Feasibility of Magnetic Resonance-Guided Focused Ultrasound Thalamotomy for Essential Tremor in the Setting of Prior Craniotomy

BACKGROUND:Magnetic resonance imaging-guided focused ultrasound (MRgFUS) thalamotomy is a rapidly evolving therapy for the treatment of essential tremor. Although the skull is a major determinant of the delivery of acoustic energy to the target, how the presence of a prior craniotomy must be accounted for during lesioning is unclear. OBJECTIVE:To demonstrate novel application of this therapeutic option in a patient with a history of prior craniotomies for unrelated intracranial pathologies. METHODS:A 55-yr-old man with a history of right frontal craniotomy for resection of a colloid cyst underwent a left ventrointermedius nucleus thalamotomy through MRgFUS. The prior craniotomy flap was not excluded in the treatment plan; however, all bony defects and hardware were marked as "no-pass" regions. Clinical outcomes were collected at the 6-mo follow-up. RESULTS:Transducer elements whose acoustic paths would have been altered by the craniotomy defect were turned off. Sonications reaching lesional temperatures of up to 56 degrees C were successfully delivered. The procedure was well-tolerated, without any persistent intra-ablation or postablation adverse effects. The presence of a lesion was confirmed on MRI, which was associated with a significant reduction in the patient's tremor that was sustained at the 6-mo follow-up. CONCLUSION:This case demonstrates the safety and efficacy of MRgFUS thalamotomy in a patient with prior craniotomies and highlights our strategy for acoustic lesioning in this setting.