Abstract
BackgroundRadiofrequency (RF) subthalamotomies have been proposed since the 1960s to treat patients suffering from Parkinson's disease (PD). Recently, the magnetic resonance (MR)-guided focused ultrasound technology (MRgFUS) offers the possibility to perform subthalamic thermocoagulations with reduced risks and optimized accuracy. We describe here the initial results of the MRgFUS pallidothalamic tractotomy (PTT), an anatomical and physiological update of the earlier subthalamotomies.MethodsThirteen consecutive patients suffering from chronic (mean disease duration 9.7 years) and therapy-resistant PD were treated unilaterally with an MRgFUS PTT. Primary relief assessment indicators were the score reduction of the Unified Parkinson Disease Rating Scale (UPDRS) and the patient estimation of global symptom relief (GSR) taken at 3 months follow-up. Final temperatures at target were between 52°C and 59°C. The MR examinations were performed before the treatment, 2 days and 3 months after it. The accuracy of the targeting was calculated on 2 days post-treatment MR pictures for each PTT lesion.ResultsThe first four patients received a PTT using the lesional parameters applied for thalamotomies. They experienced clear-cut recurrences at 3 months (mean UPDRS relief 7.6%, mean GSR 22.5%), and their MR showed no sign of thermal lesion in T2-weighted (T2w) images. As a consequence, the treatment protocol was adapted for the following nine patients by applying repetition of the final temperatures 4 to 5 times. That produced thermocoagulations of larger volumes (172 mm3 against 83 mm3 for the first four patients), which remained visible at 3 months on T2w images. These nine patients enjoyed a mean UPDRS reduction of 60.9% and a GSR of 56.7%, very close to the results obtained with radiofrequency lesioning. The targeting accuracy for the whole patient group was 0.5, 0.5, and 0.6 mm for the anteroposterior (AP), mediolateral (ML), and dorsoventral (DV) dimensions, respectively.ConclusionsThis study demonstrated the feasibility, safety, and accuracy of the MRgFUS PTT. To obtain similar results as the ones of RF PTT, it was necessary to integrate the fact that white matter, in this case, the pallidothalamic tract, requires repeated thermal exposition to achieve full lesioning and thus full therapeutic effect.
Highlights
Radiofrequency (RF) subthalamotomies have been proposed since the 1960s to treat patients suffering from Parkinson's disease (PD)
We performed a detailed histological topographical mapping of the fiber tracts in the subthalamus [14] to allow a precise targeting of the fasciculus thalamicus and proposed the term ‘pallidothalamic tractotomy’ (PTT) to indicate the targeted subthalamic structure, i.e., the pallidothalamic tract
We report here the initial results of the MRgFUS pallidothalamic tractotomy in the treatment of PD
Summary
Radiofrequency (RF) subthalamotomies have been proposed since the 1960s to treat patients suffering from Parkinson's disease (PD). To provide treatment to these chronically and severely affected patients, surgical approaches have been developed since the 1950s and 1960s They comprise radiofrequency lesion and high-frequency stimulation (HFS) at the level. We performed a detailed histological topographical mapping of the fiber tracts in the subthalamus [14] to allow a precise targeting of the fasciculus thalamicus and proposed the term ‘pallidothalamic tractotomy’ (PTT) to indicate the targeted subthalamic structure, i.e., the pallidothalamic tract. Through this tract of around 4-ml diameter, the pallidothalamic fibers of the fasciculus lenticularis (or H2 field of Forel) and of the ansa lenticularis are funneled together into the thalamus [15]
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