Anomalous cerebral structure in dyslexia revealed with magnetic resonance imaging.
OBJECTIVE
To develop quantitative methods for identifying cerebral anomalies on magnetic resonance images of subjects with language disorders and other learning disabilities.


METHODS
Partially blinded comparison of subjects with dyslexia, unaffected relatives, and a control group balanced for age and socioeconomic status. Criterion standard: clinical diagnosis of dyslexia by physician or learning disabilities specialist on the basis of clinical assessment and family history.


METHODS
Hospital pediatric neurology clinic and private reading clinic.


METHODS



METHODS
individuals with dyslexia (seven male and two female, aged 15 to 65 years) from professional families; unaffected first- and second-degree relatives (four male and six female, aged 6 to 63 years) available in the geographical area; and controls (five male and seven female, aged 14 to 52 years).


METHODS
Gradient echo three-dimensional scan in Seimens 1-Tesla Magnetom; 128 1.25-mm consecutive sagittal images.


METHODS
(1) Average length of the temporal (T) and parietal (P) banks of the planum temporale; (2) interhemispheric coefficients of asymmetry for T and P banks: Left-Right interhemispheric coefficients of asymmetry = (L-R)/[(L+R)/2]; (3) intrahemispheric coefficients of asymmetry = (T-P)/[(T+P)/2]; and (4) qualitative assessment of gyral variants in the parietotemporal operculum.


RESULTS
All groups had left-sided asymmetry for the temporal bank and right-sided asymmetry for the parietal bank. The group with dyslexia had exaggerated asymmetries, owing to a significant shift of right planar tissue from the temporal to parietal bank. They also had a higher incidence of cerebral anomalies bilaterally (subjects with dyslexia, six of nine; relatives, two of 10; and controls, zero of 12).


CONCLUSIONS
Quantitative assessment of high-resolution magnetic resonance images can reveal functionally relevant variations and anomalies in cerebral structure. Further refinement of these measurement techniques should improve the diagnosis, classification, and treatment of language disorders and other learning disabilities.
Leonard
C M
CM
Department of Neuroscience, University of Florida, Gainesville.
Voeller
K K
KK
Lombardino
L J
LJ
Morris
M K
MK
Hynd
G W
GW
Alexander
A W
AW
Andersen
H G
HG
Garofalakis
M
M
Honeyman
J C
JC
Mao
J
J
D000293:Adolescent; D000328:Adult; D002540:Cerebral Cortex / Q000002:abnormalities*; D004410:Dyslexia / Q000473:pathology*; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D010296:Parietal Lobe / Q000002:abnormalities; D013702:Temporal Lobe / Q000002:abnormalities