Human and mouse cerebellar inhibitory circuits in dystonic crisis and their modulation with therapeutic stimulation.

Dystonia is a neurological movement disorder characterized by abnormal muscle contractions that, at their most severe, lead to a life-threatening condition - dystonic crisis. Yet, therapeutic options remain limited by our incomplete understanding of what neural circuits underly the condition. Although cerebellar nuclei neurons are implicated in the origin of baseline dystonic symptoms, it is unclear whether their activity drives dystonic crisis. To explore this role, we found that cerebellar abnormalities and neural inhibition were recurring targets in patients with dystonic crisis, implicating cerebellar inhibitory neurons in its development. We devised a mouse genetics approach to test whether inhibitory cerebellar nuclei neurons (iCNNs) induce dystonic crisis. Directional optogenetic modulation of iCNNs induced dystonic crises on-demand and alleviated spontaneous crises in mice that mimic spontaneous dystonic crises. To investigate whether iCNNs interact with other motor areas during dystonic crisis, we identified monosynaptic iCNN projections to the centrolateral nucleus of the thalamus (CL). Deep brain stimulation of the CL alleviated dystonic crises induced by iCNN photoactivation. Our data uncover a cell type-specific cerebellar origin of dystonic crisis and highlight its therapeutic potential.