Is MRI (Magnetic Resonance Imaging) better for diagnosing hemichorea?

MRI is Superior for Diagnosing Hemichorea

MRI of the brain without IV contrast is the optimal imaging modality for diagnosing hemichorea due to its superior soft-tissue characterization compared to CT. 1

Advantages of MRI for Hemichorea Diagnosis

• MRI provides superior visualization of the basal ganglia structures, particularly the caudate nuclei and putamen, which are commonly affected in hemichorea 1
• MRI can detect both T2 hyperintensity and hypointensity changes in the striatum that may not be visible on CT 1, 2
• MRI is better at identifying subtle structural changes and atrophy patterns that may be present in neurodegenerative causes of hemichorea 1
• MRI can detect characteristic signal abnormalities in various etiologies of hemichorea:
  • T1 hyperintensity in nonketotic hyperglycemic hemichorea 3
  • T2/FLAIR signal changes in inflammatory or autoimmune causes 4
  • Evidence of acute or chronic vascular lesions in stroke-related hemichorea 5

Limitations of CT in Hemichorea Diagnosis

• CT has limited soft-tissue characterization compared to MRI, making it less sensitive for detecting subtle basal ganglia abnormalities 1
• While CT may be useful for excluding acute cerebrovascular disease or infectious/inflammatory processes, it is not the preferred primary imaging modality 1
• In some rare cases, CT may show basal ganglia abnormalities that are not visible on MRI, but this is uncommon 6

Clinical Considerations

• MRI findings in hemichorea vary based on etiology:
  • Neurodegenerative causes (like Huntington's disease) show progressive atrophy of the neostriatum, particularly the caudate nuclei 1
  • Metabolic causes (like nonketotic hyperglycemia) typically show T1 hyperintensity in the contralateral basal ganglia 3
  • Post-infectious causes (like Sydenham chorea) may show abnormal signal and enlargement of the caudate and putamen 4
• Genetic testing should be performed alongside MRI in cases of suspected Huntington's disease, as imaging may be normal early in the disease course 1, 2
• In cases of recurrent hemichorea, MRI is essential for each episode as different etiologies may be responsible 5

Important Caveats

• MRI may be normal early in the course of neurodegenerative diseases like Huntington's disease 1
• In emergency settings where MRI is not available, CT may be used as an initial screening tool 1
• IV contrast is generally not necessary for initial MRI evaluation of hemichorea but may be considered when infectious or inflammatory conditions are suspected 1
• Follow-up imaging may be valuable as some conditions like Sydenham chorea can lead to permanent basal ganglia changes visible on MRI 4