A 9-year-old male with intellectual disability and epilepsy presented with a progressive movement disorder characterized by chorea and dystonia primarily affecting the left face, arm, and leg. Neuroimaging revealed a diffuse Spetzler-Martin grade 4 arteriovenous malformation centered within the right thalamus with bilateral extension into the basal ganglia, midbrain and pons. An associated network of developmental venous anomalies was noted to coalesce into ectatic deep drainage, causing obstructive hydrocephalus (Figure 1). Surgical management was not indicated given the anatomy and location of the lesion.

The patient presented in the setting of step-wise clinical decline over several months, with worsening of chorea and dystonia resulting in loss of function of the left arm, severe left arm pain, and loss of the ability to ambulate independently (Video 1).  The involuntary movements and arm pain improved following treatment with clonazepam, baclofen, tetrabenazine, and hydrocodone/acetaminophen as well as chemodenervation with intramuscular botulinum toxin.  The patient developed somnolence in the setting of worsening hydrocephalus, which resolved with the placement of a ventriculoperitoneal shunt.

The pathogenesis of secondary movement disorders is varied; etiologies include hypoxia, stroke, and kernicterus [1]. Movement disorders resulting from congenital vascular malformations are relatively uncommon and can be difficult to treat. Apart from producing structural abnormalities, which can physically disrupt normal basal ganglia-thalamocortical circuits, vascular malformations can further complicate regional dysfunction by vascular steal phenomena [2]. In this case, surgical and medical management has been helpful. Intrathecal baclofen therapy may be an option in the future should symptoms become refractory to oral regimens.