A population-based study of 78 Swedish children with non-progressive ataxia is reported from the Department of Paediatrics, Malarsjukhuset, Eskilstuna; Department of Neuroradiology, Karolinska Institute, Stockholm; and Department of Paediatrics, University of Goteborg, Sweden. Criteria for inclusion were an ataxic gait, dyssynergia, dysmetria and intention tremor, resulting from prenatal (45%) or perinatal events (4%), and excluding patients with spasticity (51% were unclassifiable). The prevalence was 0.13 per thousand of 6- to 22-year-old children and adolescents. CT or MRI, available in 70 patients (90%), showed infratentorial pathology in 27%, including focal maldevelopments of the cerebellum: Dandy-Walker (2), Joubert syndrome (1), encephalocele (1), and hypoplasia (1). A genetic anomaly was found in 18 patients, including Angelman syndrome in 3. Forty-seven patients (60%) had mental retardation, severe in 25 and mild in 22; sixty nine (88%) had delayed speech development; 58% had visual dysfunction; and only 17 (22%) had normal cognitive function. 
COMMENT. Simple non-progressive ataxias comprise less than 10% of cases of cerebral palsy. Of 50% with known pathologies, the majority were prenatal in origin, many with a genetic background. No abnormality was revealed by imaging studies in 61%.