Radiofrequency ablation of the pallidothalamic tract and ventral intermediate nucleus for dystonic tremor through the parietal approach

Background

The thalamic ventral intermediate nucleus (Vim) and globus pallidus internus are far apart and cannot be captured using a single electrode.

Case Description

We describe our experience with a patient with dystonic tremors of the head and upper and lower extremities who showed symptomatic improvement after radiofrequency (RF) ablation using a parietal lobe approach with a single trajectory to capture the pallidothalamic tract and Vim. A 46-year-old man developed head tremors at 41 and a right-sided neck tilt three years later. Five years after the onset of the head tremors, tightness of the larynx during speech and tremors in both the upper and lower limbs also appeared. The Toronto Western Spasmodic Torticollis Rating Scale (TWSTRS) score was 24, and the Fahn-Tolosa-Marin Tremor Rating Scale (FTM) score was 48. We captured the pallidothalamic tract and Vim along a single trajectory by locating the entry point in the inferior parietal lobule. One week after treatment, the TWSTRS and FTM scale scores were 9 (62.5%) and 30 (37.5%), respectively. No adverse events were observed.

Conclusion

This case suggests that in dystonic tremors involving abnormalities of the basal ganglia-thalamo-cortical and cerebello-thalamo-cortical circuits, a single electrode can be used to approach both circuits through the parietal lobe approach.

Stepwise Dual-Target Magnetic Resonance-Guided Focused Ultrasound in Tremor-Dominant Parkinson Disease: A Feasibility Study

BACKGROUND

Magnetic resonance-guided focused ultrasound (MRgFUS) has been applied successfully in treating refractory tremors in Parkinson disease (PD). It generates a precise thermal ablation in a specific nucleus or tract, such as ventral intermediate nucleus (VIM) or pallidothalamic tract (PTT). Despite a single lesion improving parts of the PD symptoms, the feasibility and efficacy of a stepwise dual-lesion in VIM and PTT are yet to be explored.

METHODS

Three patients with tremor-dominant PD (aged 60.7 ± 6.0 years) received dual-target MRgFUS treatment with a series of primary and secondary outcome measures. The VIM and PTT were navigated based on individual magnetic resonance imaging planning of the brain. The primary outcome measures were the off-status Clinical Rating Scale for Tremor and Unified Parkinson's Disease Rating Scale part III (UPDRS-III). The secondary outcome measures included UPDRS I, II, IV, Hohen and Yahr score, Neuropsychiatry Inventory, Quality of life in PD Rating Scale, Non-Motor Symptoms Scale, and Clinical Global Impression. The baseline data were compared with those acquired 1 day and 1 month following the treatment.

RESULTS

The severity of tremor and motor deficits represented by Clinical Rating Scale for Tremor-part B and UPDRS III were significantly improved (P < 0.05 by nonparametric Mann-Whitney U tests) after dual-target ablations. The nonmotor symptoms investigated by UPDRS II and Non-Motor Symptoms Scale also showed significant improvement at the 1-day and 1-month follow-up. There was no adverse effect except temporary procedure-related headache and dizziness during the treatment.

CONCLUSIONS

Stepwise dual-lesion targeting VIM and PTT is a safe and effective MRgFUS therapeutic strategy for patients with PD.

Revisiting Forel Field Surgery

BACKGROUND

Lesioning the Forel field or the subthalamic region is considered a possible treatment for tremoric patients with Parkinson disease, essential tremor, and other diseases. This surgical treatment was performed in the 1960s to 1970s and was an alternative to thalamotomy. Recently, there has been increasing interest in the reappraisal of stimulating and/or lesioning these targets, partly as a result of innovations in imaging and noninvasive ablative technologies, such as magnetic resonance-guided focused ultrasonography.

OBJECTIVE

We wanted to perform a thorough review of the subthalamic region, both from an anatomic and a surgical standpoint, to offer a comprehensive and updated analysis of the techniques and results reported for patients with tremor treated with different techniques.

METHODS

We performed a systematic review of the literature, gathering articles that included patients who underwent ablative or stimulation surgical techniques, targeting the pallidothalamic pathways (pallidothalamic tractotomy), cerebellothalamic pathway (cerebellothalamic tractotomy), or subthalamic area.

RESULTS

Pallidothalamic tractotomy consists of a reduced area that includes pallidofugal pathways. It may be considered an interesting target, given the benefit/risk ratio and the clinical effect, which, compared with pallidotomy, involves a lower risk of injury or involvement of vital structures such as the internal capsule or optic tract. Cerebellothalamic tractotomy and/or posterior subthalamic area are other alternative targets to thalamic stimulation or ablative surgery.

CONCLUSIONS

Based on the significant breakthrough that magnetic resonance-guided focused ultrasonography has meant in the neurosurgical world, some classic targets such as the pallidothalamic tract, Forel field, and posterior subthalamic area may be reconsidered as surgical alternatives for patients with movement disorders.