Hyperosmolar hyperglycemic nonketotic syndrome in an unknown diabetic patient

A 48-year-old male presented with a week history of headache, lack of speech, and left hand/ankle paraesthesia. Personal history of hypertension. Neurological examination revealed weakness on the left leg. Laboratory data revealed elevated glycemia (737 mg /dl), creatinine and sodium. 72h later, he describes dystonic movements and weakness on the left hand as well as involuntary movements on his feet.

Initial imaging with non-contrast CT was done in the emergency department which showed unilateral hyperdensity within the right lentiform nucleus and minimum in ipsilateral caudate, without mass effect or significant surrounding oedema.

MRI evaluation was required for further evaluations. T1, T2 fast spin eco, T2 FLAIR, diffusion-weighted imaging (DWI) and susceptibility-weighted imaging (SWI) were obtained.

T1-weighted MR images demonstrated intrinsic T1 shortening confined to the right corpus striatum (putamen and caudate nucleus) corresponding to the hyperdensity seen on presenting CT.

Axial T2 fast spin-echo and FLAIR images demonstrated low signal intensity at these locations, without signs of haemorrhage in SWI.

Furthermore, DWI showed an acute lacunar infarction of the posterior limb of the right internal capsule in probable relation to acute neurologic symptoms he presented.

Repeat MRI brain 2 months later, after treatment with excellent glycemic control, showed significant improvement, with resolution of signal abnormalities.

Hyperosmolar hyperglycemic non-ketotic syndrome (HHNS) is the most serious complication of type 2 diabetes mellitus. HHNS is characterized by hyperglycemia, hyperosmolarity and dehydration in the absence of ketoacidosis.

In terms of symptom presentation, chorea and ballismus develops rapidly and can be either unilateral or bilateral and is seen during episodes of non-ketotic hyperglycemia. Clinically, they also may present partial seizure and global neurologic dysfunction (encephalopathy and coma).

It has a good prognosis. Symptoms and imaging findings usually resolve upon normalization of glucose levels. However, imaging findings tend to return to baseline more slowly than the clinical finding.

In the radiology literature, non-ketotic hyperglycemia has been associated with a characteristic appearance of unilateral or asymmetric basal ganglia hyperdensity, namely, caudate nucleus, putamen, and globus pallidus. If unilateral, the imaging findings are are contralateral to the symptomatic side.

The presence of both findings (clinical finding of hemichorea-hemibalism and neuroimaging findings) is highly suggestive of non-ketotic hyperglycemia [1].

As far as we know, this case is an exception to the majority of the published cases, being a patient with pathognomonic neuroimaging findings without hyperkinetic movement disorder, presenting as acute-subacute neurologic deficit.

In MRI images, the most common findings are the high signal intensity basal ganglia lesions on T1-weighted on the side contralateral to patient symptoms. The T2-weighted findings are much more variable with the majority of basal ganglia lesions described as either hypointense or isointense [2, 3].

The pathophysiological mechanisms underlying the imaging findings are controversial. The most established hypothesis attribute the T1 hyperintensity to the protein hydration layer in the cytoplasm of reactive astrocytes.

The most common alternate hypothesis claims hyperintensity is due to the petechial haemorrhage. However, a hemorrhagic aetiology is less likely because the manner hyperintensity in T1 respects neuroanatomic boundaries and because the lack of positive SWI findings.

Nagai et al. have suggested signal alteration to demyelination, similar to peripheral diabetic neuropathy. Other authors have suggested that imaging findings are related to chronic ischemic events and describes the strong associations with other manifestations as diffuse white matter changes and the increased incidence of lacunar infarction. 

Shan et al. biopsied a hyperintense putaminal lesion demonstrated multiple ischemia injuries and abundant reactive astrocytes; not petechial haemorrhage or calcification was found [4].

In conclusion, non-ketotic hyperglycemia should be a diagnostic consideration even without movement disorders when the typical neuroimaging findings are present. It is important to diagnose as early as possible because the clinical outcome is excellent with the insulin therapy [5].