Neuroglycopenia is a shortage of glucose (glycopenia) in the brain, usually due to hypoglycemia. Glycopenia affects the function of neurons, and alters brain function and behavior. Prolonged or recurrent neuroglycopenia can result in loss of consciousness, damage to the brain, and eventual death. Signs and symptoms Abnormal mentation, impaired judgment Nonspecific dysphoria, anxiety, moodiness, depression, crying, fear of dying, suicidal thoughts Negativism, irritability, belligerence, combativeness, rage Personality change, emotional lability Fatigue, weakness, apathy, lethargy, daydreaming Confusion, amnesia, dizziness, delirium Staring, "glassy" look, blurred vision, double vision Automatic behavior Difficulty speaking, slurred speech Ataxia, incoordination, sometimes mistaken for "drunkenness" Focal or general motor deficit, paralysis, hemiparesis Paresthesia, headache Stupor, coma, abnormal breathing Generalized or focal seizures Plasma glucose 20 mg/dL (1.1 mmol/L) or lower Not all of the above manifestations occur in every case of hypoglycemia. There is no consistent order to the appearance of the symptoms. Specific manifestations vary by age and by the severity of the hypoglycemia. In older children and adults, moderately severe hypoglycemia can resemble mania, mental illness, drug intoxication, or drunkenness. In the elderly, hypoglycemia can produce focal stroke-like effects or a hard-to-define malaise. The symptoms of a single person do tend to be similar from episode to episode. In the large majority of cases, hypoglycemia severe enough to cause seizures or unconsciousness can be reversed without obvious harm to the brain. Cases of death or permanent neurological damage occurring with a single episode have usually involved prolonged, untreated unconsciousness, interference with breathing, severe concurrent disease, or some other type of vulnerability. Nevertheless, brain damage or death has occasionally resulted from severe hypoglycemia. Metabolic responses Most neurons have the ability to use other fuels besides glucose (e.g. lactic acid, ketones). Knowledge of the "switchover" process is incomplete. The most severe neuroglycopenic symptoms occur with hypoglycemia caused by excess insulin because insulin reduces the availability of other fuels by suppressing ketogenesis and gluconeogenesis. A few types of specialized neurons, especially in the hypothalamus, act as glucose sensors, responding to changing levels of glucose by increasing or decreasing their firing rates. They can elicit a variety of hormonal, autonomic, and behavioral responses to neuroglycopenia. The hormonal and autonomic responses include release of counterregulatory hormones. There is some evidence that the autonomic nervous system can alter liver glucose metabolism independently of the counterregulatory hormones. Adjustment of efficiency of transfer of glucose from blood across the blood–brain barrier into the