Objective: To describe our preliminary results of MRIgFUS subthalamotomy in two PD patients.

Background: MRIgFUS thalamotomy has become the preferred surgical approach for refractory essential tremor patients. Few clinical trials have shown that STN-MRIgFUS is an effective and safe procedure for refractory unilateral PD patients.

Method: Patients: PD patients were eligible if they had unilateral refractory parkinsonian signs that negatively impact their quality of life despite dopaminergic medication. Patients with axial symptoms, psychiatric comorbidities or intracranial bleeding history were not considered. Follow-up was scheduled at 1 week, 1, 3 and 6 months. Procedure: Only patients with a skull density ratio (SDR)³ 0.36 were considered. STN was targeted with a 3-Tesla MRI. All patients were assessed under Off medication conditions. Overall, two ablative sonications over 55ºC were performed.

Results: Patient 1 was a 68 years-old male with a mean PD duration of 6 years. He suffered from right side refractory resting tremor and moderate rigidity and bradykinesia. SDR was 0.52. Left STN MRIgFUS was performed. An average peak target temperature of 65ºC to induce a subthalamic ablation was reached with 6 sonications. A 30% benefit in UPDRS-III was obtained post-operatively. Resting tremor mainly resolved. Mild right facial asymmetry was noted as an adverse event. Final volume lesion was 6.5×3.9mm. Motor benefit was sustained at 6 months with a 63% improvement in UPDRS-III. Patient 2 was a 59 years-old male. He suffered from PD since 51. He presented with markedly asymmetric right rigid-akinetic parkinsonism. Left STN was selected under stereotactic coordinates. SDR was 0.54. In order to achieve symptom control, 5 sonications were needed. Average peak target temperature of the two last sonications was 65ºC. Immediately after the procedure, a 45% improvement in UPDRS-III part was achieved. No adverse events were noted. Final volume lesion was 4.7×4.5mm. Follow-up evaluations (1, 3, 6 months) are under way.

Conclusion: STN MRIgFUS was an effective and safe procedure for refractory unilateral PD patients treated in our center. Nevertheless, appropriate patient selection, accurate surgical targeting and technique optimization are still aspects of this novel technique that should be addressed.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/magnetic-resonance-image-guided-high-intensity-focused-ultrasound-mrigfus-subthalamotomy-in-spanish-parkinsons-disease-pd-patients/