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

Abstract

BackgroundIn this pooled 2-center series LINAC radiosurgery (SRS) has been applied as a treatment option for a subset of refractory trigeminal neuralgia (TN) patients. This study approached to retrospectively assess the efficacy and safety of LINAC SRS and to provide a brief overview addressed to the technical development from frame-based towards frameless robotic SRS.MethodsFrom 2001 to 2017 n = 55 patients (pts) were treated, n = 28 were female (51%), mean age: 66 years (range 36–93 years); TN etiology: 37 classic TN, 15 multiple sclerosis (MS)-related TN, 2 symptomatic TN, and 1 atypical TN. Previous treatment was present in n = 35 (63.6%) pts. (some multiple or combined) with n = 23 microsurgical vascular decompression and n = 17 percutaneous retrogasserian rhizotomy. A 6 MV LINAC (4–5 mm collimators) was applied in all pts. (n = 26 framebased - n = 29 frameless robotic). The dorsal root entry zone (DREZ) was targeted in n = 35 cases and the retrogasserian target in n = 20 pts. with a homogeneous dose for the entire study cohort (90 Gy). SRS outcome was measured using the Barrow Neurological Institute (BNI) score for pain and hypaesthesia and statistically evaluated by univariate and multivariate analyzes.ResultsMean follow-up (FU) was 30 months (2 lost FU); the total rate of post SRS BNI pain I-IIIa (=painfree w or w/o medication) was 69% (88% for the classic TN pts), 29% (38.8% classic TN) were classified as BNI pain I-II (=painfree w/o medication). A BNI hypaesthesia II-III was present in 9.4% (n = 5) and BNI hypaesthesia IV in n = 2. Between groups analysis demonstrated no correlation of SRS responsiveness with age, gender, MS- or not MS-associated TN, previous surgery, framebased/frameless robotic SRS. DREZ targeting significantly better suppressed TN compared to RG targeting (p = 0.01). Additionally, a statistical trend for a better BNI pain outcome (p = 0.07) along with a significant increase in BNI hypaesthesia (p = 0.01) was found when using a larger partial trigeminal 70 Gy volume.ConclusionOur retrospective analysis support LINAC SRS as an effective and safe treatment option in TN. Frameless robotic SRS of TN is safe when using a dedicated LINAC system. A target definition closer to the brainstem and tendencially a larger target volume were associated with a better outcome for pain.

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

“…Rashid et al treated with 90 Gy maximum dose to REZ and retrogasserian targets. Comparison of the two treatment groups identified improved pain freedom in the REZ target patients, and no difference in the development of new facial numbness [26]. Xu et al retrospectively evaluated 141 patients with TN treated using GKR prescribed to a maximum dose of 80 Gy targeting either the REZ or the retrogasserian nerve.…”

Recent update on trigeminal neuralgia

“…The use of a linear accelerator and robotic-assisted SRS for TN treatment has become more common in recent years. Although it is not a curative for TN, it is a viable treatment choice due to its acceptable effectiveness even in pretreated and MS-related patients [36].…”

Radiotherapy of non-tumoral refractory neurological pathologies

“…Eye dryness and eye irritation were reported in 8.3% and 11.2% of patients, respectively. Radiotherapy in functional Neurology -Jacob Rashid et al have published the data of 55 patients treated for TN with SRS delivered by a linear accelerator in two centers [73]. The prescription dose was 90 Gy to the 100% isodose point in most patients.…”