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Aim&Background:
MR-guided high intensity focussed ultrasound (MRgFUS) allows ablation of deep brain structures without affecting surrounding tissue. Dyphagia and dysarthria following pallidotomy and subthalamotomy1,2 have been described in the past but comprehensive swallowing assessments including instrumental testing (Fiberoptic Endoscopic Evaluation of Swallowing, FEES) are lacking. After one of our first PD patients treated with unilateral MRgFUS therapy developed dysphagia after 8 months, we decided to study this further. Therefore we aimed to investigate safety regarding swallowing and speech in MRgFUS ablation in patients with movement disorders.
Methods:
Prospective, open label observational study of swallowing and speech after unilateral MRgFUS ablation within the pallidothalamic tract (PTT) or cerebellothalamic tract (CTT) in patients with Parkinson’s disease (PD) and Essential tremor (ET). Unilateral ablation of the PTT (in PD patients) or CTT (in ET patients) was done with the ExAblate Neuro MRgFUS system. Swallowing assessment consisted of a comprehensive clinical assessment by the speech and swallowing specialists including instrumental testing (FEES) before and 6 months after intervention. Dysphagia was graded using the penetration-aspiration scale3 ranging from 1 (no penetration) to 8 (aspiration). Speech intelligibility was graded using the speech intelligibility rating scale4 (SIRS) ranging from 1 (no intelligibility) to 5 (normal intelligibility). Motor symptoms were assessed using the UPDRS III in PD and Fahn Tolosa Marin Score in ET patients pre, post and 1,3 & 6 months after the intervention.
Results:
3 PD (1 m, 65y ±12) and 6 ET patients (2 m, 71y ± 8) received unilateral MRgFUS ablation. None of the patients reported dysphagia and clinical assessment remained unchanged with an aspiration-penetration score of 1 at baseline and at follow up. Swallowing assessment 24 months after intervention of one patient with bilateral PTT ablation was normal (grade 1). Speech intelligibility remained normal (SIRS 1) after treatment in all patients. The PD patient with bilateral treatment progressed from SIRS 3 (baseline) to SIRS 4 (24 months).
In PD patients the mean UPDRS III (ON) score improved from 32.5 ± 12.5 at baseline to 8.7 ± 4.4 after 6 months. In ET patients, tremor of the treated hand was improved by 84.3%.
Conclusion:
Unilateral MRgFUS ablation of the PTT in PD patients or CCT in ET patients is safe regarding dysphagia and dysarthria and highly effective regarding motor improvement.

Literature:
1 L. Alvarez et al. Brain 2005 ;128: 570–583.
2 Robert E. et al. Neurotherapeutics 2008;5:281-293.
3 Rosenbek JC et al. Dysphagia 1996;11:93-98.
4 Samar VJ et al. Journal of Speech and Hearing Research 1988;31:307-316.