The developmental, neurologic, and seizure outcome and prognostic factors of 57 cases of infantile spasms were evaluated in relation to etiology (cryptogenic 17 cases, symptomatic 40 cases) at the Hospital for Sick Children, Toronto, Canada. Age of onset ranged from 4 weeks to 13 months (mean, 5 months), and duration of follow-up was 12-60 months. Cerebral dysgenesis was the most common cause (20%) in the symptomatic group. Neurologic deficits, especially hypotonia, were present in 23% of cryptogenic cases cf 75% of symptomatic. A mean developmental score of 71 in cryptogenic cases was significantly higher than 48 in symptomatic. Additional forms of seizures were more common in symptomatic cases (57% cf 35%). Unfavorable prognostic factors, particularly cognitive deficits, were the association of other seizures, neurologic deficits, delay in treatment, poor response to ACTH, and persistent EEG abnormalities after 2 weeks of therapy. All patients in the cryptogenic group responded to ACTH (80 IU/IM/d for 2 weeks, tapered over 6 to 8 weeks). Of 30 symptomatic cases receiving ACTH, 12 (40%) were completely controlled initially, and 11 had a partial response. Response was higher in patients with developmental scores >70, both cryptogenic and symptomatic cases. 
COMMENT. With improved diagnostic techniques, particularly the MRI, the increased recognition of cerebral dysgenesis as a frequent cause for infantile spasms has resulted in a lowered percentage of cryptogenic cases compared to earlier reports. In a study involving 61 cases at the Mayo Clinic , 43% were of undetermined etiology and only 7% were recognized with cerebral dysgenesis. The anticonvulsant efficacy and outcome of treatment with ACTH in 21 patients was related significantly to the age at the time of diagnosis and treatment; 80% of infants less than 1 year old were benefited whereas only 22% of those over 1 year showed reduction in seizures and EEG improvement. Control of seizures and hypsarrythmia was not significantly related to the etiology, but patients of borderline or normal intelligence tended to respond more frequently than did those with developmental quotients <70. 
Posterior fossa abnormalities in children with infantile spasms were associated with a poor developmental outcome in a study of 98 children from New England Medical Center and Children’s Hospital, Boston, and Hadassah University Hospital, Jerusalem . Brain stem dysfunction and atrophy were remarkable in a study of 10 patients with infantile spasms, employing evoked potentials and MRI, at the University of Tokushima, Japan.