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Adult Hypoglycemia


KEY FACTS

Terminology

  • Adult hypoglycemic encephalopathy

  • Imbalance between glucose supply, utilization → brain injury

  • Hypoglycemia: Sudden decrease in serum glucose level < 50 mg/dL

Imaging

  • Stroke/coma in adult diabetic on insulin replacement therapy (IRT)

  • Parietal/temporal/occipital lobes, basal ganglia, ± hippocampi

  • Hyperintensity in parietooccipital cortex and basal ganglia

  • Thalami, subcortical/deep white matter and cerebellum generally spared

  • Restricted diffusion, ↓ ADC (may be transient)

  • MRS shows ↓ NAA, ↑ lactate

Top Differential Diagnoses

  • Acute cerebral ischemia/infarction

  • Hypoxia, hypoperfusion

  • Acute hypertensive encephalopathy (PRES)

Pathology

  • Caused by IRT either without adequate glucose intake or excessive glucose utilization

  • Ingestion of oral hypoglycemic medication, either accidental or intentional

  • Accumulation/release of excitatory neurotransmitters increases glucose utilization

  • Patchy or diffuse laminar necrosis

    • Varying severity, white matter generally spared

Clinical Issues

  • Often elderly diabetic, altered dietary glucose intake

  • Coma, depressed level of consciousness

  • May be preceded by seizures

Axial FLAIR MR in a diabetic patient with altered sensorium and a blood glucose of 36 mg/dL shows symmetric hyperintensity involving the hippocampus
, temporal and occipital cortex bilaterally
.

Axial DWI in the same patient shows corresponding areas of restricted diffusion in the hippocampus
, temporal and occipital cortex
. Prognosis in adult hypoglycemic encephalopathy varies with severity and duration of hypoglycemia, as well as extent of brain injury.

Axial DWI in patient with overdose of glipizide and blood glucose level of 20 mg/dL shows severe changes of hypoglycemic encephalopathy. There is extensive symmetric diffusion restriction in the basal ganglia
and cerebral cortex
.

Intermediate TE MRS in a hypoglycemic patient shows a relatively low NAA peak
and a prominent lactate peak
. Using an intermediate TE inverts only lactate, allowing it to be distinguished from lipid. Lactate is a marker of anaerobic metabolism with no peak seen in normal spectra.

TERMINOLOGY

Abbreviations

  • Adult hypoglycemic encephalopathy (AHE)

Synonyms

  • Hypoglycemic brain injury

  • Diabetic coma (nonspecific; term may include AHE)

Definitions

  • Imbalance between glucose supply, utilization → brain injury

  • Hypoglycemia: Sudden decrease in serum glucose level < 50 mg/dL

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