Objective: To evaluate the neural activity at the optimal site of ablation or deep brain stimulation (DBS), targeting on caudal Zona incerta (cZi) through ventral thalamic nuclear group ventral oral posterior/ventral intermediate (Vop/Vim).

Background: While ventral oral anterior/posterior (Voa/Vop) is often selected as the optimal target for upper limb dystonia, we targeted cZi through Vop/Vim and selected the ablation or DBS at these sites. The effect was compared with the neural activity pattern.

Methods: During the MRI-guided stereotactic surgery, neural activity was recorded by microelectrodes in 5 nonanaesthetized patients (one female, averaged age 35 years old). The response to cutaneous and deep sensory stimuli as well as the response to movement were also checked while neural activity was being recorded. The site of ablation or DBS was finally chosen from the effect obtained by a microelectrode stimulation. In off-line analysis, the spike train and background activity at rest were assessed by the power spectral analysis. The recorded site was presumed based on the Schaltenbrand atlas.

Results: All 5 patients showed satisfactory improvement after surgery, where two patients by ablation and two by DBS. One patient recurred within four months after ablation, but added DBS was plausible to retrieve his symptoms to the level immediately after ablation. In one representative case, neural activity showed the low frequency (2-3 Hz) spike train both at Vim and Vop. In addition, predominantly low frequency dominance (5-7 Hz) was seen at Vop, while higher frequency band (14 and 35 Hz) was seen at Vim. Ablation site was mainly corresponded to the Vim where higher frequency band was predominant with low frequency spike train. However, DBS was effective near the contacts where low frequency was dominant at the presumed site of Vop. In the case of one patient who was treated both ablation and DBS, ablation sites covered mainly on Vim and DBS contacts almost corresponded to Vop.

Conclusions: Although the patient number is small, ablation and DBS contacts were supposed to effect on the different neural activity patterns.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/stereotactic-surgery-targeting-on-ventral-oral-posteriorventral-intermediate-vopvim-in-patients-with-upper-limb-dystonia-neuronal-activity-and-optimal-effective-site/