SPECIFIC LEARNING-DISABILITY IN CHILDREN WITH NEUROFIBROMATOSIS TYPE-1 - SIGNIFICANCE OF MRI ABNORMALITIES

To determine whether previously reported areas of increased T-2 signal intensity on MRI examination in children with neurofibromatosis type 1 (NF 1) are associated with deficits in development and learning comm on in this population, we evaluated 51 children with NF 1 (aged 8 to 1 6 years). Forty children completed the full assessment protocol (MRI, medical, psychometric, speech therapy, and occupational therapy assess ments). The mean Full Scale IQ scores for the entire study population showed a left, shift compared with the normal population, and the dist ribution of IQ scores was bimodal, suggesting that there are two popul ations of patients with NF 1-those with and those without a variable d egree of cognitive impairment. There was no association between lower IQ scores and any clinical variable. Areas of increased T-2 signal int ensity unidentified bright objects (UBO+) were present in 62.5% of the study population, and their presence was not related to clinical seve rity, sex, age, socioeconomic status, macrocephaly, or family history of NF 1. However, compared with children without areas of increased T- 2 signal intensity (UBO-), the UBO+ group had significantly lower mean values for IQ and language scores and significantly impaired visuomot or integration and coordination. Children with areas of increased T-2 signal intensity were at a much higher risk for impaired academic achi evement. Children without increased T-2 signal on MRI (UBO-) did not s ignificantly differ from the general population in any measure of abil ity or performance. Areas of increased T-2 signal on MRI represent dys plastic glial proliferation and aberrant myelination in the developing brain and are associated with deficits in higher cognitive function. The presence of these abnormal signals on MRI divides the NF 1 populat ion into two distinct groups anatomically and developmentally (UBO+ an d UBO-). These two groups should be considered separately in the asses sment and management of learning disability in children with NF 1.