Category: Gamma Knife radiosurgery

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Repeat gamma knife radiosurgery for recurrent trigeminal neuralgia

Acta Neurochirurgica (2026) 168:143

This systematic review and meta-analysis evaluates outcomes after repeat Gamma Knife radiosurgery (GKRS) for recurrent trigeminal neuralgia, pooling data from 21 studies comprising 2,020 retreatments. It quantifies efficacy (BNI I–III favourable pain control ~77% after retreatment, 62% at long-term follow-up) and recurrence (~29%), and reports complication rates, notably facial hypoesthesia (~39%).

The paper follows PRISMA and Cochrane guidance, performs single-arm GLMM meta-analyses, sensitivity checks, and meta-regressions that found no consistent predictors of outcome. Limitations include retrospective series, moderate–severe bias, substantial heterogeneity, and variable dosimetry and reporting; prospective standardized studies are recommended.

Clinical context Trigeminal neuralgia causes intense, episodic, shock-like facial pain; Gamma Knife radiosurgery (GKRS) is used for medically refractory cases, and recurrence after initial GKRS can prompt consideration of repeat GKRS.

Study design Systematic review and meta-analysis conducted under PRISMA guidance; included English-language studies of patients needing repeat GKRS after inadequate response to medications and/or a single GKRS, with ≥12 months follow-up.

Evidence base 21 studies were included, comprising 2,486 initially treated patients and 2,020 undergoing repeat GKRS; most were female, median ages ranged 54.5–79.6 years, and ~85% were idiopathic trigeminal neuralgia.

Treatment patterns Most repeat procedures targeted the trigeminal root entry zone (REZ), typically using 70–80 Gy marginal doses; intervals between procedures varied widely (5–138 months; median ≈36 months).

Effectiveness Pain relief after repeat GKRS commonly occurred in ~70–90% of patients with typical improvement in BNI pain scores (often IV–V to I–IIIb); pooled favourable pain control (BNI I–III) after the latest treatment was 76.68%.

Durability & recurrence Median follow-up ranged 14–74 months; recurrence after repeat GKRS was reported around 10–35% (pooled recurrence 29.07%), and favourable pain control at last follow-up decreased to 61.94%.

Safety profile Facial sensory disturbances were frequent (reported 20–45%; pooled facial hypoesthesia 39.04%); bothersome dysesthesias and anesthesia dolorosa were uncommon (<3%).

Predictors/heterogeneity Meta-regression found no significant association between pain relief and age, pain duration, interval since prior GKRS, or dose, with substantial inter-study heterogeneity persisting.

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The role of salvage stereotactic radiosurgery for tumor progression following incomplete microsurgical resection of vestibular schwannoma

J Neurosurg 144:1403–1409, 2026

This clinical study evaluates salvage stereotactic radiosurgery (SRS) for vestibular schwannoma (VS) that progresses after incomplete microsurgical resection, reporting long-term tumor control, freedom from additional treatment (FFAT), and complication rates in a 64-patient cohort. Key outcomes include 10- and 15-year tumor control of 87.5% and 84.4%, and FFAT of 95.3% and 92.2%, respectively.

The methods describe retrospective selection, radiosurgical dosimetry (median margin 12.5 Gy), imaging and follow-up protocols, and statistical analyses using Kaplan–Meier and Cox models; no factors significantly predicted control or FFAT, and common complications included trigeminal neuropathy and hearing worsening.

Objective Assess safety/efficacy of salvage stereotactic radiosurgery (SRS) for vestibular schwannoma (VS) that progresses after incomplete microsurgical resection, including factors affecting tumor control and freedom from additional treatment (FFAT).

Cohort Retrospective series of 64 adults treated with salvage SRS for post-resection tumor progression; median age 51.5 years and 46.9% male.

Treatment parameters Median marginal dose 12.5 Gy (median isodose 50%); median tumor volume 1.6 cm³; median time from surgery to salvage SRS 38.8 months.

Long-term control Tumor control rates after salvage SRS were 87.5% at 10 years and 84.4% at 15 years.

Durability (FFAT) FFAT rates were 95.3% at 10 years and 92.2% at 15 years, indicating most patients avoided further intervention long term.

Predictors No evaluated factors (e.g., Koos grade, age/sex, cranial nerve neuropathies, marginal dose, extent of resection, tumor volume) were significantly associated with tumor control or FFAT in Cox modeling.

Complications Most common post-SRS issue was worsening/new trigeminal neuropathy (15.6% total); hearing worsened in 14.1% (Gardner-Robertson class), and facial nerve function worsened in 4.7% (House-Brackmann).

Conclusion Salvage SRS is a safe and effective long-term strategy for VS tumor progression after incomplete resection, supporting continued monitoring and consideration of SRS once progression is documented.

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Stereotactic Radiosurgery Versus Observation in Small- and Medium-Sized Vestibular Schwannoma Patients With Normal Hearing: A Retrospective International Multicenter Study

Neurosurgery 98:887–894, 2026

This multicenter retrospective study compares stereotactic radiosurgery (SRS) with observation (OBS) for small-to-medium vestibular schwannomas (Koos I–II) in patients presenting with normal (AAO‑HNS class A) hearing. Propensity-score–matched cohorts (57 SRS, 57 OBS) were analyzed for serviceable hearing preservation (SHP), tumor control (TC), and cranial nerve outcomes over median follow-ups of 49 and 37 months.

Results show SRS achieved markedly superior tumor control (≈98% at 5–10 years) while producing noninferior hearing outcomes versus observation (5‑year SHP: SRS 76.2% vs OBS 56.1%; difference not statistically significant). The authors conclude SRS is preferable for TC without compromising hearing, emphasizing individualized decision-making given study limitations.

Clinical question Comparison of stereotactic radiosurgery (SRS) vs observation (OBS) for small/medium Koos I–II vestibular schwannomas in patients with AAO-HNS class A (normal) hearing at presentation, focusing on hearing preservation and tumor control

Design Retrospective international multicenter study with propensity score matching (age, sex, tumor volume, PTA, SDS) yielding 57 SRS vs 57 OBS matched patients

Serviceable hearing preservation No statistically significant difference in long-term serviceable hearing preservation between SRS and OBS in the matched analysis (log-rank P = .17), despite numerically higher SRS rates

Hearing rates over time Matched-cohort 5-/9-year serviceable hearing preservation: SRS 76.2% / 42.4% vs OBS 56.1% / 16.8%

Class A hearing Class A preservation was similar: 57.9% (SRS) vs 52.6% (OBS) (P = .70)

Tumor control SRS achieved markedly superior tumor control (log-rank P < .0001); 5-/10-year tumor control: SRS 97.9% / 97.9% vs OBS 40.9% / 15.1%

Other clinical outcomes No significant matched-cohort differences in cranial nerve deficits, vestibulopathy, or composite CN/tinnitus worsening; tinnitus worsening trended higher with OBS (21.1% vs 8.8%) but was not significant (P = .066)

Overall conclusion SRS provided noninferior hearing outcomes while being significantly better for tumor control, supporting SRS as a favored option while still emphasizing individualized decision-making

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Single-Fraction Stereotactic Radiosurgery as Primary Management of Sporadic Meningiomas: A 25-Year Cohort Study

Neurosurgery 97:1267–1274, 2025

This study reports long-term outcomes of single‑fraction Gamma Knife stereotactic radiosurgery (SRS) as primary treatment for 653 sporadic intracranial meningiomas in 616 patients over a 25‑year period. With median margin dose 15 Gy and median imaging follow-up 6.3 years, progression‑free survival was excellent (99.8% at 5 years, 99.0% at 10 years), and raw tumor control reached 98.6%.

Treatment‑related neurological sequelae were uncommon (1.8% permanent/intervention), though larger tumor volume, higher V12, and greater number of isocenters increased complication risk. The authors conclude single‑fraction SRS at studied doses offers high long‑term control for small‑to‑medium sporadic meningiomas, emphasizing careful patient selection.

Stereotactic Radiosurgery (SRS) Effectiveness: Single-fraction SRS is highly effective as a primary treatment for sporadic, small- to medium-volume intracranial meningiomas, achieving a 99% tumor control rate at 10 years and 93% at 15 years progression-free survival (PFS).

Low Permanent Morbidity: The risk of permanent treatment-related neurological complications is low (1.8%), with most side effects being temporary or minor.

Key Predictors of Outcome: Larger tumor volume is the main predictor of both tumor progression and treatment-related complications, emphasizing the importance of patient selection for SRS.

Radiosurgical Parameters: Increased number of isocenters, higher 12-Gy volume (V12), larger tumor volume, and lower maximal dose are associated with higher risk of treatment-related complications.

Comparison to Observation: SRS provides superior tumor control compared to observation in patients with incidentally discovered, asymptomatic meningiomas, with similar rates of new neurological deficits.

Radiation Dose Recommendations: A median margin dose of 13–15 Gy balances long-term tumor control and risk of complications; doses below 12 Gy may increase recurrence risk, while higher doses increase morbidity.

Biological Effective Dose (BED): In this cohort, higher BED was not predictive of improved PFS, likely due to the already high dosing protocol; however, other studies suggest BED can be a useful predictor when a wider dose range is used.

Limitations: The study is retrospective and single-institution, with potential selection bias and incomplete follow-up; findings may not generalize to syndromic or radiation-induced meningiomas.

 

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Factors Affecting Long-Term Pain Control After Gamma Knife Radiosurgery in Secondary Tumor-Related Trigeminal Neuralgia

Neurosurgery 97:1003–1011, 2025

This clinical study evaluates long-term pain outcomes after Gamma Knife radiosurgery (GKRS) for secondary tumor-related trigeminal neuralgia in 156 patients, reporting complete pain relief (BNI 1) in 38.8% and adequate relief (BNI 2–3) in 47.4% over a median 48.5-month follow-up. The cohort—predominantly schwannomas and meningiomas—received tumor-targeted single-session GKRS with a median dose of 12 Gy and facial hypesthesia noted in 8.3%.

Multivariable analysis identified age ≥50 years and decreased or stable tumor volume at follow-up as strong predictors of favorable pain outcomes, while tumor progression and younger age predicted failure. The authors conclude tumor control contributes to pain relief but is not the sole mechanism, and targeting tumor alone achieved similar BNI 1–3 rates as reports that also targeted the nerve.

• Gamma Knife Radiosurgery (GKRS) Efficacy: GKRS provides complete pain relief (BNI 1) in 38.8% and adequate pain relief (BNI 2-3) in 47.4% of patients with secondary tumor-related trigeminal neuralgia, with a median follow-up of about 48.5 months.

• Predictors of Pain Relief: Age ≥50 years (odds ratio: 6.95) and decreased or stable tumor volume at follow-up (odds ratio: 40.38) significantly predict successful pain relief (BNI 1-3) after GKRS.

• Tumor Control and Pain Relief Relationship: While tumor control (stable or reduced volume) strongly correlates with pain relief, pain relief can still occur without significant tumor shrinkage, indicating other contributing mechanisms.

• Most Common Tumor Types: Schwannomas (67.9%) and meningiomas (29.6%) are the most frequent causes of secondary tumor-related trigeminal neuralgia treated with GKRS.

• Complications: Facial hypesthesia is the most common complication post-GKRS, affecting 8.3% of patients; no cases of anesthesia dolorosa or worsening pain were reported.

• Tumor Volume Impact: Larger pre-treatment tumor volume is associated with higher rates of pain relief failure; patients with pain relief failure had a median tumor volume of 5.9 cc versus 3.1–4 cc in those with successful outcomes.

• Prior Procedures: Previous interventions (such as radiofrequency ablation, rhizotomy, or tumor resection) do not significantly affect pain relief outcomes after GKRS.

• Alternative Approaches: Targeting the tumor alone with GKRS is effective; nerve targeting may be reserved for cases where tumor-targeted GKRS fails.

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Gamma Knife radiosurgery for relapsing trigeminal neuralgia following microvascular decompression

J Neurosurg 142:1247–1255, 2025

Salvage Gamma Knife radiosurgery (GKRS) offers effective, noninvasive treatment for relapsing trigeminal neuralgia after microvascular decompression, with a favorable complications profile. Patients with facial numbness and better initial pain responses may experience more durable pain relief following salvage GKRS.

• Gamma Knife radiosurgery (GKRS) is explored as a treatment for relapsing trigeminal neuralgia (TN) following microvascular decompression (MVD).

• The study aimed to assess the response rate, complications, and predictors of pain relapse for salvage GKRS after MVD.

• 83.1% of patients experienced initial pain relief after salvage GKRS, with a median time to relapse of 1.75 years.

• Facial numbness post-GKRS decreased pain relapse risk, while a worse initial pain response increased it.

• Radiofrequency ablation (RFA) prior to MVD reduced the likelihood of an initial response to GKRS.

• Salvage GKRS is presented as an effective, noninvasive option for recurring TN after MVD, with a favorable complications profile compared to salvage MVD.

• The study acknowledges limitations, including potential selection bias and small sample size, and suggests further research with larger cohorts

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Predictors of trigeminal neuropathy in patients receiving Gamma Knife stereotactic radiosurgery for vestibular schwannoma

J Neurosurg 142:1134–1140, 2025

The study investigates predictors of trigeminal neuropathy (Tn) in patients receiving Gamma Knife stereotactic radiosurgery for vestibular schwannoma. It identifies the volume of cranial nerve V receiving ≥11 Gy as a significant factor in Tn development, suggesting it be included in dosimetric planning to minimize risk.

• Objective: Validate predictors of trigeminal neuropathy (Tn) in patients receiving stereotactic radiosurgery (SRS) for vestibular schwannoma (VS).

• Methodology: Study included 204 patients treated with SRS, excluding those with pre-existing Tn symptoms or less than 2 years of follow-up.

• Key Finding: The volume of cranial nerve (CN) V receiving ≥ 11 Gy is the only significant predictor of Tn development post-SRS.

• Results: 11.3% of patients developed Tn, with 7.8% experiencing permanent symptoms.

• Statistical Analysis: Maximum dose to CN V was significant in univariate analysis but not in multivariate analysis.

• Tumor Compression: Not significantly correlated with Tn development.

• Clinical Implication: Dosimetric planning should account for CN V volume receiving ≥ 11 Gy to minimize Tn risk.

• Recommendation: Early treatment advised to maintain gap between VS and CN V, reducing Tn risk.

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Gamma Knife Radiosurgery for Hypothalamic Hamartoma: A Multi-Institutional Retrospective Study on Safety, Efficacy, and Complication Profile

Neurosurgery 96:426–437, 2025

• Study Overview:

•Retrospective multicentric study on 39 patients with hypothalamic hamartomas (HH).

•Mean age of patients was 16 years, with a range from 6 months to 53 years.

•Ethical clearance obtained for data sharing from participating centers.

• Treatment Details:

•Gamma Knife Radiosurgery (GKRS) used with a median margin dose of 16 Gy.

•Target volume median was 0.55 cc, ranging from 0.1 to 10.00 cc.

•Majority of patients received ≥16 Gy targeting complete HH.

• Seizure Outcomes:

•55.2% achieved good seizure control (Engel I/II).

•44.8% were in Engel III/IV status.

•No significant difference in seizure outcomes based on prescribed dose.

• Complications and Side Effects:

•Two patients developed new onset hormonal deficiency.

•No new onset visual deterioration observed.

•Eight patients experienced a transient increase in seizures.

• Endocrinological Impact:

•17.9% of patients presented with both precocious puberty (PP) and epilepsy.

•No significant change in endocrinological profile post-radiosurgery.

• Follow-up and Long-term Effects:

•Median follow-up duration was 5 years.

•Regression in hamartoma volume observed in 28% of patients.

•Long-term follow-up essential for observing significant outcomes

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Multistaged Stereotactic Radiosurgery for Complex Large Lobar Arteriovenous Malformations

Neurosurgery 96:223–232, 2025

Although stereotactic radiosurgery (SRS) has well defined outcomes in the management of smaller-volume arteriovenous malformations (AVM), this report evaluates the outcomes when SRS is used for large-volume (≥10 cc) lobar AVMs.

METHODS: Between 1990 and 2022, a cohort of 1325 patients underwent Leksell Gamma Knife SRS for brain AVMs. Among these, 40 patients (25 women; median age: 37 years) with large lobar AVMs underwent volume-staged SRS followed by additional SRS procedures if needed (2-5 procedures). The patients presented with diverse AVM locations and Spetzler-Martin Grades. Before SRS, 16 patients underwent a total of 43 embolization procedures.

RESULTS: Over a median follow-up of 73 months, 20 patients achieved AVM obliteration. The 3, 5, and 10-year obliteration rates were 9.3%, 15.3%, and 53.3%, respectively. During the latency interval between the first SRS procedure and the last follow-up, 11 patients had intracerebral hemorrhages (ICH) and 6 developed new neurological deficits unrelated to ICH. The postoperative hemorrhage risk after the first SRS was 13.8% at 3 years, 16.6% at 5 years, and 36.2% at 10 years. No hemorrhagic event was documented after confirmed obliteration. Compared with the modified Rankin Scale (mRS) scores before SRS, the mRS improved or remained stable in 28 patients. Nine patients died during the observation interval. Five were related to ICH.

CONCLUSION: These outcomes underscore both the potential effectiveness and the limitations of multistage SRS procedures for complex high-risk large volume AVMs in critical brain lobar locations. Most patients retained either stable or improved long-term mRS scores. During the latency interval from the first SRS until obliteration, achieved after two or more procedures, the risk of hemorrhage and treatment-related complications persists.

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Extended Long-Term Outcome After Conservative Decompressive Microsurgery and Routine Adjuvant Fractionated Stereotactic Radiotherapy for Symptomatic Cavernous Sinus Meningiomas

Neurosurgery 95:834–841, 2024

Cavernous sinus meningiomas (CSM) pose one of the most difficult to treat subgroup of skull base meningiomas. The purpose of this study was to evaluate the efficacy of an interdisciplinary treatment approach for symptomatic CSM which incorporated conservative function preserving microsurgery and routine adjuvant fractionated stereotactic radiotherapy (FSRT).

METHODS: A homogenous group of patients with symptomatic primary CSM with extracavernous extension was treated between 2005 and 2012. All patients were available for a minimum follow-up of 5 years. Clinical follow-up included detailed examination of oculomotor deficits, visual status, and endocrinologic function. Radiologic follow-up was conducted by tumor volumetry.

RESULTS: Overall, 23 patients were included in this study (78.3% women; median age 58 years). Diplopia was the most common presenting symptom, followed by headache and visual disturbances. Surgical morbidity was low (3/23; 13%). FSRT was applied after a median of 2 months after surgery. At a median clinical follow-up of 113 months, 70.45% of the presenting symptoms had improved, 25% remained unchanged, and in 2 cases (4.54%), worsening occurred. Overall tumor regression was evident in 19/21 World Health Organization 1 and in 1/2 of World Health Organization 2 CSM, respectively, at a median radiological follow-up of 103 months.

CONCLUSION: Our findings demonstrate the efficacy of an interdisciplinary treatment approach for symptomatic primary CSM with extracavernous extension with decompression of neurovascular elements followed by FSRT. Precise preoperative planning and intraoperative decision making in combination with routine postoperative radiotherapy can achieve excellent tumor control, improve neurologic function, and minimize long-term morbidity.

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The relevance of biologically effective dose for pain relief and sensory dysfunction after Gamma Knife radiosurgery for trigeminal neuralgia: an 871-patient multicenter study

J Neurosurg 141:461–473, 2024

Recent studies have suggested that biologically effective dose (BED) is an important correlate of pain relief and sensory dysfunction after Gamma Knife radiosurgery (GKRS) for trigeminal neuralgia (TN). The goal of this study was to determine if BED is superior to prescription dose in predicting outcomes in TN patients undergoing GKRS as a first procedure.

METHODS This was a retrospective study of 871 patients with type 1 TN from 13 GKRS centers. Patient demographics, pain characteristics, treatment parameters, and outcomes were reviewed. BED was compared with prescription dose and other dosimetric factors for their predictive value.

RESULTS The median age of the patients was 68 years, and 60% were female. Nearly 70% of patients experienced pain in the V2 and/or V3 dermatomes, predominantly on the right side (60%). Most patients had modified BNI Pain Intensity Scale grade IV or V pain (89.2%) and were taking 1 or 2 pain medications (74.1%). The median prescription dose was 80 Gy (range 62.5–95 Gy). The proximal trigeminal nerve was targeted in 77.9% of cases, and the median follow-up was 21 months (range 6–156 months). Initial pain relief (modified BNI Pain Intensity Scale grades I–IIIa) was noted in 81.8% of evaluable patients at a median of 30 days. Of 709 patients who achieved initial pain relief, 42.3% experienced at least one pain recurrence after GKRS at a median of 44 months, with 49.0% of these patients undergoing a second procedure. New-onset facial numbness occurred in 25.3% of patients after a median of 8 months. Age ≥ 63 years was associated with a higher probability of both initial pain relief and maintaining pain relief. A distal target location was associated with a higher probability of initial and long-term pain relief, but also a higher incidence of sensory dysfunction. BED ≥ 2100 Gy 2.47 was predictive of pain relief at 30 days and 1 year for the distal target, whereas physical dose ≥ 85 Gy was significant for the proximal target, but the restricted range of BED values in this subgroup could be a confounding factor. A maximum brainstem point dose ≥ 29.5 Gy was associated with a higher probability of bothersome facial numbness.

CONCLUSIONS BED and physical dose were both predictive of pain relief and could be used as treatment planning goals for distal and proximal targets, respectively, while considering maximum brainstem point dose < 29.5 Gy as a potential constraint for bothersome numbness.

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Third Stereotactic Radiosurgery for Residual Arteriovenous Malformations: A Retrospective Multicenter Study

Neurosurgery 94:1174–1182, 2024

There are no studies evaluating the efficacy and safety of more than 2 stereotactic radiosurgery (SRS) procedures for cerebral arteriovenous malformations (AVM). The aim of this study was to provide evidence on the role of third single-session SRS for AVM residual.

METHODS: This multicenter, retrospective study included patients managed with a third single-session SRS procedure for an AVM residual.  The primary study outcome was defined as AVM nidus obliteration without AVM bleeding or symptomatic radiation-induced changes (RIC). Secondary outcomes evaluated were AVM obliteration, AVM hemorrhage, asymptomatic, and symptomatic RIC.

RESULTS: Thirty-eight patients (20/38 [52.6%] females, median age at third SRS 34.5 [IQR 20] years) were included. The median clinical follow-up was 46 (IQR 14.8) months, and 17/38 (44.7%) patients achieved favorable outcome. The 3-year and 5year cumulative probability rates of favorable outcome were 23% (95% CI = 10%-38%) and 53% (95% CI = 29%-73%), respectively. The cumulative probability of AVM obliteration at 3 and 5 years after the third SRS was 23% (95% CI= 10%-37%) and 54% (95% CI = 29%-74%), respectively. AVM bleeding occurred in 2 patients, and 1 of them underwent subsequent resection. The cumulative probability rate of post-SRS AVM hemorrhage remained constant at 5.3% (95% CI = 1%-16%) during the first 5 years of follow-up. Transient symptomatic RIC managed conservatively occurred in 5/38 patients (13.2%) at a median time of 12.5 (IQR 22.5) months from third SRS. Radiation-induced cyst formation was noted in 1 patient (4.2%) 19 months post-SRS. No mortality, radiation-associated malignancy, or permanent symptomatic RIC was noted during follow-up.

CONCLUSION: A third single-session SRS to treat a residual intracranial AVM offers obliteration in most patients. The risk of RIC was low, and these effects were transient. While not often required, a third SRS can be performed in patients with persistent residual AVMs.

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Preoperative Versus Postoperative Radiosurgery of Brain Metastases: A Meta-Analysis

World Neurosurg. (2024) 182:35-41

OBJECTIVE: While postoperative resection cavity radiosurgery (post-SRS) is an accepted treatment paradigm for brain metastasis (BM) patients who undergo surgical resection, there is emerging interest in preoperative radiosurgery (preSRS) followed by surgical resection as an alternative treatment paradigm. Here, we performed a meta-analysis of the available literature on this matter.

METHODS: Following Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines, a search of all studies evaluating pre-SRS and postSRS was completed. Local recurrence (LR), overall survival (OS), radiation necrosis (RN), and leptomeningeal disease (LMD) were evaluated from the available data. Moderator analysis and pooled effect sizes were performed using a proportional meta-analysis with R using the metafor package. Statistics are presented as mean [95% confidence interval].

RESULTS: We identified 6 pre-SRS and 33 post-SRS studies with comparable tumor volume (4.5-17.6 cm3 ). There were significant differences in the pooled estimates of LR and LMD, favoring pre-SRS over post-SRS. Pooled aggregate for LR was 11.0% [4.9-13.7] and 17.5% [15.1-19.9] for pre- and post-SRS studies (P [ 0.014). Similarly, pooled estimates of LMD favored pre-SRS, 4.4% [2.6-6.2], relative to post-SRS, 12.3% [8.9-15.7] (P [ 0.019). In contrast, no significant differences were found in terms of RN and OS. Pooled estimates for RN were 6.4% [3.1-9.6] and 8.9% [6.3-11.6] for pre- and post-SRS studies (P [ 0.393), respectively. Pooled estimates for OS were 60.2% [55.8-64.6] and 60.5% [56.9-64.0] for pre- and post-SRS studies (P [ 0.974).

CONCLUSIONS: This meta-analysis supports further exploration of pre-SRS as a strategy for the treatment of BM.

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Intratumoral Hemorrhage in Vestibular Schwannomas After Stereotactic Radiosurgery: Multi-Institutional Study

Neurosurgery 94:289–296, 2024

Intratumoral hemorrhage (ITH) in vestibular schwannoma (VS) after stereotactic radiosurgery (SRS) is exceedingly rare. The aim of this study was to define its incidence and describe its management and outcomes in this subset of patients.

METHODS: A retrospective multi-institutional study was conducted, screening 9565 patients with VS managed with SRS at 10 centers affiliated with the International Radiosurgery Research Foundation.

RESULTS: A total of 25 patients developed ITH (cumulative incidence of 0.26%) after SRS management, with a median ITH size of 1.2 cm3 . Most of the patients had Koos grade II-IV VS, and the median age was 62 years. After ITH development, 21 patients were observed, 2 had urgent surgical intervention, and 2 were initially observed and had late resection because of delayed hemorrhagic expansion and/or clinical deterioration. The histopathology of the resected tumors showed typical, benign VS histology without sclerosis, along with chronic inflammatory cells and multiple fragments of hemorrhage. At the last follow-up, 17 patients improved and 8 remained clinically stable.

CONCLUSION: ITH after SRS for VS is extremely rare but has various clinical manifestations and severity. The management paradigm should be individualized based on patient-specific factors, rapidity of clinical and/or radiographic progression, ITH expansion, and overall patient condition.

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Repeat Gamma Knife radiosurgery for recurrent trigeminal neuralgia in patients with multiple sclerosis

Acta Neurochirurgica (2024) 166:15

Gamma Knife radiosurgery (GKRS) has emerged as an effective treatment option for trigeminal neuralgia (TN) in patients with multiple sclerosis (MS). To date, the outcomes of repeat GKRS for patients with TN and MS with recurrent pain have been investigated in a few patients. This study aims to report the outcomes and predictive factors of pain reduction for MS patients undergoing repeat GKRS for recurrent TN.

Methods Eighteen patients with MS underwent repeat GKRS for recurrent TN. A retrospective chart review and telephone interviews were conducted to determine background medical history, dosimetric data, and outcomes of the procedure. Facial pain and sensory function were evaluated using the Barrow Neurological Institute (BNI) scales.

Results Fifteen patients achieved a BNI pain score of IIIa or better, indicating pain reduction, within a median period of 21 days after repeat GKRS. The maximum dose for repeat GKRS ranged from 70 to 85 Gy. Pain recurred in 5 patients after a median period of 12 months after GKRS. Percentages of patients with pain reduction at 1, 2, 3, 5, and 7 years were 60%, 60%, 50%, 50%, and 50%, respectively. Older age at repeat GKRS predicted sustained pain reduction (P = 0.01). Seven patients developed facial sensory disturbances, which were bothersome in two patients.

Conclusions Repeat GKRS may be used as an effective treatment modality for prolonging the duration of pain reduction time in patients with MS and TN. After repeat GKRS, facial sensory disturbances are common; however, they are often not bothersome.

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Clinical and Imaging Outcomes After Trigeminal Schwannoma Radiosurgery: Results From a Multicenter, International Cohort Study

Neurosurgery 94:165–173, 2024

An international, multicenter, retrospective study was conducted to evaluate the long-term clinical outcomes and tumor control rates after stereotactic radiosurgery (SRS) for trigeminal schwannoma.

METHODS: Patient data (N = 309) were collected from 14 international radiosurgery centers. The median patient age was 50 years (range 11-87 years). Sixty patients (19%) had prior resections. Abnormal facial sensation was the commonest complaint (49%). The anatomic locations were root (N = 40), ganglion (N = 141), or dumbbell type (N = 128). The median tumor volume was 4 cc (range, 0.2-30.1 cc), and median margin dose was 13 Gy (range, 10-20 Gy). Factors associated with tumor control, symptom improvement, and adverse radiation events were assessed.

RESULTS: The median and mean time to last follow-up was 49 and 65 months (range 6–242 months). Greater than 5-year follow-up was available for 139 patients (45%), and 50 patients (16%) had longer than 10-year follow-up. The overall tumor control rate was 94.5%. Tumors regressed in 146 patients (47.2%), remained unchanged in 128 patients (41.4%), and stabilized after initial expansion in 20 patients (6.5%). Progression-free survival rates at 3 years, 5 years, and 10 years were 91%, 86%, and 80 %. Smaller tumor volume (less than 8 cc) was associated with significantly better progression-free survival (P = .02). Seventeen patients with sustained growth underwent further intervention at a median of 27 months (3-144 months). Symptom improvement was noted in 140 patients (45%) at a median of 7 months. In multivariate analysis primary, SRS (P = .003) and smaller tumor volume (P = .01) were associated with better symptom improvement. Adverse radiation events were documented in 29 patients (9%).

CONCLUSION: SRS was associated with long-term freedom (10 year) from additional management in 80% of patients. SRS proved to be a valuable salvage option after resection. When used as a primary management for smaller volume tumors, both clinical improvement and prevention of new deficits were optimized.

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Association Between Pseudoprogression of Vestibular Schwannoma After Radiosurgery and Radiological Features of Solid and Cystic Components

Neurosurgery 93:1383–1392, 2023

The pathophysiology of vestibular schwannoma (VS) pseudoprogression after Gamma Knife radiosurgery (GKRS) remains unclear. Radiological features in pretreatment magnetic resonance images may help predict VS pseudoprogression. This study used VS radiological features quantified using an automated segmentation algorithm to predict pseudoprogression after GKRS treatment.

METHODS: This is a retrospective study comprising 330 patients with VS who received GKRS. After image preprocessing and T2W/contrast-enhanced T1-weighted image (CET1W) image generation, with fuzzy C-means clustering, VSs were segmented into solid and cystic components and classified as solid and cystic. Relevant radiological features were then extracted. The response to GKRS was classified into “nonpseudoprogression” and “pseudoprogression/fluctuation”. The Z test for two proportions was used to compare solid and cystic VS for the likelihood of pseudoprogression/fluctuation. Logistic regression was used to assess the correlation between clinical variables and radiological features and response to GKRS.

RESULTS: The likelihood of pseudoprogression/fluctuation after GKRS was significantly higher for solid VS compared with cystic VS (55% vs 31%, P < .001). For the entire VS cohort, multivariable logistic regression revealed that a lower mean tumor signal intensity (SI) in T2W/CET1W images was associated with pseudoprogression/fluctuation after GKRS (P = .001). For the solid VS subgroup, a lower mean tumor SI in T2W/CET1W images (P = .035) was associated with pseudoprogression/fluctuation after GKRS. For the cystic VS subgroup, a lower mean SI of the cystic component in T2W/ CET1W images (P = .040) was associated with pseudoprogression/fluctuation after GKRS.

CONCLUSION: Pseudoprogression is more likely to occur in solid VS compared with cystic VS. Quantitative radiological features in pretreatment magnetic resonance images were associated with pseudoprogression after GKRS. In T2W/ CET1W images, solid VS with a lower mean tumor SI and cystic VS with a lower mean SI of cystic component were more likely to have pseudoprogression after GKRS. These radiological features can help predict the likelihood of pseudoprogression after GKRS.

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Vestibular Schwannoma Stereotactic Radiosurgery in Octogenarians

Neurosurgery 93:1099–1105, 2023

The management of octogenarians with vestibular schwannomas (VS) has received little attention. However, with the increase in octogenarian population, more effort is needed to clarify the value of stereotactic radiosurgery (SRS) in this population. The aim of this study was to evaluate the safety and efficacy of SRS in this patient age group.

METHODS: A retrospective study of 62 patients aged 80 years or older who underwent single-session SRS for symptomatic VS during a 35-year interval was performed. The median patient age was 82 years, and 61.3% were male. SRS was performed as planned adjuvant management or for delayed progression after prior partial resection in 5 patients.

RESULTS: SRS resulted in a 5-year tumor control rate of 95.6% with a 4.8% risk of adverse radiation effects (ARE). Tumor control was unrelated to patient age, tumor volume, Koos grade, sex, SRS margin dose, or prior surgical management. Four patients underwent additional management including 1 patient with symptomatic progression requiring surgical resection, 2 patients with symptomatic hydrocephalus requiring cerebrospinal fluid diversion, and 1 patient whose tumor-related cyst required delayed cyst aspiration. Three patients developed ARE, including 1 patient with permanent facial weakness (House-Brackmann grade II), 1 who developed trigeminal neuropathy, and 1 who had worsening gait disorder. Six patients had serviceable hearing preservation before SRS, and 2 maintained serviceable hearing preservation after 4 years. A total of 44 (71%) patients died at an interval ranging from 6 to 244 months after SRS.

CONCLUSION: SRS resulted in tumor and symptom control in most octogenarian patients with VS.

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Formation of internal carotid artery aneurysms following gamma knife radiosurgery for pituitary adenomas

Acta Neurochirurgica (2023) 165:2257–2265

Only two aneurysm formations in the internal carotid artery after gamma knife radiosurgery (GKRS) for pituitary adenomas are reported so far.

Here, out of the 482 patients who underwent GKRS for pituitary adenomas at our institute, at least five developed aneurysms within the area of high single-dose irradiation. Three patients presented with epistaxis due to aneurysmal rupture and one presented with abducens paralysis due to nerve compression, while one was asymptomatic.

The interval between irradiation and aneurysmal detection ranged from 14 to 21 years. Aneurysm formation in those conditions may be higher than previously thought.

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Gamma Knife Stereotactic Radiosurgery for Trigeminal Neuralgia Secondary to Multiple Sclerosis

Neurosurgery 93:453–461, 2023

The efficacy of stereotactic radiosurgery (SRS) for the relief of trigeminal neuralgia (TN) is well established. Much less is known, however, about the benefit of SRS for multiple sclerosis (MS)–related TN (MS-TN). OBJECTIVE: To compare outcomes in patients who underwent SRS for MS-TN vs classical/idiopathic TN and identify relative risk factors for failure.

METHODS: We conducted a retrospective, case-control study of patients who underwent Gamma Knife radiosurgery at our center for MS-TN between October 2004 and November 2017. Cases were matched 1:1 to controls using a propensity score predicting MS probability using pretreatment variables. The final cohort consisted of 154 patients (77 cases and 77 controls). Baseline demographics, pain characteristics, and MRI features were collected before treatment. Pain evolution and complications were obtained at follow-up. Outcomes were analyzed using the Kaplan-Meir estimator and Cox regressions.

RESULTS: There was no statistically significant difference between both groups with regards to initial pain relief (modified Barrow National Institute IIIa or less), which was achieved in 77% of patients with MS and 69% of controls. In responders, 78% of patients with MS and 52% of controls eventually had recurrence. Pain recurred earlier in patients with MS (29 months) than in controls (75 months). Complications were similarly distributed in each group and consisted, in the MS group, of 3% of new bothersome facial hypoesthesia and 1% of new dysesthesia.

CONCLUSION: SRS is a safe and effective modality to achieve pain freedom in MS-TN. However, pain relief is significantly less durable than in matched controls without MS.

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