Lesion-induced hemichorea-ballism: A systematic review of 586 cases

Hemichorea-ballism has historically been linked to lesions involving the subthalamic nucleus (STN). This continues to influence clinical acumen despite several reports describing more heterogenous lesion locations, and the clinical relevance of the lesion locations within hemichorea-ballism is largely unknown. Here, we aimed to conduct the first systematic review of lesion-induced hemichorea-ballism to provide a comprehensive account of the clinical characteristics of this disorder including examination of clinico-radiological correlations. Reports of cases with lesion-induced hemichorea-ballism published up until January 2025 were identified by a systematic search. Demographic and clinical data were examined across all cases, and according to lesion locations. Of the 586 cases identified, only 24.6 % had lesions intersecting the STN. The majority of cases (83.1 %) had acute symptom-onset within 7 days. Response rate to symptomatic pharmacotherapy was 82.2 %, and 52.8 % of cases remitted. Cases with STN lesions more often showed ballism, had a shorter symptom latency, benefited less often from symptomatic pharmacotherapy, more often underwent functional neurosurgery, and showed a longer delay to remission, compared to cases with non-STN lesions (P < 0.05). Within cases with non-STN lesions, pure cortical lesions were associated with a more favorable prognosis and a shorter delay to remission compared to non-STN lesions involving subcortical structures (P < 0.001). Our results show that lesions causing hemichorea-ballism occur in heterogeneous locations, with only 1 in 4 involving the STN. Crucially, lesion locations were associated with the disorder's clinical characteristics and prognosis. These findings provide clinically useful descriptive evidence and may have ramifications for other lesion-induced movement disorders beyond hemichorea-ballism.