[Fast rhythms in metabolic diseases in children]

The authors study fast EEG rhythms in amino acidopathies of the newborn and in progressive encephalopathy of the central nervous system in children, when an inborn error of metabolism has either been found or is suspected. In the first group: amino acidopathies (including phenylketonuria), fast rhythms on the EEG of the neonates are of low amplitude, spindle-like bursts of 7-13 Hz and usually located in rolandic areas. This activity progressively disappears. Later, fast rhythms of beta-frequency and low voltage are spread on the whole scalp with a normal EEG organisation. They are seen in the favourable or rather favourable development of children receiving a diet. In the second group: progressive encephalopathy of the central nervous system, fast rhythms of 14-24 Hz appearing at a rather late stage of the disease, while the normal background activity completely disappears. In neuro-axonal dystrophy, where they are considered as 'specific,' they are of very high voltage, i.e., 50-200 microV. The authors insist on the importance of EEG fast rhythms both in amino acidopathies of the newborn, as a contributive factor to diagnosis and prognosis, and in progressive encephalopathies of the central nervous system, as a valuable tool in the diagnosis of numerous affections.