Specific Imaging Findings

Hypoglycemia may affect different areas in infants and older patients. In neonates it causes symmetric cortical and subcortical abnormalities, predominantly in the posterior cerebral hemispheres. CT demonstrates edema affecting the parietal and occipital lobes. MRI shows subtle cortical and subjacent white matter T1 hypointensity and T2 hyperintensity. Reduced diffusion is a very sensitive early finding. MRS demonstrates reduced NAA and the presence of lipids and/or lactate. Subacutely, the cortex will develop increased T1 and low T2 signal. Atrophy and gliosis occur in the chronic stage. Diffuse white matter injury may be more common in hypoglycemic neonates than previously believed.

In adults, hypoglycemia can affect either gray matter (primarily cortex) alone, white matter alone, or both. Abnormalities are again typically bilateral and symmetric. White matter T2 hyperintensities with reduced diffusion are found in the centrum semiovale and periventricular area, and, more characteristically in the internal capsule and corpus callosum (typically in the splenium – “boomerang” lesion). The findings may resolve with treatment, especially the white matter lesions.

Pertinent Clinical Information

Symptoms and signs of hypoglycemia in neonates are nonspecific and include cyanotic spells, apnea, refusal to feed, hypothermia, and seizures. Ultimately convulsions or coma may occur. Long-term sequelae include cerebral palsy, epilepsy, developmental delay, and visual impairment. In adults and older children, symptoms of hypoglycemia reflect two major mechanisms. One is related to catecholamine release from activation of the autonomic nervous system, which is the physiologic counterregulatory response to hypoglycemia. These symptoms include tachycardia, anxiety, sweating, and palpitations.