Single photon emission tomography was used to study regional cerebral activity in 24 children with developmental learning disabilities and 15 age matched controls at the John F. Kennedy Institute, Glostrup, and Department of Neurology, Rigshospitalet, Copenhagen, Denmark. The distribution of regional cerebral activity was abnormal - low in striatal and posterior periventricular regions and high in occipital regions - in nine children with pure attention deficit and hyperactivity disorder, low in striatal and posterior ventricular areas in eight children with ADHD plus phonologic-syntactic dysphasia, and low in the left temporofrontal regions in seven children with dysphasia without hyperactive behavior. 
COMMENT. The use of PET in children is restricted by the radiation dose and invasive procedure. The smaller dose of radiation associated with SPET was considered less invasive and hazardous. The MRI avoids the risk of radiation side effects and has illuminated structural cerebral defects underlying various learning disabilities, e.g. cortical heterotopias in dyslexic patients, and temporal lobe cysts in children with auditory perceptual problems. The regional cerebral blow flow abnormalities demonstrated by SPET may reveal focal cerebral dysfunction not demonstrated by MRI but correlating with expressive language dysfunction and other developmental learning disabilities.