LINAC-based stereotactic radiosurgery for the third treatment of refractory Trigeminal Neuralgia

Summary: Case Report-Introduction: Trigeminal neuralgia (TN) is a severe facial pain syndrome characterized by episodic, electric shock-like pain along the trigeminal nerve distribution. Stereotactic radiosurgery (SRS) is an effective treatment modality for refractory TN, typically reserved for cases that do not respond to pharmacological or surgical interventions. Although repeat SRS for refractory TN has been documented, data on third-treatment SRS, particularly with linear accelerator-based (LINAC) frameless SRS using a cone, is sparse. This case report presents a unique case of third-treatment SRS using LINAC-SRS in a patient with refractory TN. Case Report-Case Presentation: A 77-year-old woman with a 20-year history of refractory TN, as well as comorbid hypertension, diabetes, migraine, and prior stroke, presented in January 2024 with worsening right-sided facial pain exacerbated by talking, brushing her teeth, and eating. Her treatment history included balloon rhizotomy (approximately 10 years prior), LINAC-SRS (75 Gy) in 2017, and a second LINAC-SRS (60 Gy) in July 2022. Patient had pain relief for several years after the ballon rhizotomy and first SRS course. She also had good control for around 8 months after 2022 SRS treatment. At this time and despite multiple medications, her pain remained uncontrolled, prompting a decision to pursue a third LINAC-SRS treatment. In March 2024, the patient underwent frameless LINAC-SRS with an 80 Gy dose (4 mm cone, 7 arcs) targeted more distally from the brainstem compared to prior treatments, limiting the brainstem’s maximal dose to 3.66 Gy. Her pain initially worsened which was managed with increased methadone. However, at her six-month follow-up, she reported substantial pain relief, a reduced pain medication regimen, reported no new neurological symptoms, and had an unremarkable cranial nerve examination. Case Report- Discussion: TN is a profoundly debilitating condition for which SRS remains a well-established treatment for refractory cases. However, recurrence of symptoms often necessitates repeated interventions. The literature on third-time SRS is limited, primarily addressing Gamma Knife® treatments and indicating around 80% efficacy durable for more than three years with a 20% incidence of new neurological disturbances¹. To our knowledge, this is the first documented case of a patient with refractory TN undergoing three rounds of LINAC-SRS with sustained pain relief and no new neurological deficits at six months post-treatment. Case Report-Conclusion: A third course of LINAC-SRS may be a viable, safe, and effective option for patients with refractory TN, providing symptom relief without significant neurological sequelae. Further studies are warranted to better understand the efficacy and safety of repeat LINAC-SRS in this patient population. Aria Shakeri (he/him/his), MD (Presenting Author) - University of Rochester Medical Center; Jihyung Yoon, PhD (Co-Author) - University of Rochester Medical Center; Kenneth Usuki, MD (Co-Author) - University of Rochester Medical Center