One Side of the Story; Clues to Etiology in Patients with Asymmetric Chorea

Background: Chorea can be due to a large number of etiologies. Unilateral chorea is classical iy related to a contralateral structural lesion, e.g. of the putamen or subthalamic nucleus, however, based upon personal impressions, we have observed that systemic disease, in particular metabolic or autoimmune conditions, can also lead to a unilateral or markedly asymmetric presentations. We sought to investigate this impression by reviewing the literature. Methods: A PubMed search was conducted using the terms asymmetric" AND "chorea" OR "hemichorea" OR "unilateral" AND "chorea" OR "monochorea" OR right greater than left" AND "chorea" OR "left greater than right" AND "chorea" OR "right more than left" AND "chorea" OR "left more than right" AND "chorea" as well as "hemiballismus" NOT "stroke" NOT "infarct" NOT "dyskinesia. A total of 243 sources were felt to meet criteria and were reviewed. Results: The most common etiology of reported hemi- or asymmetric chorea was diabetic non-ketotic hyperglycemic hemichorea/hemiballismus. Other common diagnoses were Sydenham's disease, antiphospholipid syndrome and drug-induced chorea. The vast majority of patients with hemi- or asymmetric chorea had acquired rather than genetic, degenerative or congenital causes. Conclusion: Despite the potential limitations of our literature review, the evidence presented here supports the observation that the vast majority of asymmetric or unilateral chorea presentations are due to acquired causes, and in this situation an exhaustive search for reversible etiology should be undertaken. However, presentation with symmetric, generalized chorea does not exclude reversible causes, and investigations should address these in addition to genetic and neurodegenerative etiologies.