A 65-year-old man with a 1-month history of left upper and lower limb chorea was admitted to the medical ward of our institution in February 2021. Blood tests revealed new-onset diabetes mellitus with markedly elevated fasting glucose level of 28.5 mmol/L. Urinalysis for ketones was negative. Urgent non-contrast computed tomography (CT) of the brain showed subtle hyperdensity at the right putamen without mass effect or surrounding oedema (Fig 1). The patient was started on subcutaneous insulin, and upon normalisation of blood glucose level, his hemichorea subsided without additional antichorea medications. Follow-up non-contrast magnetic resonance imaging of the brain performed 2 months later revealed T1-weighted hyperintensity in the right putamen, without restricted diffusion (Fig 2). Imaging findings were in keeping with non-ketotic hyperglycaemic hemichorea (NHH). The patient was prescribed a biphasic insulin regimen upon discharge.

An 87-year-old man with a 2-day history of left upper limb chorea was hospitalised in April 2022. He had known diabetes mellitus but was noncompliant with oral hypoglycaemic therapy. Blood tests revealed markedly elevated random glucose level of 30.8 mmol/L. Urgent non-contrast CT of the brain showed asymmetric subtle hyperdensity in bilateral putamen and caudate nuclei, more extensive on the right, but without mass effect or surrounding oedema (Fig 3). Findings were compatible with NHH. The patient resumed metformin, with gliclazide and subcutaneous insulin injection added for optimal control. Upon normalisation of blood glucose level, his hemichorea resolved without antichorea medications.

Unilateral or asymmetric basal ganglia hyperdensity in brain CT of patients with focal neurological symptoms can be alarming, and intracerebral haemorrhage may be suspected. Nonetheless NHH, a rare complication of uncontrolled diabetes, should not be overlooked.

Case reports of NHH have been documented as early as 1960.1 Previously reported cases were frequent in Asian elderly women with uncontrolled diabetes. In most patients, unilateral chorea was observed, although bilateral involvement could be present.2 3 4 Of note, the aetiology of hemichorea is diverse, and other causes include infarct, haemorrhage and neoplasm. Imaging of the brain is therefore crucial.

Non-contrast CT of the brain of NHH typically shows subtle hyperdensity in contralateral putamen and/or caudate nucleus, although bilateral involvement is also seen. There will be no mass effect or perilesional oedema, and this differentiates NHH from haemorrhage or tumour.2 3 4

Similarly, magnetic resonance imaging of the brain typically shows corresponding signal changes in striatal regions contralateral to the symptomatic side. There will be T1-weighted hyperintense signal. Differentials of increased basal ganglia T1-weighted signal are diverse. They include toxin-related causes such as methanol poisoning or hepatic-related causes such as acquired hepatocerebral degeneration, but they commonly show bilateral and symmetrical involvement.5 T2-weighted or fluid-attenuated inversion recovery signals can be variable. Of note, restricted diffusion is not expected in NHH,2 3 4 and this differentiates it from acute ischaemic stroke.

The pathophysiology of NHH is not fully understood. Proposed mechanisms include depleted gamma-aminobutyric acid and disrupted blood-brain barrier at the corpus striatum.2 3 4 Recognising this rare complication of uncontrolled diabetes mellitus enables prompt medical intervention. Neurological symptoms of NHH usually show substantial improvement after normalisation of blood glucose level without additional intervention.2 3 4

All authors contributed to the concept and design of the study, acquisition of data, analysis and interpretation of data, drafting of the manuscript, and critical revision of the manuscript for important intellectual content. All authors had full access to the data, contributed to the study, approved the final version for publication, and take responsibility for its accuracy and integrity.

All authors have disclosed no conflicts of interest.

This study received no specific grant from any funding agency in the public, commercial, or not-for-profit sectors.

The patients were treated in accordance with the Declaration of Helsinki. They provided informed consent for all treatments and procedures, and consent for publication.

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2. Zheng W, Chen L, Chen JH, et al. Hemichorea associated with non-ketotic hyperglycemia: a case report and literature review. Front Neurol 2020;11:96. Crossref

3. Narayanan S. Hyperglycemia-induced hemiballismus hemichorea: a case report and brief review of the literature. J Emerg Med 2012;43:442-4. Crossref

4. Cherian A, Thomas B, Baheti NN, Chemmanam T, Kesavadas C. Concepts and controversies in nonketotic hyperglycemia-induced hemichorea: further evidence from susceptibility-weighted MR imaging. J Magn Reson Imaging 2009;29:699-703. Crossref

5. Hegde AN, Mohan S, Lath N, Lim CC. Differential diagnosis for bilateral abnormalities of the basal ganglia and thalamus. Radiographics 2011;31:5-30. Crossref