Electroencephalographic abnormalities in phenylpyruvic oligophrenia

Infantile spasms (West syndrome) in children with inborn errors of metabolism: a review of the literature

West syndrome (infantile spasms) is an epileptic encephalopathy that includes psychomotor deterioration. In rare cases, it is due to an inherited, progressive metabolic disease. More than 25 inborn errors of metabolism have been considered etiologic or predisposing factors for infantile spasms. This is a review of the literature on reported cases of children diagnosed with a metabolic disease who developed infantile spasms. This article presents in brief the most frequent inborn errors of metabolism that have been associated with West syndrome and also illustrates the importance of screening for inborn errors of metabolism in infantile spasms.

Clinical analysis of West syndrome associated with phenylketonuria

OBJECTIVE

To explore the incidence and clinical characteristics of West syndrome associated with phenylketonuria (WS-PKU) and significance of early combination therapy of low phenylalanine (PHE) diet and anticonvulsants (antiepileptic drugs, AEDs) in WS-PKU.

SUBJECTS AND METHODS

Sixty-two WS-PKU patients (41 boys and 21 girls) out of 503 PKU patients were enrolled in the study. Age at PKU diagnosis varied from 4 months to 7 years old. Serum PHE levels were 20-38.5mg/dl. In the majority of cases, infantile spasms (IS) became manifest first preceding the PKU diagnosis, except eight cases in which spasms appeared after starting the diet therapy. All patients were subjected to mental and electroencephalographic (EEG) examination. Brain myelination was evaluated by using brain magnetic resonance imaging (MRI) with Staudt's standard.

RESULTS

WS-PKU patients accounted for 12.3% of PKU patients. No patients who were given low PHE diet before age 3 months suffered from WS, whereas 17 out of 156 patients who started the diet between age 4 and 12 months developed WS later (10.9%), and similarly, 45 out of 283 patients who started the diet after 12 months of age developed WS later (15.9%). Moderate and severe mental retardation were noted in 58.8% of patients who received the diet before age 1 and in 84.4% of those after age 1 (P<0.05). EEG displayed hypsarrhythmia and diffuse background abnormality. MRI scans showed delayed myelination mainly in the cerebral lobes and corpus callosum and abnormal high T(2)-signal intensity (100%) in the periventricular region around anterior and posterior horns of both lateral ventricles. With the start of diet, spasms began to decrease its frequency, but relapsed frequently (78%) when no AEDs were given. Seizure relapse was significantly lower when valproic acid or nitrazepam were given concomitantly with the diet (18.2%).

CONCLUSIONS

IS often occurred as the initial clinical sign of PKU. Early diagnosis of PKU and early therapy with low PHE diet seem to be highly effective in preventing WS.

EEG as a possible prognostic tool in phenylketonuria

Clinical EEG and biochemical data were recorded in 10 children with classical PKU and 5 with variant forms of hyperphenylalaninaemias during the first year of life. A semiquantitative evaluation of the EEG showed a high correlation between epileptiform abnormalities and phenylalanine blood levels in the first 90 days of life and therefore with the delay before dietary therapy in PKU children. Although performed on a limited population, such an approach may indicate an additional non-computerized EEG tool for the clinical management of hyperphenylalaninaemias, and suggest some criteria for neurophysiological risk evaluation during the first year of life.