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Background: Neurofibromatosis type 1 (NF-1) is associated with learning disabilities and cognitive impairment in childhood and adolescence. Individuals with NF-1 have a propensity for brain hyperintensities on T2-weighted magnetic resonance images, macrocephaly, and optic gliomas. Few clear relationships between these central nervous system abnormalities and cognitive function, however, have been found in this population., Objectives: To determine whether planum temporale (PT) and planum parietale (PP) morphologic features are associated with learning disabilities in NF-1., Patients and Methods: We measured and compared the surface area, gray matter volume, and asymmetry of the PT and PP on T1-weighted MRIs from 24 children and adolescents with NF-1 and an equal number of controls. Relationships between these measurements and cognitive and academic achievement scores were examined., Results: The left PT in boys with NF-1 was significantly smaller in both surface area and gray matter volume compared with girls with NF-1 and controls. Boys with NF-1 also showed greater symmetry between the left and right hemispheres in this region compared with girls with NF-1 and controls, who showed a pattern of left greater than right asymmetry of the PT. Intelligence-based discrepancy scores of reading and math achievement, which are commonly used to define learning disabilities, were significantly related to PT asymmetry in the NF-1 group as a whole. Less leftward asymmetry of the PT was associated with poorer reading and math achievement in relation to intellectual test scores., Conclusions: The high susceptibility of individuals with NF-1 to develop reading and other learning disabilities seems to be related to the development of the sylvian fissure. These results provide further support for the hypothesized association between sylvian fissure morphologic features and learning disabilities.

Thirty-three survivors of childhood cancer were tested with event-related potentials (P300), motor reaction time tests, and neuropsychological tests to assess the underlying physiological basis of treatment-related cognitive sequelae. Thirteen patients had received intrathecal chemotherapy, 11 had received intrathecal chemotherapy plus cranial radiotherapy, and nine had been treated without any form of central nervous system therapy. Neuropsychological performance of the groups treated without cranial radiotherapy was normal, but the group given cranial radiotherapy was significantly impaired. Mean reaction time and P300 latency were somewhat slower in the group given intrathecal chemotherapy relative to the group given no central nervous system treatment, but were significantly delayed in the group given cranial radiotherapy. Correlations of reaction time and P300 latency with neuropsychological test scores were also obtained. Results suggest that slowing of cortical activity secondary to white-matter damage may underlie cognitive decline in children treated with intensive central nervous system therapies, especially cranial radiotherapy.

Cortical evoked potentials and dichotic listening test scores were used to assess the extent of activation of the two cerebral hemispheres during various language tasks in a group of 21 recovering aphasics, 15 nonaphasic patients with right-hemisphere stroke, and 17 normal volunteers. In agreement with previous findings, both measures suggest greater right-hemisphere activation during language processing in the recovering aphasics than in nonaphasic patients and normal subjects. These data support the view that restitution of language entails reorganization of brain function with increased participation of the nondominant hemisphere.

A probe evoked potentials procedure was used to assess the relative engagement of both cerebral hemispheres during a language task in the following four groups of dextral adults: left hemisphere (LH)-damaged aphasics recovering from stroke, dysarthrics, right hemisphere (RH)-damaged nonaphasic patients, and normal control subjects. In agreement with previous findings using the probe procedure, the present results indicate greater task-specific RH activation in recovering aphasics and, to a lesser degree, dysarthric patients and greater LH activation in both nonaphasic, RH-damaged patients and normal control subjects. On the basis of these data, we suggest that increasing participation of the nondominant hemisphere may subserve restitution of language in adults sustaining LH lesions.