Linac‐based stereotactic radiosurgery (SRS) in the treatment of refractory trigeminal neuralgia: Detailed description of SRS procedure and reported clinical outcomes

Abstract

Purpose/ObjectivesTo present our linac‐based SRS procedural technique for medically and/or surgically refractory trigeminal neuralgia (TN) treatment and simultaneously report our clinical outcomes.Materials and MethodsTwenty‐seven refractory TN patients who were treated with a single fraction of 80 Gy to TN. Treatment delivery was performed with a 4 mm cone size using 7‐arc arrangement with differential‐weighting for Novalis‐TX with six MV‐SRS (1000 MU/min) beam and minimized dose to the brainstem. Before each treatment, Winston–Lutz quality assurance (QA) with submillimeter accuracy was performed. Clinical treatment response was evaluated using Barrow Neurological Institute (BNI) pain intensity score, rated from I to V.ResultsOut of 27 patients, 22 (81%) and 5 (19%) suffered from typical and atypical TN, respectively, and had median follow‐up interval of 12.5 months (ranged: 1–53 months). For 80 Gy prescriptions, delivered total average MU was 19440 ± 611. Average beam‐on‐time was 19.4 ± 0.6 min. Maximum dose and dose to 0.5 cc of brainstem were 13.4 ± 2.1 Gy (ranged: 8.4–15.9 Gy) and 3.6 ± 0.4 Gy (ranged: 3.0–4.9 Gy), respectively. With a median follow‐up of 12.5 months (ranged: 1–45 months) in typical TN patients, the proportion of patients achieving overall pain relief was 82%, of which half achieved a complete pain relief with BNI score of I‐II and half demonstrated partial pain reduction with BNI score of IIIA‐IIIB. Four typical TN patients (18%) had no response to radiosurgery treatment. Of the patients who responded to treatment, actuarial pain recurrence free survival rates were approximately 100%, 75%, and 50% at 12 months, 15 months, and 24 months, respectively. Five atypical TN patients were included, who did not respond to treatment (BNI score: IV–V). However, no radiation‐induced cranial‐toxicity was observed in all patients treated.ConclusionLinac‐based SRS for medically and/or surgically refractory TN is a fast, effective, and safe treatment option for patients with typical TN who had excellent response rates. Patients, who achieve response to treatment, often have durable response rates with moderate actuarial pain recurrence free survival. Longer follow‐up interval is anticipated to confirm our clinical observations.

Dosimetric Comparison of 6 MV Flattening Filter Free and 6 MV Stereotactic Radiosurgery Beam Using 4 mm Conical Collimator for Trigeminal Neuralgia Radiosurgery

“…Pokhrel et al reported a detailed study for the treatment of TN with clinical outcomes for Novalis Tx with 27 patients and found that the average MU were 19,440 ± 611, average BOT was 19.4 ± 0.6 minutes and the maximum brainstem dose 15.9 Gy for an 80 Gy prescription. In our study, we were also able to achieve the same for Novalis Tx with average MU 19,869 ± 543, average BOT 19.72 ± 1.1 minutes and a maximum brainstem dose of 14.8 Gy [23]. There is only one study reported using Truebeam with FFF beams for the treatment of TN [24].…”

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

“…The reported patient numbers in series using LINAC SRS for the treatment of TN are comparatively fewer [ 19 – 24 , 28 , 35 – 38 ], consequentially fewer numbers of patients can be reviewed in total, but there are also some smaller prospective LINAC studies (for review see [ 25 ]). Synoptically, the reported success rates are very similar to the published rates of GK therapy.…”

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

“… 3 , 4 , 5 , 6 , 7 , 8 , 9 Although these methods have supplanted cones in the treatment of metastases and larger benign targets such as arteriovenous malformations and acoustic schwannomas, cones remain the standard for functional targets, in particular trigeminal neuralgia. 10 , 11 , 12 , 13 , 14 , 15 , 16 …”