Objective: To report on a patient with HD and disabling truncal dystonia who was treated with bilateral GPi DBS.

Background: HD is an autosomal-dominant disorder characterized by progressive movement disorders (chorea, dystonia, parkinsonism), cognitive impairment and psychiatric symptoms. Pharmacologic therapy is limited by its effectiveness and side effect profile. Several case reports have outlined the effect of GPi DBS in HD patients with a choreic phenotype, but less is known about the effect of DBS in HD patients with a predominately dystonic phenotype.

Methods: A 66 yo man with HD (41 CAG repeats) of 30 years duration presented with progressive and disabling truncal dystonia. The dystonia interfered with his ability to partake in all daily activities. The movements were most severe in the seated position, but also present while supine, standing and walking. He was unable to sit without displacing the chair backward. Falling asleep and feeding were challenging because of the constant dystonic movement. The global dystonia severity rating scale (GDSRS) score for items trunk and neck were 10 out of 10 pre-operatively. Medications including aripiprazole, tetrabenazine and haloperidol were tried without benefit. Bilateral para-spinal botulinum toxin injections minimally reduced the amplitude but not the frequency of movement. The patient was referred to the DBS clinic to surgically address his primary complaint of truncal dystonia. His MMSE score was 28/30 and he had no depressive or psychotic symptoms.

Results: Bilateral GPi DBS was completed in March of 2014. Lead implantation was challenging due to severe atrophy of the basal ganglia. Stimulation was initiated 1 month after lead placement. The patient started to note significant improvement in the dystonic movement within 2 weeks after stimulation was initiated. The movement continues to be controlled at current time of 21 months post-operatively. The GDSRS scores for trunk and neck were 4 and 1 respectively. The patient is able to sit comfortably without displacing his seat and can partake in activities he could not do pre-operatively.

Conclusions: This report illustrates that GPi DBS may provide sustained benefit in carefully selected HD patients with severe dystonia refractory to other treatment modalities. As was the case in our patient, preserved cognition, lack of significant psychiatric disease, clear goals and expectations, and an involved caregiver are essential for a satisfactory outcome.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/when-dbs-can-be-of-benefit-in-huntingtons-disease/