To describe a case of effective contralateral ventralis  intermedius nucleus (Vim) of the thalamus deep brain stimulation (DBS) therapy for symptom progression of essential tremor (ET), in a patient previously treated with ipsilateral MR-guided focused ultrasound (MRgFUS) thalamotomy.

MRgFUS has gained popularity as an alternative to DBS for ET. Its long-term efficacy remains uncertain, and the progression of tremor following MRgFUS challenges clinicians to weigh the risks of additional lesions from MRgFUS, and the operative procedure and programming sessions required for DBS. Currently, there is no consensus regarding optimal strategies for managing disabling tremor after MRgFUS. In cases where MRgFUS loses efficacy, further management with Vim DBS may be advantageous.

Case report.

A 59-year-old right-handed man with longstanding, debilitating ET underwent left thalamic MRgFUS to treat his dominant-side tremor. Despite initial improvement, the tremor recurred within a year and the tremor on the untreated side worsened. One-day post-operative and two-year follow-up MRI showed that the initial thalamic lesion was adequate. After careful analysis of the advantages and disadvantages of DBS versus MRgFUS, Vim DBS surgery was performed for his worsening, untreated tremor. Post-operatively, he experienced 90% reduction of left-sided tremor severity without any post-surgical or stimulation-induced adverse effects. The benefit was sustained at 12-month follow-up. The patient is scheduled to undergo left-sided rescue Vim DBS to manage his remaining symptoms.

For patients with persistent or worsening ET, despite the initial MRgFUS thalamotomy, DBS may be considered as an adjunctive or rescue procedure based on its known safety and efficacy. In this case, key factors in choosing DBS over MRgFUS included the historical risk of aggressive bilateral lesional therapy, a more established safety profile for bilateral implementation of DBS, and the ability to adjust stimulation parameters over time for a patient with demonstrated disease progression.