Objective: To describe the clinical response to bilateral GPi-DBS in a patient with MC4DN11-associated dystonia.

Background: Mitochondrial Complex IV Deficiency, Nuclear Type 11 (MC4DN11), caused by biallelic pathogenic variants in COX20, is a rare autosomal recessive mitochondrial disorder characterized by childhood-onset sensory neuronopathy and a variable combination of hypotonia, cerebellar ataxia, tremor, dystonia, choreoathetosis, dysarthria, and developmental delay.

Method: We report a 36-year-old woman with progressive movement disorder symptoms beginning in childhood, initially with hand tremor at age 10 and followed by dysarthria and imbalance at age 13. Neurological examination showed moderate dysarthria, ‘no-no’ head tremor, bilateral sternocleidomastoid hypertrophy with retrocollis, right hemidystonia, right-sided dysmetria, brisk reflexes, positive Romberg sign, and impaired tandem gait. Brain MRI revealed spinocerebellar atrophy. Genetic testing in the proband was reported to show a homozygous pathogenic COX20 variant. Botulinum toxin injections provided only partial relief. Because of persistent disabling dystonia, bilateral globus pallidus internus deep brain stimulation (GPi-DBS) was performed.

Results: Following initial programming, the Burke-Fahn-Marsden Dystonia Rating Scale motor score improved from 86 to 48.5 (43.6% improvement), while the disability score improved from 25 to 13 (48% improvement). Functional gains were observed particularly in gait and speech.

Conclusion: To the best of our knowledge, this is the first reported case of GPi-DBS for dystonia in MC4DN11. This observation suggests that GPi-DBS may represent a applicable symptomatic treatment option in carefully selected patients with COX20-related secondary dystonia.

Figure 1. Pedigree

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MDS Abstracts - https://www.mdsabstracts.org/abstract/globus-pallidus-internus-deep-brain-stimulation-for-dystonia-in-cox20-related-mitochondrial-complex-iv-deficiency-mc4dn11-first-reported-case/