Jennifer Kieltyka

Comparison of thalamotomy to deep brain stimulation of the thalamus in essential tremor

To compare outcome in Essential Tremor (ET) patients who have undergone either thalamotomy or Deep Brain Stimulation (DBS) of the thalamus.

Neuropsychological and quality of life outcome after thalamic stimulation for essential tremor

Objective: To evaluate short-term effects of unilateral thalamic deep brain stimulation (DBS) on cognition, mood state, and quality of life in patients with essential tremor (ET). Background: Unilateral thalamotomy and thalamic DBS are effective in alleviating refractory tremor contralateral to the side of surgery. Thalamotomy can lead to cognitive morbidity, and DBS might be a preferable surgical intervention given potential avoidance or reversibility of such morbidity. Although unilateral thalamic DBS is cognitively safe and leads to quality of life improvement in PD, its neurobehavioral effects in ET are unknown. Methods: Forty patients with ET were administered a broad neuropsychological test battery, measures of mood state, and generic and disease-specific quality of life measures approximately 1 month before and 3 months after surgery (left hemisphere, 38 patients). Results: Unilateral thalamic DBS was associated with significant improvements in tremor and dominant-hand fine visuomotor coordination. Statistically significant but clinically modest gains were observed on tasks of visuoperceptual and constructional ability, visual attention, delayed word list recognition, and prose recall. Only lexical verbal fluency declined significantly after surgery. Patients rated themselves as less anxious after surgery, and they perceived their quality of life as improved significantly. In particular, patients reported improved quality of life with respect to activities of daily living, stigma, emotional well-being, and communication. Conclusions: Unilateral thalamic DBS for ET is cognitively safe and associated with improvements in anxiety and quality of life in the near term and in the absence of operative complications. Patients were better able to carry out activities of daily living after surgery, and they reported improvement in several psychosocial domains of quality of life.

Comparison of Actual Pallidotomy Lesion Location with Expected Stereotactic Location

Accuracy of pallidotomy lesion placement was assessed by comparing actual lesion locations with expected pallidotomy lesion locations based on stereotaxy. Actual and expected lesions were compared in anteroposterior, dorsoventral and lateral axes. In 22 pallidotomies, actual lesion locations were determined using axial MR images. Expected lesion locations were calculated using a starting point derived from preoperative computerized tomography, displacements from the starting point based on microelectrode-driven electrophysiological refinement, and the trajectory angle of the lesioning tract relative to the anterior-posterior commissural plane. On average, actual lesion locations were found 2.91 ± 2.23 mm posterior, 3.22 ± 2.49 mm ventral, and 0.05 ± 1.80 mm lateral compared to the expected lesion location. Discrepancies between the actual lesion and expected lesion locations may be mostly accounted for by posterior and ventral lesion spread from the exposed electrode tip, in-plane and volume averaging effects associated with MR images, and possible brain shifting during surgery. However, despite the remaining small differences between actual and expected lesion location, good clinical outcome of reduced dyskinesias and ‘off’ time along with UPDRS-based improvement in mentation, motor and activity of daily living measures was observed.

Lesion Volume and Clinical Outcome in Stereotactic Pallidotomy and Thalamotomy

Postoperative lesion volume and clinical outcome were assessed in 19 Parkinson’s disease (PD) patients who received posteroventral pallidotomy, and in 14 essential tremor (ET) patients who received ventrolateral thalamotomy. Before and after surgery, PD patients were evaluated using the Unified PD Rating Scale (UPDRS), and ET patients were evaluated using the Fahn-Tolosa-Marin (FTM) tremor rating scale. Inner and total lesion volumes were determined with postoperative MR imaging and three-dimensional data segmentation. Lesion volumes were compared to percent improvement in UPDRS and FTM scores, using Spearman’s rank-order correlation test. No rank-order correlations were found between lesion volume and clinical improvement in either the PD or the ET patients. In performing stereotactic surgery for movement disorders, any lesion volume within a prescribed range may be equally effective in relieving symptoms associated with PD or ET.

Comparative Magnetic Resonance Image-Based Evaluation of Thalamotomy and Pallidotomy Lesion Volumes

Acute thalamotomy and pallidotomy lesion volumes based on magnetic resonance (MR) images were measured in 22 patients (11 thalamotomy and 11 pallidotomy patients). Thalamotomy inner lesion volumes (0.06 ± 0.04 ml; thermocoagulative zone) were smaller than pallidotomy inner lesion volumes (0.14 ± 0.08 ml) as determined using T1-weighted 3D-MPRAGE (1.5-mm slice spacing). Similar results were found using T1-weighted (6-mm slice spacing) image sets (0.09 ± 0.05 ml, thalamotomy; 0.13 ± 0.05 ml, pallidotomy). No differences were found when comparing thalamic or pallidal inner lesion volumes when the comparison was based on T2 weighted images. Thalamotomy total lesion volumes (thermocoagulative and surrounding edematous zones) were less than pallidotomy total lesion volumes independent of the MR protocol. The difference in thalamotomy and pallidotomy lesion volumes is most likely based on the distance between each discrete lesion placed along the lesioning tracts. In 7 of 11 thalamotomies, this distance was 1 mm with the remaining having 2 mm between each discrete lesion. All pallidotomy discrete lesions were 2 mm apart. More overlap between discrete lesioning sites for thalamotomies is likely to produce reduced lesion volumes.