William H. Sweet Young Investigators Award: Focused ultrasound central lateral thalamotomy for refractory trigeminal neuralgia: interim phase I trial results

Introduction: Trigeminal neuralgia (TN), a form of neuropathic pain (NP), is the most common cause of facial pain. In the case of an impinging vessel loop, a microvascular decompression (MVD) is often curative, and in other cases, several compressive or ablative approaches to the gasserian ganglion are effective. Some patients remain refractory. To treat refractory NP, evidence for targeting the posterior central lateral nucleus (CLp) of the thalamus is longstanding. This pilot study sought to evaluate the safety and efficacy of bilateral MR-guided focused ultrasound (MRgFUS) CLp thalamotomy to treat refractory TN.

Methods: A prospective, single arm, investigator-initiated trial was developed (NCT04579692). Patients eligible for MR imaging, and tolerant of treatment were included. Patients underwent bilateral MRgFUS CLp thalamotomy. Safety data were collected. Scores for screening, one month, and six month Brief Pain Inventory-Facial (BPI-Facial), Patient Global Impression of Change (PGIC), and Barrow Neurological Institute Pain Intensity (BNI) were collected. Comparative statistics were conducted with an alpha level set at 0.05.

Results: Five patients have received treatment, with two exiting the study at six months follow up, and two currently with one month follow-up. Mean age is 54.6 years (SD:16.1), with a sex ratio of 3:2. Diagnosis duration ranged from 3 to 21 years. Four patients had prior MVDs, one patient prior gamma knife radiosurgery. Bilateral treatment was accomplished in all patients. Mean sonication time was 128.8 minutes (SD:54.0). There were no serious adverse events. Adverse events were all transient and included headache, nausea, transient facial paresthesia. For four patients with one month follow up, mean BPI-Facial decreased 61.7 percent (t-test, p=0.017). BPI-Facial and BNI Pain Intensity Scores trended toward decreasing, while PGIC trended toward increasing. Several patients discontinued TN-directed medications after treatment.

Conclusion : In this preliminary analysis we have observed that bilateral MRgFUS CLp thalamotomy for refractory TN has an acceptable safety profile. This treatment has the potential to be an option for TN patients when medications and/or surgery have failed.