Gamma knife surgery for trigeminal neuralgia: outcomes and prognostic factors

Evaluation of the efficacy of ultrasound-guided maxillary and mandibular nerve pulsed radiofrequency treatment for trigeminal neuralgia and factors associated with successful response: a retrospective study

BACKGROUND

This study aimed to investigate the treatment efficacy and clinical and demographic characteristics affecting treatment success in patients who underwent ultrasound (US)-guided pulsed radiofrequency (PRF) to the maxillary and/or mandibular nerves for trigeminal neuralgia.

METHODS

The data of patients with trigeminal neuralgia who underwent US-guided maxillary and/or mandibular nerve PRF between September 2022 and December 2023 were reviewed and the study was retrospectively designed. Good analgesia was defined as ≥ 50% reduction in pain score at 3 months after the procedure, and the demographic and clinical characteristics of the patients were assessed.

RESULTS

Among the 72 included patients, 39 (54.2%) and 33 (45.8%) were classified as responders and non-responders, respectively. The age, pre- and post-procedural Numerical Rating Scale (NRS) scores, pain duration, and presence of constant pain were significantly lower in the responders. Logistic regression analysis revealed that older age (OR = 0.899, p < 0.001), high pre-procedural NRS scores (OR = 0.177, p = 0.009) and non-idiopathic (secondary or classic) etiology (OR = 0.062, p = 0.048) were significantly associated with an unsuccessful response to maxillary/mandibular PRF treatment.

CONCLUSION

This study is the first clinical trial to evaluate the efficacy of PRF therapy of the maxillary and mandibular nerves in the treatment of trigeminal neuralgia and demonstrated a significant reduction in pain scores at 3 months. Older age, high pre-procedural NRS scores, and non-idiopathic (secondary or classical) etiology are independent predictors of poor response to ultrasound-guided maxillary/mandibular nerve pulse radiofrequency treatment.

Radiosurgery for Facial Pain: A Narrative Review

The surgical treatment of pain has been an integral part of neurosurgery since the early 20th century when Harvey Cushing pioneered ganglionectomy for trigeminal neuralgia. Over the ensuing years, as anatomic and physiologic knowledge of pain systems grew, new techniques aimed at new targets were developed for various pain conditions. Our objective was to provide an informative and up-to-date summary of radiosurgery for chronic facial pain, emphasizing trigeminal neuralgia and discussing the advantages and challenges of this modality. A PubMed search with keywords ("trigeminal neuralgia" or "cluster headache" or "glossopharyngeal neuralgia") and ("radiosurgery") and ("systematic review" or "review") was conducted. Relevant publications in English published from January 2000 to May 2022 were screened manually for their title, abstract, and even full text to determine their relevance. References from the searched articles were also searched as other supplementary articles. We excluded original articles and personal series from the analysis and only considered systematic reviews to maintain the transparency in the record. A total of 19 studies for trigeminal neuralgia (n > 100), 52 cases of cluster headache, and 42 cases of glossopharyngeal neuralgia were found. Radiosurgery remains the safest among various treatment options with equitable pain control with other percutaneous procedures. MVD remains the gold standard for long-term pain control. There is no difference in efficacy or tolerance between patients treated with gamma knife, linear accelerator, or CyberKnife. The minimum recommended prescription dose was 70 Gy (level of evidence II), and the maximum dose was 90 Gy (level of evidence III) in a single fraction. Radiosurgery provides 5-year pain control in 50% of patients without medication (85% of patients with/without medication) with an average latency period of 1-3 months. Approximately 8-15% of patients will experience a recurrence of pain after an average period of 1 year. Prospective pain relief will be about 60% at 3 years, 40% at 7 years, and 37% in 10 years. The main complication was facial hypoesthesia occurring in 25-50% of patients within 6 months-3 years and disabling in 10% of cases. Cluster headache and glossopharyngeal neuralgia are emerging conditions for treatment with GKRS, although long-term efficacy remains to be studied. Having searched PubMed and other databases and summarized the application of radiosurgery for facial pain, we concluded that radiosurgery is undoubtedly a promising tool for chronic facial pain, but further studies are needed to realize its long-term efficiency and advanced applications of the same.

Anatomical measurements of trigeminal ganglion: a cadaver study

It is difficult to obtain specific information regarding the trigeminal ganglion (TG), especially pediatric TG. The aim of present study was to determine the parameters of the TG and assist in the neuroablative treatment of trigeminal neuralgia (TN). Thirty-seven sides of cadaver heads that had undergone gross anatomical examination were included, with 29 sides of adults and 8 sides of infants. The distance and angles were measured among 12 points, with nine points adjacent to the TG and three points on the foramen ovale (FO). The three points on FO were represented as three different surgical approaches for TN: posterior FO approach (PFO), lateral FO approach (LFO), and anterior FO approach (AFO). A high similarity was found in pediatric TG. No statistical difference was detected in either the distance or the angles between the 12 points. Statistical difference was found in adult heads in some of the distances, which included PFO to point 5 (17.97 ± 3.35 mm in the left and 15.52 ± 2.28 mm in the right; p = 0.03) and LFO to point 5 and point 8. Moreover, the angle for PFO to point 5 showed a statistically significant difference (60.10 ± 14.02 in the left and 46.63 ± 10.48 in the right; p = 0.01). These findings revealed that surgical neuroablation for patients with TN should be performed more carefully when the PFO or LFO approach is adopted, with a precise preoperative evaluation to avoid corneal complications. Two safety radiofrequency rhizotomy points are also presented to deal with two different kinds of TN.

Case report: use of high-intensity laser therapy for treatment of trigeminal neuralgia

Trigeminal neuralgia represents a form of chronic facial pain that is characterized by its incapacitating nature. The current therapeutic approaches encompass pharmacological agents with carbamazepine or non-pharmacologic options including utilization of percutaneous rhizotomy, Gamma knife radiosurgery or microvascular decompression may be indicated in certain cases. While the interventions may be effective, medications have negative side effects and procedures are invasive which can pose challenges for patients with various comorbidities. High-intensity laser therapy (HILT) has demonstrated safety and efficacy for many types of chronic pain such as musculoskeletal, autoimmune and neuropathic. Herein, we demonstrate the benefits of HILT therapy in the management of trigeminal neuralgia in a 72 year-old patient with a complex history of facial surgery and radiation who had failed pharmacological treatments and denied any invasive procedures.

Gamma Knife Radiosurgery for Trigeminal Neuralgia : Review and Update

Accurate diagnosis of trigeminal neuralgia (TN) is the starting point for optimal treatment. Gamma knife radiosurgery (GKRS) is currently regarded as one of the first-line treatment options for medically refractory TN. GKRS is a less invasive treatment with a low risk of complications than other surgical procedures that provides a favorable pain control (BNI I–IIIb) rate of >75% at short-term follow-up. Drawbacks of GKRS include the latency period before pain relief and higher recurrence rate compared with microvascular decompression. Therefore, repeat treatment is necessary if the initial GKRS was effective but followed by recurrence. The concept of dose rate and the biologically effective dose of radiation has been actively studied in radiation oncology and is also applied in GKRS for TN to achieve high safety and efficacy by prescribing the optimal dose. Recent progress in functional imaging, such as diffusion tensor imaging, enables us to understand the pathophysiology of TN and predict the clinical outcome after GKRS. Here, we review TN, GKRS, and recent updates, especially in the concepts of radiation dose, diffusion tensor imaging studies, and repeat treatment in GKRS for TN.

Percutaneous radiofrequency trigeminal rhizotomy benefits in patients with refractory trigeminal neuralgia

A significant number of patients suffers from refractory trigeminal neuralgia (TN) after receiving microvascular decompression (MVD) or other neuro-destructive procedure such as gamma knife radiosurgery (GKRS). This study aims to demonstrate a remediable, reproducible approach to treating refractory pain effectively by percutaneous radiofrequency trigeminal rhizotomy (RF-TR).A total of 392 patients with TN were treated by RF-TR during the past 10 years. Among these patients, 48 cases who had received either MVD, GKRS alone, or a combination of both were assigned to group A. Those who had not received any form of treatment (125 patients) or failed to respond medically (130 patients) were assigned as the control group (group B). All the RF-TR were performed by a single surgeon with the aid of intraoperative computed tomography (iCT)-based neuronavigation with magnetic resonance (MR) image fusion. The outcome measure was the numerical rating scale (NRS) expressed subjectively by patients. The paired Student t test and the analysis of covariance (ANCOVA) were used for statistical analysis.In group A, 21 of 24 patients (88%) had significant improvement (NRS change ≥5) in facial pain after RF-TR. The average NRS score was 9.75 ± 0.53 before the procedure and 1.92 ± 3.35 post-treatment (significant NRS decrease [P = .000]). On the other hand, in group B, 226 of 255 patients (89%) also had dramatic amelioration of facial pain after RF-TR. The average NRS score was 9.46 ± 0.69 before the procedure and 1.62 ± 2.85 post-treatment (7.84 ± 2.82 in NRS decrease [P = .008]). By using a univariate ANCOVA, no statistical significance was found in NRS score improvement between the two groups.Repeated MVD and GKRS for refractory TN may be less desirable due to a greater risk of mortality (up to 0.8%) and morbidity (4% of serious complications). Conversely, RF-TR administration with the novel navigation technique by using iCT and MR image fusion is free from any remarkable and irreversible morbidities. In this study, RF-TR not only provided an alternative and effective strategy if TN recurred but also resulted in the same NRS score improvement regardless of the status of prior treatment.

Role of Gamma Knife radiosurgery in trigeminal neuralgia - Its long term outcome and prediction using Artificial neural Network model

PURPOSE

We aimed to study the long-term efficacy, prognostic factors and complications associated with the GKRS for trigeminal neuralgia.

METHODS AND MATERIALS

Prospectively created database was analyzed for these patients. We created an Artificial neural Network - using Multilayer perceptron model in SPSS 23 by including all variables whose p value were<0.5 in univariate analysis.

RESULTS

A total of 36 patients were included in the study. Patients pain free at 6 months were 25(69.44%), which reduced to 6(40 %) at 6 years. Median time to pain relief was 18.5 days. Only 5(13.88%) of them developed new onset or worsened numbness post Gamma Knife radio surgery. Median radiation dose was 80 Gy (prescribed at 100 percent isodose line). 1st GKT (P value < 0.05) and post GKT numbness (P value < 0.05) were the only factors favouring good outcome. Prior history of MVD was associated with poor pain relief post GKRS although p value was not significant (p = 0.136). ANN model could predict with 90.0 percent accuracy the favourable or unfavourable response on 11 Tested cases. In ANN model, a greater number of Pre GKT medications, previous MVD history, V2 dermatome involvement and negative history of post GKT numbness were negative prognostic factors.

CONCLUSIONS

Lesser number of pre GKRS drugs used, involvement of V1 dermatome, post GKT numbness are favourable prognostic factors. Also, history of failed MVD for trigeminal neuralgia is associated with poor outcome. Repeat GKRS failed to show improvement in BNI grades.

Efficacy of Gamma Knife radiosurgery in the management of multiple sclerosis-related trigeminal neuralgia: a systematic review and meta-analysis

Trigeminal neuralgia (TN) is the most frequent craniofacial pain condition, which commonly affects patients suffering from multiple sclerosis (MS). Stereotactic radiosurgery, especially Gamma Knife radiosurgery (GKRS), represents a safe and effective treatment for TN, and it has been adopted also for MS-TN, with a lower success rate. Therefore, we aimed to analyze the outcome of GKRS for MS-TN. PubMed, Web of Science, and Google Scholar and the reference list of relevant articles were searched for GKRS in MS-TN. Two investigators independently identified the articles, assessed the study quality, and extracted the data. Endpoints of interest were initial pain responders, successful treatments at the end of follow-up, and factors influencing the outcome. Data analyses were performed using R software. Twelve articles involving 646 patients met our inclusion criteria. Pooled proportion of patients who experienced an initial response to GKRS treatment was 83% (CI 74-90%). The cumulative proportion of successful treatments at the end of follow-up was 47% (CI 33-60%). No variables were found to have a significant contribution to heterogeneity regarding the initial response outcome. The only variable significantly explaining the heterogeneity found in the proportion of successful treatments was the length of the follow-up, with a negative b coefficient (- 0.0051, p value = 0.0047). Regarding the efficacy of GKRS in MS-TN, the initial pain response rate was 83%, which dramatically decreases to 47% during follow-up. GKRS still represents a valuable option for MS-TN; however, its long-term efficacy should be always considered.

Factors affecting outcome in frameless non-isocentric stereotactic radiosurgery for trigeminal neuralgia: a multicentric cohort study

BACKGROUND

Stereotactic radiosurgery (SRS) is an effective treatment for trigeminal neuralgia (TN). Nevertheless, a proportion of patients will experience recurrence and treatment-related sensory disturbances. In order to evaluate the predictors of efficacy and safety of image-guided non-isocentric radiosurgery, we analyzed the impact of trigeminal nerve volume and the nerve dose/volume relationship, together with relevant clinical characteristics.

METHODS

Two-hundred and ninety-six procedures were performed on 262 patients at three centers. In 17 patients the TN was secondary to multiple sclerosis (MS). Trigeminal pain and sensory disturbances were classified according to the Barrow Neurological Institute (BNI) scale. Pain-free-intervals were investigated using Kaplan Meier analyses. Univariate and multivariate Cox regression analyses were performed to identify predictors.

RESULTS

The median follow-up period was 38 months, median maximal dose 72.4 Gy, median target nerve volume 25 mm³, and median prescription dose 60 Gy. Pain control rate (BNI I-III) at 6, 12, 24, 36, 48, and 60 months were 96.8, 90.9, 84.2, 81.4, 74.2, and 71.2%, respectively. Overall, 18% of patients developed sensory disturbances. Patients with volume ≥ 30 mm³ were more likely to maintain pain relief (p = 0.031), and low integral dose (< 1.4 mJ) tended to be associated with more pain recurrence than intermediate (1.4-2.7 mJ) or high integral dose (> 2.7 mJ; low vs. intermediate: log-rank test, χ² = 5.02, p = 0.019; low vs. high: log-rank test, χ² = 6.026, p = 0.014). MS, integral dose, and mean dose were the factors associated with pain recurrence, while re-irradiation and MS were predictors for sensory disturbance in the multivariate analysis.

CONCLUSIONS

The dose to nerve volume ratio is predictive of pain recurrence in TN, and re-irradiation has a major impact on the development of sensory disturbances after non-isocentric SRS. Interestingly, the integral dose may differ significantly in treatments using apparently similar dose and volume constraints.

Gamma knife radiosurgery for trigeminal neuralgia: first case series from Latin America

INTRODUCTION

Gamma Knife® radiosurgery (GKRS) for trigeminal neuralgia is an effective treatment with at least a 50% reduction of pain in 75-95% of patients.

OBJECTIVE

To present the first series of patients treated for trigeminal neuralgia using GKRS in Latin America.

METHODS

Retrospective analysis. Analysis consisted of time to improvement of symptoms, best Barrow Neurological Institute scale (BNI) score after procedure, time without pain, time to recurrence and post-procedural hypoesthesia.

RESULTS

Nineteen cases of classical trigeminal neuralgia were analyzed and three cases of symptomatic trigeminal neuralgia were described. Mean time from symptom onset to radiosurgery was 99.6 months, and 78.9% of patients had undergone invasive procedures before treatment. Patients were followed for a mean of 21.7 months. BNI I was achieved in 36.8%, IIIa in 21.1%, IIIb in 21.1%, IV in 5.3% and V in 15.7%. New hypoesthesia developed in 12.1% patients, which was associated with achieving BNI I after the procedure (p < 0.05). Time from diagnosis to GKRS was higher in patients who failed to achieve BNI I (143 vs. 76 months). The distance from the root entry zone in patients who achieved BNI I was greater than patients who did not (1.94 vs. 1.14 mm). Mean distance from the root entry zone in patients with new hypoesthesia was 2.85 mm vs. 1.06 mm (p = 0.06).

CONCLUSION

Clinical response to GKRS is related to the time between diagnosis and procedure, thus its indication should be considered early in the management of these patients.

Gamma Knife Radiosurgery on the Trigeminal Root Entry Zone for Idiopathic Trigeminal Neuralgia: Results and a Review of the Literature

Trigeminal neuralgia (TN) is a chronic disorder of the trigeminal nerve characterized by repeated electrical shock-like sensations on one side of the face. It can cause severe pain in the face and disrupt or impair quality of life in patients. Options for the management of TN consist of pharmacological and surgical treatments, including Gamma Knife radiosurgery (GKRS). GKRS has been used for TN for a long time because of its low rate of complications and high success rate. Moreover, GKRS can be of use for drug-resistant TN patients who are poor surgical candidates due to medical comorbidities, patients of older age, or patients who refuse invasive therapy. We reviewed the rationale, effects, safety, and current treatment policies of GKRS for TN in view of our institution's results and a review of the literature to date.

Gamma Knife radiosurgery for bilateral trigeminal neuralgia

OBJECTIVE

A small subset of patients with trigeminal neuralgia (TN) will experience bilateral symptoms. Treatment in these patients is controversial because the population is heterogeneous and patients may have nonvascular etiologies of their pain. This study reports treatment outcomes in the largest cohort of patients with bilateral TN who have undergone Gamma Knife radiosurgery (GKRS) to date.

METHODS

A retrospective chart review identified 51 individual nerves in 34 patients with bilateral TN who were treated with GKRS at the authors’ institution between 2001 and 2015, with 12 nerves in 11 patients undergoing repeat GKRS for recurrent or persistent symptoms. Long-term follow-up was obtained by telephone interview. Pain outcomes were measured using the Barrow Neurological Institute (BNI) pain scale, with BNI IIIb or better considered a successful treatment.

RESULTS

There was sufficient follow-up to determine treatment outcomes for 48 individual nerves in 33 patients. Of these nerves, 42 (88%) achieved at least BNI IIIb pain relief. The median duration of pain relief was 1.9 years, and 1-, 3-, and 5-year pain relief rates were 64%, 44%, and 44%, respectively. No patients experienced bothersome facial numbness, and 1 case of anesthesia dolorosa and 2 cases of corneal dryness were reported. Patients with a history of definite or possible multiple sclerosis were significantly more likely to experience BNI IV–V relapse. There was no statistically significant difference in treatment outcomes between patients in this series versus a large cohort of patients with unilateral TN treated at the authors’ institution. There was sufficient follow-up to determine treatment outcomes for 11 individual nerves in 10 patients treated with repeat GKRS. Ten nerves (91%) improved to at least BNI IIIb after treatment. The median duration of pain relief was 2.8 years, with 1-, 3-, and 5-year rates of pain relief of 79%, 53%, and 53%, respectively. There was no statistically significant difference in outcomes between initial and repeat GKRS. One case of bothersome facial numbness and 1 case of corneal dryness were reported, with no patients developing anesthesia dolorosa with retreatment.

CONCLUSIONS

GKRS is a safe, well-tolerated treatment for patients with medically refractory bilateral TN. Efficacy of treatment appears similar to that in patients with unilateral TN. GKRS can be safely repeated in this population if necessary.

Cyberknife Radiosurgery for Trigeminal Neuralgia

Introduction

Image-guided robotic radiosurgery is an emerging minimally-invasive treatment option for trigeminal neuralgia (TN). Our group has treated 560 cases up to date, and report here the clinical outcomes of 387 treatments with three years follow-up. This study represents the largest single-center experience on CyberKnife radiosurgery for the treatment of TN so far reported.

Methods

CyberKnife radiosurgery treatment was offered to patients with drug-resistant TN, after the failure of other treatments or refusal of invasive procedures. A second treatment was offered to patients with a poor response after the first treatment or with recurrent pain. Treatment protocol required the non-isocentric delivery of 60 Gy prescribed to the 80% isodose to a 6 mm retrogasserian segment of the affected trigeminal nerve. Retreatments typically received 45 Gy, again prescribed to the 80% isodose. The final plan was developed accordingly to individual anatomy and dose distribution over the trigeminal nerve, gasserian ganglion, and brainstem. Clinical outcomes such as pain control and hypoesthesia/numbness have been evaluated after 6, 12, 24, and 36 months. 

Results

Our group has treated 527 patients with Cyberknife radiosurgery at Centro Diagnostico Italiano (CDI), Milan, Italy, during the last decade. A minimum follow-up of six months was available on 496 patients. These patients received 560 treatments: 435 patients (87.7%) had a single treatment, 60 patients (12.1%) had two treatments, and one patient (0.2%) had five treatments (two on the right side, three on the left side). Twenty four patients had multiple sclerosis (4.8%). Four hundred and forty-three patients (84%) received the treatment without previous procedures, while 84 patients (16%) underwent radiosurgery after the failure of other treatments. A neurovascular conflict was identified in 59% of the patients. Three hundred and forty-three patients (receiving a total of 387 treatments) had a minimum of 36 months follow up. Pain relief rate at 6, 12, 18, 24, 30 and 36 months was respectively 92, 87, 87, 82, 78 and 76%. Forty-four patients out of 343 (12.8%) required a second treatment during the observed period. At 36 months post-treatment, 21 patients (6,1%) reported the presence of bothering facial hypoesthesia. Eighteen patients out of 21 (85.7%) developed this complication after a repeated treatment. 

Conclusions

Frameless image-guided robotic radiosurgery in experienced hands is a safe and effective procedure for the treatment of TN, providing excellent pain control rates in the absence of major neurological complications. Repeated treatments due to recurrent pain are associated with restored pain control but at the price of a higher rate of sensory complications. 

Gamma Knife Radiosurgery for Trigeminal Neuralgia: A Comparison of Dose Protocols

Purpose: A variety of treatment plans including an array of prescription doses have been used in radiosurgery treatment of trigeminal neuralgia (TN). However, despite a considerable experience in the radiosurgical treatment of TN, an ideal prescription dose that balances facial dysesthesia risk with pain relief durability has not been determined. Methods and Materials: This retrospective study of patients treated with radiosurgery for typical TN evaluates two treatment doses in relation to outcomes of pain freedom, bothersome facial numbness, and patient satisfaction with treatment. All patients were treated with radiosurgery for intractable and disabling TN. A treatment dose protocol change from 80 to 85 Gy provided an opportunity to compare two prescription doses. The variables evaluated were pain relief, treatment side-effect profile, and patient satisfaction. Results: Typical TN was treated with 80 Gy in 26 patients, and 85 Gy in 37 patients. A new face sensory disturbance was reported after 80 Gy in 16% and after 85 Gy in 27% (p = 0.4). Thirteen failed an 80 Gy dose whereas seven failed an 85 Gy dose. Kaplan–Meier analysis found that at 29 months 50% failed an 80 Gy treatment compared with 79% who had durable pain relief after 85 Gy treatment (p = 0.04). Conclusion: The 85 Gy dose for TN provided a more durable pain relief compared to the 80 Gy one without a significantly elevated occurrence of facial sensory disturbance.

Immediate Pain Relief Elicited After Radiosurgery for Classical and Symptomatic Trigeminal Neuralgia

Background

Immediate relief following radiosurgery for trigeminal neuralgia (TN) has been observed in a minority of cases.

Objective

Our goals were to determine the occurrence of immediate pain relief as real vs. placebo effect and to search for factors associated with this desirable outcome.

Methods

Between January 2003 and June 2008, 150 patients were treated with radiosurgery for classical or symptomatic TN. A commercially available linear accelerator (Novalis®, BrainLab) device was used to deliver 90 Gy to the root-entry zone with a 4- or 5-mm collimator. Pain outcomes were graded using a four-point scale. Complications were recorded through standardized follow-up evaluations. Treatment plans were retrieved and brainstem/trigeminal nerves were retrospectively re-contoured using standard anatomical landmarks. Dose-volume histograms were used to calculate the volume of brainstem/trigeminal nerve receiving 20%, 30%, and 50% of the prescribed radiation doses.

Results

Twenty-five (19.84%) patients presented with immediate pain relief, defined as pain cessation within 48 hours post-radiosurgery. Kaplan-Meier analysis showed that good/excellent pain outcomes were sustained and significantly better in the immediate pain relief group (p = 0.006) compared to non-immediate relief. Univariate and multivariate logistic regression analyses failed to show the correlation between brainstem/trigeminal nerve volumes, trigeminal nerve-pontine angle, prior surgical procedures, TN etiology, age, gender, and immediate pain relief. Neither post-radiosurgery complications nor recurrence rates were different between groups.

Conclusion

Immediate pain relief leads to sustained relief and patients present significantly better pain outcomes in comparison to those without immediate relief. The mechanism triggering immediate relief is still unknown and did not correlate with the volume of brainstem/trigeminal nerve receiving pre-specified doses of radiation.

Stereotactic radiosurgery for trigeminal neuralgia: a systematic review

OBJECTIVES

The aims of this systematic review are to provide an objective summary of the published literature specific to the treatment of classical trigeminal neuralgia with stereotactic radiosurgery (RS) and to develop consensus guideline recommendations for the use of RS, as endorsed by the International Society of Stereotactic Radiosurgery (ISRS).

METHODS

The authors performed a systematic review of the English-language literature from 1951 up to December 2015 using the Embase, PubMed, and MEDLINE databases. The following MeSH terms were used in a title and abstract screening: "radiosurgery" AND "trigeminal." Of the 585 initial results obtained, the authors performed a full text screening of 185 studies and ultimately found 65 eligible studies. Guideline recommendations were based on level of evidence and level of consensus, the latter predefined as at least 85% agreement among the ISRS guideline committee members.

RESULTS

The results for 65 studies (6461 patients) are reported: 45 Gamma Knife RS (GKS) studies (5687 patients [88%]), 11 linear accelerator (LINAC) RS studies (511 patients [8%]), and 9 CyberKnife RS (CKR) studies (263 patients [4%]). With the exception of one prospective study, all studies were retrospective.The mean maximal doses were 71.1-90.1 Gy (prescribed at the 100% isodose line) for GKS, 83.3 Gy for LINAC, and 64.3-80.5 Gy for CKR (the latter two prescribed at the 80% or 90% isodose lines, respectively). The ranges of maximal doses were as follows: 60-97 Gy for GKS, 50-90 Gy for LINAC, and 66-90 Gy for CKR.Actuarial initial freedom from pain (FFP) without medication ranged from 28.6% to 100% (mean 53.1%, median 52.1%) for GKS, from 17.3% to 76% (mean 49.3%, median 43.2%) for LINAC, and from 40% to 72% (mean 56.3%, median 58%) for CKR. Specific to hypesthesia, the crude rates (all Barrow Neurological Institute Pain Intensity Scale scores included) ranged from 0% to 68.8% (mean 21.7%, median 19%) for GKS, from 11.4% to 49.7% (mean 27.6%, median 28.5%) for LINAC, and from 11.8% to 51.2% (mean 29.1%, median 18.7%) for CKR. Other complications included dysesthesias, paresthesias, dry eye, deafferentation pain, and keratitis. Hypesthesia and paresthesia occurred as complications only when the anterior retrogasserian portion of the trigeminal nerve was targeted, whereas the other listed complications occurred when the root entry zone was targeted. Recurrence rates ranged from 0% to 52.2% (mean 24.6%, median 23%) for GKS, from 19% to 63% (mean 32.2%, median 29%) for LINAC, and from 15.8% to 33% (mean 25.8%, median 27.2%) for CKR. Two GKS series reported 30% and 45.3% of patients who were pain free without medication at 10 years.

CONCLUSIONS

The literature is limited in its level of evidence, with only one comparative randomized trial (1 vs 2 isocenters) reported to date. At present, one can conclude that RS is a safe and effective therapy for drug-resistant trigeminal neuralgia. A number of consensus statements have been made and endorsed by the ISRS.

Image-Guided Robotic Radiosurgery for Trigeminal Neuralgia

BACKGROUND

Frameless, non-isocentric irradiation of an extended segment of the trigeminal nerve introduces new concepts in stereotactic radiosurgery for medically resistant trigeminal neuralgia (TN).

OBJECTIVE

To report the results of the largest single-center experience about image-guided robotic radiosurgery for TN.

METHODS

A cohort of 138 patients treated with CyberKnife® (Accuray Incorporated, Sunnyvale, California) radiosurgery with a minimum follow-up of 36 mo were recruited. Pain relief, medications, sensory disturbances, rate and time of pain recurrence were prospectively analyzed.

RESULTS

Median follow-up was 52.4 mo; median dose 75 Gy; median target length 5.7-mm; median target volume 40 mm³; median prescription dose 60 Gy (80% isodose line). Actuarial pain control rate (Barrow Neurological Institute [BNI] class I-IIIa) at 6, 12, 24, and 36 mo were 93.5%, 85.8%, 79.7%, and 76%, respectively. Overall, 33 patients (24%) required a second treatment. Overall, 18.1% developed sensory disturbances after 16.4 ± 8.7 mo. One patient (0.7%) developed BNI grade IV dysfunction; 6 (4.3%) developed BNI grade III (somewhat bothersome) hypoesthesia after retreatment; BNI grade II (not bothersome) hypoesthesia was reported by 18 patients (11 after retreatment). Shorter nerve length (<6 mm vs 6 mm), smaller nerve volume (<30 mm3 vs >30 mm3), and lower prescription dose (<58 vs >58 Gy) were associated with treatment failure (P = .01, P = .02, P = .03, respectively). Re-irradiation independently predicted sensory disturbance (P < .001).

CONCLUSION

Targeting a 6-mm segment of the trigeminal nerve with a prescribed dose of 60 Gy appears safe and effective. Persistent pain control was achieved in most patients with acceptable risk of sensory complications, which were typically found after re-irradiation.

LINAC stereotactic radiosurgery for trigeminal neuralgia -retrospective two-institutional examination of treatment outcomes

BACKGROUND

In this pooled 2-center series LINAC radiosurgery (SRS) has been applied as a treatment option for a subset of refractory trigeminal neuralgia (TN) patients. This study approached to retrospectively assess the efficacy and safety of LINAC SRS and to provide a brief overview addressed to the technical development from frame-based towards frameless robotic SRS.

METHODS

From 2001 to 2017 n = 55 patients (pts) were treated, n = 28 were female (51%), mean age: 66 years (range 36-93 years); TN etiology: 37 classic TN, 15 multiple sclerosis (MS)-related TN, 2 symptomatic TN, and 1 atypical TN. Previous treatment was present in n = 35 (63.6%) pts. (some multiple or combined) with n = 23 microsurgical vascular decompression and n = 17 percutaneous retrogasserian rhizotomy. A 6 MV LINAC (4-5 mm collimators) was applied in all pts. (n = 26 framebased - n = 29 frameless robotic). The dorsal root entry zone (DREZ) was targeted in n = 35 cases and the retrogasserian target in n = 20 pts. with a homogeneous dose for the entire study cohort (90 Gy). SRS outcome was measured using the Barrow Neurological Institute (BNI) score for pain and hypaesthesia and statistically evaluated by univariate and multivariate analyzes.

RESULTS

Mean follow-up (FU) was 30 months (2 lost FU); the total rate of post SRS BNI pain I-IIIa (=painfree w or w/o medication) was 69% (88% for the classic TN pts), 29% (38.8% classic TN) were classified as BNI pain I-II (=painfree w/o medication). A BNI hypaesthesia II-III was present in 9.4% (n = 5) and BNI hypaesthesia IV in n = 2. Between groups analysis demonstrated no correlation of SRS responsiveness with age, gender, MS- or not MS-associated TN, previous surgery, framebased/frameless robotic SRS. DREZ targeting significantly better suppressed TN compared to RG targeting (p = 0.01). Additionally, a statistical trend for a better BNI pain outcome (p = 0.07) along with a significant increase in BNI hypaesthesia (p = 0.01) was found when using a larger partial trigeminal 70 Gy volume.

CONCLUSION

Our retrospective analysis support LINAC SRS as an effective and safe treatment option in TN. Frameless robotic SRS of TN is safe when using a dedicated LINAC system. A target definition closer to the brainstem and tendencially a larger target volume were associated with a better outcome for pain.

The timing of stereotactic radiosurgery for medically refractory trigeminal neuralgia: the evidence from diffusion tractography images

BACKGROUND

Diffusion tensor imaging (DTI) is a novel MRI technique that enables noninvasive evaluation of microstructural alterations in white matter of brain. Initially, DTI was used in intra- or inter-hemispheric association bundles. Recent technical advances are overcoming the challenges of imaging small white matter bundles, such as the cranial nerves. In this study, we use DTI to shed more light on the microstructure changes in long-standing trigeminal neuralgia. We also utilize DTI to study the effect of early stereotactic radiosurgery (SRS) on the microstructures of the trigeminal nerve and to predict the effectiveness of early SRS in the treatment of medically refractory trigeminal neuralgia (TN).

METHODS

To analyze the presentation of trigeminal nerve, the DTI was reconstructed in 21 cases pre- and post-SRS. DTI parameters recorded include fractional anisotropy (FA), mean diffusivity (MD), radial diffusivity (RD), axial diffusivity (AD), linear anisotropy coefficient (Cl), planar anisotropy coefficient (Cp), and spherical anisotropy coefficient (Cs). Comparisons between ipsilateral (symptomatic) and contralateral (asymptomatic) trigeminal nerves and symptom durations of < 5 and ≧ 5 years were performed.

RESULTS

The study cohort comprised 21 patients with TN with a median age of 66 years. Initial adequate facial pain relief (Barrow Neurological Institute facial pain scores I-IIIb) was achieved in 16 (76%) patients. For the pre-SRS DTI findings, ipsilateral trigeminal nerve was associated with higher baseline root entry zone (REZ) Cs compared to contralateral nerve (0.774 vs. 0.743, p = 0.04). Ipsilateral trigeminal nerve with symptoms of < 5 years was associated with higher baseline FA compared to trigeminal nerve with symptoms of ≧ 5 years (0.314 vs. 0.244, p = 0.02). For the post-SRS DTI findings, ipsilateral trigeminal nerves with symptoms of <5 years demonstrated decrease in Cl, while those with symptoms ≧ 5 years demonstrated increase in Cl after SRS at the ipsilateral REZ (- 0.025 vs. 0.018, p = 0.04). At the cisternal segment of ipsilateral trigeminal nerve, symptoms of < 5 years were associated with decreased FA and increased λ₂, while symptoms of ≧ 5 years were associated with increased FA and decreased λ₂ after SRS (FA - 0.068 vs. 0.031, p = 0.04, λ₂ 0.0003 vs. - 0.0002, p = 0.02).

CONCLUSIONS

SRS provides high rates of initial pain relief with moderate rates of facial hypoesthesia. Ipsilateral trigeminal nerve was associated with higher baseline REZ Cs, and baseline FA was associated with duration of symptoms. There were significant associations between duration of symptoms and changes in ipsilateral REZ Cl, cisternal segment FA, and cisternal segment λ₂ after SRS. These preliminary findings serve as comparisons for future studies investigating the use of DTI in radiosurgical planning for patients with TN.

Early Stereotactic Radiosurgery for Medically Refractory Trigeminal Neuralgia

OBJECTIVE

To evaluate effectiveness of early Gamma Knife radiosurgery (GKRS) in treatment of medically refractory trigeminal neuralgia (TN).

METHODS

This retrospective review comprised 108 consecutive patients with medically refractory idiopathic TN between 2006 and 2014. All patients underwent GKRS targeting the root entry zone with a median maximum dose of 90 Gy and isodose line of 20%. Outcomes pertaining to pain and facial numbness were scored using Barrow Neurological Institute scales.

RESULTS

Following a median latency period of 4 weeks, we observed complete or adequate pain relief (Barrow Neurological Institute scores of I-IIIB) in 86 of 108 patients (90%). At a median time of 17 months, 22 patients (26%) experienced pain recurrence. New-onset facial numbness was reported by 59 patients (55%). Treatment failure rates were highest among patients with a longer history of pain. Compared with patients with pain history of ≤5 years, patients with pain history of >5 years experienced longer latency before pain relief (P = 0.027). Univariate and multivariate analyses demonstrated that pain history of ≤5 years was a significant predictor of pain relief (P = 0.049 and P = 0.045, respectively).

CONCLUSIONS

GKRS achieves a high rate of pain relief among patients with medically refractory idiopathic TN. Pain history of ≤5 years is a reliable predictor of pain relief and appears to be associated with shorter latency to pain relief after GKRS. Therefore, early GKRS for patients with medically refractory idiopathic TN is recommended.

Long-Term Outcomes in the Treatment of Classical Trigeminal Neuralgia by Gamma Knife Radiosurgery: A Retrospective Study in Patients With Minimum 2-Year Follow-up

BACKGROUND

Gamma knife radiosurgery (GKRS) is one of the alternatives for treatment for classical trigeminal neuralgia (TN).

OBJECTIVE

To retrospectively analyze long-term outcomes for TN using GKRS achieved at our institution.

METHODS

One hundred seventeen patients with medically refractory TN treated by GKRS at our institution were followed up between 1993 and 2011. Mean maximum dose was 86.5 Gy (range: 80-90 Gy; median: 90 Gy). Clinical response was defined based on the Burchiel classification. We considered classes I and II as a complete response. For toxicity, we use the Barrow Neurological Institute facial numbness scale. Mean duration of follow-up was 66 months (range: 24-171 months).

RESULTS

Complete response at last follow-up in our patients was 81%, with an excellent response while off medication in 52%. Pain-free rates without medication (class I) were 85% at 3 years (confidence interval [CI]: 78%-94%), 81% at 5 years (CI: 72%-91%), and 76% at 7 years (CI: 65%-90%). Complete response rates (classes I-II) were 91% at 3 years (CI: 86%-97%), 86% at 5 years (CI: 79%-93%), and 82% at 7 years (CI: 72%-93%). Poor treatment response rates differed significantly between patients who had undergone previous surgery and were refractory to management with medication prior to GKRS. New or worsening facial numbness was reported in 32.5% (30% score II and 2.5% score III). No anesthesia dolorosa was reported. Permanent recurrence pain rate was 12%.

CONCLUSION

GKRS achieved favorable outcomes compared with surgery in terms of pain relief and complication rates in our cohort of patients, notwithstanding decreasing pain-free survival rates over time. We consider GKRS to be an initial treatment in the management of medically intractable TN in selected patients.

ABBREVIATIONS

CI, confidence intervalGKRS, gamma knife radiosurgeryMVD, microvascular decompressionRS, radiosurgeryTN, trigeminal neuralgia.

Outcomes of Two-Isocenter Gamma Knife Radiosurgery for Patients with Typical Trigeminal Neuralgia: Pain Response and Quality of Life

OBJECTIVE

To evaluate the effectiveness and safety of 2-isocenter Gamma Knife surgery (GKS) by reviewing patients with trigeminal neuralgia (TN) from the last 10 years.

METHODS

A total of 247 patients were followed up and the Barrow Neurological Institute scale was used to evaluate pain degree. Patients' age, gender, pain duration and location, preoperative/postoperative Barrow Neurological Institute scale score, time to initial pain relief, recurrence time, and complications were documented and analyzed.

RESULTS

Patients who underwent a 2-isocenter GKS achieved earlier initial pain relief. The median time of initial pain relief was 2.0 months. Kaplan-Meier analysis showed that the patients with a shorter history of TN and the patients without preoperative surgery achieved earlier initial pain relief. During the 122.8 months of follow-up, the median time of recurrence-free pain relief was 49.7 months. Age was found to be a risk factor of recurrence. Patients who underwent 2-isocenter GKS had a higher rate of postoperative facial numbness, but only 9 cases reported bothersome facial numbness. Multibranch involvement was a risk factor for postoperative facial numbness.

CONCLUSIONS

Compared with other modalities, 2-isocenter GKS was a safe and highly effective option for patients with TN. However, more data need to be collected to verify its long-term effect.

The clinical significance of persistent trigeminal nerve contrast enhancement in patients who undergo repeat radiosurgery

OBJECTIVE Contrast enhancement of the retrogasserian trigeminal nerve on MRI scans frequently develops after radiosurgical ablation for the management of medically refractory trigeminal neuralgia (TN). The authors sought to evaluate the clinical significance of this imaging finding in patients who underwent a second radiosurgical procedure for recurrent TN. METHODS During a 22-year period, 360 patients underwent Gamma Knife stereotactic radiosurgery (SRS) as their first surgical procedure for TN at the authors' center. The authors retrospectively analyzed the data from 59 patients (mean age 72 years, range 33-89 years) who underwent repeat SRS for recurrent pain at a median of 30 months (range 6-146 months) after the first SRS. The isocenter was 4 mm, and the median maximum doses for the first and second procedures were 80 Gy and 70 Gy, respectively. A neuroradiologist and a neurosurgeon blinded to the treated side evaluated the presence of nerve contrast enhancement on MRI series at the time of the repeat procedure. The authors correlated the presence of this imaging change with clinical outcomes. Pain outcomes and development of trigeminal sensory dysfunction were evaluated with the Barrow Neurological Institute (BNI) Pain Scale and BNI Numbness Scale, respectively. The mean length of follow-up after the second SRS was 58 months (95% CI 49-68 months). RESULTS At the time of the repeat SRS, contrast enhancement of the trigeminal nerve on MRI scans was observed in 31 patients (53%). Five years after the SRS, patients with this enhancement had lower actuarial rates of complete pain relief after the repeat SRS (27% [95% CI 7%-47%]) than patients without the enhancement (76% [95% CI 58%-94%]) (p < 0.001). At the 5-year follow-up, patients with the contrast enhancement also had a higher risk for trigeminal sensory loss after repeat SRS (75% [95% CI 59%-91%]) than patients without contrast enhancement (26% [95% CI 10%-42%]) (p = 0.001). Dysesthetic pain after repeat SRS was observed for 8 patients with and for 2 patients without contrast enhancement. CONCLUSIONS Trigeminal nerve contrast enhancement on MRI scans observed at the time of a repeat SRS for TN was associated with less satisfactory pain control and more frequently detected facial sensory loss. Residual contrast enhancement at the time of a repeat SRS may warrant consideration of dose reduction or further separation of the radiosurgical targets.

Frameless Stereotactic Radiosurgery for Treatment of Multiple Sclerosis-Related Trigeminal Neuralgia

BACKGROUND

Trigeminal neuralgia (TN) affects 7% of patients with multiple sclerosis (MS). In such patients, TN is difficult to manage either pharmacologically and surgically. Radiosurgical rhizotomy is an effective treatment option. The nonisocentric geometry of radiation beams of CyberKnife introduces new concepts in the treatment of TN. Its efficacy for MS-related TN has not yet been demonstrated.

METHODS

Twenty-seven patients with refractory TN and MS were treated. A nonisocentric beams distribution was chosen; the maximal target dose was 72.5 Gy. The maximal dose to the brainstem was <12 Gy. Effects on pain, medications, sensory disturbance, rate, and time of pain recurrence were analyzed.

RESULTS

Median follow-up was 37 (18-72) months. Barrow Neurological Institute pain scale score I-III was achieved in 23/27 patients (85%) within 45 days. Prescription isodose line (80%) accounting for a dose of 58 Gy incorporated an average of 4.85 mm (4-6 mm) of the nerve and mean nerve volume of 26.4 mm³ (range 20-38 mm³). Seven out of 27 patients (26%) had mild, not bothersome, facial numbness (Barrow Neurological Institute numbness score II). The rate of pain control decreased progressively after the first year, and only 44% of patients retained pain control 4 years later.

CONCLUSIONS

Frameless radiosurgery can be effectively used to perform retrogasserian rhizotomy. Pain relief was satisfactory and, with our dose/volume constraints, no sensory complications were recorded. Nonetheless, long-term pain control was possible in less than half of the patients. This is a limitation that CyberKnife radiosurgery shares with other techniques in MS patients.

Stereotactic radiosurgery in the treatment of parasellar meningiomas: long-term volumetric evaluation

OBJECTIVE Parasellar meningiomas tend to invade the suprasellar, cavernous sinus, and petroclival regions, encroaching on adjacent neurovascular structures. As such, they prove difficult to safely and completely resect. Stereotactic radiosurgery (SRS) has played a central role in the treatment of parasellar meningiomas. Evaluation of tumor control rates at this location using simplified single-dimension measurements may prove misleading. The authors report the influence of SRS treatment parameters and the timing and volumetric changes of benign WHO Grade I parasellar meningiomas after SRS on long-term outcome. METHODS Patients with WHO Grade I parasellar meningiomas treated with single-session SRS and a minimum of 6 months of follow-up were selected. A total of 189 patients (22.2% males, n = 42) form the cohort. The median patient age was 54 years (range 19-88 years). SRS was performed as a primary upfront treatment for 44.4% (n = 84) of patients. Most (41.8%, n = 79) patients had undergone 1 resection prior to SRS. The median tumor volume at the time of SRS was 5.6 cm³ (0.2-54.8 cm³). The median margin dose was 14 Gy (range 5-35 Gy). The volumes of the parasellar meningioma were determined on follow-up scans, computed by segmenting the meningioma on a slice-by-slice basis with numerical integration using the trapezoidal rule. RESULTS The median follow-up was 71 months (range 6-298 months). Tumor volume control was achieved in 91.5% (n = 173). Tumor progression was documented in 8.5% (n = 16), equally divided among infield recurrences (4.2%, n = 8) and out-of-field recurrences (4.2%, n = 8). Post-SRS, new or worsening CN deficits were observed in 54 instances, of which 19 involved trigeminal nerve dysfunction and were 18 related to optic nerve dysfunction. Of these, 90.7% (n = 49) were due to tumor progression and only 9.3% (n = 5) were attributable to SRS. Overall, this translates to a 2.64% (n = 5/189) incidence of direct SRS-related complications. These patients were treated with repeat SRS (6.3%, n = 12), repeat resection (2.1%, n = 4), or both (3.2%, n = 6). For patients treated with a margin dose ≥ 16 Gy, the 2-, 4-, 6-, 8-, 10-, 12-, and 15-year actuarial progression-free survival rates are 100%, 100%, 95.7%, 95.7%, 95.7%, 95.7%, and 95.7%, respectively. Patients treated with a margin dose < 16 Gy, had 2-, 4-, 6-, 8-, 10-, 12-, and 15-year actuarial progression-free survival rates of 99.4%, 97.7%, 95.1%, 88.1%, 82.1%, 79.4%, and 79.4%, respectively. This difference was deemed statistically significant (p = 0.043). Reviewing the volumetric patient-specific measurements, the early follow-up volumetric measurements (at the 3-year follow-up) reliably predicted long-term volume changes and tumor volume control (at the 10-year follow-up) (p = 0.029). CONCLUSIONS SRS is a durable and minimally invasive treatment modality for benign parasellar meningiomas. SRS offers high rates of growth control with a low incidence of neurological deficits compared with other treatment modalities for meningiomas in this region. Volumetric regression or stability during short-term follow-up of 3 years after SRS was shown to be predictive of long-term tumor control.

A proposed plan for personalized radiosurgery in patients with trigeminal neuralgia

OBJECTIVE During the last 25 years, more than 100,000 patients worldwide with trigeminal neuralgia (TN) have undergone stereotactic radiosurgery (SRS) with a standard dose of radiation. However, the radiobiological effect of radiation is determined by the amount of energy delivered to the tissue (integral dose [ID] = mean dose × target volume) and is directly associated with the nerve volume. Although the trigeminal nerve volume varies among patients with TN, the clinical impact of this variation in delivered energy is unknown. The objective of this study was to evaluate the effect of delivered ID on the outcome of TN radiosurgery. METHODS The authors evaluated 155 patients with unilateral TN who had undergone SRS as their initial surgical management over a 13-year period. The authors measured the postganglionic ID within the SRS target and retrospectively stratified patients into 3 groups: low (< 1.4 mJ), medium (1.4-2.7 mJ), and high (> 2.7 mJ) ID. Clinical outcomes, which included pain status (scored using the Barrow Neurological Institute Pain Scale) and sensory dysfunction (scored using the Barrow Neurological Institute Numbness Scale), were evaluated at a median follow-up of 71 months. RESULTS Patients who were treated with a medium ID had superior pain relief either with or without medications (p = 0.006). In the medium ID group, the rates of complete pain relief without medications at 1, 3, and 6 years after SRS were 67%, 54%, and 33%, respectively, while the rates in the rest of the cohort were 55%, 36%, and 19%, respectively. Patients given a high ID had a higher rate of post-SRS trigeminal sensory deterioration (p < 0.0001). At 1, 3, and 6 years after SRS, the high ID group had an estimated rate for developing sensory dysfunction of 35%, 45%, and 50%, respectively, while the rates in patients receiving low and medium IDs were 3%, 4%, and 9%, respectively. The optimal clinical outcome (maximum pain relief and minimal trigeminal sensory dysfunction) was obtained in patients who had received a medium ID. CONCLUSIONS With current dose selection methods, nerve volume affects long-term clinical outcomes in patients with TN who have undergone SRS. This study suggests that the prescribed SRS dose should be customized for each TN patient based on the nerve volume.

Radiosurgical target distance from the root entry zone in the treatment of trigeminal neuralgia

PURPOSE

Stereotactic radiosurgery (SRS) provides a noninvasive treatment modality for patients with medically refractory trigeminal neuralgia. The root entry zone (REZ) has been proposed to be an ideal stereotactic target because it is partially composed of centrally produced myelin, conferring a theoretical increased sensitivity to irradiation as well as increased susceptibility to neurovascular conflict, making it the site in which nociceptive signals likely arise. The aim of this study is to determine if there is a statistically and clinically significant difference in pain relief or facial hypesthesia following SRS based on distance of the stereotactic isocenter from REZ.

METHODS AND MATERIALS

Patients undergoing Novalis radiosurgery for the treatment of trigeminal neuralgia with at least 3 months' follow-up were included in this study. Postoperative outcomes were stratified by Barrow Neurological Institute (BNI) score for pain relief and BNI facial numbness score for facial hypesthesia.

RESULTS

Sixty-seven patients met inclusion criteria and were included in this study. BNI score of I-IIIa was attained in 82% of patients at 3 months and 65% at 1 year following SRS. Distance from isocenter to REZ varied from 0 to 8.6 mm, with a mean of 1.94 ± 1.62 mm. Logistic regression of target-REZ distance against pain relief outcome (patients with score I-IIIa and IIIb-V) was insignificant at 3 months (P = .988), 6 months (P = .925), 9 months (P = .845), and 12 months (P = .547) postoperatively. Furthermore, no significant correlation was found with logistic regression of target-REZ distance with pain relief outcome (patients with score I and score II-IV) (P = .544).

CONCLUSIONS

The current analysis suggests that distance from REZ does not correlate with degree of postoperative pain relief or facial hypesthesia; thus, targeting specific regions within the trigeminal nerve in relation to these anatomical characteristics may not afford any advantage from this perspective.

Repeat Radiosurgery for Trigeminal Neuralgia

BACKGROUND

Repeat Gamma Knife radiosurgery (GKRS) is an established option for patients whose pain has recurred after the initial procedure, with reported success rates varying from 68% to 95%. Predictive factors for response to the repeat GKRS are ill-defined.

OBJECTIVE

This cohort study aimed to report the outcomes and factors predictive of success for patients who have undergone repeated GKRS for trigeminal neuralgia at Wake Forest University Baptist Medical Center.

METHODS

Between 1999 and 2013, 152 patients underwent repeat GKRS at Wake Forest, 125 of whom were available for long-term follow-up. A retrospective chart review and telephone interviews were conducted to determine background medical history, dosimetric data, outcomes, and adverse effects of the procedure.

RESULTS

Eighty-four percent of patients achieved at least Barrow Neurological Institute (BNI) IIIb pain relief, with 46% achieving BNI I. The 1-, 3-, and 5-year rates of BNI I pain relief were 63%, 50%, and 37%, respectively. The 1-, 3-, and 5-year rates of BNI IIIb or better pain relief were 74%, 59%, and 46%, respectively. One patient experienced bothersome numbness and 2 patients developed anesthesia dolorosa. The dominant predictive factors for pain relief were facial numbness after the first GKRS and a positive pain response to the first GKRS.

CONCLUSION

Repeat GKRS is an effective method of treating recurrent trigeminal neuralgia. Patients who have facial numbness after the first treatment and a positive pain response to the first GKRS are significantly more likely to respond well to the second treatment.

Occurrence of Herpes Simplex Virus Reactivation Suggests a Mechanism of Trigeminal Neuralgia Surgical Efficacy

Common to the types of surgery that are effective for the treatment of trigeminal neuralgia (TN) is reactivation of herpes simplex virus (HSV). It is likely that such HSV reactivation following surgery indicates altered trigeminal ganglion neuron function, which was caused by the surgery. It is not thought that HSV infection is related to the cause of TN or that HSV reactivation is important for surgical treatment efficacy. Rather, it is thought that HSV reactivation is a marker of altered trigeminal ganglion neuron function resulting from the TN surgery. It is suggested that HSV reactivation is a surrogate marker of ganglion neuron injury. The correlation between effective types of surgery and evidence that they alter ganglion neuron function suggests that altered trigeminal ganglion neuron function may be the basis of the surgical efficacy.

Update on neuropathic pain treatment for trigeminal neuralgia. The pharmacological and surgical options

Trigeminal neuralgia is a syndrome of unilateral, paroxysmal, stabbing facial pain, originating from the trigeminal nerve. Careful history of typical symptoms is crucial for diagnosis. Most cases are caused by vascular compression of the trigeminal root adjacent to the pons leading to focal demyelination and ephaptic axonal transmission. Brain imaging is required to exclude secondary causes. Many medical and surgical treatments are available. Most patients respond well to pharmacotherapy; carbamazepine and oxcarbazepine are first line therapy, while lamotrigine and baclofen are considered second line treatments. Other drugs such as topiramate, levetiracetam, gabapentin, pregabalin, and botulinum toxin-A are alternative treatments. Surgical options are available if medications are no longer effective or tolerated. Microvascular decompression, gamma knife radiosurgery, and percutaneous rhizotomies are most promising surgical alternatives. This paper reviews the medical and surgical therapeutic options for the treatment of trigeminal neuralgia, based on available evidence and guidelines.

Gamma Knife Stereotactic Radiosurgery for Trigeminal Neuralgia Caused by a Developmental Venous Anomaly

Background: Trigeminal neuralgia (TN) is mostly caused by vascular compression of the nerve's root entry zone due to an ectatic artery. Rarer causes include compression from tumors, vascular malformations or multiple sclerosis plaques. Developmental venous anomalies (DVAs) are benign, aberrantly appearing venous structures that drain normal cerebral tissue. DVAs are a rare etiology of TN. The management of TN caused by a DVA is controversial as disruption of the DVA can be catastrophic. Methods: We report a case of a young man with severe medically refractory TN related to a brachium pontis DVA who was successfully treated by gamma knife stereotactic radiosurgery (GKSR) to the trigeminal nerve. Results: Within 2 weeks of GKSR, the patient reported experiencing 60% pain relief; 5 years postoperatively, he remains completely pain free with some mild sensory loss in the V2 and V3 areas. Conclusions: GKSR has an established role in the management of TN. This is the first reported case of using GKSR to treat TN caused by a DVA. In the setting of a DVA, GKSR should be an initial consideration for TN therapy after medical failure because of the high surgical risk related to disrupting the DVA. © 2015 S. Karger AG, Basel.

Radiosurgery target location and individual anatomical variation in trigeminal nerves

OBJECT

The authors evaluated individual anatomical variations in the trigeminal nerves of patients with medically intractable trigeminal neuralgia and clarified the relationships among the variations, radiosurgical target locations, and the clinical outcomes after high-dose Gamma Knife surgery (GKS).

METHODS

From 2006 through 2011, the authors conducted a retrospective review of 106 cases of primary or secondary trigeminal neuralgia consecutively treated with GKS targeting the dorsal root entry zone (DREZ) for which a maximal dose of 90 Gy and a 20% isodose line to the brainstem were used. A questionnaire was used to evaluate patients' pre- and post-GKS clinical conditions. To evaluate individual anatomical variations among trigeminal nerves, the authors used 3 parameters: the length of the trigeminal nerve in the cistern (nerve length), the length of the target between the radiation shot and the brainstem (targeting length), and the ratio between nerve length and targeting length (targeting ratio).

RESULTS

The median length of the trigeminal nerves in the 106 patients was 9.6 mm (range 6.04-20.74 mm), the median targeting length was 3.8 mm (range 1.81-10.84 mm), and the median targeting ratio was 38% (range 13%- 80%). No statistically significant differences in pain relief and pain recurrence were detected among patients with these various nerve characteristics. However, radiation-induced facial hypesthesia correlated with nerve length and targeting ratio (p < 0.05) but not with absolute distance from the brainstem (targeting length).

CONCLUSIONS

In trigeminal neuralgia patients who received DREZ-targeted GKS, the rate of pain relief did not differ according to anatomical nerve variations. However, the frequency of facial hypesthesia was higher among patients in whom the nerve was longer (> 11 mm) or the targeting ratio was lower (< 36%). Adjusting the target according to the targeting ratio, especially for patients with longer nerves, can reduce facial hypesthesia and enable maintenance of effective pain control.

The results of a third Gamma Knife procedure for recurrent trigeminal neuralgia

OBJECT

Gamma Knife radiosurgery (GKRS) is the least invasive treatment option for medically refractory, intractable trigeminal neuralgia (TN) and is especially valuable for treating elderly, infirm patients or those on anticoagulation therapy. The authors reviewed pain outcomes and complications in TN patients who required 3 radiosurgical procedures for recurrent or persistent pain.

METHODS

A retrospective review of all patients who underwent 3 GKRS procedures for TN at 4 participating centers of the North American Gamma Knife Consortium from 1995 to 2012 was performed. The Barrow Neurological Institute (BNI) pain score was used to evaluate pain outcomes.

RESULTS

Seventeen patients were identified; 7 were male and 10 were female. The mean age at the time of last GKRS was 79.6 years (range 51.2–95.6 years). The TN was Type I in 16 patients and Type II in 1 patient. No patient suffered from multiple sclerosis. Eight patients (47.1%) reported initial complete pain relief (BNI Score I) following their third GKRS and 8 others (47.1%) experienced at least partial relief (BNI Scores II–IIIb). The average time to initial response was 2.9 months following the third GKRS. Although 3 patients (17.6%) developed new facial sensory dysfunction following primary GKRS and 2 patients (11.8%) experienced new or worsening sensory disturbance following the second GKRS, no patient sustained additional sensory disturbances after the third procedure. At a mean follow-up of 22.9 months following the third GKRS, 6 patients (35.3%) reported continued Score I complete pain relief, while 7 others (41.2%) reported pain improvement (BNI Scores II–IIIb). Four patients (23.5%) suffered recurrent TN following the third procedure at a mean interval of 19.1 months.

CONCLUSIONS

A third GKRS resulted in pain reduction with a low risk of additional complications in most patients with medically refractory and recurrent, intractable TN. In patients unsuitable for other microsurgical or percutaneous strategies, especially those receiving long-term oral anticoagulation or antiplatelet agents, GKRS repeated for a third time was a satisfactory, low risk option.

Trigeminal Neuralgia: Outcomes after Gamma Knife Radiosurgery

Background:

Trigeminal neuralgia (TN) often remains difficult to treat despite multiple available medications, and can severely impact on the quality of life of affected patients. Gamma knife radiosurgery has recently emerged as a minimally-invasive alternative to surgery for patients suffering from drug-resistant TN. The goal of this study was to report the short-term efficacy of gamma knife radiosurgery for TN and assess its impact on the quality of life of patients treated in the first 18 months of our experience.

Methods:

Patients with medically-refractory TN or with unacceptable drug side effects were considered for radiosurgery. A maximum dose of 80 Gy was administered to the affected nerve using a single 4-mm isocenter. Follow-up assessments were made at 2, 4 and 6 months, with evaluation of pain relief, drug reduction and quality of life. Factors impacting treatment response were assessed using Cox regression analysis.

Results:

A total of 67 patients were treated. Significant pain relief was seen in 77.6% of patients, including 32.6% who became pain-free. Patients were able to discontinue all medications in 34.3% or reduce drug intake by more than 50% in an additional 28.4% of cases. No variable was found to predict pain relief although older age (>66 years) approached statistical significance. Sensory side effects were seen in 14.9% of patients. Quality of life improved in the majority of patients after radiosurgery.

Conclusions:

Gamma knife radiosurgery is a safe and effective management alternative for trigeminal neuralgia, providing good or excellent pain relief and improvement in quality of life in the majority of patients with few side effects.

Repeat Gamma Knife surgery for recurrent trigeminal neuralgia: long-term outcomes and systematic review

Object

The purpose of this study was to establish the safety and efficacy of repeat Gamma Knife surgery (GKS) for recurrent trigeminal neuralgia (TN).

Methods

Using the prospective database of TN patients treated with GKS in Timone University Hospital (Marseille, France), data were analyzed for 737 patients undergoing GKS for TN Type 1 from July 1992 to November 2010. Among the 497 patients with initial pain cessation, 34.4% (157/456 with ≥ 1-year follow-up) experienced at least 1 recurrence. Thirteen patients (1.8%) were considered for a second GKS, proposed only if the patients had good and prolonged initial pain cessation after the first GKS, with no other treatment alternative at the moment of recurrence. As for the first GKS, a single 4-mm isocenter was positioned in the cisternal portion of the trigeminal nerve at a median distance of 7.6 mm (range 4–14 mm) anterior to the emergence of the nerve (retrogasserian target). A median maximum dose of 90 Gy (range 70–90 Gy) was delivered. Data for 9 patients with at least 1-year followup were analyzed. A systematic review of literature was also performed, and results are compared with those of the Marseille study.

Results

The median time to retreatment in the Marseille study was 72 months (range 12–125 months) and in the literature it was 17 months (range 3–146 months). In the Marseille study, the median follow-up period was 33.9 months (range 12–96 months), and 8 of 9 patients (88.9%) had initial pain cessation with a median of 6.5 days (range 1–180 days). The actuarial rate for new hypesthesia was 33.3% at 6 months and 50% at 1 year, which remained stable for 7 years. The actuarial probabilities of maintaining pain relief without medication at 6 months and 1 year were 100% and 75%, respectively, and remained stable for 7 years. The systematic review analyzed 20 peer-reviewed studies reporting outcomes for repeat GKS for recurrent TN, with a total of 626 patients. Both the selection of the cases for retreatment and the way of reporting outcomes vary widely among studies, with a median rate for initial pain cessation of 88% (range 60%–100%) and for new hypesthesia of 33% (range 11%–80%).

Conclusions

Results from the Marseille study raise the question of surgical alternatives after failed GKS for TN. The rates of initial pain cessation and recurrence seem comparable to, or even better than, those of the first GKS, according to different studies, but toxicity is much higher, both in the Marseille study and in the published data. Neither the Marseille study data nor literature data answer the 3 cardinal questions regarding repeat radiosurgery in recurrent TN: which patients to retreat, which target is optimal, and which dose to use.