Outcome of Essential Tremors with Stereotactic Thalamotomy: Noble Art of Lesioning

Objective: Objective of study is to identify the effects of Stereotactic thalamotomy of the nucleus ventral intermediate (VIM) for treatment of essential tremor. Material and Methods: This is a descriptive study.It was performed at NCCI, Karachi, duration of study was 7 years, from 2-10-2012 to 7-10-2019. Those patients were included who were with tremors refractory to medication, their duration of disease was > 3 years, and with grade 4 tremors. The thalamotomy was performed in all cases, and follow-up was conducted at 3, 6, and 12 months respectively. The success of the surgery was measured in the form of a reduction in medication number and reduction in dose >50% and by calculating the Essential Tremor Rating Assessment Scale (tetras). Results: Total of 26 patients were included. All patients showed remarkable improvement post-procedure at 12 month follow-up. 20 (77%) patient required no medications. In 6 (23%) patients, the dose of medication was reduced to less than half post-treatment. The tetras score showed marked improvement in all a patient; 4 (15%) patients who had grade 4 tremor, showed the symptoms of minimal tremors graded 0.5 on last visit 3rd visit. Side effect post-procedure were mild transient numbness on the contralateral side was observed in 11 (42.3%) patient, 1 (3.8%) patient had dysarthria. Conclusion: We concluded that stereostatic Ventral intermedius nucleus thalamotomy was effective in reducing tremor grades and improved all functionality with few mild side effects.

Thalamic lesions produced by gamma thalamotomy for movement disorders

Object. The treatment of Parkinson disease and other kinds of involuntary movement by gamma knife radiosurgery (GKS) is presented. This is an extension of previous work. The clinical course and thalamic lesions were the main factors examined. Methods. Seventeen new cases were added to the previously reported 36 cases. The course and results for the whole series of 53 patients were examined. Treatment was undertaken using a single 4-mm collimator shot to deliver 130 Gy to the target. The target was determined in the previously treated patients by using classic methods involved in conventional stereotactic thalamotomy with microrecording. More recently, target localization has been performed by relating the target point to the total length of the thalamus. Points may then be defined as percentages of that length measured from the anterior pole. Targets can then be determined in relationship to the appropriate percentage. Thirty-five patients have been followed for more than 2 years and the longest follow up was 8 years. Two kinds of thalamic lesion were seen after GKS. Volumetric analysis on MR imaging revealed that the larger lesion was 400 to 500 mm3 at the beginning and gradually decreased in size. The smaller lesion occupied approximately 200 mm3 and also shrank over several months. Eighty percent of the treated cases showed good results and no significant complications, with the tremor subsiding at 1 year (Type 1). Several cases deviated from this standard course in four different ways (Types 2–5). If tremor persisted, conventional stereotactic thalamotomy with microrecording was performed. During such operations, normal neuronal activity was recorded from the region adjacent to the GKS thalamotomy target. This was the region showing a high signal on MR imaging. The activity patterns included the rhythmical grouped discharge of tremor rhythm. Conclusions. Gamma thalamotomy for functional disorders is still under development, but because the results with careful target planning are satisfactory, there are grounds for increasing optimism.

Optimal location of thalamotomy lesions for tremor associated with Parkinson disease: a probabilistic analysis based on postoperative magnetic resonance imaging and an integrated digital atlas

Object. Renewed interest in stereotactic neurosurgery for movement disorders has led to numerous reports of clinical outcomes associated with different treatment strategies. Nevertheless, there is a paucity of autopsy and imaging data that can be used to describe the optimal size and location of lesions or the location of implantable stimulators. In this study the authors correlated the clinical efficacy of stereotactic thalamotomy for tremor with precise anatomical localization by using postoperative magnetic resonance (MR) imaging and an integrated deformable digital atlas of subcortical structures. Methods. Thirty-one lesions were created by stereotactic thalamotomy in 25 patients with tremor-dominant Parkinson disease. Lesion volume and configuration were evaluated by reviewing early postoperative MR images and were correlated with excellent, good, or fair tremor outcome categories. To allow valid comparisons of configurations of lesions with respect to cytoarchitectonic thalamic boundaries, the MR image obtained in each patient was nonlinearly deformed into a standardized MR imaging space, which included an integrated atlas of the basal ganglia and thalamus. The volume and precise location of lesions associated with different clinical outcomes were compared using nonparametric statistical methods. Probabilistic maps of lesions in each tremor outcome category were generated and compared. Statistically significant differences in lesion location between excellent and good, and excellent and fair outcome categories were demonstrated. On average, lesions associated with excellent outcomes involved thalamic areas located more posteriorly than sites affected by lesions in the other two outcome groups. Subtraction analysis revealed that lesions correlated with excellent outcomes necessarily involved the interface of the nucleus ventralis intermedius (Vim; also known as the ventral lateral posterior nucleus [VLp]) and the nucleus ventrocaudalis (Vc; also known as the ventral posterior [VP] nucleus). Differences in lesion volume among outcome groups did not achieve statistical significance. Conclusions. Anatomical evaluation of lesions within a standardized MR image—atlas integrated reference space is a useful method for determining optimal lesion localization. The results of an analysis of probabilistic maps indicates that optimal relief of tremor is associated with lesions involving the Vim (VLp) and the anterior Vc (VP).