Neuroanatomical correlates of developmental dyslexia (DD), defined by isolated reading deficits, and specific language impairment (SLI), defined by poor receptive and expressive language skills, were examined using MR imaging in a heterogeneous sample of 14 boys and 8 girls (11-16 yers of age) with learning disabilities, in a study at University of Florida; Georgetown University, Washington, DC; and other centers. Using a quantitative anatomical risk index, children with smaller and symmetrical brain structures (negative risk indices) had severe comprehension impairments typical of SLI, whereas those with larger, asymmetrical brain structures (positive risk indices) had DD (reading deficit with preserved comprehension). Children with normal anatomy and near zero risk indices had the best learning performance. Speed of rapid automatic naming was not related to the anatomical risk index but was predicted by variation in frontal lobe and cerebellar anatomic measures. Comprehension deficits distinguish SLI from DD. [1]

COMMENT. Children with negative anatomical risk indices (smaller symmetrical brain structures including Heschl's gyri) have severe deficits in reading and language function, including comprehension, typical of SLI, whereas children with positive anatomical risk indices (larger cerebral volume and Heschl's gyri, more asymmetrical brain structures, including planum temporale and cerebellar anterior lobe) have fewer learning deficits, with relative sparing of receptive language and reading comprehension, typical of DD. Further research with larger samples is needed to confirm the correlation of the anatomical risk index with reading and language deficits, and the value of MRI studies in predicting learning impairments and need for academic accommodations.