J Neurol Surg A Cent Eur Neurosurg 2022; 83(04): 361-367
DOI: 10.1055/s-0041-1735856
Original Article

Should the Globus Pallidus Targeting Be Refined in Dystonia?

1   Neurosurgery Unit, Fundação de Beneficiência Hospital de Cirurgia, Cirurgia, Aracaju, Sergipe, Brazil
2   Division of Functional Neurosurgery, Department of Neurology, University of São Paulo, School of Medicine, Sao Paulo, São Paulo, Brazil
,
Fábio Luiz Franceschi Godinho
2   Division of Functional Neurosurgery, Department of Neurology, University of São Paulo, School of Medicine, Sao Paulo, São Paulo, Brazil
,
Manoel Jacobsen Teixeira
3   Department of Neurosurgery, University of São Paulo, São Paulo, São Paulo, Brazil
,
Clarice Listik
4   Movement Disorders Center, Department of Neurology, School of Medicine, University of Sao Paulo, Sao Paulo, São Paulo, Brazil
,
Ricardo Ferrareto Iglesio
2   Division of Functional Neurosurgery, Department of Neurology, University of São Paulo, School of Medicine, Sao Paulo, São Paulo, Brazil
,
Kleber Paiva Duarte
2   Division of Functional Neurosurgery, Department of Neurology, University of São Paulo, School of Medicine, Sao Paulo, São Paulo, Brazil
,
Rubens Gisbert Cury
4   Movement Disorders Center, Department of Neurology, School of Medicine, University of Sao Paulo, Sao Paulo, São Paulo, Brazil
› Author Affiliations

Abstract

Background and Study Aims Deep brain stimulation (DBS) of the globus pallidus internus (GPi) is a highly effective therapy for primary generalized and focal dystonias, but therapeutic success is compromised by a nonresponder rate of up to 20%. Variability in electrode placement and in tissue stimulated inside the GPi may explain in part different outcomes among patients. Refinement of the target within the pallidal area could be helpful for surgery planning and clinical outcomes. The objective of this study was to discuss current and potential methodological (somatotopy, neuroimaging, and neurophysiology) aspects that might assist neurosurgical targeting of the GPi, aiming to treat generalized or focal dystonia.

Methods We selected published studies by searching electronic databases and scanning the reference lists for articles that examined the anatomical and electrophysiologic aspects of the GPi in patients with idiopathic/inherited dystonia who underwent functional neurosurgical procedures.

Results The sensorimotor sector of the GPi was the best target to treat dystonic symptoms, and was localized at its lateral posteroventral portion. The effective volume of tissue activated (VTA) to treat dystonia had a mean volume of 153 mm3 in the posterior GPi area. Initial tractography studies evaluated the close relation between the electrode localization and pallidothalamic tract to control dystonic symptoms.

Regarding the somatotopy, the more ventral, lateral, and posterior areas of the GPi are associated with orofacial and cervical representation. In contrast, the more dorsal, medial, and anterior areas are associated with the lower limbs; between those areas, there is the representation of the upper limb. Excessive pallidal synchronization has a peak at the theta band of 3 to 8 Hz, which might be responsible for generating dystonic symptoms.

Conclusions Somatotopy assessment of posteroventral GPi contributes to target-specific GPi sectors related to segmental body symptoms. Tractography delineates GPi output pathways that might guide electrode implants, and electrophysiology might assist in pointing out areas of excessive theta synchronization. Finally, the identification of oscillatory electrophysiologic features that correlate with symptoms might enable closed-loop approaches in the future.



Publication History

Received: 14 October 2020

Accepted: 09 March 2021

Article published online:
22 November 2021

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