Focused Ultrasound Thalamotomy for Tremor-dominant Parkinson's Disease: A Prospective 1-year Follow-up Study.

Transcranial magnetic resonance (MR)-guided focused ultrasound (FUS) therapy is an emerging and minimally invasive treatment for movement disorders. There are limited reports on its long-term outcomes for tremor-dominant Parkinson's disease (TDPD). We aimed to investigate the 1-year outcomes of ventralis intermedius (VIM) thalamotomy with FUS in patients with TDPD. Patients with medication-refractory TDPD were enrolled and underwent unilateral VIM-FUS thalamotomy. Neurologists specializing in movement disorders evaluated the tremor symptoms and disability using Parts A, B, and C of the Clinical Rating Scale for Tremor (CRST) at baseline and at 1, 3, and 12 months. In all, 11 patients (mean age: 71.6 years) were included in the analysis. Of these, five were men. The median (interquartile range) improvement from baseline in hand tremor score, the total score, and functional disability score were 87.9% (70.5-100.0), 65.3% (55.7-87.7), and 66.7% (15.5-85.1), respectively, at 12 months postoperatively. This prospective study demonstrated an improvement in the tremor and disability of patients at 12 months after unilateral VIM-FUS thalamotomy for TDPD. In addition, there were no serious persistent adverse events. Our results indicate that VIM-FUS thalamotomy can be safely and effectively used to treat patients with TDPD. A randomized controlled trial with a larger cohort and long blinded period would help investigate the recurrence, adverse effects, placebo effects, and longer efficacy of this technique.

Two-year Follow-up Results of Magnetic Resonance Imaging-guided Focused Ultrasound Unilateral Thalamotomy for Medication-refractory Essential Tremor.

Objective To investigate the long-term efficacy and safety of magnetic resonance imaging-guided focused ultrasound (MRgFUS) unilateral ventral intermediate nucleus (Vim) thalamotomy for medication-refractory essential tremor (ET). Methods We performed MRgFUS left-sided Vim thalamotomy for 10 medication-refractory ET patients (8 men and 2 women, aged 67.1±17.5 years, all right-handed). We followed them for 2 years using the clinical rating scale for tremor (CRST) and the quality of life in essential tremor questionnaire (QUEST). Results Right-handed tremor improved immediately after the left Vim thalamotomy in all patients. The tremor became re-exacerbated in 2 patients by 6 months after treatment; however, an approximately 60% decrease in the average CRST score of the right hand persisted until 2 years. On the other hand, the average CRST score of the left hand and the average QUEST score showed no improvement. Headache was the most common adverse event during the sonication (8 patients), followed by a floating sensation (4 patients). On the other hand, sensory disturbances (4 patients) and gait instability (4 patients) were observed after the treatment, but most of them were mild and transient. There were no delayed adverse events. Conclusion MRgFUS unilateral Vim thalamotomy could be adopted as one of the therapeutic options for intractable ET. Further improvement of tremor in the targeted hand or contralateral Vim thalamotomy may be necessary to improve the quality of life.

Factors Associated with Heating Efficiency in Transcranial Focused Ultrasound Therapy.

Transcranial magnetic resonance-guided focused ultrasound (FUS) therapy is a less invasive stereotactic treatment for tremor and other movement disorders. A sufficiently high temperature in the target brain tissue is crucial during ablation procedures for good outcomes. Therefore, maximizing the heating efficiency is critical in cases where high temperature cannot be achieved because of patient-related characteristics. However, a strategy to achieve the desired therapeutic temperature with FUS has not yet been established. This study aimed to investigate the procedural factors associated with heating efficiency in FUS.We retrospectively reviewed and analyzed data from patients who underwent FUS for ventralis intermedius (VIM) nucleus thalamotomy. In all, 30 consecutive patients were enrolled. 18 with essential tremor (ET), 11 with tremor-dominant Parkinson's disease (TDPD), and 1 with Holmes tremor. Multivariate regression analysis showed that decline in heating efficiency was associated with lower skull density ratio (SDR) and a greater subtotal rise in temperature until the previous sonication. To maximize heating efficiency, the temperature increase should be set to the least value in the target alignment and verification phases, and subsequently should be increased sufficiently in the treatment phase. This strategy may be particularly beneficial in cases where high ablation temperatures cannot be achieved because of patient-related characteristics. Importantly, a broad patient population would benefit from this strategy as it could reduce the need for high energy to achieve therapeutic temperatures, thereby decreasing the risks of adverse events.

Movement during focused ultrasound therapy caused by an unstable magnetic resonance table: case report.

Transcranial MR-guided focused ultrasound (MRgFUS) therapy is a less invasive form of stereotactic treatment for tremors and other movement disorders. Its stereotactic accuracy is ensured by stability of the stereotactic frame and MR table. The authors report a case wherein the patient's movement was detected, and the MR images were repeated to continue the treatment. A 72-year-old man with essential tremor underwent unilateral ventralis intermedius thalamotomy using MRgFUS. The stereotactic frame was correctly fixed to the patient's skull and the table. During the seventh sonication, the patient pressed the emergency button and vomited several times. Before the eighth sonication, the patient's movement was detected and was verified on coronal images. The MR images were repeated, and the treatment was successfully completed with significant improvement in the tremors. After treatment, it was discovered that the MR table was laterally unstable due to the absence of ball bearings, which should be present on both sides of the guide rail of the MR table. The ball bearings were attached to the reverse side of the table, and the table was stabilized. Stereotactic accuracy of MRgFUS is not only ensured by rigid fixation of the stereotactic frame, but also by stability of the MR table.