title: Diffusion tractography imaging-guided frameless linear accelerator stereotactic radiosurgical thalamotomy for tremor: case report.
abstract: Essential tremor and Parkinson's disease-associated tremor are extremely prevalent within the field of movement disorders. The ventral intermediate (VIM) nucleus of the thalamus has been commonly used as both a neuromodulatory and neuroablative target for the treatment of these forms of tremor. With both deep brain stimulation and Gamma Knife radiosurgery, there is an abundance of literature regarding the surgical planning, targeting, and outcomes of these methodologies. To date, there have been no reports of frameless, linear accelerator (LINAC)-based thalomotomies for tremor. The authors report the case of a patient with tremor-dominant Parkinson's disease, with poor tremor improvement with medication, who was offered LINAC-based thalamotomy. High-resolution 0.9-mm isotropic MR images were obtained, and simulation was performed via CT with 1.5-mm contiguous slices. The VIM thalamic nucleus was determined using diffusion tensor imaging (DTI)-based segmentation on FSL using probabilistic tractography. The supplemental motor and premotor areas were the cortical target masks. The authors centered their isocenter within the region of the DTI-determined target and treated the patient with 140 Gy in a single fraction. The DTI-determined target had coordinates of 14.2 mm lateral and 8.36 mm anterior to the posterior commissure (PC), and 3 mm superior to the anterior commissure (AC)-PC line, which differed by 3.30 mm from the original target determined by anatomical considerations (15.5 mm lateral and 7 mm anterior to the PC, and 0 mm superior to the AC-PC line). There was faint radiographic evidence of lesioning at the 3-month follow-up within the target zone, which continued to consolidate on subsequent scans. The patient experienced continued right upper-extremity resting tremor improvement starting at 10 months until it was completely resolved at 22 months of follow-up. Frameless LINAC-based thalamotomy guided by DTI-based thalamic segmentation is a feasible method for achieving radiosurgical lesions of the VIM thalamus to treat tremor.
authors.affiliation: Departments of1Neurosurgery.
authors.forename: Won
authors.initials: W
authors.lastname: Kim
authors.affiliation: 2David Geffen School of Medicine at UCLA, Los Angeles, California.
authors.forename: Justin
authors.initials: J
authors.lastname: Sharim
authors.affiliation: 3Radiation Oncology, and.
authors.forename: Stephen
authors.initials: S
authors.lastname: Tenn
authors.affiliation: 3Radiation Oncology, and.
authors.forename: Tania
authors.initials: T
authors.lastname: Kaprealian
authors.affiliation: 4Neurology, UCLA Health System; and.
authors.forename: Yvette
authors.initials: Y
authors.lastname: Bordelon
authors.affiliation: 3Radiation Oncology, and.
authors.forename: Nzhde
authors.initials: N
authors.lastname: Agazaryan
authors.affiliation: Departments of1Neurosurgery.|3Radiation Oncology, and.
authors.forename: Nader
authors.initials: N
authors.lastname: Pouratian
mesh_terms: D000369:Aged, 80 and over; D056324:Diffusion Tensor Imaging; D006801:Humans; D053783:Magnetic Resonance Imaging, Interventional; D008297:Male; D010300:Parkinson Disease / Q000000981:diagnostic imaging / Q000503:physiopathology / Q000532:radiotherapy; D010315:Particle Accelerators; D016634:Radiosurgery / Q000295:instrumentation / Q000379:methods; D061089:Radiotherapy, Image-Guided; D013788:Thalamus; D014202:Tremor / Q000000981:diagnostic imaging* / Q000503:physiopathology / Q000532:radiotherapy*
keywords: AC = anterior commissure; ADL = activity of daily living; DBS = deep brain stimulation; DTI = diffusion tensor imaging; GKRS = Gamma Knife radiosurgery; LINAC; LINAC = linear accelerator; PC = posterior commissure; Parkinson's disease; SRS = stereotactic radiosurgery; VIM = ventral intermediate nucleus; diffusion tractography; functional neurosurgery; stereotactic neurosurgery; tremor