Glucide metabolism comprises pathways for transport, intermediate metabolism, utilization, and storage of
carbohydrates. Defects affect multiple organs and present as systemic diseases. Neurological symptoms result from
hypoglycemia,
lactic acidosis, or inadequate storage of complex glucide molecules in neurological tissues. In
glycogen storage disorders
hypoglycemia indicates hepatic involvement, weakness and
muscle cramps muscle involvement.
Hypoglycemia is also the leading neurological symptom in disorders of gluconeogenesis. Disorders of
galactose and
fructose metabolism are rare, detectable by neonatal screening, and manifest following dietary intake of these
sugars. Rare defects within the
pentose metabolism constitute a new area of inborn metabolic disorders and may present with neurological symptoms. Treatment of these disorders involves the avoidance of fasting, dietary treatment eliminating specific
carbohydrates, and
enzyme replacement therapy in individual
glycogen storage diseases.
GLUT1 deficiency syndrome, a specific disorder of
glucose transport into brain, results in global developmental delay, early-onset
epilepsy, and a complex
movement disorder. Treatment with a high-fat, low-
carbohydrate ketogenic diet provides
ketones as an alternative fuel to the brain and restores brain energy metabolism. Recently
paroxysmal exertion-induced dyskinesia and stomatin-deficient
cryohydrocytosis have been identified as an allelic disorder to GLUT1 deficiency equally responding to a
ketogenic diet.