Objective: Our objective is to describe experience with new targets for deep brain stimulation in children with genetic or acquired dystonias.

Background: Although DBS has shown significant benefit in several genetic dystonias, results are variable and incomplete in many etiologies.  We suggest that improved outcomes will require discovery of new DBS targets that need to be selected using personalized evaluation.

Method: We have developed a new method for DBS targeting based on techniques commonly used for surgical treatment of epilepsy.  Temporary stereo EEG depth electrodes are placed at multiple potential targets for each patient, and efficacy is tested using stimulation and recording during a one-week hospitalization in a neuromodulation monitoring unit (NMU).  Targets include GPi, VA, Voa/Vop, Vim, and VPL nuclei of the thalamus, STN, SNr, and PPN.  Electrodes are often inserted so as to contact more than one target.  Final targets for implantation of permanent electrodes are selected based on results from stimulation and recording in the NMU.  In almost all cases we implant 4 permanent electrodes to provide broad control of symptoms.

Results: We have performed the test procedure in 37 patients with dystonia, ages 5-23years.   The total number of targets for temporary leads was 379 (GPi 114, VA 48, Voa/Vop 74, Vim 72, VPL 14, STN 41, SNr 4, PPN 12).  The total number of targets for permanent leads was 147 (GPi 68, VA 12 Voa/Vop 19, Vim 26, VPL 1, STN 9, SNr 2, PPN 8).  

Of note, subjects with similar diagnoses often required very different targets.  The number of patients is insufficient to draw strong conclusions on the relationship between symptoms and optimal targets, but our experience suggests that limb hypertonia responds to GPi while axial hypertonia responds to PPN or SNr.  Limb hyperkinetic movements respond to thalamus, but the target varies between children.  Cervical or pharyngeal symptoms respond to STN, SNr, or PPN.  In all cases, stimulation at 4 permanent leads was superior to stimulation at only 2 leads. BFMDRS rating shows improvement in all implanted subjects.

Conclusion: Our experience suggests that additional targets in thalamus and brainstem, including SNr and PPN, may be effective in a subset of children and young adults with dystonia.  The larger number of targets requires individualized testing for optimization.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/new-dbs-targets-for-dystonia-in-thalamus-and-brainstem/