Outcome after Stereotactic Thalamotomy for Parkinsonian, Essential, and Other Types of Tremor:

Displaced center of pressure on the treated side in individuals with essential tremor after radiofrequency ablation: a longitudinal case-control study

Background

Essential tremor (ET) is a common involuntary movement disorder (IMD). Radiofrequency ablation (RFA) targeting the ventral intermediate nucleus (Vim) of the thalamus is a stereotactic neurosurgery performed in individuals with ET when pharmacotherapy is no longer effective. Though the reasons remain largely unclear, certain adverse events are known to appear post-RFA. These may be due to functional changes in the Vim, related to RFA-induced tremor reduction, or an adverse reaction to compensatory movement patterns used to perform movements in the presence of tremor symptoms.

Objective

This study aimed to understand the characteristics of post-RFA symptoms in individuals with ET.

Methods

In a longitudinal case-control study, we compared post-RFA symptoms between individuals with ET who underwent Vim-targeted RFA and those with IMD who underwent non-Vim-targeted RFA. Symptoms were compared preoperatively and 1-week and 1-month postoperatively. Quantitative assessments included center-of-pressure (COP) parameters, grip strength, Mini-Mental State Examination, two verbal fluency tests, and three types of physical performance assessments (upper extremity ability, balance ability, and gait ability).

Results

Individuals with ET after RFA showed horizontal displacements of the COP to the treated side (the dominant side of the RFA target's hemisphere) at 1-week postoperatively compared to the preoperative period. The horizontal COP displacement was associated with balance dysfunction related to postural stability post-RFA. Other COP parameters did not significantly differ between the ET and IMD groups.

Conclusion

COP displacement to the treated side may be due to a time lag in adjusting postural holding strategies to the long-standing lateral difference in tremor symptoms associated with tremor improvement after RFA.

Surgical Management of Parkinson’s Disease: The Role of Lesioning Procedures in Developing Countries in the Modern Era

BACKGROUND: The known loss of dopaminergic cells in the pars-compacta of the substantia nigra that is the hallmark of PD. The cellular pathophysiology of the motor dysfunction is beginning to be better understood, thereby providing a stronger scientific rationale for surgical interventions. Yet, to date, there are no treatments that prevent, halt, or cure PD. Surgical strategies, offer symptomatic relief or control of motor complications associated with drug treatment. Both pallidotomy and thalamotomy were extensively used in the treatment of PD in the1950’s and 1960’s. With the introduction of levodopa (L-dopa) in the1960’s and the realization of its striking benefits, surgery was almost abandoned and used only for patients with severe tremor. Surgical therapy is now being used earlier and more often. There are currently three brain regions being considered as targets for functional neurosurgery for PD (other than transplantation). Either CNS lesions (thalamotomy, pallidotomy or subthalamic nucleus lesions) or deep brain stimulation [DBS]. These targets are: The ventral intermediate nucleus of the thalamus (Vim), the internal segment of the Globus Pallidus (GPi) and the subthalamic nucleus (STN). OBJECTIVE: To assess the outcome (3 months & 6 months) of lesioning procedures in parkinson’s disease (PD) patients meeting the inclusion criteria. METHODS: A prospective clinical study conducted on 10 IPD patients during the period from October 2018 to March 2021 at Cairo University Hospitals. This study was concerned to improve the motor symptoms of IPD patients by stereotactic radiofrequency ablative procedures. Cases were restricted to 10 patients due to the Covid-19 pandemic and restriction of elective cases for chronic patients at Cairo University hospitals. RESULTS: In our study we operated upon 10 IPD patients who were meeting our selection criteria by ablative procedures contralateral to parkinsonian symptoms. Age of the patients ranged 17 – 70y with mean of 50.5 ± 16.35 y with predominance in males representing 6 patients. Mean duration of Parkinson`s disease according to history ranged from 2 to 12 y with mean of 8 ± 3.1 years. Patients were divided into three groups according to their presentation and the operation done for them. Thalamotomy group: Pre-operatively, the UPDRS III off & on respectively was 24.4/15.2 and post-operatively was 13/7.4 with improvement 47% / 51%. The tremor subscore was 5.4/2.8 pre-operatively and 1.4/0.8 post-operatively with average of 72% improvement. The UPDRS II pre was 17.2/11.6 and post it became 10.6/7 with 39% improvement. Modified H&Y 2.4/1.7 pre & post-operatively (29% improvement). Pallidotomy group: Pre-operatively, the UPDRS III off & on respectively was 38.5/23.5 and post-operatively was 28/16 with improvement 27% / 32%. The rigidity subscore was 5/2.5 pre-operatively and 2/1 post-operatively with average of 60% improvement. The bradykinesia subscore was 9/5.5 pre-operatively and 5.5/2.5 post-operatively with average of 47% improvement. The dyskinesia subscore was 4.5 pre-operatively and 1.2 post-operatively with average of 71% improvement. The UPDRS II pre was 22/12.5 and post it became 16/10 with 25% improvement. Modified H&Y 2.75/2.25 pre & post-operatively (18% improvement). Combined group: Pre-operatively, the UPDRS III off & on respectively was 41.33/28.67 and post-operatively was 15.67/11.33 with improvement 62% /60%. The rigidity subscore was 5/3.33 pre-operatively and 1.67/1 post-operatively with average of 68% improvement. The bradykinesia subscore was 10/6 pre-operatively and 4/1.33 post-operatively with average of 72% improvement. The UPDRS II pre was 28.33/19.33 and post it became 16.33/10.67 with 43% improvement. Modified H&Y 2.83/2 pre & post-operatively (29% improvement). Postoperatively, there was a high significant statistical finding in all clinical score and subscore of parkinsonian symptoms. CONCLUSION: The study concludes that lesioning procedure should be revisited globally using the modern techniques of targeting and controlled thermal lesion protocols guided by capsular somatotopy and intraoperative macroelectrode stimulation, that will improve the outcome dramatically. Ablative procedures proved their efficacy in controlling motor symptoms of IPD and their cost-benefit in low & middle-income nations.

Focused Ultrasound Thalamotomy for Tremor-dominant Parkinson's Disease: A Prospective 1-year Follow-up Study

Transcranial magnetic resonance (MR)-guided focused ultrasound (FUS) therapy is an emerging and minimally invasive treatment for movement disorders. There are limited reports on its long-term outcomes for tremor-dominant Parkinson's disease (TDPD). We aimed to investigate the 1-year outcomes of ventralis intermedius (VIM) thalamotomy with FUS in patients with TDPD. Patients with medication-refractory TDPD were enrolled and underwent unilateral VIM-FUS thalamotomy. Neurologists specializing in movement disorders evaluated the tremor symptoms and disability using Parts A, B, and C of the Clinical Rating Scale for Tremor (CRST) at baseline and at 1, 3, and 12 months. In all, 11 patients (mean age: 71.6 years) were included in the analysis. Of these, five were men. The median (interquartile range) improvement from baseline in hand tremor score, the total score, and functional disability score were 87.9% (70.5-100.0), 65.3% (55.7-87.7), and 66.7% (15.5-85.1), respectively, at 12 months postoperatively. This prospective study demonstrated an improvement in the tremor and disability of patients at 12 months after unilateral VIM-FUS thalamotomy for TDPD. In addition, there were no serious persistent adverse events. Our results indicate that VIM-FUS thalamotomy can be safely and effectively used to treat patients with TDPD. A randomized controlled trial with a larger cohort and long blinded period would help investigate the recurrence, adverse effects, placebo effects, and longer efficacy of this technique.

The differential diagnosis and treatment of tremor

BACKGROUND

Essential tremor is the most common type of tremor, with a prevalence of 0.4% in the overall population and 4-7% in persons over age 65. In general, tremor is so common that patients with tremor are frequently treated not only by neurologists, but also by physicians from other specialties.

METHOD

This review is based on publications retrieved by a selective PubMed search and on guidelines from Germany and abroad.

RESULTS

Particular tremor syndromes are usually diagnosed on the basis of their typical clinical presentation and whatever accompanying manifestations may be present. Ancillary tests are usually unnecessary. Unilateral rest tremor accompanied by rigidity and bradykinesia is typical of Parkinson's disease. Essential tremor is a bilateral postural tremor. The most common cause of intention tremor is multiple sclerosis. Mild tremor syndromes can often be treated satisfactorily with drugs. In case of severe tremor, which is rarer, a stereotactic operation can be considered. The usual outcome of such procedures is the complete suppression of tremor.

CONCLUSION

Most patients with tremor can be given a precise diagnosis and offered specific treatment. It is important for the physician to inform the patient about the expected course of tremor over time, its possible genetic causes, and the various available treatments.

Factors involved in long-term efficacy of deep brain stimulation of the thalamus for essential tremor

OBJECT

Although nucleus ventralis intermedius stimulation has been shown to be safe and efficacious in the treatment of essential tremor, there is a subset of patients who eventually lose benefit from their stimulation. Proposed causes for this phenomenon include tolerance, disease progression, and suboptimal location. The goal of this study was to assess the factors that may lead to both stimulation failure, defined as loss of meaningful tremor relief, and less satisfactory outcomes, defined as leads requiring voltages>3.6 V for effective tremor control.

METHODS

The authors present their clinical outcomes from 31 leads in 27 patients who had effective tremor control for >1 year following nucleus ventralis intermedius stimulation. All patients postoperatively had a mean decrease in both the writing and drawing subscales of the Fahn-Tolosa-Marin Tremor Rating Scale (p<0.001).

RESULTS

After a mean follow-up of 40 months, 22 patients continued to have tremor control with stimulation. Four patients eventually lost efficacy of their stimulation at a mean of 39 months. There was no difference in age, duration of disease, or disease severity between the groups. Examination of perioperative factors revealed that suboptimal anteroposterior positioning as evidenced on intraoperative fluoroscopy occurred significantly more frequently in patients with stimulation failure (p=0.018). In patients with less satisfactory outcomes, no difference was seen between group demographics. Fluoroscopy again revealed suboptimal positioning more frequently in these patients (p=0.005).

CONCLUSIONS

This study provides further evidence that suboptimal lead position in combination with disease progression or tolerance may result in less satisfactory long-term outcomes.

Gamma Knife thalamotomy for essential tremor

Object

The purpose of this study was to evaluate the results following Gamma Knife thalamotomy (GKT) for medically refractory essential tremor in a series of patients in whom open surgical techniques were not desirable.

Methods

Thirty-one patients underwent GKT for disabling essential tremor after medical therapy had failed. Their mean age was 77 years. Most patients were elderly or had concomitant medical illnesses. A single 4-mm isocenter was used to target a maximum dose of 130 or 140 Gy to the nucleus ventralis intermedius. Items from the Fahn-Tolosa-Marin clinical tremor rating scale were used to grade tremor and handwriting before and after radiosurgery.

Results

The median follow-up was 36 months. In the group of 26 evaluable patients, the mean tremor score (± standard deviation) was 3.7 ± 0.1 preoperatively and 1.7 ± 0.3 after radiosurgery (p < 0.000015). The mean handwriting score was 2.8 ± 0.2 before GKT and 1.7 ± 0.2 afterward (p < 0.0002). After radiosurgery, 18 patients (69%) showed improvement in both action tremor and writing scores, 6 (23%) only in action tremor scores, and 3 (12%) in neither tremor nor writing. Permanent mild right hemiparesis and speech impairment developed in 1 patient 6 months after radiosurgery. Another patient had transient mild right hemiparesis and dysphagia.

Conclusions

Gamma Knife thalamotomy is a safe and effective therapy for medically refractory essential tremor. Its use is especially valuable for patients ineligible for radiofrequency thalamotomy or deep brain stimulation. Patients must be counseled on potential complications, including the low probability of a delayed neurological deficit.

Surgical considerations in movement disorders: deep brain stimulation, ablation and transplantation

Surgical therapy for movement disorders has been practiced since the early 20th century, mostly for Parkinson's disease. At its onset, large destructive procedures like open resection of cortex, parts of the basal ganglia or its fibre connections produced variable, ill-documented results. With the introduction of the stereotactic operating technique in the second half of the century, ablative surgery became more refined, and more selective interventions became possible to alleviate the suffering of those patients for whom no other treatment modalities were yet available. However, the introduction of levodopa-based pharmacological therapy pushed surgical therapy almost completely to the background. In the past two decades, there has been a resurgence of interest in surgery for movement disorders, due to both limitations of long-term pharmacological therapy and the advent of the treatment modality of deep brain stimulation. The subject has now grown into a large field of clinical and scientific interest. Parkinson's disease is the most widespread surgical indication, but in other movement disorders considerable improvement can be achieved by surgery as well, most notably in dystonia. A short review of the surgical therapy for these disorders is presented.

Three-tesla magnetic resonance imaging of the ventrolateral thalamus: a correlative anatomical description

Object

Surgery for tremor targets the ventrolateral nuclei of the thalamus. An initial radiological estimation of this target can be further refined through intraoperative physiological confirmation. Direct visualization of these nuclei has not yet been described. The improved signal-to-noise ratio associated with 3-tesla (3T) magnetic resonance (MR) imaging makes increased spatial resolution possible, which may aid in the identification of subtle morphological features. This study was conducted to describe the anatomy of the nuclei and fiber projections within the ventral thalamus by using 3T MR imaging.

Methods

Using a commercially available 3T MR unit, the authors obtained images of a formalin-fixed, paraffin-embedded brain. Slices with a 2-mm thickness and 0.2-mm gap were obtained parallel to the anterior commissure–posterior commissure (AC–PC) line. The brain was then sectioned through the cerebral hemispheres to obtain tissue slices encompassing the same levels. Adjacent 10-μm paraffin sections from the middle of each level were stained with Luxol fast blue and cresyl violet. The MR image and histological sections at the level of the AC–PC line were then compared in detail. In a separate study, the human thalamus was scanned in vivo using 3T and 1.5T MR imaging for anatomical comparison.

Conclusions

The anatomy of the nuclei and fiber projections within the ventrolateral thalamus in humans can be described using 3T MR imaging. The findings were reproducible in vivo with 3T but not 1.5T MR imaging. Additional studies are needed to confirm the accuracy of this observation for clinical purposes.

A review of neurophysiological testing

The rapid advances in the technology of, and accumulation of pertinent data in, electrophysiological testing has increased exponentially in the past decade. This is attributable to continued advances in computer technology, biomedical engineering, and now the coregistration of the electrophysiological data with neuroimaging results. Knowledge of normal function and electrophysiological response at rest or on stimulation of the central and peripheral nervous systems is important to the neurosurgeon. Only by a basic understanding of normal and abnormal recordings may diagnoses and localizations be achieved. Intraspinal and intracranial surgical procedures are predicated on nontrauma to the neuraxis. This can be accomplished by performing electrophysiological testing to monitor the function of the spinal and cranial nerves, spinal cord, brainstem, basal ganglia, and cerebrum. If the surgeon cannot delineate critical cortex or pathways, he or she will be unable to avoid these areas in the patient.

A comparison of continuous thalamic stimulation and thalamotomy for suppression of severe tremor

BACKGROUND

Deep-brain stimulation through an electrode implanted in the thalamus was developed as an alternative to thalamotomy for the treatment of drug-resistant tremor. Stimulation is thought to be as effective as thalamotomy but to have fewer complications. We examined the effects of these two procedures on the functional abilities of patients with drug-resistant tremor due to Parkinson's disease, essential tremor, or multiple sclerosis.

METHODS

Sixty-eight patients (45 with Parkinson's disease, 13 with essential tremor, and 10 with multiple sclerosis) were randomly assigned to undergo thalamotomy or thalamic stimulation. The primary outcome measure was the change in functional abilities six months after surgery, as measured by the Frenchay Activities Index. Scores for this index can range from 0 to 60, with higher scores indicating better function. Secondary outcome measures were the severity of tremor, the number of adverse effects, and patients' assessment of the outcome.

RESULTS

Functional status improved more in the thalamic-stimulation group than in the thalamotomy group, as indicated by increases in the score for the Frenchay Activities Index (from 31.4 to 36.3 and from 32.0 to 32.5, respectively; difference between groups, 4.4 points; 95 percent confidence interval, 2.0 to 6.9). After adjustment for base-line characteristics, multivariate analysis also showed that the thalamic-stimulation group had greater improvement (difference between groups, 5.1 points; 95 percent confidence interval, 2.3 to 7.9). Tremor was suppressed completely or almost completely in 27 of 34 patients in the thalamotomy group and in 30 of 33 patients in the thalamic-stimulation group. One patient in the thalamic-stimulation group died perioperatively after an intracerebral hemorrhage. With the exception of this incident, thalamic stimulation was associated with significantly fewer adverse effects than thalamotomy. Functional status was reported as improved by 8 patients in the thalamotomy group, as compared with 18 patients in the thalamic-stimulation group (P=0.01).

CONCLUSIONS

Thalamic stimulation and thalamotomy are equally effective for the suppression of drug-resistant tremor, but thalamic stimulation has fewer adverse effects and results in a greater improvement in function.

Parkinson's disease. Second of two parts

At no time in the past have the basic and clinical sciences applied to Parkinson's disease been so active. Experimental therapies under study at present promise to improve on the limitations of existing treatments. Future progress in understanding the causation and pathogenesis of the disorder will permit the development of new treatments that will slow, halt, or even reverse the currently inexorable progressive course of Parkinson's disease.

Gamma knife radiosurgery for thalamotomy in Parkinsonian tremor: a five-year experience

Certain patients, for example elderly, high-risk surgical patients, may be unfit for radiofrequency thalamotomy to treat Parkinsonian tremor. Some patients, when given the opportunity, may choose to avoid an invasive surgical procedure. The authors retrospectively reviewed their experience using gamma knife radiosurgery for thalamotomies in this patient subpopulation.

Radiosurgical nucleus ventralis intermedius thalamotomy using the gamma knife unit was performed to make 38 lesions in 24 men and 10 women (median age 73 years, range 58-87 years) over a 5-year period. A median radiation dose of 130 Gy (range 100-165 Gy) was delivered to 38 nuclei (four patients underwent bilateral thalamotomy) using a single 4-mm collimator following classic anatomical landmarks. Twenty-nine lesions were made in the left nucleus ventralis intermedius thalamus for right-sided tremor. Patients were followed for a median of 28 months (range 6-58 months). Independent neurological evaluation of tremor based on the change in the Unified Parkinson's Disease Rating Scale tremor score was correlated with subjective patient evaluation. Comparison was made between a subgroup of patients in whom “low-dose” lesions were made (range 110-135 Gy, mean 120 Gy) and those in whom “high-dose” lesions were made (range 140-165 Gy, mean 160 Gy) for purposes of dose-response information.

Four thalamotomies (10.5%) failed, four (10.5%) produced mild improvement, 11 (29%) produced good improvement, and 10 (26%) produced excellent relief of tremor. In nine thalamotomies (24%) the tremor was eliminated completely. The median time to onset of improvement was 2 months (range 1 week-8 months) Concordance between an independent neurologist's evaluation and that of the patient was statistically significant (p < 0.001). Two patients who underwent unilateral thalamotomy experienced bilateral improvement of their tremor. There were no neurological complications. There was better tremor reduction in the high-dose group when compared with the low-dose group (p < 0.04).

Although less effective than other stereotactic techniques, gamma knife radiosurgical thalamotomy offers tremor control with minimal risk to a patient population unsuited for open surgery.

Gamma knife radiosurgery as a lesioning technique in movement disorder surgery

Fifty-five patients underwent radiosurgical placement of lesions either in the thalamus (27 patients) or globus pallidus (28 patients) for treatment of movement disorders. Patients were evaluated pre- and postoperatively by a team of observers skilled in the assessment of gait and movement disorders who were blinded to the procedure performed. They were not associated with the surgical team and concomitantly and blindly also assessed a group of 11 control patients with Parkinson's disease who did not undergo any surgical procedures. All stereotactic lesions were made with the Leksell gamma unit using the 4-mm secondary collimator helmet and a single isocenter with dose maximums from 120 to 160 Gy. Clinical follow-up evaluation indicated that 88% of patients who underwent thalamotomy became tremor free or nearly tremor free. Statistically significant improvements in performance were noted in the independent assessments of Unified Parkinson's Disease Rating Scale (UPDRS) scores in the patients undergoing thalamotomy. Eighty-five and seven-tenths percent of patients undergoing pallidotomy who had exhibited levodopa-induced dyskinesias had total or near-total relief of that symptom. Clinical assessment indicated improvement of bradykinesia and rigidity in 64.3% of patients who underwent pallidotomy. Independent blinded assessments did not reveal statistically significant improvements in Hoehn and Yahr scores or UPDRS scores. On the other hand, 64.7% of patients showed improvements in subscores of the UPDRS, including activities of daily living (58%), total contralateral score (58%), and contralateral motor scores (47%). Ipsilateral total UPDRS and ipsilateral motor scores were both improved in 59% of patients. One (1.8%) of 55 patients experienced a homonymous hemianopsia 9 months after pallidotomy due to an unexpectedly large lesion. No other complications of any kind were seen. Follow-up neuroimaging confirmed correct lesion location in all patients, with a mean maximum deviation from the planned target of 1 mm in the vertical axis. Measurements of lesions at regular interals on postoperative magnetic resonance images demonstrated considerable variability in lesion volumes. The safety and efficacy of functional lesions made with the gamma knife appear to be similar to those made with the assistance of electrophysiological guidance with open functional stereotactic procedures.

Functional lesions may be made safely and accurately using gamma knife radiosurgical techniques. The efficacy is equivalent to that reported for open techniques that use radiofrequency lesioning methods with electrophysiological guidance. Complications are very infrequent with the radiosurgical method. The use of functional radiosurgical lesioning to treat movement disorders is particularly attractive in older patients and those with major systemic diseases or coagulopathies; its use in the general movement disorder population seems reasonable as well.