and December 1999, 68 patients underwent radiosurgery for trigeminal neuralgia with use of the Leksell gamma knife (Elekta Instruments, Norcross, GA) and a single 4-mm isocenter of radiation. Twenty-seven patients (40%) received 70 Gy (low dose) of irradiation and 41 patients (60%) received 90 Gy (high dose). The groups were similar with regard to age, sex, duration of pain, number of prior surgeries, and preexisting trigeminal deficits. The primary facial pain outcomes for analysis were excellent (pain-free, no medications) and good (pain-free, reduced medications). The mean length of follow-up after radiosurgery was 14.4 months (range, 2-36 mo). RESULTS: At last follow-up examination, 11 (41%) of the 27 patients with low-dose radiosurgery remained pain-free compared with 25 (61%) of the 41 patients with high-dose radiosurgery (P = 0.17). Additional surgery was performed in 12 low-dose patients (44%) and 8 high-dose patients (20%) (P = 0.05). High-dose radiosurgery was associated with an increased rate of permanent trigeminal nerve dysfunction (54% versus 15%, P = 0.003). Bothersome dysesthesias occurred in 13 high-dose patients (32%), whereas only 1 low-dose patient had this complication (P = 0.01). Three high-dose patients (8%) developed corneal numbness after radiosurgery. Pain recurred with more frequency in patients not developing trigeminal nerve dysfunction after radiosurgery (9 of 22 patients, 41 %) compared with those who sustained facial numbness, paresthesias, or dysesthesias (4 of 27 patients, 15%); however, the difference was not statistically significant (P = 0.08). CONCLUSION: Higher doses of radiation may correlate with better facial pain outcomes after radiosurgery for trigeminal neuralgia. However, the incidence of significant trigeminal nerve dysfunction is markedly increased after radiosurgery for patients receiving high-dose radiosurgery. Because of the nonselective nature of this ablative technique, dose prescription should be limited to less than 90 Gy.