MR-based stereotactic mesencephalic tractotomy

Medically refractory pain related to cancer is a major indication for pain surgery. Stereotactic mesencephalic tractotomy (SMT) constitutes a widely accepted procedure in treating unilateral head and neck cancer pain.

We report a case of a MRI-based right-sided SMT for treating intractable craniofacial pain, in a 38-year-old patient, related to a previously resected adenocystic carcinoma of the parotid gland. The patient had undergone an implantation of an intrathecal morphine/clonidine pump and subsequent radiofrequency cingulotomy with only temporary improvement. Prior to SMT the patient developed left-sided chest wall pain, secondary to metastasis, in addition to her left-sided facial, dysesthetic pain. The MRI-based SMT was performed with the assistance of a side-extruding monopolar electrode (Leibinger GmbH, Freiburg, Germany) for intraoperative, topographic mapping of the spinothalamic tract. Two lesions were made at 8 and 5 mm off the midline on the right side at the level of the superior colliculus at 70 degrees C for 90 s with a 2 x 4 mm radiofrequency bipolar electrode (Leibinger GmbH).

The patient developed intraoperatively left-sided facial, bodily and extremity thermoanalgesia. She had an unremarkable postoperative course. No early proprioceptive or gaze deficits were noted. Her facial and truncal pain was well controlled with intrathecal morphine and clonidine at the preoperative dosology for 17 months. Left-sided upper extremity dysesthesia developed 15 months after the procedure. The patient expired 18 months after this procedure due to an extensive metastatic disease.

The use of high-resolution MRI (MPRAGE) and side-extruding electrode represent technical maneuvers that could decrease the morbidity and further improve the long-term outcome of SMT in treating patients with chronic, medically refractory cancer pain, who have a likely survival time in the order of 1 year +/- 6 months.