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

Single Fraction Radiosurgical Tolerance of Brainstem, Trigeminal Nerve, and Meckel's Cave for Facial Numbness

PURPOSE

This article reviews toxicity outcomes for a series of patients treated with stereotactic radiosurgery for trigeminal neuralgia, focusing on dose to the brainstem, trigeminal nerve, and Meckel's cave as possible explanatory variables for the development of the most common posttreatment neuropathy, facial numbness.

METHODS AND MATERIALS

A retrospective review of 136 cases treated with CyberKnife radiosurgery for trigeminal neuralgia was performed. Dose was initially (cohort 1) prescribed to 57 to 64 Gy covering a 6-mm cylindrical shaped target volume ≥2 mm from the dorsal root entry zone. Subsequently, a deliberate change to isocentric treatment planning occurred, resulting in delivery of 85 Gy to a spherical target (cohort 2). Brainstem, trigeminal nerve, and Meckel's cave were contoured, and a variety of dosimetric and clinical factors were analyzed for association with development of treatment-related facial numbness.

RESULTS

Treatment-related numbness occurred in 59 of 136 (43%) patients and did not differ between the treatment cohorts. Fifty-two patients experienced Barrow Neurological Institute (BNI) grade II toxicity, and 7 patients experienced BNI grade III toxicity. Time to numbness was 16.0 months for cohort 1 and 10.4 months for cohort 2 (P = .184). The median brainstem maximum dose was 26.1 Gy, ranging from 4.2 Gy to 57.3 Gy. Maximum dose to the trigeminal nerve was 85 Gy. Mean trigeminal nerve dose was 47.3 Gy. The median Meckel's cave maximum and mean doses were 26.0 Gy and 6.8 Gy, respectively. No definitive upper limit dose threshold was detected for the structures analyzed, but trends were noted for maximum trigeminal nerve dose of 85 Gy (P = .083) and for prescription dose (P = .057) and trigeminal nerve V40 (P = .077) in the type I subset.

CONCLUSIONS

Brainstem, trigeminal nerve, and Meckel's cave tolerated doses within the range delivered. Discussion of the literature is provided to guide treatment planning and management.

Retreatment predictors after percutaneous balloon gangliolysis for trigeminal neuralgia

Percutaneous balloon ganglyolysis (PBG) for trigeminal neuralgia (TN) is an inexpensive and minimally invasive treatment modality that is effective and safe. While there are reports of its efficacy, there is still a lack of evidence of which patients are at a higher risk of treatment failures and needing retreatment. We performed a retrospective study at a major academic institution from 2012 to 2023, including TN patients who underwent PBG procedures to evaluate predictors of retreatment. Patients without imaging available from the PBG were excluded. Fifty-two patients who underwent 83 procedures in total were included in the analysis. All patients had typical TN and were primarily female (59.6%), with a median age of 61.5 years. Immediately after PBG, 42.3% had pain resolution, and 57.7% had improved but persistent pain. 30.8% underwent retreatment with PBG in a median of 32 months. From multiple factors assessed, TN disease duration ≤ 6 months and trigeminal nerve enhancement on pre-operative MRI were identified as significant retreatment predictors on univariate analysis. However, after performing logistic regression, only TN disease duration ≤ 6 months remained significant OR 3.99 (95% CI 1.59-10.0; p = 0.003). This was further confirmed in a Kaplan-Meier survival analysis, which showed that patients with TN duration ≤ 6 months require retreatment earlier (22 vs. 41 months; p = 0.01). Retreatment after PBG occurs roughly in a third of patients, and TN disease duration of ≤ 6 months is an important predictor in this study. Further studies should be performed to confirm these findings, which may impact treatment considerations in the future.

Exploring long-term outcomes following CyberKnife robotic radiosurgery for trigeminal neuralgia

Background and purpose

Radiosurgery has been extensively studied for its efficacy and safety in the management of trigeminal neuralgia (TN). However, among the plethora of relevant studies in the literature, only a restricted number have been conducted targeting an elongated trigeminal nerve segment with the CyberKnife radiosurgery (CKRS) system. Herein, we report long-term clinical outcomes of TN patients treated with CKRS.

Materials and methods

Fifty patients treated with CKRS for medically refractory TN were analyzed. Pain response and sensory dysfunction post CKRS were assessed using the Barrow Neurological Institute (BNI) scale. Kaplan-Meier analysis was used to assess the maintenance of pain control and the risk of onset of facial numbness. The Cox proportional hazards regression model was employed for both univariate and multivariate analyses to identify predictive factors among the collected variables.

Results

The median follow-up period was 63 months (range: 12-174 months). The median values of treated nerve volume, prescription dose, and integral dose were 59 mm3, 60 Gy and 3.9 mJ, respectively. Pain control (BNI I-III) was achieved in 37 patients (74%). Among them, the actuarial freedom from pain (FFP) rate was 82%, 78% and 74% at 24, 36 and beyond 48 months post-CKRS, respectively. A correlation of FFP rate with patient gender, treated nerve volume, and mean dose was revealed in multivariate analysis. Twenty-three patients (62%) reported onset of new or aggravation of pre-existing, facial numbness with twenty-one of them (57%) characterizing it as "mild facial numbness, not bothersome" (BNI-II) and two (5%) as "somewhat bothersome" (BNI-III). We did not encounter any case with very bothersome facial numbness (BNI-IV).

Conclusions

Long-term results of this work contribute to the body of evidence supporting the safety and efficacy of CKRS in the treatment of TN patients, in view of excellent pain control for an acceptable toxicity profile.

A history of stereotactic radiosurgery may predict failure of procedure following percutaneous glycerol rhizotomy for trigeminal neuralgia

BACKGROUND

Both stereotactic radiosurgery (SRS) and percutaneous glycerol rhizotomy are excellent options to treat TN in patients unable to proceed with microvascular decompression. However, the influence of prior SRS on pain outcomes following rhizotomy is not well understood.

METHODS

We retrospectively reviewed all patients undergoing percutaneous rhizotomy at our institution from 2011 to 2022. Only patients undergoing percutaneous glycerol rhizotomy following SRS (SRS-rhizotomy) or those undergoing primary glycerol rhizotomy were considered. We collected basic demographic, clinical, and pain characteristics for each patient. Additionally, we characterized pain presentation and perioperative complications. Immediate failure of procedure was defined as presence of TN pain symptoms within 1-week of surgery, and short-term failure was defined as presence of TN pain symptoms within 3-months of surgery. A multivariate logistic regression model was used to evaluate the relationship of a history SRS and failure of procedure following percutaneous glycerol rhizotomy.

RESULTS

Of all patients reviewed, 30 had a history of SRS prior to glycerol rhizotomy whereas 371 underwent primary percutaneous glycerol rhizotomy. Patients with a history of SRS were more likely to endorse V3 pain symptoms, p = 0.01. Additionally, patients with a history of SRS demonstrated higher preoperative BNI pain scores, p = 0.01. Patients with a history of SRS were more likely to endorse preoperative numbness, p < 0.0001. A history of SRS was independently associated with immediate failure [OR = 5.44 (2.06-13.8), p < 0.001] and short-term failure of glycerol rhizotomy [OR = 2.41 (1.07-5.53), p = 0.03]. Additionally, increasing age was found to be associated with lower odds of short-term failure of glycerol rhizotomy [OR = 0.98 (0.97-1.00), p = 0.01] CONCLUSIONS: A history of SRS may increase the risk of immediate and short-term failure following percutaneous glycerol rhizotomy. These results may be of use to patients who are poor surgical candidates and require multiple noninvasive/minimally invasive options to effectively manage their pain.

Dosimetric impact of rotational errors in trigeminal neuralgia radiosurgery using CyberKnife

PURPOSE

Trigeminal neuralgia (TN) can be treated on the CyberKnife system using two different treatment delivery paths: the general-purpose full path corrects small rotations, while the dedicated trigeminal path improves dose fall-off but does not allow rotational corrections. The study evaluates the impact of uncorrected rotations on brainstem dose and the length of CN5 (denoted as Leff) covered by the prescription dose.

METHODS AND MATERIALS

A proposed model estimates the delivered dose considering translational and rotational delivery errors for TN treatments on the CyberKnife system. The model is validated using radiochromic film measurements with and without rotational setup error for both paths. Leff and the brainstem dose is retrospectively assessed for 24 cases planned using the trigeminal path. For 15 cases, plans generated using both paths are compared for the target coverage and toxicity to the brainstem.

RESULTS

In experimental validations, measured and estimated doses agree at 1%/1 mm level. For 24 cases, the treated Leff is 5.3 ± 1.7 mm, reduced from 5.9 ± 1.8 mm in the planned dose. Constraints for the brainstem are met in 23 cases for the treated dose but require frequent treatment interruption to maintain rotational corrections <0.5° using the trigeminal path. The treated length of CN5, and plan quality metrics are similar for the two paths, favoring the full path where rotations are corrected.

CONCLUSIONS

We validated an analytical model that can provide patient-specific tolerances on rotations to meet plan objectives. Treatment using the full path can reduce treatment time and allow for rotational corrections.

Repeat CyberKnife Radiosurgery for Trigeminal Neuralgia: Outcomes and Complications

BACKGROUND

CyberKnife radiosurgery (RS), as an initial first treatment, is recognized as an efficient and safe modality for trigeminal neuralgia (TN). However, knowledge on repeat CyberKnife RS in refractory cases is limited. The objective was to evaluate the clinical outcomes of repeat CyberKnife RS for TN.

METHODS

A retrospective review of 33 patients with refractory TN treated a second time with CyberKnife RS from 2009 to 2021. The median follow-up period after the second RS was 26.0 months (range 0.3-115.8). The median dose for the repeat RS was 60 Gy (range 60.0-70.0). Pain relief after the intervention was assessed using the Barrow Neurological Institute scale for pain (I-V). Scores I to IIIb were classified as an adequate pain relief and scores IV-V were classified as a treatment failure.

RESULTS

After the second RS, initial adequate pain relief was achieved in 87.9% of cases. The actuarial probabilities of maintaining an adequate pain relief at 6, 12, 24, and 36 months were 92.1%, 74.0%, 58.2%, and 58.2%, respectively. Regarding sustained pain relief, there was no significant difference between the first and the second RS. Sensory toxicity after the first RS was predictive of a better outcome following the second RS. The onset of hypesthesia rate was the same after the first or the second RS (21%).

CONCLUSION

Repeat RS is an effective and safe method for the treatment of refractory TN.

A Pilot Study of Hypofractionated Radiosurgery for Trigeminal Neuralgia

The primary late toxicity of radiosurgery treatment for trigeminal neuralgia (TN) is facial numbness due to trigeminal nerve dysfunction. Although most patients prefer loss of facial sensation to TN, severe loss of facial sensation can be debilitating. In order to try to obtain high pain control rates while minimizing the risk of late facial numbness, we elected to treat patients on the distal trigeminal nerve with a three-fraction regimen over consecutive days instead of one fraction. Our goal was to relieve the pain while also allowing the trigeminal nerve time to repair radiation damage between treatments in an attempt to minimize the risk of permanent facial numbness. Patients in a pilot study, approved by an Institutional Review Board (IRB), received a treatment regimen of 99 Gy, administered in three consecutive daily fractions of 33 Gy each, with the dosage targeted to the 80% line. This dose was selected to approximate a biologically equivalent dose of 80 Gy maximal dose to the trigeminal nerve. Forty-eight patients were treated with CyberKnife Radiosurgery (CKRS; 99 Gy/3 fractions) for TN from 2016 to 2022, with at least one year of follow-up. The Barrow Neurological Institute (BNI) scale was used to assess facial pain, and Kaplan-Meier analysis was used to assess adequate pain relief. Thirty-eight (84%) patients experienced adequate pain relief, defined as a BNI score of I-IIIb, after a median of 1.5 months following CKRS. Treatment failure (BNI=IV-V) occurred in 12 (25%) patients after a median of 6 months following initial pain relief. The actuarial probability of pain relief at 6, 12, and 24 months post-CKRS were 87.4%, 83.7%, and 83.7%, respectively. Facial numbness was experienced in 24 (50%) cases after a median of 10 months following CKRS. Typical facial pain (p=0.034) and vascular compression (p=0.039) were the only predictors of better treatment outcomes using univariate Cox survival analysis, and vascular compression (p= 0.037) was the only predictor in multivariate Cox survival analysis. Hypofractionated treatment to the distal trigeminal nerve segment does not appear to offer an advantage in treating TN, due to similar rates of pain relief but with an unacceptably high rate of late facial numbness.

Intra-fractional corrections and clinical outcomes in frameless image-guided radiosurgery for trigeminal neuralgia

Purpose

Precision targeting is crucial to successful stereotactic radiosurgery for trigeminal neuralgia (TGN). We investigated the impact of intra-fractional 6-dimensional corrections during frameless image-guided radiosurgery (IGRS) for pain outcome in TGN patients.

Materials and methods

A total of 41 sets of intra-fractional corrections from 35 patients with TGN treated by frameless IGRS from 2009 to 2013 were retrospectively studied. For each IGRS, the intra-fractional 6-dimensional shifts were conducted at 6 couch angles. Clinical pain outcome was recorded according the Barrow Neurological Institute (BNI) 5-points score. The relationship in 6-dimensional corrections and absolute translational distances between patients with pain relief score points <2 versus ≥2 were analyzed.

Results

The absolute mean lateral, longitudinal, and vertical translational shifts were 0.46 ± 0.15 mm, 0.36 ± 0.16 mm and 0.21 ± 0.08 mm, respectively, with 97% of translational shifts being within 0.7 mm. The absolute mean lateral (pitch), longitudinal (roll), and vertical (yaw) rotational corrections are 0.33 ± 0.24°, 0.18 ± 0.09°, and 0.27 ± 0.15°, respectively, with 97% of rotational corrections being within 0.6°. The median follow-up duration for pain outcome was 26 months after IGRS. The average calculated absolute shift for patients with pain relief <2 and ≥2 BNI points, were 0.228 ± 0.008 mm and 0.259 ± 0.007 mm, respectively. There was no statistically significant difference in the translational shifts, rotational corrections or absolute distances between these two patient groups.

Conclusions

Our data demonstrate high spatial targeting accuracy of frameless IGRS for TGN with only nominal intra-fraction 6-dimensional corrections.

High-Dose Frameless Stereotactic Radiosurgery for Trigeminal Neuralgia: A Single-Institution Experience and Systematic Review

OBJECTIVE

Stereotactic radiosurgery is an effective treatment option for trigeminal neuralgia (TN), with frameless stereotactic radiosurgery (fSRS) allowing for a less invasive experience. A single-institutional series and systematic review of the literature were performed for cases of TN treated with fSRS.

METHODS

Patients at our institution with TN that were treated with fSRS from the years 2012-2021 were included. Similarly, multiple databases were searched for studies regarding TN treated with fSRS where patient-level data was included from 2004-2020. Pain levels, via the Barrow Neurological Institute (BNI) scale, before and after treatment were analyzed. Pooled analysis was performed to compare treatment outcomes between studies using CyberKnife and LINAC modalities.

RESULTS

Twenty-three patients at our institution were treated with LINAC fSRS (median treatment dose: 85 Gy). Most patients had TN refractory to previous procedural treatments. Eight (35%) patients had an excellent posttreatment response (BNI I-II), while 11 (48%) patients had a good result (BNI IIIa/b). Eight patients had recurrence of pain. A total of 30 articles were included in the systematic review, encompassing 1705 patients. At last follow-up, 63.1% (774/1227) of patients endorsed an excellent response, while 16.1% (197/1227) had a good response, and 22.5% (215/957) of patients had recurrence. Pain response, facial numbness rates, and pain recurrence rates were not significantly different between CyberKnife and LINAC modalities.

CONCLUSIONS

Frameless SRS for TN appears to be an efficacious noninvasive option for patients with substantial comorbidities, who have failed other treatment methods, although it can be limited by higher recurrence rates.

CyberKnife radiosurgery for trigeminal neuralgia: a retrospective review of 168 cases

OBJECTIVE

Gamma Knife radiosurgery is recognized as an efficient intervention for the treatment of refractory trigeminal neuralgia (TN). The CyberKnife, a more recent frameless and nonisocentric radiosurgery alternative, has not been studied as extensively for this condition. This study aims to evaluate the clinical outcomes of a first CyberKnife radiosurgery (CKRS) treatment in patients with medically refractory TN.

METHODS

A retrospective cohort study of 166 patients (168 procedures) with refractory TN treated from 2009 to 2021 at the Centre Hospitalier de l’Université de Montréal was conducted. The treatment was performed using a CyberKnife (model G4, VSI, or M6). The treatment median maximum dose was 80 (range 70.0–88.9) Gy.

RESULTS

Adequate pain relief, evaluated using Barrow Neurological Institute pain scale scores (I–IIIb), was achieved in 146 cases (86.9%). The median latency period before adequate pain relief was 35 (range 0–202) days. The median duration of pain relief for cases with a recurrence of pain was 8.3 (range 0.6–85.0) months. The actuarial rates of maintaining adequate pain relief at 12, 36, and 60 months from the treatment date were 77.0%, 62.5%, and 50.2%, respectively. There was new onset or aggravation of facial numbness in 44 cases (26.2%). This facial numbness was predictive of better maintenance of pain relief (p < 0.001). The maintenance of adequate pain relief was sustained longer in idiopathic cases compared with cases associated with multiple sclerosis (MS; p < 0.001).

CONCLUSIONS

In the authors’ experience, CKRS for refractory TN is efficient and safe. The onset or aggravation of facial hypoesthesia after treatment was predictive of a more sustained pain relief, and idiopathic cases had more sustained pain relief in comparison with MS-related cases.