Effects of Hypoglycemia on the Brain: Cerebral Energy Metabolism, Autonomic Regulation, and Electroencephalographic Changes

Hypoglycemia is a frequent complication of diabetes treatment and is usually reversible after glucose administration. However, severe or prolonged hypoglycemia can lead to seizures, coma, and irreversible neurological injury. The brain is particularly vulnerable because it relies predominantly on glucose for energy production. Sustained hypoglycemia may impair cerebral energy metabolism, disrupt ionic homeostasis, and trigger excitotoxic neuronal injury. Physiological protection against hypoglycemia depends on counterregulatory responses, including suppression of insulin secretion, stimulation of glucagon and epinephrine release, and autonomic warning symptoms. Recurrent hypoglycemia may induce hypoglycemiaassociated autonomic failure, thereby increasing the risk of severe hypoglycemia. Electroencephalography (EEG) offers a real-time measure of cortical dysfunction during hypoglycemia. Typical changes include attenuation of alpha activity and progressive theta–delta slowing, whereas severe cases may show background suppression or other abnormal patterns. Because these EEG findings are not specific to hypoglycemia and have limited independent prognostic value, EEG should be interpreted as an adjunctive physiological tool in combination with blood glucose levels, clinical course, neurological examination, and neuroimaging findings.