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Significance of Planum Temporale and Planum Parietale Morphologic Features in Neurofibromatosis Type 1
Rebecca L. Billingsley, PhD;
Gregory W. Schrimsher, PhD;
Edward F. Jackson, PhD;
John M. Slopis, MD;
Bartlett D. Moore III, PhD
Arch Neurol. 2002;59:616-622.
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.
From the Division of Pediatrics (Drs Billingsley, Schrimsher, Slopis,
and Moore) and the Departments of Neuro-Oncology (Drs Slopis and Moore) and
Diagnostic Imaging (Dr Jackson), University of Texas, M. D. Anderson Cancer
Center, Houston.
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