- Department of Neurosurgery, Gamma Knife of Spokane, Spokane, WA USA
- Department of Radiation Oncology, Gamma Knife of Spokane and Cancer Care Northwest, Spokane, Washington, USA
- Department of Radiation Oncology, Rockwood Health System, Spokane, WA, USA
- Data Works Northwest, Coeur d’Alene, Idaho, USA
Christopher M. Lee
Department of Radiation Oncology, Gamma Knife of Spokane and Cancer Care Northwest, Spokane, Washington, USA
DOI:10.4103/2152-7806.115163Copyright: © 2013 Elaimy AL This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
How to cite this article: Elaimy AL, Lamm AF, Demakas JJ, Mackay AR, Lamoreaux WT, Fairbanks RK, Pfeffer RD, Cooke BS, Peressini BJ, Lee CM. Gamma knife radiosurgery for typical trigeminal neuralgia: An institutional review of 108 patients. Surg Neurol Int 17-Jul-2013;4:92
How to cite this URL: Elaimy AL, Lamm AF, Demakas JJ, Mackay AR, Lamoreaux WT, Fairbanks RK, Pfeffer RD, Cooke BS, Peressini BJ, Lee CM. Gamma knife radiosurgery for typical trigeminal neuralgia: An institutional review of 108 patients. Surg Neurol Int 17-Jul-2013;4:92. Available from: http://sni.wpengine.com/surgicalint_articles/gamma-knife-radiosurgery-for-typical-trigeminal-neuralgia-an-institutional-review-of-108-patients/
Background:In this study, we present the previously unreported pain relief outcomes of 108 patients treated at Gamma Knife of Spokane for typical trigeminal neuralgia (TN) between 2002 and 2011.
Methods:Pain relief outcomes were measured using the Barrow Neurological Institute (BNI) pain intensity scale. In addition, the effects gender, age at treatment, pain laterality, previous surgical treatment, repeat Gamma Knife radiosurgery (GKRS), and maximum radiosurgery dose have on patient pain relief outcomes were retrospectively analyzed. Statistical analysis was performed using Andersen 95% confidence intervals, approximate confidence intervals for log hazard ratios, and multivariate Cox proportional hazard models.
Results:All 108 patients included in this study were grouped into BNI class IV or V prior to GKRS. The median clinical follow-up time was determined to be 15 months. Following the first GKRS procedure, 71% of patients were grouped into BNI class I-IIIb (I = 31%; II = 3%; IIIa = 19%; IIIb = 18%) and the median duration of pain relief for those patients was determined to be 11.8 months. New facial numbness was reported in 19% of patients and new facial paresthesias were reported in 7% of patients after the first GKRS procedure. A total of 19 repeat procedures were performed on the 108 patients included in this study. Following the second GKRS procedure, 73% of patients were grouped into BNI class I-IIIb (I = 44%; II = 6%; IIIa = 17%, IIIb = 6%) and the median duration of pain relief for those patients was determined to be 4.9 months. For repeat procedures, new facial numbness was reported in 22% of patients and new facial paresthesias were reported in 6% of patients.
Conclusions:GKRS is a safe and effective management approach for patients diagnosed with typical TN. However, further studies and supporting research is needed on the effects previous surgical treatment, number of radiosurgery procedures, and maximum radiosurgery dose have on GKRS clinical outcomes.
Keywords: Barrow Neurological Institute pain intensity scale, gamma knife radiosurgery, trigeminal neuralgia
Trigeminal neuralgia (TN) is a disorder of cranial nerve (CN) V that affects approximately 4.3 per 100,000 persons per year. [
With >15,000 patients diagnosed with TN per year, finding optimal courses of treatment in select patient subsets is imperative for clinicians. [
Beginning in the 1950s, Professor Lars Leksell used radiosurgical techniques to perform gangliotomies targeted at the gasserian ganglion. [
Between 2002 and 2011, 143 patients with medically refractory TN were treated at Gamma Knife of Spokane (Deaconess Hospital, Spokane, WA). Of the 143 patients, 23 were excluded from this study due to a diagnosis of atypical TN (continuous burning pain confined to the trigeminal nerve). An additional 12 patients with typical TN were lost during follow-up, which leaves 108 patients in the present retrospective analysis.
After obtaining approval from institutional review board (IRB) Spokane (IRB 1554) and the University of Washington Human Subjects Division (Human Subjects Application 36306), the following pretreatment factors were recorded from the patient’s medical records: Gender, age at first GKRS treatment, age at repeat GKRS treatment (if applicable), history of MS, pain laterality, original pain distribution, and previous surgical treatment. [
Gamma knife radiosurgery technique
All patients were treated using the Model C Leksell60Co Gamma Knife. Before the GKRS procedure, a local anesthetic was applied to the patient’s head to facilitate pain-free placement of the stereotactic head frame. Gadolinium enhanced magnetic resonance imaging of the head within the coordinate frame was performed to allow a neurosurgeon, radiation oncologist, and medical physicist to concurrently plan the radiosurgery treatment. In the majority of patients, the dorsal root entry zone of CN V was the radiosurgical target where a single 4-mm isocenter was placed. However, a 4-mm isocenter was placed at the retrogasserian zone of CN V if the prepontine cistern was determined to be too shallow. This decision is based on an effort to avoid including the brainstem in the 4-mm target. For patients who underwent multiple GKRS procedures, the 4-mm isocenter was placed directly anterior to the first target. The median maximum GKRS dose delivered to the 50% isodose line was 86 Gy (70-90) for the first treatment and 60 Gy (40-86) for repeat treatments.
Treatment episodes were categorically grouped by gender (male, female), age at treatment (20-39, 40-59, 60-79, and ≥80), pain laterality (left, right), original pain distribution (V1, V1-V2, V2, V2-V3, V3), previous surgical treatment (yes, no), maximum GKRS dose in Gy (<84, 84, 86, >86), and number of GKRS procedures (first, repeat). For patients who underwent multiple GKRS procedures, each treatment and its subsequent outcome was considered a separate data point. As a result, 127 GKRS procedures were performed on the 108 patients included in this study. Patient age at treatment and maximum GKRS dose were considered continuous variables in multivariate hazard ratio analysis.
Every patient in this study was grouped into class IV or V of the Barrow Neurological Institute (BNI) pain intensity scale prior to GKRS. [
We also constructed Andersen 95% confidence intervals for the median time of pain relief for the gender groups, age at GKRS groups, pain laterality groups, previous surgical treatment groups, number of GKRS procedures groups, and maximum radiosurgery dose groups. Exact conditional maximum likelihood estimates were used to calculate the hazard ratio of each group and Fisher 95% confidence intervals were constructed for statistical significance testing between the hazard ratios of each group. Finally, the Cox proportional hazard model was used in a multivariate analysis of the gender groups, age at GKRS groups, pain laterality groups, previous surgical treatment groups, number of GKRS procedures groups, and maximum radiosurgery dose groups. All statistical analyses used StatsDirect Version 2.5.7 (StatsDirect Ltd., Altrincham, UK) and SigmaPlot Version 11.0 (SYSTAT Software, Inc., San Jose, CA). Statistical Significance was set at a P < 0.05.
Pain relief outcomes
We performed a total of 127 GKRS procedures on 108 patients with a diagnosis of typical TN between 2002 and 2011. Specifically, 108 patients underwent at least one GKRS procedure, 18 patients underwent at least two GKRS procedures, and one patient underwent three GKRS procedures for a total of 19 repeat treatments. The median clinical follow-up time was determined to be 15 months (0-113). Following the first GKRS procedure, 71% of patients were grouped into BNI class I-IIIb (I = 31%; II = 3%; IIIa = 19%; IIIb = 18%) and the median duration of pain relief for those patients was determined to be 11.8 months.
An initial statistical analysis was performed using univariate hazard ratio confidence intervals. Within each treatment category, a reference group was selected (gender = female, age ≤60 years, pain laterality = right, previous surgical treatment = no, number GKRS procedures = one, maximum GKRS dose ≤84 Gy) and was tested against the other group’s hazard ratios. Univariate hazard ratio analysis of age groups indicated that patients <60 years of age experienced superior levels of facial pain relief when compared with patients ≤60 years of age (P = 0.038). Univariate hazard ratio analysis of gender groups, pain laterality groups, previous surgical treatment groups, number of GKRS procedures groups, and maximum radiosurgery dose groups did not yield any statistically significant results.
Further statistical analysis was conducted using multivariate Cox regression analysis with hazard ratio estimates and confidence intervals. The multivariate analysis utilized the same reference groups as the univariate analysis. However, patient age at treatment and maximum radiosurgery dose were considered continuous variables. It was found on multivariate hazard ratio analysis that gender (P = 0.210), age at treatment (P = 0.343), pain laterality (P = 0.375), previous surgical treatment (P = 0.196), number of GKRS procedures (P = 0.374), and maximum radiosurgery dose (P = 0.533) did not statistically impact facial pain relief.
Of the 12 patients who underwent previous surgical treatment, 6 (50%) reported facial numbness prior to GKRS and 1 (8%) reported facial paresthesias prior to GKRS. Following the first GKRS procedure, new facial numbness was reported in 20 patients (19%) and new facial paresthesias were reported in 8 patients (7%). Of the 18 patients who underwent repeat GKRS procedures (19 treatments), 3 (17%) had already experienced facial numbness as a result of the first GKRS procedure. Following repeat GKRS procedures, new facial numbness was reported in four patients (22%) and new facial paresthesias were reported in one patient (6%). No other complications were observed in the 108 patients included in this study.
Because the difficulty of radiosurgical targeting of the trigeminal nerve virtually disappeared with the advent of magnetic resonance imaging, GKRS has emerged as an effective and minimally invasive treatment modality for patients with medically refractory TN. In addition, many physicians have grown to recognize GKRS as the primary management approach for patients who are thought to be poor surgical candidates due to comorbidities or advanced age. Although several retrospective and some prospective studies have been published analyzing the efficacy of GKRS in the management of TN-related facial pain, questions remain regarding treating patients in specific clinical scenarios and their subsequent outcomes. [
The BNI pain intensity scale is a commonly used entity to assess the efficacy of radiosurgical treatment for patients with TN. [
Many clinicians take into account the surgical history of TN patients when recommending GKRS. In our analysis, previous surgical history did not significantly impact pain relief. Fountas et al. [
At our institution, patients who underwent one GKRS procedure did not statistically differ in term of facial pain relief when compared with patients who underwent more than one GKRS procedure. Similar to our results, Verheul et al. [
Defining the optimal maximum GKRS dose that can be delivered safely to select patient subsets is an area of controversy in the radiosurgical management of TN. In our study, maximum GKRS dose did not impact facial pain relief when treated as a continuous variable in multivariate hazard ratio analysis. Kim et al. [
GKRS is an effective treatment modality for patients diagnosed with typical TN that provides patients with a significant duration of facial pain relief when used as a primary or repeat management approach. Although our retrospective analysis did not find previous surgical treatment, number of radiosurgery procedures, and maximum radiosurgery dose to statistically impact facial pain relief, further clinical studies and supporting research is needed to assess the durability of GKRS for specific patient subsets.
The authors thank Eric Reynolds for his hard work and dedication throughout this project. They also thank Jill Adams and the rest of the Gamma Knife of Spokane research staff for their contributions to this manuscript.
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