Pure severe dyslexia after a perinatal focal lesion: evidence of a specific module for acquisition of reading.

A child with a small, residual "localized" perinatally acquired left hemisphere temporal tip lesion is described. He presents with pure and severe dyslexia and average to high-average cognitive skills, which are usually in the low-average range in patients with developmental dyslexia. A highly circumscribed deficit of rote auditory verbal memory was the only deficit other than the dyslexia; his verbal semantic memory and visuospatial memory were intact. Two previously reported cases present a similar functional profile and lesion locus. This profile indicates that there may exist, at birth, a localized neural network dedicated to "reading acquisition" and that the layout of this network may differ from the systems identified as defective in developmental dyslexia, as well as in cases of acquired dyslexia in adults.