Non-ketotic hyperglycemic hemichorea

Last revised by Connor C Gemmell on 6 May 2023

Non-ketotic hyperglycemic hemichorea (NHH), also known as diabetic striatopathy or chorea, hyperglycemia, basal ganglia (C-H-BG) syndrome, is a rare neurological complication of non-ketotic hyperglycemia, along with non-ketotic hyperosmolar coma and non-ketotic hyperglycemic seizures. It is a cause of hemichorea-hemiballismus syndrome.

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Non-ketotic hyperglycemic hemichorea is most frequently reported in elderly patients, typically of Asian ethnicity, who have type 2 diabetes mellitus, although this may represent publication bias 2. The majority of cases published involved female patients 4.

Chorea and ballismus develops rapidly and can be either unilateral or bilateral and is seen during episodes of non-ketotic hyperglycemia. Symptoms usually resolve upon normalization of glucose levels. 

The exact underlying pathophysiology of changes seen on imaging of patients with non-ketotic hyperglycemic hemichorea is not fully understood 1,2. 

Some hypothesized mechanisms include 5: 

  • hyperviscosity secondary to hyperglycemia, leading to regional blood-brain barrier disruption and metabolic damage

  • the augmented sensitivity of dopaminergic receptors in a postmenopausal period (possibly explaining the female predominance in reported case series)

  • decreased gamma-aminobutyric acid (GABA) availability in the striatum secondary to the non-ketotic state

CT of the brain initially is normal, but later it can demonstrate hyperdensity in the striatal region (caudate nuclei and putamen) 2,7. Findings tend to be contralateral to the body side affected by hemiballistic/hemichoreic movements. 

MRI of the brain is the modality of choice for assessing possible non-ketotic hyperglycemic hemichorea and typically demonstrates signal changes, particularly in the putamen and/or caudate 1-3. If the changes are unilateral, then they are contralateral to the symptomatic side 2. 

  • T1: hyperintense

  • T2/FLAIR: variable but generally hypointense 

  • SWI: increased susceptibility

  • DWI: high diffusion signal

Overall, the T1 hyperintensity is the most consistent finding of the disease. The increase in T1 signal is hypothesized to be due to increased protein hydration within gemistocytes 8. Other associated findings do not present to the same frequency and tend to vary 6.

Imaging findings gradually resolve after hyperglycemia correction. However, they tend to return to baseline more slowly than the clinical findings 3.

Symptoms and imaging findings usually gradually resolve upon normalization of glucose levels 7, and there is no need for specific management.

The main MRI differentials are that of other causes of increased T1 signal in the basal ganglia (including Wilson disease) and of a striatocapsular infarct 6. 

Some causes of striatal hyperdensity on CT include 6:

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