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

Long-Term Results of Gamma Knife Radiosurgery for Trigeminal Neuralgia

OBJECTIVE

Although the short- to medium-term efficacy of Gamma Knife therapy for drug-resistant essential trigeminal neuralgia has been reported, long-term evaluations are limited. We evaluated patient data obtained at least 10 years post-treatment and examined the significance of this treatment using new end points.

METHODS

Among 249 consecutive patients with essential trigeminal neuralgia who were treated with Gamma Knife radiosurgery (retrogasserian target/4-mm single isocenter/90 Gy at 100%) at our institution between January 2003 and October 2011, 103 patients who were followed up for at least 10 years (mean, 174 [120-219] months) after treatment and whose data were amenable to accurate evaluation, were included in this retrospective study. Herein, we used the Barrow Neurological Institute (BNI) pain intensity scale as a clinical evaluation method for pain and the BNI numbness scale to evaluate complications (namely facial dysesthesia).

RESULTS

The initial and final follow-up pain attack cessation (BNI pain intensity score I-IIIa) rate was 82.5% (85 of 103) and 58.2% (60 of 103), respectively. Furthermore, sensory impairment (BNI numbness score ≥ II) at the last follow-up was observed in 24.3% (25 of 103) of the cases, while very bothersome status (BNI numbness score IV) was observed in 2.9% of the cases.

CONCLUSIONS

Gamma Knife radiosurgery for essential trigeminal neuralgia showed good therapeutic effects during long-term follow-up. Serious complications of significant concern in the short- to mid-term follow-up, resolved spontaneously. Therefore, the indications for treatment should be expanded to include patients who strongly desire Gamma Knife therapy.

Trigeminal neuralgia and other cranial pain syndromes

Spontaneous Trigeminal Neuralgia is a painful condition of the face which may require interventional treatment if medicines fail to control the pain. These include microvascular decompression (MVD) and GKNS. The former is moderately more effective but GKNS has become accepted both as an alternative to MVD or as an adjunct. Like all treatments of the condition, it is successful in a majority of patients but by no means all. Repeat treatments are possible. When Trigeminal Neuralgia is secondary to other conditions the response to GKNS is different. With AVMs, Dural Arteriovenous Fistulae and Epidermoids, the dose to treat the visible lesion usually cures the neuralgia. With meningiomas it is necessary to treat the neuralgia as a separate entity with a neuralgia dose focused on the nerve. GKNS does not improve the rare neuralgia associated with Vestibular Schwannomas. It works with Multiple Sclerosis but not as well as with the spontaneous illness. There is some evidence that GKNS can be useful with the rare Glossopharyngeal and Sphenopalatine Neuralgias.

Factors affecting long-lasting pain relief after Gamma Knife radiosurgery for trigeminal neuralgia: a single institutional analysis and literature review

Gamma Knife radiosurgery (GKRS) is a well-established safe and effective treatment for trigeminal neuralgia (TN) with high initial success rate (80-90%). Why the pain relief is progressively decreased with time is a matter of considerable debate. To investigate factors related to long-lasting pain relief, the authors conducted a retrospective analysis focusing on anatomical and radiosurgical related parameters, chosen according to literature review. One hundred and twelve patients with classical trigeminal neuralgia and follow-up longer than 12 months were selected from our institutional consecutive series of patients treated by GKRS. Patients were followed for a mean period of 61.5 ± 3.5 months (range, 12-126 months) to evaluate, as endpoints, long-term pain relief and hypoesthesia onset. The median maximum radiation dose was 80 Gy (range 70-90 Gy). Factors related to poor long-term pain relief were prescription dose < 80 Gy (p = 0.038), calibration dose rate < 2.5 Gy/min (p = 0.018), and distance between isocenter and trigeminal nerve emergence > 8 mm (p < 0.001). When analyzing patients who received 80 Gy as maximum dose without any sector blocking, we notice that ID₅₀ < 2.7 mJ was predictive for longer period of pain control (p = 0.043). It was experienced also among patients in which a small volume of the nerve (< 35%) received more than 80% of the maximal dose, compared to those in which a larger volume of the nerve was irradiated with maximal dose (p 0.034). This last result was significant if the shot was 8 mm or less from the pons. Several single-patient anatomical and radiosurgical parameters should be considered to improve GKRS effectiveness.

Optimizing Radiosurgery for Trigeminal Neuralgia: Impact of Radiation Dose and Anatomic Target on Patient Outcomes

OBJECTIVE

Radiosurgery is an increasingly popular treatment for trigeminal neuralgia (TN); however, several treatment variables require further study. This meta-analysis was conducted to clarify ambiguity in the literature and optimize treatment parameters.

METHODS

A random-effects proportions meta-analysis using subgroup analysis and meta-regression investigated the association of prescription dose and anatomic target on outcomes in patients with typical TN. The PRISMA guidelines were used. Radiation doses used ranged from 70 to 90 Gy and the anatomic targets were either the root entry zone or a more distal nerve location. Outcome measures were pain at last follow-up and the development of bothersome numbness.

RESULTS

Increasing radiation prescription dose was associated with improved outcomes across all analyzed doses (P < 0.001). Patients treated at a distal trigeminal nerve target had better pain control compared with a root entry zone target (P < 0.001). Despite a higher median dose, a distal target was independently associated with improved pain control. There were similar rates of bothersome numbness across radiation doses and both treatment targets.

CONCLUSIONS

Higher radiation dose was associated with superior pain control without increasing bothersome numbness. Independent of dose, the distal target was also associated with improved pain control. Bothersome numbness was not related to dose or target.

Gamma Knife Radiosurgery for Trigeminal Neuralgia: Role of Trigeminal Length and Pontotrigeminal Angle on Target Definition and on Clinical Effects

OBJECTIVE

Gamma Knife radiosurgery (GKRS) is a well-defined treatment for trigeminal neuralgia. The aim of this study was to determine how the GKRS planning might change on the basis of the patient's own anatomy and how to best choose the target location.

METHODS

Trigeminal cisternal length, pontotrigeminal angle, and distance between middle of the shot and emergence were evaluated in 112 consecutive GKRS plans for trigeminal neuralgia. Correlations with pain outcomes and facial hypoesthesia were analyzed.

RESULTS

The mean angle was 29° ± 4.4° and 37° ± 0.9°, respectively, in patients developing and not developing severe hypoesthesia (P = 0.045), despite no significant difference on brainstem dose (11.9 ± 0.8 and 10.5 ± 0.3 Gy; P = 0.22). The length of the nerve was not relevant on clinical outcomes but the shot-emergence distance (mean 8.1 ± 0.2 mm) depended on both trigeminal length and angle (P = 0.01). At constant prescription dose, 6-month cumulative rates of pain relief and control without therapy were 52.9% when the shot-emergence distance was ≤8 mm, whereas 25% when this distance was >8 mm (P = 0.017). The maintenance of good pain control was more long lasting in the first group (49.5 ± 6.6 vs. 25.4 ± 5 months; P = 0.006) with a 5-year cumulative rate of 70% and 26%, respectively (P < 0.001).

CONCLUSIONS

The pontotrigeminal angle and the shot-emergence distance should be considered during GKRS planning: the first as a potential risk factor for hypoesthesia, and the second should not exceed 8 mm.

Trigeminal Nerve Atrophy Predicts Pain Recurrence After Gamma Knife Stereotactic Radiosurgery for Classical Trigeminal Neuralgia

BACKGROUND

Trigeminal nerve atrophy and neurovascular compression (NVC) are frequently observed in classical trigeminal neuralgia (CTN).

OBJECTIVE

To determine whether nerve characteristics contribute to Gamma Knife (Elekta AB, Stockholm, Sweden) surgery (GKS) outcomes in unilateral CTN without previous surgery.

METHODS

From 2006 to 2012, 67 patients with unilateral CTN without previous surgery received GKS with a maximal dose of 90 Gy delivered to the trigeminal nerve juxta brainstem. Two evaluators, blinded to the side of pain, analyzed the magnetic resonance images before GKS to obtain the parameters, including nerve cross-sectional area (CSA), vessel type of NVC, and site of NVC along the nerve. Correlations of the parameters with pain relief (Barrow Neurological Institute [BNI] grades I-IIIb) and recurrence (BNI grades VI-V) were made by using Cox regression and Kaplan-Meier analyses.

RESULTS

The median CSA of the symptomatic nerves was significantly smaller than that of the asymptomatic nerves (4.95 vs 5.9 mm2, P < .001). After adjustment for age and sex, larger nerve CSA was associated with lower initial pain relief (hazard ratio 0.81, P = .03) and lower pain recurrence after initial response (hazard ratio 0.58, P = .02). Patients with nerve atrophy (CSA of ≤ 4.4 mm2 after receiver operating characteristic curve analysis) had a lower 5-yr probability of maintaining pain relief after initial response than those without nerve atrophy (65% vs 86%, P = .04).

CONCLUSION

Trigeminal nerve atrophy may predict pain recurrence in patients with initial post-GKS relief of CTN. Arterial and proximal NVC are not predictive of GKS outcomes. Future studies are required to determine optimal treatments for long-term pain relief in patients with CTN and trigeminal nerve atrophy.

Treatment Outcomes in Trigeminal Neuralgia-A Systematic Review of Domains, Dimensions and Measures

BACKGROUND

Trigeminal neuralgia (TN) is a painful disorder characterized by sudden electric shock-like pain. It is a rare condition for which multiple treatments are available, including medical and surgical. The best treatment option is yet to be defined, and this is related to the lack of definition in the treatment outcomes and outcome measures. The aim of this systematic review was to summarize all the outcomes and outcomes measures that have been published to date and highlight variability in their use.

METHODS

We have conducted a literature search using a wide range of databases (1946-2019 for medical and 2008-2019 for surgical treatment), for all intervention studies in TN. Four hundred and sixty-seven studies were selected for data extraction on TN classification, data collection method, intervention, and treatment outcomes mapped to the Initiative on Methods, Measurement, and Pain Assessment in Clinical Trials (IMMPACT guidelines).

RESULTS

Most studies collected data on pain (n = 459) and side effects (n = 386) domains; however, very few collected data on the impact of treatment on physical (n = 46) and emotional functioning (n = 17) and on patient satisfaction (n = 35). There was high variability on outcome measures used for pain relief (n = 10), pain intensity (n = 9), and frequency of pain episodes (n = 3).

CONCLUSIONS

A clear definition of what are the important outcomes for patients with TN is essential. The choice of standardized outcome measures allowing for consistent reporting in TN treatment will allow for comparison of studies and facilitate treatment choice for patients and clinicians thus, improving health outcomes and reducing health care cost.

Stereotactic radiosurgery for WHO grade I posterior fossa meningiomas: long-term outcomes with volumetric evaluation

OBJECTIVEResearch over the past 2 decades has been characterizing the role of stereotactic radiosurgery (SRS) in the treatment of benign intracranial tumors, including meningiomas. However, few studies have examined the long-term outcomes of SRS treatment for posterior fossa meningiomas (PFMs). Furthermore, previous studies have typically used single diameter measurements when reporting outcomes, which can yield misleading results. The authors describe the use of SRS in the treatment of benign WHO grade I PFMs and correlate volumetric analysis with long-term outcomes.METHODSThis study is a retrospective analysis of a prospectively maintained IRB-approved database. Inclusion criteria were a diagnosis of WHO grade I PFM with subsequent treatment via single-session SRS and a minimum of 3 follow-up MRI studies available. Volumetric analysis was performed on the radiosurgical scan and each subsequently available follow-up scan by using slice-by-slice area calculations of the meningioma and numerical integration with the trapezoid rule.RESULTSThe final cohort consisted of 120 patients, 76.6% (92) of whom were female, with a median age of 61 years (12-88 years). Stereotactic radiosurgery was the primary treatment for 65% (78) of the patients, whereas 28.3% (34) had 1 resection before SRS treatment and 6.7% (8) had 2 or more resections before SRS. One patient had prior radiotherapy. Tumor characteristics included a median volume of 4.0 cm3 (0.4-40.9 cm3) at treatment with a median margin dose of 15 Gy (8-20 Gy). The median clinical and imaging follow-ups were 79.5 (15-224) and 72 (6-213) months, respectively. For patients treated with a margin dose ≥ 16 Gy, actuarial progression-free survival rates during the period 2-10 years post-SRS were 100%. In patients treated with a margin dose of 13-15 Gy, the actuarial progression-free survival rates at 2, 4, 6, 8, and 10 years were 97.5%, 97.5%, 93.4%, 93.4%, and 93.4%, respectively. Those who were treated with ≤ 12 Gy had actuarial progression-free survival rates of 95.8%, 82.9%, 73.2%, 56.9%, and 56.9% at 2, 4, 6, 8, and 10 years, respectively. The overall tumor control rate was 89.2% (107 patients). Post-SRS improvement in neurological symptoms occurred in 23.3% (28 patients), whereas symptoms were stable in 70.8% (85 patients) and worsened in 5.8% (7 patients). Volumetric analysis demonstrated that a change in tumor volume at 3 years after SRS reliably predicted a volumetric change and tumor control at 5 years (R2 = 0.756) with a p < 0.001 and at 10 years (R2 = 0.421) with a p = 0.001. The authors also noted that the 1- to 5-year tumor response is predictive of the 5- to 10-year tumor response (R2 = 0.636, p < 0.001).CONCLUSIONSStereotactic radiosurgery, as an either upfront or adjuvant treatment, is a durable therapeutic option for WHO grade I PFMs, with high tumor control and a low incidence of post-SRS neurological deficits compared with those obtained using alternate treatment modalities. Lesion volumetric response at the short-term follow-up of 3 years is predictive of the long-term response at 5 and 10 years.

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.

Gamma knife radiosurgery on the trigeminal ganglion for idiopathic trigeminal neuralgia: Results and review of the literature

Background

In the present study, we evaluate the results of gamma knife surgery (GKS) for the treatment of trigeminal neuralgia (TN) using the trigeminal ganglion (TG') and the adjacent fibers of trigeminal nerve as a target.

Methods

From February 2013 to July 2017, we treated 30 cases of TN with GKS. In this group, all patients had an idiopathic typical TN. The radiosurgical target was conformed through two isocenters, 8 and 4 mm at the cavum de Meckel. The maximum dose was 86 Gy using the isodose line of 50%. The median age of the patients was 58.5 (range 28-94) years old, and the median time from diagnosis to GKS was 94 months (range 13-480 months). The median follow-up was 28.5 (range 12-49) months. Clinical outcomes were analyzed. Univariate and multivariate analyses were performed to evaluate factors that correlated with a favorable, pain-free outcome.

Results

The mean time to relief of pain was 7 (range 1-40) days. The percentage of patients with significant pain relief was 93.3%. Relapse in pain was noted in four patients at 3, 16, 19, and 36 months. Nine patients were treated in acute status. Fourteen patients had intense pain between 1 and 7 days before the procedure. Among those with the recurrence of their symptoms, one patient had a microvascular decompression. Multivariate regression adjusted for age and sex suggests that, by 40 months, 70% of the patients treated with radiosurgery will remain pain free. At the last follow-up, GKS resulted in pain relief in 86.6% of patients. Our analysis suggests that, using this technique, we can expect that approximately 70% of patients with TN will have some degree of pain improvement at 3 years' post radiosurgery.

Conclusions

GKS on TG appears to be a reasonable treatment option with short latency period, minor collateral effects, and high percentage of pain control. The mechanism of action of radiosurgery could be related to the inactivation of the satellite glial cells in the TG.

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.

Time course of pain response and toxicity after whole-nerve-encompassing LINAC-based stereotactic radiosurgery for trigeminal neuralgia-a prospective observational study

PURPOSE

To prospectively evaluate the time course of pain response and toxicity after linear accelerator-based whole-nerve-encompassing radiosurgery (LINAC-SRS) using a uniform treatment schedule for dosing and target volume definition in patients with refractory trigeminal neuralgia.

METHODS

From December 2012 to December 2016, 21 patients were treated using a standardized protocol. Patients received LINAC-SRS with 70 Gy to the cisternal portion while aiming for the 90% isodose to fully envelope the nerve in one cross-sectional plane. Data on pain, analgesics, and toxicity were gathered prospectively. Four time intervals (1-6, 6-12, 12-18, and 18-24 months) were defined and compared to baseline and each other.

RESULTS

The median follow-up from radiotherapy was 16 months. Freedom from pain was achieved at least once in 90.5, 81.0, and 85.7% of patients for everyday pain, rest pain, and pain peaks, respectively. At 1-6 months, pain was significantly reduced in everyday routine (mean VAS, 2.0/10 vs. 5.8/10; P = 0.004), at rest (1.5/10 vs. 4.0/10; P = 0.002), and for pain peaks (2.9/10 vs. 10/10; P < 0.001), as was the number of analgesics (mean 1.5 vs. 2.9; P < 0.001). No significant increase in pain or analgesics was observed for subsequent time intervals. At last follow-up, reduction in pain compared to baseline for everyday routine (2.1/10 vs. 5.8/10; P = 0.010) and for pain peaks (3.3/10 vs. 10/10; P < 0.001) was significant, whereas it was not for rest pain (1.8/10 vs. 3.9/10; P = 0.073). Most toxicities were related to trigeminal nerve impairment, with 42.9% reporting new-onset hypoesthesia at last follow-up.

CONCLUSION

This study provides prospective data after whole nerve encompassing LINAC-SRS for trigeminal neuralgia. No significant pain relapse was observed.

Evaluation of CyberKnife Radiosurgery for Recurrent Trigeminal Neuralgia

Stereotactic radiosurgery (SRS) has evolved as an accepted treatment for medication resistant trigeminal neuralgia. Initial results are very good but follow-up over three to five years shows a gradual return of pain in up to 50% of treated patients, often requiring further treatment. The results with repeat SRS using the isocentric Gamma Knife (GK) (Elekta, Stockholm, Sweden), especially in patients having initially good results, are very similar to the outcomes after the initial treatment although there is an increased risk of residual facial numbness secondary to the additional radiation dose to the trigeminal nerve. However, after 2000, non-isocentric SRS systems began to be used for treating trigeminal neuralgia including the CyberKnife (CK) (Accuray, Sunnyvale, California) as well as various linear accelerator (LINAC) based systems. This report specifically examines a series of recurrent trigeminal cases treated by the same group of physicians with the CK system. Similar doses and locations on the trigeminal nerve and/or the root entry zone were used for both initial and repeat SRS treatment regardless of system used. Although there are numerous series reporting the use of GK for recurrent treatment for recurrent trigeminal neuralgia, there are no series reviewing the results and long-term effectiveness using CK for repeat SRS for recurrent trigeminal pain. We reviewed 23 cases that had initial treatment for trigeminal neuralgia either surgically or with SRS with either the GK or CK and then a later second procedure only with CK. The follow-up after the second CK SRS ranged from three to 13 years found that the results are very similar to the multiple reports in the literature describing second or third SRS treatments with the GK. Results of repeat radiosurgery treatment of recurrent trigeminal neuralgia appear to be independent of the system used and are primarily based on proper target and dose to the trigeminal nerve.

Glossopharyngeal neuralgia treated by Gamma Knife radiosurgery: safety and efficacy through long-term follow-up

OBJECTIVE

Glossopharyngeal neuralgia (GPN) is a rare and disabling condition. Just as for trigeminal neuralgia, Gamma Knife radiosurgery (GKRS) is increasingly proposed as a therapeutic option for GPN. The purpose of this study was to assess long-term safety and efficacy of GKRS for this indication.

METHODS

From 2007 to 2015, 9 patients (4 male and 5 female) underwent a total of 10 GKRS procedures. All of the patients presented with GPN that was refractory to all medical treatment, and all had a long history of pain. One patient had previously undergone surgical microvascular decompression. In 5 cases, a neurovascular conflict had been identified on MRI. For the GKRS procedure, the glossopharyngeal nerve was localized on MRI and CT under stereotactic conditions. The target was located at the glossopharyngeal meatus of the jugular foramen. The dose administered to the nerve was 80 Gy in 3 procedures and 90 Gy in the others. Follow-up was planned for 3, 6, and 12 months after the procedure and annually thereafter.

RESULTS

Eight patients experienced an improvement in their pain. The median length of time from GKRS to symptom improvement in this group was 7 weeks (range 2–12 months). At the first follow-up, 6 patients were pain-free (pain intensity scores of I–III, based on an adaptation of the Barrow Neurological Institute scoring system for trigeminal neuralgia), including 4 patients who were also medication-free (I). One patient had partial improvement (IV) and 2 patients had no change. The mean duration of follow-up was 46 months (range 10–90 months). At the last follow-up 6 patients remained pain-free (pain scores of I–III), including 4 patients who were pain free with no medication (I). No side effect was observed.

CONCLUSIONS

Because of its safety and efficacy, GKRS appears to be a useful tool for treatment of GPN, including first-line treatment.

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.

The relationship of dose to nerve volume in predicting pain recurrence after stereotactic radiosurgery in trigeminal neuralgia

OBJECTIVE Approximately 75%-92% of patients with trigeminal neuralgia (TN) achieve pain relief after Gamma Knife surgery (GKS), although a proportion of these patients will experience recurrence of their pain. To evaluate the reasons for durability or recurrence, this study determined the impact of trigeminal nerve length and volume, the nerve dose-volume relationship, and the presence of neurovascular compression (NVC) on pain outcomes after GKS for TN. METHODS Fifty-eight patients with 60 symptomatic nerves underwent GKS for TN between 2013 and 2015, including 15 symptomatic nerves secondary to multiple sclerosis (MS). High-resolution MRI was acquired the day of GKS. The median maximum dose was 80 Gy for initial GKS and 65 Gy for repeat GKS. NVC, length and volume of the trigeminal nerve within the subarachnoid space of the posterior fossa, and the ratio of dose to nerve volume were assessed as predictors of recurrence. RESULTS Follow-up was available on 55 patients. Forty-nine patients (89.1%) reported pain relief (Barrow Neurological Institute [BNI] Grades I-IIIb) after GKS at a median duration of 1.9 months. The probability of maintaining pain relief (BNI Grades I-IIIb) without requiring resumption or an increase in medication was 93% at 1 year and 84% at 2 years for patients without MS, and 68% at 1 year and 51% at 2 years for all patients. The nerve length, nerve volume, target distance from the brainstem, and presence of NVC were not predictive of pain recurrence. Patients with a smaller volume of nerve (< 35% of the total nerve volume) that received a high dose (≥ 80% isodose) were less likely to experience recurrence of their TN pain after 1 year (mean time to recurrence: < 35%, 32.2 ± 4.0 months; > 35%, 17.9 ± 2.8 months, log-rank test, χ² = 4.3, p = 0.039). CONCLUSIONS The ratio of dose to nerve volume may predict recurrence of TN pain after GKS. Prospective studies are needed to determine the optimal dose to nerve volume ratio and whether this will result in longer pain-free outcomes.

Gamma Knife radiosurgery for posterior fossa meningiomas: a multicenter study

OBJECT

Posterior fossa meningiomas represent a common yet challenging clinical entity. They are often associated with neurovascular structures and adjacent to the brainstem. Resection can be undertaken for posterior fossa meningiomas, but residual or recurrent tumor is frequent. Stereotactic radiosurgery (SRS) has been used to treat meningiomas, and this study evaluates the outcome of this approach for those located in the posterior fossa.

METHODS

At 7 medical centers participating in the North American Gamma Knife Consortium, 675 patients undergoing SRS for a posterior fossa meningioma were identified, and clinical and radiological data were obtained for these cases. Females outnumbered males at a ratio of 3.8 to 1, and the median patient age was 57.6 years (range 12-89 years). Prior resection was performed in 43.3% of the patient sample. The mean tumor volume was 6.5 cm(3), and a median margin dose of 13.6 Gy (range 8-40 Gy) was delivered to the tumor.

RESULTS

At a mean follow-up of 60.1 months, tumor control was achieved in 91.2% of cases. Actuarial tumor control was 95%, 92%, and 81% at 3, 5, and 10 years after radiosurgery. Factors predictive of tumor progression included age greater than 65 years (hazard ratio [HR] 2.36, 95% CI 1.30-4.29, p = 0.005), prior history of radiotherapy (HR 5.19, 95% CI 1.69-15.94, p = 0.004), and increasing tumor volume (HR 1.05, 95% CI 1.01-1.08, p = 0.005). Clinical stability or improvement was achieved in 92.3% of patients. Increasing tumor volume (odds ratio [OR] 1.06, 95% CI 1.01-1.10, p = 0.009) and clival, petrous, or cerebellopontine angle location as compared with petroclival, tentorial, and foramen magnum location (OR 1.95, 95% CI 1.05-3.65, p = 0.036) were predictive of neurological decline after radiosurgery. After radiosurgery, ventriculoperitoneal shunt placement, resection, and radiation therapy were performed in 1.6%, 3.6%, and 1.5%, respectively.

CONCLUSIONS

Stereotactic radiosurgery affords a high rate of tumor control and neurological preservation for patients with posterior fossa meningiomas. Those with a smaller tumor volume and no prior radiation therapy were more likely to have a favorable response after radiosurgery. Rarely, additional procedures may be required for hydrocephalus or tumor progression.

Gamma knife radiosurgery to the trigeminal ganglion for treatment of trigeminal neuralgia secondary to vertebrobasilar ectasia

Background:

We report the result obtained using Gamma knife stereotactic radiosurgery on the trigeminal ganglion (TG) in a patient with trigeminal neuralgia (TN) secondary to vertebrobasilar ectasia (VBE).

Case Description:

Retrospective review of medical records corresponding to one patient with VBE-related trigeminal pain treated with radiosurgery. Because of the impossibility of visualization of the entry zone or the path of trigeminal nerve through the pontine cistern, we proceeded with stereotactic radiosurgery directed to the TG. The maximum radiation dose was 86 Gy with a 8-mm and a 4-mm collimator. The follow-up period was 24 months. The pain disappeared in 15 days, passing from Barrow Neurological Institute (BNI) grade V to BNI grade IIIa in 4 months and then to grade I. The patient did not experience noticeable subjective facial numbness.

Conclusions:

This experience showed that Gamma knife radiosurgery was effective in the management of VBE-related trigeminal pain, using the TG as radiosurgical target.

A review of percutaneous treatments for trigeminal neuralgia

BACKGROUND

Common treatments for trigeminal neuralgia include percutaneous techniques, microvascular decompression, and Gamma Knife radiosurgery. Although microvascular decompression is considered the gold standard for treatment, percutaneous techniques remain an effective option for select patients.

OBJECTIVE

To review the historical development, advantages, and limitations of the most common percutaneous procedures for trigeminal neuralgia: balloon compression (BC), glycerol rhizotomy (GR), and radiofrequency thermocoagulation (RF).

METHODS

Publications reporting clinical outcomes after BC, GR, and RF were reviewed and included. Operative technique was based on the experience of the primary surgeon and senior author.

RESULTS

All 3 percutaneous techniques (BC, GR, and RF) provide effective pain relief but differ in method and specificity of nerve injury. BC selectively injures larger pain fibers while sparing small fibers and does not require an awake, cooperative patient. Pain control rates up to 91% at 6 months and 66% at 3 years have been reported. RF allows somatotopic nerve mapping and selective division lesioning and provides pain relief in up to 97% of patients initially and 58% at 5 years. Multiple treatments improve outcomes but carry significant morbidity risk. GR offers similar pain-free outcomes of 90% at 6 months and 54% at 3 years but with higher complication rates (25% vs. 16%) compared with BC. Advantages of percutaneous techniques include shorter procedure duration, minimal anesthesia risk, and in the case of GR and RF, immediate patient feedback.

CONCLUSION

Percutaneous treatments for trigeminal neuralgia remain safe, simple, and effective for achieving good pain control while minimizing procedural risk.

Predictive nomogram for the durability of pain relief from gamma knife radiation surgery in the treatment of trigeminal neuralgia

PURPOSE

To determine factors associated with the durability of stereotactic radiation surgery (SRS) for treatment of trigeminal neuralgia (TN).

METHODS AND MATERIALS

Between 1999 and 2008, 446 of 777 patients with TN underwent SRS and had evaluable follow-up in our electronic medical records and phone interview records. The median follow-up was 21.2 months. The Barrow Neurologic Institute (BNI) pain scale was used to determine pre- and post-SRS pain. Dose-volume anatomical measurements, Burchiel pain subtype, pain quality, prior procedures, and medication usage were included in this retrospective cohort to identify factors impacting the time to BNI 4-5 pain relapse by using Cox proportional hazard regression. An internet-based nomogram was constructed based on predictive factors of durable relief pre- and posttreatment at 6-month intervals.

RESULTS

Rates of freedom from BNI 4-5 failure at 1, 3, and 5 years were 84.5%, 70.4%, and 46.9%, respectively. Pain relief was BNI 1-3 at 1, 3, and 5 years in 86.1%, 74.3%, and 51.3% of type 1 patients; 79.3%, 46.2%, and 29.3% of type 2 patients; and 62.7%, 50.2%, and 25% of atypical facial pain patients. BNI type 1 pain score was achieved at 1, 3, and 5 years in 62.9%, 43.5%, and 22.0% of patients with type 1 pain and in 47.5%, 25.2%, and 9.2% of type 2 patients, respectively. Only 13% of patients with atypical facial pain achieved BNI 1 response; 42% of patients developed post-Gamma Knife radiation surgery (GKRS) trigeminal dysfunction. Multivariate analysis revealed that post-SRS numbness (hazard ratio [HR], 0.47; P<.0001), type 1 (vs type 2) TN (HR, 0.6; P=.02), and improved post-SRS BNI score at 6 months (HR, 0.009; P<.0001) were predictive of a durable pain response.

CONCLUSIONS

The durability of SRS for TN depends on the presenting Burchiel pain type, the post-SRS BNI score, and the presence of post-SRS facial numbness. The durability of pain relief can be estimated pre- and posttreatment by using our nomogram for situations when the potential of relapse may guide the decision for initial intervention.

Clair W, Bush HM. Long-term outcome of high-dose Gamma Knife surgery in treatment of trigeminal neuralgia

Object

Despite the widespread use of Gamma Knife surgery (GKS) for trigeminal neuralgia (TN), controversy remains regarding the optimal treatment dose and target site. Among the published studies, only a few have focused on long-term outcomes (beyond 2 years) using 90 Gy, which is in the higher range of treatment doses used (70–90 Gy).

Methods

The authors followed up on 315 consecutive patients treated with the Leksell Gamma Knife unit using a 4-mm isocenter without blocks. The isocenter was placed on the trigeminal nerve with the 20% isodose line tangential to the pontine surface (18 Gy). At follow-up, 33 patients were deceased; 282 were mailed an extensive questionnaire regarding their outcomes, but 32 could not be reached. The authors report their analysis of the remaining 250 cases. The patients' mean age at the time of survey response and the mean duration of follow-up were 70.8 ± 13.1 years and 68.9 ± 41.8 months, respectively.

Results

One hundred eighty-five patients (85.6%) had decreased pain intensity after GKS. Modified Marseille Scale (MMS) pain classifications after GKS at follow-up were: Class I (pain free without medication[s]) in 104 (43.7%), Class II (pain free with medication[s]) in 66 (27.7%), Class III (> 90% decrease in pain intensity) in 23 (9.7%), Class IV (50%–90% decrease in pain intensity) in 20 (8.4%), Class V (< 50% decrease in pain intensity) in 11 (4.6%), and Class VI (pain becoming worse) in 14 (5.9%). Therefore, 170 patients (71.4%) were pain free (Classes I and II) and 213 (89.5%) had at least 50% pain relief. All patients had pain that was refractory to medical management prior to GKS, but only 111 (44.4%) were being treated with medication at follow-up (p < 0.0001). Eighty patients (32.9%) developed numbness after GKS, and 74.5% of patients with numbness had complete pain relief. Quality of life and patient satisfaction on a 10-point scale were reported at mean values (± SD) of 7.8 ± 3.1 and 7.7 ± 3.4, respectively. Most of the patients (87.7%) would recommend GKS to another patient. Patients with prior surgical treatments had increased latency to pain relief and were more likely to continue medicines (p < 0.05). Moreover, presence of altered facial sensations prior to radiosurgery was associated with higher pain intensity, longer pain episodes, more frequent pain attacks, worse MMS pain classification, and more medication use after GKS (p < 0.05). Conversely, increase in numbness intensity after GKS was associated with a decrease in pain intensity and pain length (p < 0.05).

Conclusions

Gamma Knife surgery using a maximum dose of 90 Gy to the trigeminal nerve provides satisfactory long-term pain control, reduces the use of medication, and improves quality of life. Physicians must be aware that higher doses may be associated with an increase in bothersome sensory complications. The benefits and risks of higher dose selection must be carefully discussed with patients, since facial numbness, even if bothersome, may be an acceptable trade-off for patients with severe pain.

Stereotactic Radiotherapy for Malignancies Involving the Trigeminal and Facial Nerves

Involvement of a cranial nerve caries a poor prognosis for many malignancies. Recurrent or residual disease in the trigeminal or facial nerve after primary therapy poses a challenge due to the location of the nerve in the skull base, the proximity to the brain, brainstem, cavernous sinus, and optic apparatus and the resulting complex geometry. Surgical resection caries a high risk of morbidity and is often not an option for these patients. Stereotactic radiosurgery and radiotherapy are potential treatment options for patients with cancer involving the trigeminal or facial nerve. These techniques can deliver high doses of radiation to complex volumes while sparing adjacent critical structures. In the current study, seven cases of cancer involving the trigeminal or facial nerve are presented. These patients had unresectable recurrent or residual disease after definitive local therapy. Each patient was treated with stereotactic radiation therapy using a linear accelerator based system. A multidisciplinary approach including neuroradiology and surgical oncology was used to delineate target volumes. Treatment was well tolerated with no acute grade 3 or higher toxicity. One patient who was reirradiated experienced cerebral radionecrosis with mild symptoms. Four of the seven patients treated had no evidence of disease after a median follow up of 12 months (range 2–24 months). A dosimetric analysis was performed to compare intensity modulated fractionated stereotactic radiation therapy (IM-FSRT) to a 3D conformal technique. The dose to 90% (D90) of the brainstem was lower with the IM-FSRT plan by a mean of 13.5 Gy. The D95 to the ipsilateral optic nerve was also reduced with IM-FSRT by 12.2 Gy and the D95 for the optic chiasm was lower with FSRT by 16.3 Gy. Treatment of malignancies involving a cranial nerve requires a multidisciplinary approach. Use of an IM-FSRT technique with a micro-multileaf collimator resulted in a lower dose to the brainstem, optic nerves and chiasm for each case examined.

Tractography delineates microstructural changes in the trigeminal nerve after focal radiosurgery for trigeminal neuralgia

Purpose

Focal radiosurgery is a common treatment modality for trigeminal neuralgia (TN), a neuropathic facial pain condition. Assessment of treatment effectiveness is primarily clinical, given the paucity of investigational tools to assess trigeminal nerve changes. Since diffusion tensor imaging (DTI) provides information on white matter microstructure, we explored the feasibility of trigeminal nerve tractography and assessment of DTI parameters to study microstructural changes after treatment. We hypothesized that trigeminal tractography provides more information than 2D-MR imaging, allowing detection of unique, focal changes in the target area after radiosurgery. Changes in specific diffusivities may provide insight into the mechanism of action of radiosurgery on the trigeminal nerve.

Methods and Materials

Five TN patients (4 females, 1 male, average age 67 years) treated with Gamma Knife radiosurgery, 80 Gy/100% isodose line underwent 3Tesla MR trigeminal nerve tractography before and sequentially up to fourteen months after treatment. Fractional anisotropy (FA), radial (RD) and axial (AD) diffusivities were calculated for the radiosurgical target area defined as the region-of-interest. Areas outside target and the contralateral nerve served as controls.

Results

Trigeminal tractography accurately detected the radiosurgical target. Radiosurgery resulted in 47% drop in FA values at the target with no significant change in FA outside the target, demonstrating highly focal changes after treatment. RD but not AD changed markedly, suggesting that radiosurgery primarily affects myelin. Tractography was more sensitive than conventional gadolinium-enhanced post-treatment MR, since FA changes were detected regardless of trigeminal nerve enhancement. In subjects with long term follow-up, recovery of FA/RD correlated with pain recurrence.

Conclusions

DTI parameters accurately detect the effects of focal radiosurgery on the trigeminal nerve, serving as an in vivo imaging tool to study TN. This study is a proof of principle for further assessment of DTI parameters to understand the pathophysiology of TN and treatment effects.

Repeat gamma knife radiosurgery for trigeminal neuralgia

PURPOSE

Repeat gamma knife stereotactic radiosurgery (GKRS) for recurrent or persistent trigeminal neuralgia induces an additional response but at the expense of an increased incidence of facial numbness. The present series summarized the results of a repeat treatment series at Wake Forest University Baptist Medical Center, including a multivariate analysis of the data to identify the prognostic factors for treatment success and toxicity.

METHODS AND MATERIALS

Between January 1999 and December 2007, 37 patients underwent a second GKRS application because of treatment failure after a first GKRS treatment. The mean initial dose in the series was 87.3 Gy (range, 80-90). The mean retreatment dose was 84.4 Gy (range, 60-90). The dosimetric variables recorded included the dorsal root entry zone dose, pons surface dose, and dose to the distal nerve.

RESULTS

Of the 37 patients, 81% achieved a >50% pain relief response to repeat GKRS, and 57% experienced some form of trigeminal dysfunction after repeat GKRS. Two patients (5%) experienced clinically significant toxicity: one with bothersome numbness and one with corneal dryness requiring tarsorraphy. A dorsal root entry zone dose at repeat treatment of >26.6 Gy predicted for treatment success (61% vs. 32%, p = .0716). A cumulative dorsal root entry zone dose of >84.3 Gy (72% vs. 44%, p = .091) and a cumulative pons surface dose of >108.5 Gy (78% vs. 44%, p = .018) predicted for post-GKRS numbness. The presence of any post-GKRS numbness predicted for a >50% decrease in pain intensity (100% vs. 60%, p = .0015).

CONCLUSION

Repeat GKRS is a viable treatment option for recurrent trigeminal neuralgia, although the patient assumes a greater risk of nerve dysfunction to achieve maximal pain relief.

Clinical outcomes of gamma knife radiosurgery in the treatment of patients with trigeminal neuralgia

Since its introduction by Leksell, Gamma Knife radiosurgery (GKRS) has become increasingly popular as a management approach for patients diagnosed with trigeminal neuralgia (TN). For this reason, we performed a modern review of the literature analyzing the efficacy of GKRS in the treatment of patients who suffer from TN. For patients with medically refractory forms of the condition, GKRS has proven to be an effective initial and repeat treatment option. Cumulative research suggests that patients treated a single time with GKRS exhibit similar levels of facial pain control when compared to patients treated multiple times with GKRS. However, patients treated on multiple occasions with GKRS are more likely to experience facial numbness and other facial sensory changes when compared to patients treated once with GKRS. Although numerous articles have reported MVD to be superior to GKRS in achieving facial pain relief, the findings of these comparison studies are weakened by the vast differences in patient age and comorbidities between the two studied groups and cannot be considered conclusive. Questions remain regarding optimal GKRS dosing and targeting strategies, which warrants further investigation into this controversial matter.

Pharmacological versus microvascular decompression approaches for the treatment of trigeminal neuralgia: clinical outcomes and direct costs

In idiopathic trigeminal neuralgia (TN) the neuroimaging evaluation is usually normal, but in some cases a vascular compression of trigeminal nerve root is present. Although the latter condition may be referred to surgery, drug therapy is usually the first approach to control pain. This study compared the clinical outcome and direct costs of (1) a traditional treatment (carbamazepine [CBZ] in monotherapy [CBZ protocol]), (2) the association of gabapentin (GBP) and analgesic block of trigger-points with ropivacaine (ROP) (GBP+ROP protocol), and (3) a common TN surgery, microvascular decompression of the trigeminal nerve (MVD protocol). Sixty-two TN patients were randomly treated during 4 weeks (CBZ [n = 23] and GBP+ROP [n = 17] protocols) from cases of idiopathic TN, or selected for MVD surgery (n = 22) due to intractable pain. Direct medical cost estimates were determined by the price of drugs in 2008 and the hospital costs. Pain was evaluated using the Numerical Rating Scale (NRS) and number of pain crises; the Hospital Anxiety and Depression Scale, Sickness Impact Profile, and satisfaction with treatment and hospital team were evaluated. Assessments were performed at day 0 and 6 months after the beginning of treatment. All protocols showed a clinical improvement of pain control at month 6. The GBP+ROP protocol was the least expensive treatment, whereas surgery was the most expensive. With time, however, GBP+ROP tended to be the most and MVD the least expensive. No sequelae resulted in any patient after drug therapies, while after MDV surgery several patients showed important side effects. Data reinforce that, (1) TN patients should be carefully evaluated before choosing therapy for pain control, (2) different pharmacological approaches are available to initiate pain control at low costs, and (3) criteria for surgical interventions should be clearly defined due to important side effects, with the initial higher costs being strongly reduced with time.

Predictive Variables for the Successful Treatment of Trigeminal Neuralgia With Gamma Knife Radiosurgery

Background:

Gamma Knife radiosurgery (GKRS) has been reported to be an effective modality to treat trigeminal neuralgia.

Objective:

To determine predictive factors for the successful treatment of trigeminal neuralgia with GKRS.

Methods:

Between 1999 and 2008, 777 GKRS procedures for patients with trigeminal neuralgia were performed at our institution. Evaluable follow-up data were obtained for 448 patients. Median follow-up time was 20.9 months (range, 3–86 months). The mean maximum prescribed dose was 88 Gy (range, 80–97 Gy). Dosimetric variables recorded included dorsal root entry zone dose, pons maximum dose, dose to the petrous dural ridge, and cisternal nerve length.

Results:

By 3 months after GKRS, 86% of patients achieved Barrow Neurologic Institute I to III pain scores, with 43% of patients achieving a Barrow Neurologic Institute I pain score. Twenty-six percent of patients reported posttreatment facial numbness; 28% of patients reported a post-GKRS procedure for relapsed pain, and median time to next procedure was 4.4 years. Multivariate analysis revealed that the development of postsurgical numbness (odds ratio [OR], 2.76; P = .006) was the dominant factor predictive of efficacy. Longer cisternal nerve length (OR, 0.85; P = .005), prior radiofrequency ablation (OR, 0.35; P = .028), and diabetes mellitus (OR, 0.38; P = .013) predicted decreased efficacy. The mean dose delivered to the dorsal root entry zone dose in patients who developed facial numbness (57.6 Gy) was more than the mean dose (47.3 Gy) given to patients who did not develop numbness (P = .02).

Conclusion:

The development of post-GKRS facial numbness is a dominant factor that predicts for efficacy of GKRS. History of diabetes mellitus or previous radio-frequency ablation may portend worsened outcome.

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.

Gamma knife radiosurgery for idiopathic trigeminal neuralgia as primary vs. secondary treatment option

OBJECTIVE

To enable physicians to remain informed of secondary GKR after multiple surgical choices. This study compares gamma knife radiosurgery (GKR) as a first and a second treatment for the management of medically refractory idiopathic trigeminal neuralgia (TN).

METHODS

Between May 1998 and May 2008, a total of 86 patients with idiopathic TN underwent GKR, with 62 patients receiving the treatment as a first therapy (primary GKR group) and 24 patients receiving the treatment as a second procedure (secondary GKR group). The median follow-up time was 76.4 months (range 12-161 months). The mean prescription marginal dose delivered to the involved trigeminal nerve root entry zone was 82.4±6.25Gy for the primary GKR group, and 81.0±4.89Gy for the secondary GKR group. In the secondary group, eleven patients underwent percutaneous radiofrequency rhizotomy (PRFR), seven underwent microvascular decompression (MVD), three underwent percutaneous glycerol rhizotomy and another three underwent GKR as their first treatment. We excluded a typical, multiple sclerosis or secondary trigeminal neuralgia.

RESULTS

No significant differences in radiation dose, time to initial response, recurrence or pain relief were observed between the use of GKR as a primary and a secondary procedure for idiopathic TN. The occurrence of new onset after GKR were the same for the two groups, but overall facial sensory changes was higher in the secondary GKR group.

CONCLUSION

For pain control, GKR can be offered both as a primary and as a secondary procedure, but shows higher overall facial sensory changes in secondary GKR group. The results of our study enable physicians to remain informed of secondary GKR after multiple surgical choices. GKR would be an alternative treatment modality after other surgical treatments including GKR, MVD, PRFR and Glycerol.

Prospective Comparison of Posterior Fossa Exploration and Stereotactic Radiosurgery Dorsal Root Entry Zone Target as Primary Surgery for Patients With Idiopathic Trigeminal Neuralgia

BACKGROUND

Trigeminal neuralgia (TN) is the most common facial pain syndrome, with an incidence of approximately 27 per 100 000 patient-years.

OBJECTIVE

To prospectively compare facial pain outcomes for patients having either a posterior fossa exploration (PFE) or stereotactic radiosurgery (SRS) as their first surgery for idiopathic TN.

METHODS

Prospective cohort study of 140 patients with idiopathic TN who had either PFE (n = 91) or SRS (n = 49) from June 2001 until September 2007. The groups were similar with regard to sex, pain location, and pain duration. Patients who had SRS were older (67.1 vs 58.2 years; P &lt; .001). The median follow-up after surgery was 38 months.

RESULTS

Patients who had PFE more commonly were pain free off medications (84% at 1 year, 77% at 4 years) compared with the SRS patients (66% at 1 year, 56% at 4 years; hazard ratio = 2.5; 95% confidence interval, 1.4–4.6; P = .003). Additional surgery for persistent or recurrent face pain was performed in 14 patients after PFE (15%) compared with 17 patients after SRS (35%; P = .009). Nonbothersome facial numbness occurred more frequently in the SRS group (33% vs 18%; P = .04). No difference was noted in other complications between patients who had PFE (12%) (dysesthetic facial pain, n = 3; cerebrospinal fluid leakage, n = 3; hearing loss, n = 2; wound infection, n = 1; pneumonia, n = 1; deep vein thrombosis, n = 1) and patients who had SRS (8%) (dysesthetic facial pain, n = 4; P = .47).

CONCLUSION

PFE is more effective than SRS as a primary surgical option for patients with idiopathic TN.

Gamma Knife irradiation–induced histopathological changes in the trigeminal nerves of rhesus monkeys

Object

The authors' goal was to observe histopathological changes in the trigeminal nerve after Gamma Knife surgery (GKS) in rhesus monkeys, and to investigate the radiobiological mechanism of GKS for primary trigeminal neuralgia. The nerve length–dosage effect of irradiation is also discussed.

Methods

One of 5 rhesus monkeys randomly served as a control, and the other 4 monkeys were randomly administered a target radiation dose of 60, 70, 80, or 100 Gy (a different dose in each animal). The size of the collimator was 4 mm, and the target point was the trigeminal nerve root. In each experimental monkey, one side was exposed to single-target-point irradiation, and the contralateral side was exposed to double-target-point irradiation. After 6 months, the trigeminal nerve root was examined using light microscopy, transmission electron microscopy, and immunohistochemistry.

Results

At each radiation dose, the damage to the nerve tissue by single-target-point irradiation was identical to that caused by double-target-point irradiation. In the trigeminal nerve tissues of the monkeys irradiated with 60 and 70 Gy, there was limited nerve demyelination and degeneration, fragmentation, or loss of axons. In the trigeminal nerve tissue of the monkey irradiated with 80 Gy, the nerve tissue showed a disordered structure. In the trigeminal nerve tissue of the monkey irradiated with 100 Gy, there was severe derangement in the structure of the nerve tissue, and extensive demyelination, fragmentation, and loss of axons.

Conclusions

The target doses of 60 and 70 Gy have very little impact on the structure of the trigeminal nerve. Irradiation at 80 Gy can cause partial degeneration and loss of axons and demyelination. A 100-Gy dose can cause some necrosis of neurons. Comparing the single-target-point with the double-target-point irradiation, the extent of damage to the nerve tissue is identical, and no difference in the nerve length–dosage effect was found.

Outcomes following single-treatment Gamma Knife surgery for trigeminal neuralgia with a minimum 3-year follow-up

Object

Gamma Knife surgery (GKS) has been shown to be effective in treating trigeminal neuralgia (TN). Existing studies have demonstrated success rates of 69.1–85% with median follow-up intervals of 19–60 months. However, series with uniform long-term follow-up data for all patients have been lacking. In the present study the authors examined outcomes in a series of patients with TN who underwent a single GKS treatment followed by a minimum follow-up of 36 months. They used a clinical scale that simplifies the reporting of outcome data for patients with TN.

Methods

Fifty-three consecutive patients with typical, intractable TN received a median maximum radiation dose of 80 Gy applied with a single 4-mm isocenter to the affected trigeminal nerve. Follow-up data were obtained by clinical examination and questionnaire. Outcome results were categorized into the following classes (in order of decreasing success): Class 1A, complete pain relief without medications; 1B, complete pain relief with either a decrease or no change in medications; 1C, ≥ 50% pain relief without medications; 1D, ≥ 50% pain relief with either a decrease or no change in medications; and Class 2, < 50% pain relief and/or increase in medications. Patients with Class 1A–1D outcome (equivalent to Barrow Neurological Institute Grades I–IIIb) were considered to have a good treatment outcome, whereas in patients with Class 2 outcome (equivalent to Barrow Neurological Institute Grades IV and V) treatment was considered to have failed.

Results

A good treatment outcome from initial GKS was achieved in 31 (58.5%) patients for whom the mean follow-up period was 48 months (range 36–66 months). Outcomes at last follow-up were reflected by class status: Class 1A, 32.1% of patients; 1B, 1.9%; 1C, 3.8%; 1D, 20.8%; and Class 2, 41.5%. Statistical analysis showed no difference in outcomes between patients previously treated with microvascular decompression or rhizotomy compared with patients with no previous surgical treatments. Thirty-six percent of patients reported some degree of posttreatment facial numbness. Anesthesia dolorosa did not develop in any patient.

Conclusions

Despite a time-dependent deterioration in the success rate of GKS for medically intractable TN, the authors' study showed that > 50% of patients can be expected to have a good outcome based on their scoring system, with ~ 33% having an ideal outcome (pain free with no need for medications). Long-term data, as those presented here, are important when counseling patients on their treatment options.

[Bilateral trigeminal neuralgia: case report]

BACKGROUND AND OBJECTIVES

Trigeminal neuralgia is an extremely painful condition characterized by recurrent episodes of sudden, lancinating, shock-like pain lasting from a few seconds to two minutes usually unilateral. It has an annual incidence of approximately 4.3 in 100,000 in the general population and only 3% of those cases present bilateral manifestation. The objective of this report was to describe a rare case of bilateral trigeminal neuralgia.

CASE REPORT

A 61 years old housewife from Maranhão, Brazil, married, with a history of hypertension, presented with a six-year history of severe pain in the left V2-V3 regions, lasting 5 to 10 seconds, in the lateral aspect of the nose and mandible, worsening by talking, chewing, and with a decrease in temperature. She had been treated with chlorpromazine (3 mg every eight hours) and carbamazepine (200 mg every eight hours) during six months without improvement. On physical exam, the patient presented thermal and mechanical allodynia in the V2-V3 regions. She was using gabapentin (1,200 mg/day) with partial relief of the pain. The dose of gabapentin was increased to 1,500 mg/day and amitriptyline 12.5 mg at night was added to the therapeutic regimen. The patient evolved with mild and sporadical pain and a reduction in pain severity during 10 months; the dose of gabapentin was progressively reduced to 600 mg/day, and amitriptyline was maintained at 12.5 mg/day. After one year, the patient developed similar pain in the region of the right mandible, which improved with an increase in the dose of gabapentin to 900 mg/day. Head CT and MRI did not show any abnormalities.

CONCLUSIONS

Carbamazepine is the first choice for the treatment of trigeminal neuralgia; however, the use of gabapentin as the first pharmacological choice or in cases refractory to conventional therapy has been increasing.

Long-term outcomes of Gamma Knife radiosurgery for classic trigeminal neuralgia: implications of treatment and critical review of the literature. Clinical article

OBJECT

Few long-term studies of Gamma Knife surgery (GKS) for trigeminal neuralgia (TN) exist. The authors report their long-term experience with the use of GKS in a previously reported cohort of patients with TN that has now been followed since 1996.

METHODS

One hundred twelve patients with TN were treated with GKS at the University of Maryland between June 1996 and July 2001. Of these, 67% had no invasive operations for TN prior to GKS, 13% had 1, 4% had 2, and 16% had >or= 3. The right side was affected in 56% of cases, predominantly involving V2 (26%), V3 (24%), or a combination of both (18%) branches. The median age at diagnosis was 56 years, and median age at GKS was 64 years. The median prescription dose of 75 Gy (range 70-80 Gy) was delivered to the involved trigeminal nerve root entry zone. The authors assessed the degree of pain before and after GKS by using the Barrow Neurological Institute (BNI) pain scale.

RESULTS

In total, 102 patients took the survey at least once, for a response rate of 91%. Although not found to alter the conclusions of this study, 7 cases of atypical TN were found and these patients were removed, for a total of 95 cases herein analyzed. The median follow-up was 5.6 years (range 13-115 months). Before GKS, 88% of patients categorized their pain as BNI IV or V (inadequate control or severe pain on medication), whereas the remainder described their pain as BNI III (some pain, but controlled on medication). After GKS, 64% reported a BNI score of I (no pain, no medications), 5% had BNI II (no pain, still on medication), 12% had BNI III, and 19% reported a BNI score of IV or V. The median time to response was 2 weeks (range 0-12 weeks) and the median response duration was 32 months (range 0-112 months). Eighty-one percent reported initial pain relief, and actuarial rates of freedom from treatment failure at 1, 3, 5, and 7 years were 60, 41, 34, and 22%, respectively. Response duration was significantly better for those who had no prior invasive treatment versus those in whom a previous surgical intervention had failed (32 vs 21 months, p < 0.02). New bothersome facial numbness was reported in 6% of cases.

CONCLUSIONS

This study represents one of the longest reported median follow-up periods and actuarial results for a cohort of patients with classic TN treated with GKS. Although GKS achieves excellent rates of initial pain relief, these results suggest a steady rate of late failure, particularly among patients who had undergone prior invasive surgical treatment. Despite a higher than expected recurrence rate, GKS remains a viable treatment option, particularly for patients who have had no prior invasive procedures. Patients with recurrences can still be offered salvage therapy with either repeat GKS, microvascular decompression, or rhizotomy.

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.

Clinical outcomes after Gamma Knife surgery for idiopathic trigeminal neuralgia: review of 76 consecutive cases

Object

Stereotactic radiosurgery is an increasingly used, and the least invasive, surgical option for patients with trigeminal neuralgia (TN). In this study, the authors performed a retrospective evaluation of the safety and efficacy of this method for idiopathic TN.

Methods

The authors reviewed data from 76 patients with idiopathic TN who underwent Gamma Knife surgery (GKS). The mean age of the patients was 64 years (range 27–83 years). All patients had typical features of TN. Thirty patients (39.5%) had previously undergone surgery. The intervention consisted of GKS on the retrogasserian cisternal portion of the fifth cranial nerve. The mean maximum GKS dose used was 85.1 Gy (range 75–90 Gy).

Results

Patients were followed-up from 6 to 42 months (mean 20.3 months) after GKS. Complete pain relief was achieved in 83.1% of the patients within 1 year, 70.9% within 2 years, and 62.5% within 3 years. Patients who underwent previous surgery demonstrated a lower rate of pain relief (p < 0.05). Twenty patients (26.3%) reported pain recurrence between 6 and 42 months after treatment. New or worsened persistent trigeminal dysfunction developed after GKS in 16 patients (21%); 8 of these patients described some facial numbness/not bothersome, and 8 reported some facial numbness/somewhat bothersome. None of the patients developed troublesome dysesthesia or anesthesia dolorosa.

Conclusions

Gamma Knife surgery for idiopathic TN proved to be safe and effective and was associated with a particularly low rate of complications.

The implementation of ablative hypofractionated radiotherapy for stereotactic treatments in the brain and body: observations on efficacy and toxicity in clinical practice

Radiosurgery has a long history dating back to the 1950s. Only in the last decade or so have advances in radiation delivery and visualization allowed export of this paradigm to extracranial sites. This review evaluates the efficacy and safety of such ablative radiation courses using dose per fraction schedules of 10 Gy or above. Retrospective published experience in functional and benign tumor radiosurgery is reviewed. Prospective controlled clinical trials in ablative cancer therapy of early-stage lung cancer and metastatic disease in the brain, liver, and spine are reviewed.

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).