Trigeminal neuralgia

Trigeminal neuralgia (tic douloureux) is a neuropathic pain syndrome of the trigeminal nerve causing sudden, severe, electric-shock or stabbing pain in the face, typically in the V2 or V3 distribution. Pain is triggered by chewing, speaking, or light touch. Most cases are caused by vascular compression of the trigeminal nerve root at its entry zone on the pons, and it becomes more common with age.

Stereotactic radiosurgery delivers a very high single dose through a tiny 4-mm beam targeted to the cisternal (pre-ganglionic) portion of the trigeminal nerve, creating a controlled partial functional lesion. This reduces the ectopic firing of the nerve while preserving normal facial sensation in most patients. Unlike microvascular decompression, radiosurgery is non-invasive, requires no craniotomy, and is performed in a single day.

A stereotactic head frame or frameless mask with fiducials is applied, and a high-resolution thin-slice MRI with contrast is performed to visualize the trigeminal nerve root entry zone in the prepontine cistern. The nerve is contoured from the brainstem to Meckel cave, and adjacent brainstem surface is contoured as the organ at risk. The plan uses a single 4-mm collimator isocenter placed on the proximal nerve, with the dose fall-off shaped so the brainstem surface receives less than 10–15% of the maximum dose.

A single fraction of 80–90 Gy prescribed to the maximum dose point at the isocenter, with the brainstem constrained to receive well under 15 Gy at its surface. Treatment is delivered in one session lasting under an hour. Pain response is delayed — median time to relief is about four to six weeks — with 70–85% of patients achieving meaningful pain control, and roughly half achieving and maintaining complete relief long-term.