Magnetic resonance–guided stereotactic laser pallidotomy for dystonia

Although DBS has replaced radiofrequency (RF) pallidotomy for various movement disorders, including dystonia, there remain circumstances where pallidotomy might be indicated. With dwindling experience with RF ablation, however, young practitioners in particular have limited options. MR thermal imaging (MRTI) has opened new possibilities, including focused ultrasound, but experience and availability are limited. MR-guided laser interstitial thermal therapy (MRgLITT), which produces thermocoagulation with a diode laser during MRTI, is being used for various indications, but it is not yet clear whether this is an appropriate tool for ablation for movement disorders. We report on the use of MRgLITT pallidotomy in 2 patients with medically refractory generalized dystonia who were not considered DBS candidates, with mixed results. Case 1 was a 12-year-old male with DYT1 primary dystonia affecting all extremities, trunk, neck, and cranial region, unable to walk with acute bilateral hip dislocations. Marked emaciation was a relative contraindication for DBS, and the family opted for bilateral pallidotomy, performed simultaneously because of acuity of his symptoms, after extensive discussion of all available options. Because he could not tolerate awake surgery, the visual thermal feedback and automatic shutoff with MRgLITT was thought to provide a potentially safer means of performing pallidotomy. Bilateral Visualase cooled laser catheters (3-mm diffusing tip; Medtronic, Minneapolis, MN) were introduced into the global pallidus interna with the ClearPoint platform (Fig. 1A; MRI Interventions, Irvine, CA), using direct targeting and proprietary digital atlas software, and a right pallidotomy was performed (see Fig. 1B and Supplementary Material). A smaller left pallidotomy was then performed because off-target temperature limits were exceeded at low power (Fig. 1C–K). No Burke-Fahn-Marsden Dystonia Rating Scale (BFMDRS) was performed preoperatively, but it improved from 94 at 3 months to 56 at 1 year (40.4%), albeit with no change in disability score. Right-sided symptoms and truncal dystonia greatly improved, particularly hand dexterity and appendicular dystonia, but gait and coordination issues persisted and the patient remaining wheelchair bound and needing assistance with all activities of daily living. Additionally, hypertonicity of the left upper extremity was noticeably worse and often associated with pain, likely related to the larger right-sided lesion encroaching the capsule (Fig. 1G). Furthermore, the patient developed jaw-opening dystonia postoperatively, leading to anarthria and dysphagia. Case 2 was a 32-year-old male with truncal, head, and neck dystonia and spasmodic dysphonia. After adamantly refusing DBS on multiple occasions, he developed spondylotic myelopathy necessitating surgical intervention before cervical surgery. A staged bilateral pallidotomy was planned, nondominant (right) side first, after extensive discussion of the available options. Based on the previous experience, lower power settings were used (see Fig. 1L–N and Supplementary Material). Because of significant improvement and the potential risk, the contralateral pallidotomy was not performed. At 1 year, BFMDRS improved from 23 to 12.5 (45.7%) and Toronto Western Spasmodic Torticollis Rating Scale from 26 to 15 (42.3%). Axial symptoms and speech improved the most, and the patient is now able to ambulate and stand erect with noticeably decreased pain. Benefits were sustained through 2 years. This experience highlights the potential use as well as the challenges associated with this novel technique. The main advantage over RF ablation is that the damage zone can be visualized in near real time, but it is not yet clear how reliable this is with a lesion as small as a pallidotomy or thalamotomy. We caution that much more experience is needed to better understand the thermal power/lesion relationship, and emphasize that RF ablation remains the gold standard. Moreover, we are reminded that, regardless of technique, bilateral simultaneous pallidotomy should be a procedure of last resort.