Diabetic striatopathy presenting as hemichorea–hemiballismus—Pathophysiologic mechanisms and multimodal neuroimaging findings: A literature review

Hemichorea–hemiballismus syndrome (HHS) is a hyperkinetic movement disorder characterized by unilateral, irregular, involuntary movements. Although vascular lesions are the most common cause, non-ketotic hyperglycemia (often termed diabetic striatopathy ) is a distinctive and potentially reversible etiology with characteristic neuroimaging patterns. We performed a structured literature review of English-language studies published from 1998 onward in PubMed using predefined terms related to HHS, diabetic striatopathy, and hyperglycemia-associated chorea/ballism. We included reports describing patients with hyperglycemia-associated HHS with available neuroimaging (computed tomography; magnetic resonance imaging (MRI), including diffusion-weighted imaging/apparent diffusion coefficient (DWI/ADC) and susceptibility-weighted imaging; fludeoxyglucose-positron emission tomography (FDG-PET); single-photon emission computed tomography (SPECT); or magnetic resonance spectroscopy (MRS). Across included studies, the most consistent structural imaging feature was contralateral striatal T1-weighted MRI hyperintensity, typically involving the putamen and sometimes the caudate nucleus. Susceptibility weighted imaging hypointensity in the same region was frequently reported, with a smaller volume than the T1 abnormality and a tendency to persist or progress over time. DWI/ADC findings were variable, ranging from normal diffusion to transient restriction. Functional imaging (FDG-PET and SPECT) showed heterogeneous results, including reduced glucose metabolism and hypoperfusion in the affected striatum, partly dependent on the timing of imaging. MRS studies suggested metabolic distress/ischemia (elevated lactate and reduced N-acetylaspartate) in the affected basal ganglia, compatible with neuronal dysfunction. Hyperglycemia-associated HHS demonstrates a recurring multimodal imaging pattern centered on contralateral striatal involvement. A convergent mechanistic model includes (i) hyperosmolarity and hyperviscosity leading to striatal hypoperfusion in predisposed microvasculature, (ii) neurotransmitter imbalance (gamma-aminobutyric acid and acetylcholine depletion with relative dopaminergic overactivity), and (iii) reactive astrocytosis/inflammatory changes that may underpin characteristic MRI signals.