Repeat magnetic resonance imaging-guided focused ultrasound thalamotomy for recurrent essential tremor: case report and review of MRI findings.

An 86-year-old right-handed man with medically refractory essential tremor was treated using left-sided MRI-guided focused ultrasound (MRgFUS) thalamotomy targeting the dentatorubrothalamic tract (DRTT) at its intersection with the ventral intermediate nucleus of the thalamus, with immediate symptomatic improvement and immediate postprocedure imaging demonstrating disruption of the DRTT. The patient experienced a partial return of symptoms 9 weeks following the procedure, and MRI demonstrated retraction of the left thalamic ablation site. The patient underwent repeat left-sided MRgFUS thalamotomy 4 months after initial treatment, resulting in reduced tremor. MR thermometry temperature measurements during the second MRgFUS procedure were unreliable with large fluctuations and false readings, likely due to susceptibility effects from the initial MRgFUS procedure. Final sonications were therefore monitored using the amount of energy delivered. The patient fared well after the second procedure and had sustained improvement in tremor control at the 12-month follow-up. This is the first report to describe the technical challenges of repeat MRgFUS with serial imaging.