Radiofrequency thalamotomy for tremor produces focused and predictable lesions shown on magnetic resonance images

Radiofrequency thalamotomy is a neurosurgical management option for medically-refractory tremor. In this observational study, we evaluate the MRI features of the resultant lesion, their temporal dynamics, and how they vary depending on surgical factors. We report on lesion characteristics including size and location, as well as how these vary over time and across different MRI sequences. Data from 12 patients (2 essential tremor, 10 Parkinson's disease) who underwent unilateral radiofrequency thalamotomy for tremor were analysed. Lesion characteristics were compared across five structural sequences. Volumetric analysis of lesion features was performed at early (<5 weeks) and late (>5 months) timepoints by manual segmentation. Lesion location was determined after registration of lesions to standard space. All patients showed tremor improvement (clinical global impressions scale) postoperatively. Chronic side-effects included balance disturbances (n = 4) and worsening mobility due to parkinsonism progression (n = 1). Early lesion features including a necrotic core, cytotoxic oedema and perilesional oedema were best demarcated on T2-weighted sequences. Multiple lesions were associated with greater cytotoxic oedema compared with single lesions (T2-weighted mean volume: 537 ± 112 mm³ versus 302 ± 146 mm³, P = 0.028). Total lesion volume reduced on average by 90% between the early and late scans (T2-weighted mean volume: 918 ± 517 versus 75 ± 50 mm³, t = 3.592, P = 0.023, n = 5), with comparable volumes demonstrated at ∼6 months after surgery. Lesion volumes on susceptibility-weighted images were larger than those of T2-weighted images at later timepoints. Radiofrequency thalamotomy produces focused and predictable lesion imaging characteristics over time. T2-weighted scans distinguish between the early lesion core and oedema characteristics, while lesions may remain more visible on susceptibility-weighted images in the months following surgery. Scanning patients in the immediate postoperative period and then at 6 months is clinically meaningful for understanding the anatomical basis of the transient and permanent effects of thalamotomy.

Prognostic factors of unilateral prelemniscal radiations radiofrequency lesions: A surgical technique for the treatment of Parkinson's disease motor symptoms

OBJECTIVE

A group of patients with Parkinson's disease (PD) were managed with unilateral prelemniscal radiation radiofrequency lesions (U-Raprl). The current study aims to evaluate prognostic factors that could influence clinical response.

METHODS

Patients previously diagnosed with PD managed with U-Raprl were included in the study, classifying them into two groups according to their percentage of clinical response (</≥ 50%) at 5 years of follow-up in relation to the part III of the Unified Parkinson's Disease Rating Scale (UPDRS-III), analyzing the possible factors associated with their response (age, evolution of PD, Hoehn and Yahr scale (HYS), and levodopa dose). To show differences between groups before and after the intervention, a T-test was performed, and a Mann-Whitney U test was carried out to determine differences between the response groups, added to an effect size calculation using a Cohen's d (α = 0.05, and β = 0.20).

RESULTS

Thirty-four patients were included, where the most prevalent symptoms were tremor and rigidity, with 52.9% percentage of males, 59.3 ± 6.4 mean age, and 7.4 ± 2.1 of mean evolution of PD. Analysis shows differences between groups (p < 0.05) according to the HYS, UPDRS, and levodopa intake, after the intervention. The analysis of the groups according to their response showed differences between the HYS (p < 0.01, ∆ > 1.5), Age (p < 0.0001, ∆ = 2.38), Evolution (p < 0.0001, ∆ = 2.38), and post-operative UPDRS (p < 0.01, ∆ = 1.38). The qualitative analysis of the distribution regarding the responder group shows that those patients with an age under 58 years, an evolution fewer than 7 years, and a preoperative HYS score smaller than 2, showed a response ≥ 50% according to the UPDRS-III in all cases.

CONCLUSION

U-Raprl is a highly effective procedure with a 5-year persistence of improvement. The most relevant prognostic factors to consider for a clinical response according to UPDRS-III greater than 50% are age under 58 years, less than 7 years of PD evolution, and HYS less or equal to 3.

Gamma Knife central lateral thalamotomy for the treatment of neuropathic pain

OBJECTIVE

The goal of this study was to assess the safety and efficacy of stereotactic central lateral thalamotomy with Gamma Knife radiosurgery in patients with neuropathic pain.

METHODS

Clinical and radiosurgical data were prospectively collected and analyzed in patients with neuropathic pain who underwent Gamma Knife central lateral thalamotomy. The safety and efficacy of the lesioning procedure were evaluated by neurological examination and standardized scales for pain intensity and health-related quality of life. Visual analog scale (VAS) for pain, McGill Pain Questionnaire (MPQ), EuroQol-5 dimensions (EQ-5D), and the 36-Item Short Form Health Survey, version 2 (SF-36v2) were measured during baseline and postoperative follow-up evaluations at 3, 6, 12, 24, and 36 months.

RESULTS

Eight patients with neuropathic pain underwent Gamma Knife central lateral thalamotomy. Four patients suffered from trigeminal deafferentation pain, 2 from brachial plexus injury, 1 from central poststroke facial neuropathic pain, and 1 from postherpetic neuralgia. No lesioning-related adverse effect was recorded during the follow-up periods. All patients had pain reduction following thalamotomy. The mean follow-up time was 24 months. At the last follow-up visits, 5 patients reported ≥ 50% VAS pain reduction. The overall mean VAS pain score was 9.4 (range 8-10) before radiosurgery. After 1 year, the mean VAS pain score decreased significantly, from 9.4 (range 8-10) to 5.5 (mean -41.33%, p = 0.01). MPQ scores significantly decreased (mean -22.18%, p = 0.014). Statistically significant improvements of the SF-36v2 quality of life survey (mean +48.16%, p = 0.012) and EQ-5D (+45.16%, p = 0.012) were observed. At 2 years after radiosurgery, the VAS pain score remained significantly reduced to a mean value of 5.5 (p = 0.027). Statistically significant improvements were also observed for the MPQ (mean -16.05%, p = 0.034); the EQ-5D (mean +35.48%, p = 0.028); and the SF-36v2 (mean +35.84%, p = 0.043). At the last follow-up visits, pain had recurred in 2 patients, who were suffering from central poststroke neuropathic pain and brachial plexus injury, respectively.

CONCLUSIONS

Safe, nonpharmacological therapies are imperative for the management of refectory chronic pain conditions. The present series demonstrates that Gamma Knife central lateral thalamotomy is safe and potentially effective in the long term for relieving chronic neuropathic pain refractory to pharmacotherapy and for restoring quality of life.

Radiofrequency Ablation of Prelemniscal Radiations for the Treatment of Non-Parkinsonian Tremor

OBJECTIVE

Previous reports proposed prelemniscal radiations (Raprl) as a target to treat motor symptoms of Parkinson's disease, and this was found particularly effective to control rest and postural tremor. However, tremor of other etiologies has been seldom treated with deep brain stimulation or ablation in this target. We present a series of such cases successfully treated by Raprl radiofrequency (RF) lesions.

MATERIAL AND METHODS

Six patients with predominant unilateral tremor on the right arm: 4 intention, 1 cerebellar and 1 rubral tremor, incapacitating in spite of at least 2 regimes of medical treatment at maximal tolerated doses, were operated under local anesthesia. RF lesions were performed in Raprl contralateral to most prominent symptoms. Patients had monthly evaluation of tremor severity through the Fahn-Tolosa-Marin Tremor Rating Scale and disability through the Tremor Disability Scale along a 1-year follow-up.

RESULTS

In 4/6 patients tremor was stopped by the simple insertion of an RF electrode in Raprl; in the other 2 cases, stimulation through the RF electrode at 100 Hz, with 100 µs and 1.0-1.5 V, stopped the tremor without side effects. Tremor disappeared in all cases immediately after surgery and partially reappeared in 2 cases with an amplitude about 20% of the preoperative condition. RF lesions in postoperative MRI ranked from 1.8 to 2.6 mm in diameter.

CONCLUSIONS

RF lesioning in Raprl is a simple, highly effective, inexpensive way to treat tremor of different etiologies.

Volumetric analysis of magnetic resonance-guided focused ultrasound thalamotomy lesions

OBJECTIVE Magnetic resonance-guided focused ultrasound (MRgFUS) thalamotomy was recently approved for use in the treatment of medication-refractory essential tremor (ET). Previous work has described lesion appearance and volume on MRI up to 6 months after treatment. Here, the authors report on the volumetric segmentation of the thalamotomy lesion and associated edema in the immediate postoperative period and 1 year following treatment, and relate these radiographic characteristics with clinical outcome. METHODS Seven patients with medication-refractory ET underwent MRgFUS thalamotomy at Brigham and Women's Hospital and were monitored clinically for 1 year posttreatment. Treatment effect was measured using the Clinical Rating Scale for Tremor (CRST). MRI was performed immediately postoperatively, 24 hours posttreatment, and at 1 year. Lesion location and the volumes of the necrotic core (zone I) and surrounding edema (cytotoxic, zone II; vasogenic, zone III) were measured on thin-slice T2-weighted images using Slicer 3D software. RESULTS Patients had significant improvement in overall CRST scores (baseline 51.4 ± 10.8 to 24.9 ± 11.0 at 1 year, p = 0.001). The most common adverse events (AEs) in the 1-month posttreatment period were transient gait disturbance (6 patients) and paresthesia (3 patients). The center of zone I immediately posttreatment was 5.61 ± 0.9 mm anterior to the posterior commissure, 14.6 ± 0.8 mm lateral to midline, and 11.0 ± 0.5 mm lateral to the border of the third ventricle on the anterior commissure-posterior commissure plane. Zone I, II, and III volumes immediately posttreatment were 0.01 ± 0.01, 0.05 ± 0.02, and 0.33 ± 0.21 cm³, respectively. These volumes increased significantly over the first 24 hours following surgery. The edema did not spread evenly, with more notable expansion in the superoinferior and lateral directions. The spread of edema inferiorly was associated with the incidence of gait disturbance. At 1 year, the remaining lesion location and size were comparable to those of zone I immediately posttreatment. Zone volumes were not associated with clinical efficacy in a statistically significant way. CONCLUSIONS MRgFUS thalamotomy demonstrates sustained clinical efficacy at 1 year for the treatment of medication-refractory ET. This technology can create accurate, predictable, and small-volume lesions that are stable over time. Instances of AEs are transient and are associated with the pattern of perilesional edema expansion. Additional analysis of a larger MRgFUS thalamotomy cohort could provide more information to maximize clinical effect and reduce the rate of long-lasting AEs.

Focused ultrasound thalamotomy location determines clinical benefits in patients with essential tremor

Magnetic resonance guided focused ultrasound (MRgFUS) thalamotomy is a novel and minimally invasive ablative treatment for essential tremor. The size and location of therapeutic lesions producing the optimal clinical benefits while minimizing adverse effects are not known. We examined these relationships in patients with essential tremor undergoing MRgFUS. We studied 66 patients with essential tremor who underwent MRgFUS between 2012 and 2017. We assessed the Clinical Rating Scale for Tremor (CRST) scores at 3 months after the procedure and tracked the adverse effects (sensory, motor, speech, gait, and dysmetria) 1 day (acute) and 3 months after the procedure. Clinical data associated with the postoperative Day 1 lesions were used to correlate the size and location of lesions with tremor benefit and acute adverse effects. Diffusion-weighted imaging was used to assess whether acute adverse effects were related to lesions encroaching on nearby major white matter tracts (medial lemniscus, pyramidal, and dentato-rubro-thalamic). The area of optimal tremor response at 3 months after the procedure was identified at the posterior portion of the ventral intermediate nucleus. Lesions extending beyond the posterior region of the ventral intermediate nucleus and lateral to the lateral thalamic border were associated with increased risk of acute adverse sensory and motor effects, respectively. Acute adverse effects on gait and dysmetria occurred with lesions inferolateral to the thalamus. Lesions inferolateral to the thalamus or medial to the ventral intermediate nucleus were also associated with acute adverse speech effects. Diffusion-weighted imaging revealed that lesions associated with adverse sensory and gait/dysmetria effects compromised the medial lemniscus and dentato-rubro-thalamic tracts, respectively. Lesions associated with adverse motor and speech effects encroached on the pyramidal tract. Lesions larger than 170 mm3 were associated with an increased risk of acute adverse effects. Tremor improvement and acute adverse effects of MRgFUS for essential tremor are highly dependent on the location and size of lesions. These novel findings could refine current MRgFUS treatment planning and targeting, thereby improving clinical outcomes in patients.

Radiofrequency Lesioning Through Deep Brain Stimulation Electrodes in Patients with Generalized Dystonia

BACKGROUND

Deep brain stimulation (DBS) is an established treatment for generalized dystonia. However, the DBS device is sometimes removed owing to hardware complications. We present 4 cases of generalized dystonia treated with radiofrequency lesioning through DBS electrodes.

CASE DESCRIPTION

Four patients, 3 men and 1 woman (age range, 34-44 years), underwent DBS for generalized dystonia and subsequently developed complications, such as infection, necessitating removal of the devices. As stopping the stimulation caused recurrence of uncontrollable symptoms, radiofrequency lesioning was performed through the DBS electrodes under local anesthesia, and the DBS systems were removed under local or generalized anesthesia thereafter. The procedures performed were as follows: 2 patients had bilateral pallidotomy, 1 patient had unilateral pallidotomy, and 1 patient had pallidotomy and ipsilateral thalamotomy. As a result, in 4 patients, the dystonic symptoms did not worsen even after removal of the DBS systems during a follow-up period of 1-12 years. However, 1 patient had a small hemorrhage, and 2 patients showed recurrence of dystonia.

CONCLUSIONS

Radiofrequency lesioning with DBS electrodes is feasible in cases of generalized dystonia when the DBS leads have to be removed.

Rescue pallidotomy for dystonia through implanted deep brain stimulation electrode

Background:

Some patients with deep brain stimulation (DBS), where removal of implants is indicated due to hardware related infections, are not candidates for later re-implantation. In these patients a rescue lesion through the DBS electrode has been suggested as an option. In this case report we present a patient where a pallidotomy was performed using the DBS electrode.

Case Description:

An elderly woman with bilateral Gpi DBS suffered an infection around the left burr hole involving the DBS electrode. A unilateral lesion was performed through the DBS electrode before it was removed. No side effects were encountered. Burke-Fahn-Marsden (BFM) dystonia movement scale score was 39 before DBS. With DBS before lesioning BFM score was 2.5 points. The replacement of the left sided stimulation with a pallidotomy resulted in only a minor deterioration of the score to 5 points.

Conclusions:

In the case presented here a small pallidotomy performed with the DBS electrode provided a satisfactory effect on the patient's dystonic symptoms. Thus, rescue lesions through the DBS electrodes, although off-label, might be considered in patients with Gpi DBS for dystonia when indicated.

Lesion focused stereotactic thermo-coagulation of focal cortical dysplasia IIB: a new approach to epilepsy surgery?

PURPOSE

Over the last few decades, preferred epilepsy surgical approaches have developed from standard lobectomies to individually tailored resections. Yet, it remains uncertain how small surgical interventions can be without compromising the success of the surgery. Particularly in patients with epileptogenic lesions identified by magnetic resonance imaging (MRI), it is unresolved whether resection or destruction of the lesion suffices to eliminate the epileptogenic zone. We present a minimally invasive surgical approach that may provide insight into this issue.

METHODS

Two patients with pharmacoresistant epilepsy due to focal cortical dysplasia type IIB demonstrated by 3 Tesla MRI were treated with lesion-focused stereotactic radio-frequency thermo-coagulation. In both patients, pathognomonic epileptic discharges were recorded from the lesion via a stimulation device prior to coagulation. In one patient, the suspected proximity of the lesion to the pyramidal tract was verified by eliciting motor evoked potentials from the depths of the lesion.

RESULTS

Following complete and near complete lesion destruction, seizures (several per day or per week, respectively) ceased in patients A and B, with no seizures for 12 months and 5 months, respectively, at the time of this publication. Neither patient acquired persistent postoperative neurological deficits.

CONCLUSION

The fact that seizure activity stopped after destruction of small bottom-of-sulcus dysplasias implies that in these cases, the epileptogenic zone and the epileptogenic lesion may overlap. If future studies can replicate this finding, focused lesion destruction could be a further development of individually tailored epilepsy surgery. The technique described here is especially suited for high-precision surgery close to eloquent brain structures.