Vascular contribution to hyperglycaemia-induced hemichorea

Abstract

Hemichorea, due to contralateral basal ganglia dysfunction, is well described in patients with hyperglycaemia but the underlying mechanism remains poorly understood. We present clinical and radiological data that support ipsilateral vascular compromise to the basal ganglia in such cases. We suggest vascular evaluation in patients with unilateral neurological phenomena secondary to suspected systemic or metabolic disorders.

Introduction

Extremes of blood sugar are associated with neuronal damage, and while hypoglycaemic states often result in diffuse brain injury, hyperglycaemia may cause focal neurological deficits or seizures. The basal ganglia are particularly sensitive to metabolic disturbance, which gives rise to characteristic radiological findings on computed tomography (CT) and magnetic resonance imaging (MRI). We describe the case of a poorly controlled diabetic patient who presented with hemichorea and postulate why vascular insufficiency may have been contributory.

Case report

A 63-year-old woman with a history of type 2 diabetes mellitus, hypertension, and hyperlipidaemia presented with sudden onset of involuntary movements involving the left arm and leg. Clinically, she had left hemichorea, with nonsuppressible movements that worsened with stress and abated during sleep (supplementary video). There was no weakness or sensory deficit. On arrival, her blood glucose level was highly elevated (29.2 mmol/L, normal range = 4.4–6.1 mmol/L), and the elevated glycosylated haemoglobin level of 16.7% (normal range < 6.0%) represented poor diabetic control. The finding of urinalysis was negative for ketones. Brain imaging (Figure 1(a) to (c)), performed on day 2, revealed abnormal signals within the right basal ganglia. Severe focal stenosis of right terminal internal carotid artery (ICA) was noted on the magnetic resonance angiography (Figure 1(d)). Aggressive control of blood glucose with insulin resulted in rapid amelioration of her choreiform movements.

Figure 1.

(a) Hyperglycaemia-induced metabolic injury is seen in the right caudate nucleus and putamen as distinct hyperdensity on the axial noncontrast brain CT. (b) Abnormal hyperintense signals on the high-quality T1-weighted MR imaging that appeared hypointense on T2-weighted imaging (c) in the right basal ganglia exclude the possibilities of haemorrhagic or ischaemic pathology. (d) Severe stenosis (arrow) of the right terminal internal carotid artery is demonstrated on MR angiography.

Discussion

The pathogenesis of hyperglycaemia-induced basal ganglia changes, and accompanying neuroimaging findings are poorly understood and believed to be secondary to regional metabolic disturbances and vascular insufficiency. ¹ In the majority of cases, despite systemic metabolic disturbance, basal ganglia involvement is unexpectedly unilateral, which raises the possibility of dual pathology, including underlying ischaemia. Accordingly, Kim et al. ² demonstrated significantly reduced blood flow in the affected basal ganglia on single-photon emission CT evaluations in their case series.

This mechanism is supported by animal studies that demonstrated disequilibrium between direct and indirect pathways of the basal ganglia, secondary to hyperglycaemia-induced dopaminergic dysregulation. ³ We hypothesize that the unilateral involvement of basal ganglia in our case can be explained by ipsilateral slow-flow hypoxic–ischaemic insult due to severe ICA stenosis, which provided a fertile ground for neuronal damage secondary to hyperglycaemia. Perhaps, the resultant reduced ‘wash-out’ of hyperglycaemic blood led to the accumulation of reactive oxygen species and other neurotoxic glycosylated end products of hyperglycaemia, aggravating injury to the right basal ganglia. ⁴ We suggest vascular evaluation in patients with unilateral neurological phenomenon secondary to systemic and metabolic disorders.