The frequency of hypsarrhythmia variant or atypical patterns was determined by analysis of pre-ACTH EEG records of 53 consecutive patients with infantile spasms at Children’s Hospital, Harvard Medical School, Boston, MA. Hypsarrhythmia was scored (16 most severe, 0 normal EEG) based on degree of disorganization, diffuse delta, voltage, spikes, burst suppression (BS), etc. Variant patterns occurred in 69% of records. Hemihypsarrhythmia or BS was characteristic of spasms caused by cerebral dysgenesis. Sleep patterns were persistently abnormal in infants with perinatal hypoxic-ischemic encephalopathy. Lower hypsarrhythmia scores (<10), <75% delta activity, and absence of electrodecremental discharges correlated with more favorable outcome, whereas variant patterns had no prognostic significance. 
COMMENT. Analysis of pre-ACTH EEGs in patients with West syndrome may reflect the pathophysiology and prognosis. Higher severity scores of hypsarrhythmia correlate with poor outcome. Variant patterns of hypsarrhythmia are frequent and show no correlation with prognosis; they should be included within the definition and indications for treatment with ACTH.
Cortical hypometabolism and delayed myelination were reported in a study of 18 children with West syndrome at Nagoya University School of Medicine, Japan . Hypometabolism on PET scans at the onset of spasms or at 10 months is correlated with MRI evidence of delayed myelination at age 10 months.