ObjectiveTo describe a case of functional tremor occurring after a successful MR-guided focused ultrasound thalamotomy (MRgFUS) for essential tremor.MethodsA 71-year-old right-handed man with essential tremor was referred to us for consideration of deep brain stimulation surgery for worsening bilateral upper limb tremor after a successful left MRgFUS for essential tremor.ResultsOn clinical exam, signs compatible with a functional tremor were noted, including entertainability and suppressibility. Electrophysiological studies were consistent with essential tremor and superimposed tremor fulfilling the laboratory-supported criteria for functional tremor.DiscussionWe describe the first reported case of a functional movement disorder occurring after successful MRgFUS procedure for essential tremor. Recognising this entity and its development after such therapeutic interventions is essential to avoid further unnecessary invasive therapies.

Highlights We present equivocal cases of FMD, but with ES findings that supported FMD diagnosis. Suggestibility can be utilized in ES to increase its diagnostic certainty. Further application and validation studies are needed to assess its reliability.