Metabolic and Degenerative Diseases of the Central Nervous System

Abstract

This chapter discusses the clinical entities along with the neuropathological findings of the disorders of urea cycle. The liver is the most important organ for the detoxification of ammonia. Hyperammonemia occurs in all disturbances of the urea cycle. In all these diseases, both clinical and pathological abnormalities are present in the CNS. The hallmark of the effect of ammonia on the brain is the presence of Alzheimer's type II astrocytes. In the metabolic disorders of the branched-chain amino acids, severe neurological involvement, accompanied by a peculiar odor of the body and urine, reminiscent of maple syrup is observed. In an affected patient, excessive urinary excretion of the branched-chain amino acids leucine, isoleucine, and valine occurs and their concentration in the plasma also gets raised. The conditions related to maple syrup disorders are: hypervalinemia, hyperleucine-isoleucinemia, and isovalinacidemia. Hyperphenylalaninemias is the most common disorder of amino acid metabolism. The development of a simple method for the estimation of phenylalanine in the blood and the consequent wide use of a screening test led to differentiation of various forms of the disease. Group consists of homocystinuria and methylmalonic aciduria, closely linked with each other and sometimes appearing together, and also includes cystinosis and disorders of folate metabolism. In molybdenum cofactor deficiency, the most frequently noted clinical features are neonatal seizures, abnormal tone, and opisthotonos. This disorder is inherited as an autosomal-recessive trait.