Effective Interventional Magnetic Resonance Image–Guided Laser Ablations in a Parkinson's Disease Patient with Refractory Tremor

A 62-year-old man with PD was referred for medication refractory tremor. He had bilateral arm and leg tremors, hypophonia and dysarthria, anxiety, rigidity, and a slow gait. Carbidopa/ levodopa therapy was initiated, but doses higher than 600 mg/ day caused sleepiness and tremor was not improved. Other medications were poorly tolerated. He lived in a rural area and did not drive. On evaluation, there was a prominent rest tremor in both upper extremities and right leg (see Video 1, Segment 1). He had moderate rigidity, bradykinesia, and a slow gait. His UPDRS Motor Subscale (UPDRS-III) score improved 15% after taking antiparkinsonian medications (59 off score, 50 on score), reflecting only improvements in rigidity and bradykinesia. Right hemibody symptoms improved from 22 to 18 (18%). Neuropsychological testing suggested mild cognitive impairment related to PD. To address his medically refractory and disabling tremor, the multidisciplinary team recommended a palliative unilateral left pallidotomy over DBS because of his inability to access follow-up care and difficulty understanding the complexities of neuromodulation therapy. Asleep iMRI-guided lesioning was preferred over the standard radiofrequency technique because of his high level of anxiety and severe speech impairment that would preclude him from participating during awake surgery. Surgery was performed under general anesthesia in a 1.5T MRI scanner (Philips Achieva, Cleveland, OH). The globus pallidus pars interna (GPi) was targeted in the same manner as targeting for DBS using the ClearPoint system (MRI Interventions, Irvine, CA). A fiber optic laser fiber with a 3-mm exposed tip (Visualase; Medtronic, Minneapolis, MN) was advanced to the target using real-time imaging (Fig. 1). Thermal cut-off safety limits of 45°C were set at the pallidocapsular border and optic tract. Lesioning was performed with continuous thermal sensitive imaging until the medial thermal safety limit was reached. The laser was advanced 2 mm, and a second lesion was made until the posterior thermal limit was reached. The damage model prediction on the Visualase software and MR images were reviewed and the lesion was felt to be of adequate size without encroachment of the internal capsule. He had significant tremor reduction immediately postsurgery without complications, but tremor recurred within 1 to 2 days, and within 6 weeks returned to the preoperative state (see Video 1, Segment 2), which suggested that the pallidotomy may have been too small in size. Subsequently, a unilateral left thalamotomy was recommended over a second lesion to enlarge the pallidotomy, based on technical concerns about enlarging the pallidotomy and the intention to treat his most disabling symptom, tremor. Four months after the initial surgery, he underwent a left iMRI-guided laser thalamotomy again using Visualase and ClearPoint. The target in the ventral intermediate nucleus was selected 6 mm ahead of the posterior commissure, 10 mm lateral to the third ventricular wall and at the anterior commissure/posterior commissure plane. A single lesion was created with thermal safety borders on the internal capsule and 4 mm behind the target (Fig. 1). Immediately after the operation, he