PO-32 | Post-traumatic painful trigeminal neuropathy (13.1.2.3 - ICHD-3) following misguided gamma knife surgery: a case of diagnostic oversight with lasting consequences

Marta Lioi,¹ Laura Marino,¹ Michele Trimboli² | ¹Department of Neurology, Magna Graecia University, Catanzaro, Italy; ²Institute of Neurology, AOU Renato Dulbecco, Catanzaro, Italy

Background: Trigeminal neuralgia (TN) is a debilitating facial pain disorder commonly associated with neurovascular compression (NVC), frequent radiological finding, often asymptomatic and insufficient for diagnosis without clinical correlation. We present a case in which Gamma Knife radiosurgery (GKRS) was performed for presumed TN based on incidental imaging findings, leading to the development of trigeminal neuropathy. According to the International Classification of Headache Disorders (ICHD-3), secondary trigeminal neuropathy refers to facial pain or sensory deficits resulting from a structural lesion, commonly due to tumors, multiple sclerosis, or iatrogenic injury.

Methods: A 50-year-old male with a history of two self-limited episodes of right facial nerve palsy underwent brain MRI, which incidentally showed vascular contact with the right trigeminal nerve. Despite the absence of classic TN symptoms, the patient underwent GKRS in March 2024. By July 2024, the patient developed progressive right-sided trigeminal hypoesthesia and dysesthesia of ophthalmic and maxillary divisions. By the end of 2024, he reported paroxysmal, electric shock-like pain (NRS 10/10) in the right frontal, periorbital, and genian regions, up to five times daily. Brain MRI in December 2024 demonstrated a small enhancing lesion in the cisternal segment of the right trigeminal nerve and mild T2-FLAIR hyperintensity near the root entryzone. Pharmacologic treatment provided no significant benefit.

Results: The absence of prior symptoms, the temporal association of symptom onset with the procedure, and the lack of alternative neuroimaging findings strongly support an iatrogenic etiology. Secondary causes - including neoplasms, multiple sclerosis, neuroborreliosis, neurosarcoidosis, and varicella-zoster virus reactivation - were excluded by clinical and laboratory evaluation.

Conclusion: This case underscores the potential harm of relying solely on imaging findings such as NVC in the absence of clinical features. GKRS should be reserved for patients with clear symptomatic TN who are refractory to medical therapy and not suitable candidates for microvascular decompression. The patient’s clinical course is consistent with a radiosurgery-induced trigeminal neuropathy, fulfilling the criteria for post-traumatic painful trigeminal neuropathy (ICHD-3 code 13.1.2.3). This report highlights the importance of thorough clinical evaluation in facial pain syndromes. Overreliance on radiologic findings without adequate clinical correlation may result in misdiagnosis and unnecessary, potentially harmful interventions.