Clinical and imaging diagnosis for heredodegenerative diseases.

Clinical features (progressive psychomotor retardation, seizures, movement disorders and motor signs in both central and peripheral systems, sensorineural defects, and psychiatric symptoms) and brain imaging are the keys to diagnosis. CT is indicated for the detection of calcifications and blood, and for angiography. MRI in all three axes requires T1, T2, FLAIR (from 1 year on), eventually T2* or contrast administration, and diffusion in any acute condition. MR spectroscopy allows the dectection of lactate and creatine deficiency, elevated choline in high membrane turnover, and low NAA in neuronal death. The normal sequence of myelination needs to be taken into account. Pre- and neonatal anomalies include cystic and basal ganglia lesions, gyral and myelin anomalies, callosal agenesis, and large subdural spaces. Anomalies disclosed after 3 months of age include basal ganglia appearing hyper- or hypointense on T2, hypointense on T2*, or calcified white matter anomalies mainly periventricular or subcortical, or with contrast enhancement, associated with macrocephaly and/or large or very small cysts, and hypomyelination; there may be "vascular" or pseudostroke disorders, cortical atrophy, hypoplasia, or abnormal signal of the brainstem and/or cerebellum. Spectroscopy should investigate basal ganglia, white matter, and the cerebellum. MRI may reveal typical alterations of the brain at the preclinical stage in siblings of affected children.