Dedicated linear accelerator radiosurgery for the treatment of trigeminal neuralgia

Robotic-assisted stereotactic percutaneous balloon compression for trigeminal neuralgia treatment

Trigeminal neuralgia (TN) is a facial pain disorder that can be a source of significant disability. Percutaneous balloon compression (PBC) has low cost, high efficacy, and minimal invasiveness. Complications can occur due to the balloon inflation or the needle placement itself. In this paper, we describe for the first time the clinical use of robotic-assistance to perform a PBC for TN, presenting our experience in two patients. The stereotactic planning targeted the foramen ovale (FO) establishing a safe and seamless needle trajectory. This yielded a streamlined, single pass needle placement and eliminated the need to "search" for the FO. There were no immediate complications and post-operatively both patients improved their symptoms. Robotic assistance is potentially a useful tool to reduce needle placement related complications, radiation exposure and PBC learning curve.

Linear accelerator-based radiosurgery for trigeminal neuralgia: comparative outcomes of frame-based and mask-based techniques

OBJECTIVE

Precise and accurate targeting is critical to optimize outcomes after stereotactic radiosurgery (SRS) for trigeminal neuralgia (TN). The aim of this study was to compare the outcomes after SRS for TN in which two different techniques were used: mask-based 4-mm cone versus frame-based 5-mm cone.

METHODS

The authors performed a retrospective review of patients who underwent SRS for TN at their institution between 1996 and 2019. The Barrow Neurological Institute (BNI) pain score and facial hypesthesia scale were used to evaluate pain relief and facial numbness.

RESULTS

A total of 234 patients were included in this study; the mean age was 67 years. In 97 patients (41.5%) radiation was collimated by a mask-based 4-mm cone, whereas a frame-based 5-mm cone was used in the remaining 137 patients (58.5%). The initial adequate pain control rate (BNI I-III) was 93.4% in the frame-based 5-mm group, compared to 87.6% in the mask-based 4-mm group. This difference between groups lasted, with an adequate pain control rate at ≥ 24 months of 89.9% and 77.8%, respectively. Pain relief was significantly different between groups from initial response until the last follow-up (≥ 24 months, p = 0.02). A new, permanent facial hypesthesia occurred in 30.3% of patients (33.6% in the frame-based 5-mm group vs 25.8% in the mask-based 4-mm group). However, no significant association between the BNI facial hypesthesia score and groups was found. Pain recurrence occurred earlier (median time to recurrence 12 months vs 29 months, p = 0.016) and more frequently (38.1% vs 20.4%, p = 0.003) in the mask-based 4-mm than in the frame-based 5-mm group.

CONCLUSIONS

Frame-based 5-mm collimator SRS for TN resulted in a better long-term pain relief with similar toxicity profiles to that seen with mask-based 4-mm collimator SRS.

Neuromodulation via Focal Radiation: Radiomodulation Update

When radiation is focally delivered to brain tissue at sub-ablative doses, neural activity may be altered. When done at a specific brain circuit node or connection, this is referred to as “radiomodulation.” Radiation-induced effects on brain tissue, basic science, and clinical research that supports the radiomodulation hypothesis are reviewed in this article. We review progress in defining the necessary parameters in terms of dose, volumes, and anatomical location. It may be possible to deliver therapeutic neuromodulation that is non-invasive, non-destructive, and durable.

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.

Application of statistical and computational methodology to predict brainstem dosimetry for trigeminal neuralgia stereotactic radiosurgery

OBJECTIVES

To apply advanced statistical and computational methodology in evaluating the impact of anatomical and technical variables on normal tissue dosimetry of trigeminal neuralgia (TN) stereotactic radiosurgery (SRS).

METHODS

Forty patients treated with LINAC-based TN SRS with 90 Gy maximum dose were randomly selected for the study. Parameters extracted from the treatment plans for the study included three dosimetric output variables: the maximum dose to the brainstem (BSmax), the volume of brainstem that received at least 10 Gy (V10BS), and the volume of normal brain that received at least 12 Gy (V12). We analyzed five anatomical variables: the incidence angle of the nerve with the brainstem surface (A), the nerve length (L), the nerve width as measured both axially (WA) and sagittally (WS), the distance measured along the nerve between the isocenter and the brainstem surface (D), and one technical variable: the utilized cone size (CS). Univariate correlation was calculated for each pair among all parameters. Multivariate regression models were fitted for the output parameters using the optimal input parameters selected by the Gaussian graphic model LASSO. Repeated twofold cross-validations were used to evaluate the models.

RESULTS

Median BSmax, V10BS, and V12 for the 40 patients were 35.7 Gy, 0.14 cc, and 1.28 cc, respectively. Median A, L, WA, WS, D, and CS were 43.7°, 8.8 mm, 2.8 mm, 2.7 mm, 4.8 mm, and 6 mm, respectively. Of the three output variables, BSmax most strongly correlated with the input variables. Specifically, it had strong, negative correlations with the input anatomical variables and a positive correlation with CS. The correlation between D and BSmax at -0.51 was the strongest correlation between single input and output parameters, followed by that between CS and V10BS at 0.45, and that between A and BSmax at -0.44. V12 was most correlated with cone size alone, rather than anatomy. LASSO identified an optimal 3-feature combination of A, D, and CS for BSmax and V10BS prediction. Using cross-validation, the multivariate regression models with the three selected features yielded stronger correlations than the correlation between the BSmax and V10BS themselves.

CONCLUSIONS

For the first time, an advanced statistical and computational methodology was applied to study the impact of anatomical and technical variables on TN SRS. The variables were found to impact brainstem doses, and reasonably strong correlation models were established using an optimized 3-feature combination including the nerve incidence angle, cone size, and isocenter-brainstem distance.

The virtual cone: A novel technique to generate spherical dose distributions using a multileaf collimator and standardized control-point sequence for small target radiation surgery

Purpose

The study aimed to develop and demonstrate a standardized linear accelerator multileaf collimator-based method of delivering small, spherical dose distributions suitable for radiosurgical treatment of small targets such as the trigeminal nerve.

Methods and materials

The virtual cone is composed of a multileaf collimator–defined field with the central 2 leaves set to a small gap. For 5 table positions, clockwise and counter-clockwise arcs were used with collimator angles of 45 and 135 degrees, respectively. The dose per degree was proportional to the sine of the gantry angle. The dose distribution was calculated by the treatment planning system and measured using radiochromic film in a skull phantom for leaf gaps of 1.6, 2.1, and 2.6 mm. Cones with a diameter of 4 mm and 5 mm were measured for comparison. Output factor constancy was investigated using a parallel-plate chamber.

Results

The mean ratio of the measured-to-calculated dose was 0.99, 1.03, and 1.05 for 1.6, 2.1, and 2.6 mm leaf gaps, respectively. The diameter of the measured (calculated) 50% isodose line was 4.9 (4.6) mm, 5.2 (5.1) mm, and 5.5 (5.5) mm for the 1.6, 2.1, and 2.6 mm leaf gap, respectively. The measured diameter of the 50% isodose line was 4.5 and 5.7 mm for the 4 mm and 5 mm cones, respectively. The standard deviation of the parallel-plate chamber signal relative to a 10 cm × 10 cm field was less than 0.4%. The relative signal changed 32% per millimeter change in leaf gap, indicating that the parallel-plate chamber is sensitive to changes in gap width.

Conclusions

The virtual cone is an efficient technique for treatment of small spherical targets. Patient-specific quality assurance measurements will not be necessary in routine clinical use. Integration directly into the treatment planning system will make planning using this technique extremely efficient.

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.

Frameless image-guided radiosurgery for trigeminal neuralgia

Background:

Frameless image-guided radiosurgery (IGRS) is a safe and effective noninvasive treatment for trigeminal neuralgia (TN). This study evaluates the use of frameless IGRS to treat patients with refractory TN.

Methods:

We reviewed the records of 20 patients diagnosed with TN who underwent frameless IGRS treatments between March 2012 and December 2013. Facial pain was graded using the Barrow Neurological Institute (BNI) scoring system. The initial setup uncertainty from simulation to treatment and the patient intrafraction uncertainty were measured. The median follow-up was 32 months.

Results:

All patients’ pain was BNI Grade IV or V before the frameless IGRS treatment. The mean intrafraction shift was 0.43 mm (0.28–0.76 mm), and the maximum intrafraction shift was 0.95 mm (0.53–1.99 mm). At last follow-up, 8 (40%) patients no longer required medications (BNI 1 or 2), 11 (55%) patients were pain free but required medication (BNI 3), and 1 (5%) patient had no pain relief (BNI 5). Patients who did not have prior surgery had a higher odds ratio for pain relief compared to patients who had prior surgery (14.9, P = 0.0408).

Conclusions:

Frameless IGRS provides comparable dosimetric and clinical outcomes to frame-based SRS in a noninvasive fashion for patients with medically refractory TN.

Margin of error for a frameless image guided radiosurgery system: Direct confirmation based on posttreatment MRI scans

PURPOSE

To report on radiosurgery delivery positioning accuracy in the treatment of tremor patients with frameless image guided radiosurgery using the linear accelerator (LINAC) based ExacTrac system and to describe quality assurance (QA) procedures used.

METHODS AND MATERIALS

Between 2010 and 2015, 20 patients underwent radiosurgical thalamotomy targeting the ventral intermediate nucleus for the treatment of severe tremor. The median prescription dose was 140 Gy (range, 120-145 Gy) in a single fraction. The median maximum dose was 156 Gy (range, 136-162 Gy). All treatment planning was performed with the iPlan system using a 4-mm circular cone with multiple arcs. Before each treatment, QA procedures were performed, including the imaging system. As a result of the extremely high dose delivered in a single fraction, a well-defined circular mark developed on the posttreatment magnetic resonance imaging (MRI). Eight of these 20 patients were selected to evaluate treatment localization errors because their circular marks were available in posttreatment MRI. In this study, the localization error is defined as the distance between the center of the intended target and the center of the posttreatment mark.

RESULTS

The mean error of distance was found to be 1.1 mm (range, 0.4-1.5 mm). The mean errors for the left-right, anteroposterior, and superoinferior directions are 0.5 mm, 0.6 mm, and 0.7 mm, respectively.

CONCLUSIONS

The result reported in this study includes all tremor patients treated at our institution when their posttreatment MRI data were available for study. It represents a direct confirmation of target positioning accuracy in radiosurgery with a LINAC-based frameless system and its limitations. This level of accuracy is only achievable with an appropriate QA program in place for a LINAC-based frameless radiosurgery system.

Comparative analysis between 5 mm and 7.5 mm collimators in CyberKnife radiosurgery for trigeminal neuralgia

Trigeminal neuralgia (TN) is treated in CyberKnife (Accuray Inc, Sunnyvale, USA) with the 5 mm collimator whose dosimetric inaccuracy is higher than the other available collimators. The 7.5 mm collimator which is having less dosimetric uncertainty can be an alternative for 5 mm collimator provided the dose distribution with 7.5 mm collimator is acceptable. Aim of this study is to analyze the role of 7.5 mm collimator in CyberKnife treatment plans of TN. The treatment plans with 5 mm collimators were re-optimized with 7.5 mm collimator and a bi-collimator system (5 mm and 7.5 mm). The treatment plans were compared for target coverage, brainstem doses, and the dose to normal tissues. The target and brainstem doses were comparable. However, the conformity indices were 2.31 ± 0.52, 2.40 ± 0.87 and 2.82 ± 0.51 for 5 mm, bi-collimator (5mm and 7.5 mm), 7.5 mm collimator plans respectively. This shows the level of dose spillage in 7.5 mm collimator plans. The 6 Gy dose volumes in 7.5 mm plans were 1.53 and 1.34 times higher than the 5 mm plan and the bi-collimator plans respectively. The treatment time parameters were lesser for 7.5 mm collimators. Since, the normal tissue dose is pretty high in 7.5 mm collimator plans, the use of it in TN plans can be ruled out though the treatment time is lesser for these 7.5 mm collimator plans.

Preliminary results of 45 patients with trigeminal neuralgia treated with radiosurgery compared to hypofractionated stereotactic radiotherapy, using a dedicated linear accelerator

Radiosurgery (RS) and hypofractionated stereotactic radiotherapy (HSRT) were performed in 23 and 22 patients respectively for the treatment of trigeminal neuralgia. RS and HSRT were performed with a dedicated linear accelerator (LINAC): an invasive frame (for RS) or a relocatable stereotactic frame fitted with a thermoplastic mask and bite blocks (HSRT) were used for positioning patients. The RS treatment delivered 40 Gy in a single fraction, or for HSRT, the equivalent radiobiological fractionated dose - a total of 72 Gy in six fractions. The target (the retrogasserian cisternal portion of the trigeminal nerve) was identified by fusion of CT scans with 1-mm-thick T2-weighted MRI, and the radiant dose was delivered by a 10-mm-diameter cylindrical collimator. The results were evaluated using the Barrow Neurological Institute pain scale during follow-up (mean 3.9 years). The 95% isodose was applied to the entire target volume. After RS (23 patients), Class 1 results were observed in 10 patients; Class II in nine, Class IIIa in two, Class IIIb in one, and Class V results in one patient. Facial numbness occurred in two (8.7%) patients, and the trigeminal neuralgia recurred in two patients (8.7%). Following HSRT (22 patients), Class I results were achieved in eight patients, Class II in eight, Class IIIa in four, and Class IIIb in two patients; recurrence occurred in six (27.5%), and there were no complications. Thus, both RS and HSRT provided effective and safe therapy for the treatment of trigeminal neuralgia. Patients who underwent RS experienced better pain relief and a lower recurrence rate, whereas those who underwent HRST had no side effects, and in particular, no facial numbness.

Stereotactic radiosurgery for movement disorders

Initially designed for the treatment of functional brain targets, stereotactic radiosurgery (SRS) has achieved an important role in the management of a wide range of neurosurgical pathologies. The interest in the application of the technique for the treatment of pain, and psychiatric and movement disorders has returned in the beginning of the 1990s, stimulated by the advances in neuroimaging, computerized dosimetry, treatment planning software systems, and the outstanding results of radiosurgery in other brain diseases. Since SRS is a neuroimaging-guided procedure, without the possibility of neurophysiological confirmation of the target, deep brain stimulation (DBS) and radiofrequency procedures are considered the best treatment options for movement-related disorders. Therefore, SRS is an option for patients who are not suitable for an open neurosurgical procedure. SRS thalamotomy provided results in tremor control, comparable to radiofrequency and DBS. The occurrence of unpredictable larger lesions than expected with permanent neurological deficits is a limitation of the procedure. Improvements in SRS technique with dose reduction, use of a single isocenter, and smaller collimators were made to reduce the incidence of this serious complication. Pallidotomies performed with radiosurgery did not achieve the same good results. Even though the development of DBS has supplanted lesioning as the first alternative in movement disorder surgery; SRS might still be the only treatment option for selected patients.

CyberKnife radiosurgery for trigeminal neuralgia: unanticipated iatrogenic effect following successful treatment

This case report of 74-year-old man with trigeminal neuralgia is presented to underscore the importance of evaluating the entire treatment plan, especially when delivering large doses where even a low percentage of the prescription dose can contribute a substantial dose to an unintended target. The patient was treated using the CyberKnife stereotactic radiosurgery system utilizing a nonisocentric beam treatment plan with a 5-mm fixed collimator generating 111 beams to deliver 6000 cGy to the 79% isodose line with a maximum dose of 7594 cGy to the target. Two weeks after treatment the patient's trigeminal neuralgia symptoms resolved; however, the patient developed oral mucositis due to the treatment. This case report reviews the cause of mucositis and makes recommendations on how to prevent unintended targets from receiving treatment.

Outcome for patients with essential trigeminal neuralgia treated with linear accelerator stereotactic radiosurgery

BACKGROUND

Stereotactic radiosurgery (SRS) is one option for treatment of trigeminal neuralgia, after unsuccessful conservative approaches.

OBJECTIVES

The objective of this study was to retrospectively evaluate our institutional results in the management of patients with idiopathic trigeminal neuralgia treated with linear accelerator SRS.

METHODS

Fifty-two patients were treated between January 1998 and December 2009 and were followed for more than 6 months (median: 26.6 months). Forty-seven patients (90%) had undergone previous surgery before SRS. The target dose ranged from 50 to 80 Gy.

RESULTS

After SRS, 9 patients presented complete remission of the pain, and 21 were pain free but still under medication. Eleven patients reported a relief of more than 50% in crisis frequency. In 9 patients, no significant improvements were seen, and 2 presented an exacerbation of the pain. After an average period of 20 months, 15 patients reported pain recurrence. Results were better in patients older than 60 years (p = 0.019). Nineteen patients presented facial numbness after SRS, with a trend toward favorable treatment response (p = 0.06).

CONCLUSION

SRS is an effective alternative to the treatment of essential trigeminal neuralgia, with long-lasting pain relief in more than 50% of the patients. Better results were seen with patients aged more than 60 years.

Frameless image-guided radiosurgery for initial treatment of typical trigeminal neuralgia

OBJECTIVE

To review retrospectively initial experience at a single institution using frameless image-guided radiosurgery (IGRS) for trigeminal neuralgia employing the Novalis linear accelerator (LINAC) with ExacTrac robotic patient positioning device.

METHODS

Over an 18-month period, 44 patients (27 women and 17 men; median age 65 years) were treated with frameless IGRS for typical trigeminal neuralgia (14 cases involved left-sided pain and 30 cases involved right-sided pain), responsive to anticonvulsant medications, with Barrow Neurological Institute Pain Scale (BNI-PS) scores of 4 or 5. All cases were initial radiosurgery treatments with an isocenter dose of 90 Gy delivered via a 4-mm circular collimator forming a spheroid dose envelope. Intrafraction positioning data were collected for all patients. The median follow-up was 15 months.

RESULTS

Overall intrafraction positioning error was 0.49 mm ± 0.44. After treatment, 40 patients achieved a BNI-PS score of IIIb or better; 19 patients achieved a BNI-PS score of I. The median time to pain relief was 4 weeks. Overall, new hypoesthesia was seen in five patients. No other complications were seen.

CONCLUSIONS

Use of frameless IGRS methods for treatment of trigeminal neuralgia showed results similar to the authors' prior experience with frame-based treatment methods. IGRS using frameless methods is a suitable treatment method for patients with trigeminal neuralgia and may be applicable to other functional indications.

Dose Verification of Stereotactic Radiosurgery Treatment for Trigeminal Neuralgia with Presage 3D Dosimetry System

Achieving adequate verification and quality-assurance (QA) for radiosurgery treatment of trigeminal-neuralgia (TGN) is particularly challenging because of the combination of very small fields, very high doses, and complex irradiation geometries (multiple gantry and couch combinations). TGN treatments have extreme requirements for dosimetry tools and QA techniques, to ensure adequate verification. In this work we evaluate the potential of Presage/Optical-CT dosimetry system as a tool for the verification of TGN distributions in high-resolution and in 3D. A TGN treatment was planned and delivered to a Presage 3D dosimeter positioned inside the Radiological-Physics-Center (RPC) head and neck IMRT credentialing phantom. A 6-arc treatment plan was created using the iPlan system, and a maximum dose of 80Gy was delivered with a Varian Trilogy machine. The delivered dose to Presage was determined by optical-CT scanning using the Duke Large field-of-view Optical-CT Scanner (DLOS) in 3D, with isotropic resolution of 0.7mm(3). DLOS scanning and reconstruction took about 20minutes. 3D dose comparisons were made with the planning system. Good agreement was observed between the planned and measured 3D dose distributions, and this work provides strong support for the viability of Presage/Optical-CT as a highly useful new approach for verification of this complex technique.

Stereotactic Radiosurgery for Trigeminal Neuralgia Utilizing the BrainLAB Novalis System

Stereotactic radiosurgery (SRS) is one of the least invasive treatments for trigeminal neuralgia (TN). To date, most reports have been about Cobalt-based treatments ( i.e., Gamma Knife) with limited data on image-guided stereotactic linear accelerator treatments. We describe our initial experience of using BrainLAB Novalis stereotactic system for the radiosurgical treatment of TN.

A total of 20 patients were treated between July 2004 and February 2007. Each SRS procedure was performed using the BrainLAB Novalis System. Thin cuts MRI images of 1.5 mm thickness were acquired and fused with the simulation CT of each patient. Majority of the patients received a maximum dose of 90 Gy. The median brainstem dose to 1.0 cc and 0.1 cc was 2.3 Gy and 13.5 Gy, respectively. In addition, specially acquired three-dimensional fast imaging sequence employing steady-state acquisition (FIESTA) MRI was utilized to improve target delineation of the trigeminal proximal nerve root entry zone. Barrow Neurological Index (BNI) pain scale for TN was used for assessing treatment outcome. At a median follow-up time of 14.2 months, 19 patients (95%) reported at least some improvement in pain. Eight (40%) patients were completely pain-free and stopped all medications (BNI Grade I) while another 2 (10%) patients also stopped medications but reported occasional pain (BNI Grade II). Another 2 (10%) patients reported no pain and 7 (35%) patients only occasional pain while continuing medications, BNI Grade IIIA and IIIB, respectively. Median time to pain control was 8.5 days (range: 1–70 days). No patient reported severe pain, worsening pain or any pain not controlled on their previously taken medication. Intermittent or persistent facial numbness following treatments occurred in 35% of patients. No other complications were reported. Stereotactic radiosurgery using the BrainLAB Novalis system is a safe and effective treatment for TN. This information is important as more centers are obtaining image-guided stereotactic-based linear accelerators capable of performing radiosurgery.

Radiosurgery for trigeminal neuralgia: is sensory disturbance required for pain relief?

OBJECT

Over the past 15 years stereotactic radiosurgery has become an accepted surgical option for patients with medically unresponsive trigeminal neuralgia (TN). The mechanism whereby radiosurgery causes pain relief remains unclear.

METHODS

A review of recent papers on the radiosurgical management of TN reveals a correlation between maximum prescription dose and facial pain outcomes (p = 0.03) and between maximum prescription dose and new-onset trigeminal dysfunction (p < 0.01). In five of six studies in which investigators specifically analyzed whether there is any relationship between postradiosurgical trigeminal dysfunction and facial pain outcomes, there was a statistically significant greater chance of patients being pain free without medications if new trigeminal dysfunction developed after radiosurgery. Likewise, combining the results of two small series on repeated radiosurgery for TN also showed a significant correlation between postradiosurgical trigeminal dysfunction and facial pain outcomes (p = 0.02).

CONCLUSIONS

Although the quality of data available does not permit a formal metaanalysis of radiosurgery for TN, the preponderance of information supports an association between the development of facial sensory loss and pain relief after radiosurgery. Consequently, radiosurgery should be considered a destructive technique in which the goal is similar to that in other percutaneous ablative techniques used to manage TN: create sufficient damage to the trigeminal system to achieve pain relief, but not so much injury that the patient is at risk for deafferentation pain syndromes.

Nonisocentric radiosurgical rhizotomy for trigeminal neuralgia

OBJECTIVE

Although stereotactic radiosurgery is an established procedure for treating trigeminal neuralgia (TN), the likelihood of a prompt and durable complete response is not assured. Moreover, the incidence of facial numbness remains a challenge. To address these limitations, a new, more anatomic radiosurgical procedure was developed that uses the CyberKnife (Accuray, Inc., Sunnyvale, CA) to lesion an elongated segment of the retrogasserian cisternal portion of the trigeminal sensory root. Because the initial experience with this approach resulted in an unacceptably high incidence of facial numbness, a gradual dose and volume de-escalation was performed over several years. In this single-institution prospective study, we evaluated clinical outcomes in a group of TN patients who underwent lesioning with seemingly optimized nonisocentric radiosurgical parameters.

METHODS

Forty-six patients with intractable idiopathic TN were treated between January 2005 and June 2007. Eligible patients were either poor surgical candidates or had failed previous microvascular decompression or destructive procedures. During a single radiosurgical session, a 6-mm segment of the affected nerve was treated with a mean marginal prescription dose of 58.3 Gy and a mean maximal dose of 73.5 Gy. Monthly neurosurgical follow-up was performed until the patient became pain-free. Longer-term follow-up was performed both in the clinic and over the telephone. Outcomes were graded as excellent (pain-free and off medication), good (>90% improvement while still on medication), fair (50-90% improvement), or poor (no change or worse). Facial numbness was assessed using the Barrow Neurological Institute Facial Numbness Scale score.

RESULTS

Symptoms disappeared completely in 39 patients (85%) after a mean latency of 5.2 weeks. In most of these patients, pain relief began within the first week. TN recurred in a single patient after a pain-free interval of 7 months; all symptoms abated after a second radiosurgical procedure. Four additional patients underwent a repeat rhizotomy after failing to respond adequately to the first operation. After a mean follow-up period of 14.7 months, patient-reported outcomes were excellent in 33 patients (72%), good in 11 patients (24%), and poor/no improvement in 2 patients (4%). Significant ipsilateral facial numbness (Grade III on the Barrow Neurological Institute Scale) was reported in 7 patients (15%).

CONCLUSION

Optimized nonisocentric CyberKnife parameters for TN treatment resulted in high rates of pain relief and a more acceptable incidence of facial numbness than reported previously. Longer follow-up periods will be required to establish whether or not the durability of symptom relief after lesioning an elongated segment of the trigeminal root is superior to isocentric radiosurgical rhizotomy.

CYBERKNIFE RADIOSURGERY AS A FIRST TREATMENT FOR IDIOPATHIC TRIGEMINAL NEURALGIA

OBJECTIVE

To report the level of effectiveness and safety, in our experience, of CyberKnife (Accuray, Inc., Sunnyvale, CA) robotic radiosurgery as a first-line treatment against pharmacologically refractory trigeminal neuralgia.

METHODS

We treated 33 patients with the frameless CyberKnife system as a monotherapy. The retrogasserian portion of the trigeminal nerve (a length of 4 mm, 2–3 mm anterior to the root entry zone) was targeted. Doses of 55 to 75 Gy were prescribed to the 100% isodose line, according to a dose escalation protocol. The patients were evaluated for the level of pain control, time to pain relief, hypesthesia, and time to pain recurrence.

RESULTS

The median age was 74 years. All but 2 patients (94%) achieved a successful treatment outcome. The follow-up period was 9 to 37 months (mean, 23 months). The Barrow Neurological Institute Pain Intensity Scale (BPS) score before radiosurgery was III in 2 patients (6%), IV in 8 patients (24%), and V in 23 patients (70%). The time to pain relief was 1 to 180 days (median, 30 days). No facial numbness was observed. Only 1 patient developed a transitory dysesthesia of the tongue. After treatment, the BPS score was I, II, or III in 31 patients (97%). Pain recurred in 33% (11 patients) at a mean of 9 months (range, 1–43 months). Three patients with recurrences had low pain control by medication (BPS score, IV), and 1 patient (BPS score, V) needed a radiofrequency lesioning (BPS score, I at 12 months).

CONCLUSION

CyberKnife radiosurgery for trigeminal neuralgia allows pain relief at safe doses and is suggested for pharmacologically refractory trigeminal neuralgia. Higher prescribed doses were not associated with improvement in pain relief or recurrence rate.

Operative treatment of trigeminal neuralgia: review of current techniques

Surgical approaches to pain management are performed when medication cannot control pain or patients cannot tolerate the adverse effects of the medication. Microvascular decompression (MVD) is generally performed when the patient is healthy and relatively young. Partial sensory rhizotomy is performed in addition to, or instead of MVD, in patients in whom significant compression of the trigeminal sensory root does not exist or in whom MVD is technically not feasible. Three percutaneous ablative procedures and gamma knife radiosurgery (GKS) are also performed when MVD cannot be performed. The result of MVD is superior to that of the 3 ablative procedures. GKS is inferior to the 3 ablative procedures in terms of initial pain relief and recurrence, but superior in terms of complications. Peripheral procedures are usually performed in patients not suitable for or not wishing to have other procedures. However, no strict rules exist and each patient should be evaluated individually.

Cyberknife radiosurgery for trigeminal neuralgia treatment: a preliminary multicenter experience

OBJECTIVE

Radiosurgery has gained acceptance as a treatment option for trigeminal neuralgia. We report our preliminary multicenter experience treating trigeminal neuralgia with the CyberKnife (Accuray, Inc., Sunnyvale, CA).

METHODS

A total of 95 patients were treated for idiopathic trigeminal neuralgia between May 2002 and October 2005. Radiosurgical dose and volume parameters were retrospectively analyzed in relation to pain response, complications, and recurrence of symptoms. Optimal treatment parameters were identified for patients who had excellent and sustained pain relief with no complications, including severe or moderate hypesthesia.

RESULTS

Excellent pain relief was initially experienced by 64 out of 95 patients (67%). The median time to pain relief was 14 days (range, 0.3-180 d). Posttreatment numbness occurred in 45 (47%) of the patients treated. Using higher radiation doses and treating longer segments of the nerve led to both better pain relief and a higher incidence of hypesthesia. The presence of posttreatment numbness was predictive of better pain relief. The overall rate of complications was 18%. At the mean follow-up time of 2 years, 47 of the 95 patients (50%) had sustained pain relief, all of whom were completely off pain medications.

CONCLUSION

The results of this study suggest the following optimal radiosurgical treatment parameters for treatment of idiopathic trigeminal neuralgia: a median maximal dose of 78 Gy (range, 70-85.4 Gy) and a median length of the nerve treated of 6 mm (range, 5-12 mm).

PROGNOSTIC FACTORS FOR RADIOSURGERY TREATMENT OF TRIGEMINAL NEURALGIA

OBJECTIVE

Trigeminal neuralgia treatment results are thought to be highly dependent upon selection criteria. We retrospectively analyzed a series of patients to determine the likelihood of treatment success for patients treated with radiosurgery.

METHODS

A retrospective analysis of 82 patients treated with linear accelerator radiosurgery was undertaken with a median follow-up period of 18 months. Patients were evaluated with a standard inventory using the Barrow Neurological Institute pain scale as the primary means of outcome measurement. Patients were treated with a linear accelerator using a single isocenter plan delivered via a 4-mm collimator, typically with seven noncoplanar arcs to a peak dose of 85 or 90 Gy in primary treatments and 60 Gy in retreatments. The primary target was the cisternal component of the trigeminal nerve. Posttreatment outcomes were analyzed in light of pretreatment patient characteristics, including age, sex, anticonvulsant responsiveness, quality and pattern of pain, length of disease, number of previous procedures, and radiation dose exposure to the root entry zone. Univariate analysis and multivariate logistic regression analysis were used to determine the prognostic significance of various pretreatment variables.

RESULTS

Good results as defined by a Barrow Neurological Institute outcome score of IIIb or better were seen in 85.3% of patients. Excellent results as defined by a Barrow Neurological Institute outcome score of I were seen in 49% of patients. The median time to satisfactory improvement of pain was 4 weeks. Only one variable, sensitivity to anticonvulsant medication, was found to be statistically significant in both univariate (P = 0.003) and multivariate analysis (P = 0.025). All other variables analyzed failed to reach statistical significance. Complications were not common, with seven patients (8.5%) developing new-onset hypoesthesia and two patients (2%) developing dry eye symptoms.

CONCLUSION

Anticonvulsant responsiveness is the single most important prognostic indicator of treatment success for patients presenting with facial pain. Other predictive factors generally failed to reach statistical significance. Linear accelerator radiosurgery for trigeminal neuralgia is a safe and effective treatment for well-selected patients, with results similar to those obtained with gamma unit radiosurgery.

Stereotactic radiosurgery for functional disorders

✓ Stereotactic radiosurgery (SRS) with the Gamma Knife and linear accelerator has revolutionized neurosurgery over the past 20 years. The most common indications for radiosurgery today are tumors and arteriovenous malformations of the brain. Functional indications such as treatment of movement disorders or intractable pain only contribute a small percentage of treated patients. Although SRS is the only noninvasive form of treatment for functional disorders, it also has some limitations: neurophysiological confirmation of the target structure is not possible, and one therefore must rely exclusively on anatomical targeting. Furthermore, lesion sizes may vary, and shielding adjacent radiosensitive neural structures may be difficult or impossible.

The most common indication for functional SRS is the treatment of trigeminal neuralgia. Radiosurgical treatment for epilepsy and certain psychiatric illnesses is performed in several centers as part of strict research protocols, and radiosurgical pallidotomy or medial thalamotomy is no longer recommended due to the high risk of complications. Radiosurgical ventrolateral thalamotomy for the treatment of tremor in patients with Parkinson disease or multiple sclerosis, as well as in the treatment of essential tremor, may be indicated for a select group of patients with advanced age, significant medical conditions that preclude treatment with open surgery, or patients who must receive anticoagulation therapy. A promising new application of SRS is high-dose radiosurgery delivered to the pituitary stalk. This treatment has already been successfully performed in several centers around the world to treat severe pain in patients with end-stage cancer.

Image-guided stereotactic radiosurgery using a specially designed high-dose-rate linac

Stereotactic radiosurgery and image-guided radiotherapy (IGRT) place enhanced demands on treatment delivery machines. In this study, we describe a high-dose-rate output accelerator as a part of our stereotactic IGRT delivery system. The linac is a Siemens Oncor without a flattening filter, and enables dose rates to reach 1000 monitor units (MUs) per minute. Even at this high-dose-rate, the linac dosimetry system remains robust; constancy, linearity, and beam energy remain within 1% for 3 to 1000 MU. Dose profiles for larger field sizes are not flat, but they are radially symmetric and, as such, able to be modeled by a treatment planning system. Target localization is performed via optical guidance utilizing a 3-dimensional (3D) ultrasound probe coupled to an array of 4 infrared light-emitting diodes. These diodes are identified by a fixed infrared camera system that determines diode position and, by extension, all objects imaged in the room coordinate system. This system provides sub-millimeter localization accuracy for cranial applications and better than 1.5 mm for extracranial applications. Because stereotactic IGRT can require significantly longer times for treatment delivery, the advantages of the high-dose-rate design and its direct impact on IGRT are discussed.

INFLUENCE OF NERVE RADIATION DOSE IN THE INCIDENCE OF TRIGEMINAL DYSFUNCTION AFTER TRIGEMINAL NEURALGIA RADIOSURGERY

OBJECTIVE

The authors conducted a comparative study to analyze dosimetry and results to understand the significant difference in the rate of trigeminal dysfunction after gamma knife radiosurgery for trigeminal neuralgia between two centers using the same target.

METHODS

The data of 358 patients (109 patients from Brussels and 259 patients from Marseilles) were analyzed. Three different dosimetric strategies were found: treatment with less than 90 Gy and no selective beam channel blocking (Group 1; patients from Marseilles only), treatment with 90 Gy and no selective beam channel blocking (Group 2; patients from Brussels and Marseilles), or treatment with 90 Gy and use of selective beam channel blocking (Group 3; patients from Brussels only).

RESULTS

The prescription dose and the use of selective beam channel blocking have been significantly associated with a higher energy received by the retrogasserian trigeminal nerve root. The different radiation dose delivered to the nerve root in these three groups of patients was significantly associated with the incidence of mild (15, 21, and 49% for Groups 1, 2, and 3, respectively) and bothersome (1.4, 2.4, and 10% for Groups 1, 2, and 3, respectively) trigeminal dysfunction. The good and excellent rates of pain relief were 81 and 66%, respectively, for Group 1, 85 and 77%, respectively, for Group 2, and 90 and 84%, respectively, for Group 3, and were also related to the amount of energy received by nerve root volume.

CONCLUSION

Using a similar target, the incidence of trigeminal dysfunction and the pain relief rate can vary according to the radiation energy received by the retrogasserian part of the trigeminal nerve root. The prescription dose and the use of beam channel blocking modify the integrated dose delivered to the nerve and may contribute to the different rates of trigeminal numbness and pain outcome. The radiobiological effect of gamma knife radiosurgery may be related to the energy delivered to nerve root volume, rather than to the maximal dose delivered.

Impact of radiosurgery on the surgical treatment of trigeminal neuralgia

BACKGROUND

The history of the development of current available techniques to treat TN was reviewed.

METHODS

The largest peer-reviewed publications on the surgical treatment of refractory TN were analyzed, considering the pros and cons of each technique. Results of modern peer-reviewed radiosurgery series were presented, taking into consideration the approach of each research article. Radiation doses and targets for radiosurgery were discussed to maximize the understanding of this technique.

RESULTS

It is concluded that radiosurgery is the least invasive modality with the fewest side effects, although, to match the results of the competing techniques, a substantial number of patients still need some medication intake.

CONCLUSION

Further studies determining the ideal target and radiation dose may bring radiosurgery results to the level of the ones achieved with microvascular decompression, currently considered the gold-standard method.

Brainstem and trigeminal nerve changes after radiosurgery for trigeminal pain

PURPOSE

To evaluate the significance of radiological changes on follow-up MRIs after SRS for TN.

MATERIALS AND METHODS

Thirty-seven patients with follow-up MRI because of paresthesias, bilateral treatment, or failure were analyzed regarding pain outcome and complications. Mean age was 64.4 years; 14 underwent previous treatment. Twenty-nine had ETN, 5 secondary TN due to tumor or multiple sclerosis, and 3 had atypical TN. Ninety gray was prescribed for 20 patients, 70 Gy for 5, and 80/85 Gy for 2. A 5-mm collimator was used in 32 (88.9%) cases. Mean follow-up was 15 months (range, 4-52 months).

RESULTS

Excellent/good pain relief was sustained in 67% of cases at 13 months' follow-up. Enhancement on MRIs was observed in 21 cases (56.75%) with nerve enhancement in 9, pons enhancement in 4, pons-nerve enhancement in 4, and tumor enhancement in 4. Magnetic resonance images were unremarkable in 16 cases. Pain recurred in 4 cases (5.5-10 months). Pons enhancement correlated with pain relief (P = .0087) but not with nerve enhancement (P = .22). Incidence of slight paresthesias was 66.6%. No anesthesia dolorosa or ophthalmologic problems were observed. Paresthesias correlated with enhancement (P = .02), but not with brainstem volume encompassed by the 20%, 30%, and 50% isodoseline (P = .689, .525, .908). Enhancement free probability at 12 months was 48.5% (Kaplan-Meier).

CONCLUSIONS

Pons enhancement seems to be prognostic for pain relief without higher incidence of complications. Pons volume irradiated did not predict enhancement occurrence. Radiation delivery to the brainstem-REZ interface seems to improve pain outcome, although more paresthesias should be expected.

Application of high-resolution radiochromic film dosimetry in verifying a small-field stereotactic radiosurgery plan

A high-resolution radiochromic film dosimetry (Hr-RCFD) method has been applied to verify a small-field stereotactic radiosurgery (SRS) plan. This was done by exposing a RCF in a Perspex head phantom undergoing the same treatment plan as the patient. The dose distribution obtained by the Hr-RCFD was verified against that calculated by the stereotactic treatment planning system and the result was satisfactory. The Hr-RCFD method has been found to be an accurate and practical tool in verifying small-field SRS plans.

Prospective controlled trial of gamma knife surgery for essential trigeminal neuralgia

OBJECT

Stereotactic radiosurgery is an alternative to conventional surgery for the treatment of trigeminal neuralgia. The authors conducted a prospective evaluation of the safety and efficacy of this method in a large series of patients.

METHODS

A total of 100 patients presenting with trigeminal neuralgia were treated and followed up for a minimum of 12 months. The mean age was 68.2 years; 54 patients were male, and 46 were female. Seven had a history of multiple sclerosis, and 42 had already received conventional surgical treatment for trigeminal neuralgia. The intervention consisted of gamma knife surgery to the retrogasserian cisternal portion of the fifth cranial nerve. The median dose used at the maximum was 85 Gy (range 70-90 Gy). The number and intensity of pain attacks were recorded by the patient from 3 months before radiosurgery to a minimum of 12 months after treatment. Before and a minimum of 12 months after treatment, the patient completed a quality-of-life questionnaire. Neurological examination and quantitative sensory testing to evaluate sensory perception were performed by an independent neurologist over this same time period. At the last visit 83 of 100 patients were reported to be pain free. Fifty-eight of these 83 patients had stopped taking medication during the study. All quality-of-life parameters were improved (p < 0.001). Six patients reported facial paresthesia, and four patients reported hypesthesia. These symptoms were classified as mild. None of the complications reported for other techniques were observed.

CONCLUSIONS

Radiosurgery is a safe and effective alternative treatment for trigeminal neuralgia and is associated with a particularly low rate of hypesthesia.

Linear Accelerator Radiosurgery for Trigeminal Neuralgia

OBJECTIVE:

To report the clinical outcomes following treatment of trigeminal neuralgia with linear accelerator-based radiosurgery.

METHODS:

Twenty-eight patients with medication refractory idiopathic trigeminal neuralgia were treated with a single fraction of 80 Gy to the trigeminal nerve root. For treatment delivery, a 4-mm collimator and a 7-arc technique were delivered using a stereotactic floor stand system with an isocenter stability of 0.2 ± 0.1 mm to minimize dose to the brainstem. Treatment delivery time was approximately 55 minutes.

RESULTS:

With a median follow-up of 12 months (range, 1–40 mo), 57% of patients achieved complete pain relief and 75% (exact 95% confidence interval, 55 to 89%) had their pain reduced to 3 or less on a 10-point pain scale. Median time to pain relief was 1 month. Four patients did not respond to treatment. The actuarial mean time to pain recurrence in responders was 14 months, and the actuarial mean response duration in major to complete responders was 16 months. Women had significantly longer mean time to pain recurrence than men (16 versus 7 months; P = 0.05). Three patients reported new mild facial numbness after radiosurgery and one patient developed neurotrophic keratopathy.

CONCLUSION:

Linear accelerator-based radiosurgery for medication refractory trigeminal neuralgia provides effective pain relief with a low complication rate.

Comparative analyses of linac and Gamma Knife radiosurgery for trigeminal neuralgia treatments

Dedicated linac-based radiosurgery has been reported for trigeminal neuralgia treatments. In this study, we investigated the dose fall-off characteristics and setup error tolerance of linac-based radiosurgery as compared with standard Gamma Knife radiosurgery. In order to minimize the errors from different treatment planning calculations, consistent imaging registration, dose calculation and dose volume analysis methods were developed and implemented for both Gamma Knife and linac-based treatments. Intra-arc setup errors were incorporated into the treatment planning process of linac-based deliveries. The effects of intra-arc setup errors with increasing number of arcs were studied and benchmarked against Gamma Knife deliveries with and without plugging patterns. Our studies found equivalent dose fall-off properties between Gamma Knife and linac-based radiosurgery given a sufficient number of arcs (>7) and small intra-arc errors (<0.5 mm) were satisfied for linac-based deliveries. Increasing the number of arcs significantly decreased the variations in the dose fall-off curve at the low isodose region (e.g. from 40% to 10%) and also improved dose uniformity at the high isodose region (e.g. from 70% to 90%). As the number of arcs increased, the effects of intra-arc setup errors on the dose fall-off curves decreased. Increasing the number of arcs also reduced the integral dose to the distal normal brain tissues. In conclusion, linac-based radiosurgery produces equivalent dose fall-off characteristics to Gamma Knife radiosurgery with a high number of arcs. However, one must note the increased treatment time for a large number of arcs and isocentre accuracies.

CyberKnife radiosurgery for idiopathic trigeminal neuralgia

OBJECT

Gamma knife surgery is an accepted treatment option for trigeminal neuralgia (TN). The safety and efficacy of CyberKnife radiosurgery as a treatment option for TN, however, has not been established.

METHODS

Forty-one patients were treated between May 2002 and September 2004 for idiopathic TN at Stanford University and the Rocky Mountain CyberKnife Center. Patients with atypical pain, multiple sclerosis, or previous radiosurgical treatment or a follow-up duration of less than 6 months were excluded. Patients were evaluated for the level of pain control, response rate, time to pain relief, occurrence of hypesthesia, and time to pain recurrence with respect to the length of the nerve treated and the maximum and the minimum dose to the nerve margin. Thirty-eight patients (92.7%) experienced initial pain relief at a median of 7 days after treatment (range, 24 hours-4 months). Pain control was ranked as excellent in 36 patients (87.8%), moderate in two (4.9%), and three (7.3%) reported no change. Six (15.8%) of the 38 patients with initial relief experienced a recurrence of pain at a median of 6 months (range 2-8 months). Long-term response after a mean follow-up time of 11 months was found in 32 (78%) of 41. Twenty-one patients (51.2%) experienced numbness after treatment.

CONCLUSIONS

CyberKnife radiosurgery for TN has high rates of initial pain control and short latency to pain relief compared with those reported for other radiosurgery systems. The doses used for treatment were safe and effective. Higher prescribed doses were not associated with improvement in pain relief or recurrence rate. The hypesthesia rate was related to the length of the trigeminal nerve treated.

Comparison of posterior fossa exploration and stereotactic radiosurgery in patients with previously nonsurgically treated idiopathic trigeminal neuralgia

Object

Stereotactic radiosurgery (SRS) is commonly performed in patients with trigeminal neuralgia, and numerous investigators have found that facial pain outcomes after this procedure are better for patients in whom prior surgery did not fail. Researchers in some centers claim that the results of SRS are equivalent to posterior fossa exploration (PFE). The goal in this study was to verify that claim.

Methods

Information was retrieved from a prospectively maintained database of patients less than 70 years old with idiopathic trigeminal neuralgia who underwent PFE (55 patients) or SRS (28 patients) as their initial surgery between 1999 and 2004. Of the two groups, patients who underwent radiosurgery were older (60.5 compared with 50.7 years, p < 0.001). Microvascular decompression was performed in 49 patients (89%) and partial nerve section was performed in six (11%) in the PFE group. The mean maximum dose for SRS was 89.1 Gy. At a mean follow-up duration of 25.5 months, patients who had undergone PFE were more commonly pain free without medications (75% at 1 year, 72% at 3 years) compared with the patients treated with SRS (59% at 1 and 3 years; p = 0.01). Additional surgery was performed in 10 patients (18%) after PFE, compared with eight patients (29%) after SRS (p = 0.4). Eight patients (15%) had either new facial numbness (six cases) or dysesthesias (two cases) after PFE, whereas 12 (43%) had either new facial numbness (eight cases) or dysesthesias (four cases) after SRS. No correlation was noted between the development of facial numbness and facial pain outcome after PFE (p = 0.37), whereas patients in whom trigeminal dysfunction developed after radiosurgery were more frequently free of pain (p = 0.02).

Conclusions

The results support PFE as a more effective primary surgery than SRS in patients with idiopathic trigeminal neuralgia. Moreover, injury to the trigeminal nerve during PFE is not required to achieve excellent facial pain outcomes.

Three-dimensional Fast Imaging Employing Steady-state Acquisition Magnetic Resonance Imaging for Stereotactic Radiosurgery of Trigeminal Neuralgia

OBJECTIVE:

The aim of this study was to demonstrate the use and applications of the three-dimensional fast imaging employing steady-state acquisition (3-D-FIESTA) magnetic resonance imaging sequence in targeting and planning for stereotactic radiosurgery of trigeminal neuralgia.

METHODS:

A 3-D-FIESTA sequence for visualization of cranial nerves in the cranial base was added to the routine magnetic resonance imaging scan to enhance the treatment planning for trigeminal neuralgia. T1-weighted images, 1 mm thick, were directly compared with the FIESTA sequence for the exact visualization of the trigeminal entry zone and surrounding vasculature. The target accuracy was evaluated by image fusion of computed tomographic and magnetic resonance imaging scans. The anatomy visualized with the FIESTA sequence was validated by direct inspection of the gross anatomic specimens of the trigeminal complex.

RESULTS:

A total of 15 consecutive patients, 10 women and 5 men, underwent radiosurgery for essential trigeminal neuralgia between April and July, 2003. The mean age of the patients was 65.2 years (range, 24–83 yr). Nine patients had right-sided symptoms. Four patients had had previous surgery (two microvascular decompression, one percutaneous rhizotomy, and one radiofrequency thermocoagulation). The 3-D-FIESTA sequence successfully demonstrated the trigeminal complex (root entry zone, trigeminal ganglion, rootlets, and vasculature) in 14 patients (93.33%). The 3-D-FIESTA sequence also allowed visualization of the branches of the trigeminal nerve inside Meckel's cavity. This exact visualization correlated precisely with the anatomic specimens. In one patient (6.66%), it was not possible to demonstrate the related vasculature. However, the other structures were clearly visualized.

CONCLUSION:

The 3-D-FIESTA sequence is used in this study for demonstration of the exact anatomy of the trigeminal complex for the purpose of radiosurgical planning and treatment of trigeminal neuralgia. With such imaging techniques, radiosurgical targeting of specific trigeminal nerve branches may be feasible. It has not been possible previously to target individual branches of the trigeminal nerve.

Long-Term Follow-Up of Trigeminal Neuralgia Treatment Using a Linear Accelerator

While most of the studies examining radiosurgery for trigeminal neuralgia have used a Gamma Knife, a linear accelerator can also be utilized for treatment. We report on 20 patients with trigeminal neuralgia who received 23 treatments with a linear accelerator that delivered a maximum dose of 82.3-100 Gy. The median patient follow-up was 56.5 months, 70% of patients had received previous surgical treatment and 20% had secondary (nonessential) trigeminal neuralgia. Eight (35%) radiosurgery treatments resulted in complete pain relief; 5 (63%) patients with initial pain relief had pain recurrence at a mean time of 21.5 months. Ten (43%) patients reported a 50% or more decrease in pain severity but have not achieved a pain-free state. A total of 18 (78%) treatments resulted in no pain or a 50% or greater improvement in pain. Five treatments (22%) resulted in less than 50% improvement in pain. We conclude that linear accelerator stereotactic radiosurgery is a viable treatment option for trigeminal neuralgia patients, especially for patients who have not had a previous invasive treatment.

Repeat radiosurgery for idiopathic trigeminal neuralgia

PURPOSE

Although frequently performed, the efficacy and safety of repeat trigeminal neuralgia radiosurgery is not well described.

METHODS AND MATERIALS

Between August 1997 and December 2002, 19 patients (9 men, 10 women) underwent repeat trigeminal neuralgia radiosurgery. The median interval between procedures was 16 months. The median dose (based on an output factor of 0.87 for the 4-mm collimator) for repeat radiosurgery was 76.1 Gy; the median additive dose was 163.1 Gy. Outcomes were defined as excellent (no pain, no medications), good (no pain, reduced medications), fair (>50% pain reduction), and poor. Median follow-up was 24 months.

RESULTS

Outcomes after repeat radiosurgery were excellent (n = 14, 74%), good (n = 1, 5%), fair (n = 3, 16%), and poor (n = 1, 5%). Two patients had recurrent pain at 7 and 22 months; 71% and 61% of patients had an excellent outcome at 1- and 2-years after radiosurgery, respectively. Eleven patients (58%) described facial parathesias (n = 3), numbness (n = 5) or dyesthesias (n = 3). Two patients (11%) developed corneal numbness. Nine of 11 patients (82%) with new trigeminal deficits had excellent outcomes at last follow-up compared with 3 of 8 patients (38%) with unchanged facial sensation (p = 0.07).

CONCLUSIONS

Repeat trigeminal neuralgia radiosurgery at the dosage described has better facial pain outcomes than primary radiosurgery. However, because the procedure is nonselective and the rate of bothersome numbness was relatively high (16%), dose reduction is recommended to reduce the morbidity of repeat trigeminal neuralgia radiosurgery.