Supplementary Material for: Successful MRI-guided focused ultrasound thalamotomy after ipsilateral Gamma Knife radiosurgery for essential tremor: a case report with video

We report the case of a 67-year-old left-handed female patient with disabling medically-refractory essential tremor who underwent successful right-sided Magnetic Resonance-guided focused ultrasound (MRgFUS) of the ventral intermediate (VIM) nucleus after ipsilateral Gamma Knife radiosurgery (GKRS) thalamotomy performed three years earlier. The GKRS had a partial effect on her postural tremor without side effects, but there was no reduction of her kinetic tremor, nor improvement in her quality of life (QoL). The patient subsequently underwent a MRgFUS thalamotomy, which induced an immediate and marked reduction in both the postural and kinetic tremor components, with minor complications (left upper lip hypoesthesia, dysmetria in her left hand, and slight gait ataxia). The MRgFUS-induced lesion was centered more medially than the GKRS-induced lesion and extended more posteriorly and inferiorly. The MRgFUS-induced lesion interrupted remaining fibres of the dentatorubrothalamic tract (DRTT). The functional improvement one-year post-MRgFUS was significant due to a marked reduction of the patient’s kinetic tremor. The QoL score (QUEST) improved by 88% and her CRST left hand score by 62%. The side effects persisted but were minor, with no impact on her QoL. The explanation for the superior efficacy of MRgFUS compared to GKRS in our patient could be due to either a poor response to the GKRS or to a better localisation of the MRgFUS lesion with a more extensive interruption of DRTT fibers.
In conclusion, MRgFUS can be a valuable therapeutic option after unsatisfactory GKRS especially because MRgFUS has immediate clinical effectiveness, allowing intra-procedural test lesions and possible readjustment of the target if necessary.