What are the causes of hemichorea?

Hemichorea Causes

Hemichorea is most commonly caused by cerebrovascular disease (particularly stroke affecting the contralateral basal ganglia), followed by metabolic disorders (especially nonketotic hyperglycemia), autoimmune conditions, and structural lesions. 1

Primary Etiologic Categories

Cerebrovascular Disease (Most Common)

• Ischemic stroke affecting the contralateral putamen, caudate nucleus, or subthalamic nuclei is the leading cause of hemichorea 2, 3
• Hemorrhagic stroke in the basal ganglia can produce identical clinical presentations 4
• Transient ischemic attacks in the basal ganglia, even with negative diffusion-weighted imaging, can cause hemichorea—particularly when triggered by brief cardiac arrest or severe hypoperfusion 2
• Isolated temporal lobe infarction with severe middle cerebral artery stenosis has been documented as a rare stroke etiology 3
• Cerebral hypoperfusion from cardiac arrhythmias (atrial flutter, brief cardiac arrest) can cause transient basal ganglia ischemia presenting as hemichorea 2

Metabolic Disorders

• Nonketotic hyperglycemia is the second most common cause, producing characteristic CT hyperdensity and T1 hyperintensity in the contralateral basal ganglia 5, 6
• Symptoms may persist even after glycemic control is achieved 6
• Hypoparathyroidism with bilateral basal ganglia calcification can present as isolated hemichorea, despite bilateral structural lesions 7
• This is a treatable cause that must not be missed—correction of hypocalcemia can lead to significant improvement 7

Autoimmune and Inflammatory Conditions

• Systemic lupus erythematosus with CNS involvement is a well-established cause 1
• Antiphospholipid antibody syndrome can produce hemichorea through thrombotic mechanisms 8
• Other autoimmune encephalitides should be considered in the appropriate clinical context 1

Genetic and Neurodegenerative Disorders

• Huntington's disease typically presents with generalized chorea but can have asymmetric onset 4
• Dentatorubral-pallidoluysian atrophy (DRPLA) is a genetic cause requiring specific testing 1
• Benign hereditary chorea (NKX2-1/TITF1 gene mutations) presents in childhood but can be diagnosed in adults 1

Structural Lesions

• Arteriovenous malformations, dural arteriovenous fistulas, and cavernous malformations in the basal ganglia region 4
• Primary CNS neoplasms and metastatic disease affecting the basal ganglia 4
• Paraneoplastic syndromes can cause hemichorea without direct tumor involvement of the basal ganglia 1

Other Vascular Causes

• Cerebral amyloid angiopathy with microhemorrhages affecting the basal ganglia 4
• Moyamoya disease causing chronic ischemia 4
• Cerebral hyperperfusion syndrome following carotid revascularization 4

Critical Diagnostic Pitfalls

• Do not assume negative diffusion-weighted imaging excludes acute stroke—transient ischemic attacks in the basal ganglia from brief cardiac arrest can cause hemichorea without DWI abnormalities 2
• Always check serum glucose and calcium levels—these are immediately treatable causes that are frequently missed 6, 7
• Consider dynamic ECG monitoring in patients with negative basal ganglia imaging, as brief cardiac arrest (even 5-6 seconds) can cause transient basal ganglia ischemia 2
• Recurrent hemichorea may have different etiologies in the same patient—each episode requires fresh evaluation rather than assuming the same cause 5
• Bilateral basal ganglia lesions can present with unilateral symptoms—hypoparathyroidism with bilateral calcification commonly presents as isolated hemichorea 7

Optimal Diagnostic Approach

Brain MRI without contrast is the optimal initial imaging modality to identify structural causes, assess for neurodegenerative patterns, and evaluate basal ganglia signal abnormalities 4, 1, 9. MRI may reveal caudate atrophy in Huntington's disease, T1 hyperintensity in hyperglycemic hemichorea, or acute infarction 4, 6.

When MRI is negative or inconclusive, consider:

• CT perfusion to detect delayed perfusion in vascular territories that may not show restricted diffusion 3
• Dynamic ECG monitoring for at least 24-48 hours to detect paroxysmal arrhythmias or brief cardiac arrest 2
• Comprehensive metabolic panel including glucose, calcium, phosphate, and parathyroid hormone 7
• Autoimmune panel including antinuclear antibodies and antiphospholipid antibodies when clinical suspicion exists 1
• Genetic testing when family history or clinical features suggest hereditary causes 4, 1