Anomalous Cerebral Structure in Dyslexia Revealed With Magnetic Resonance Imaging

Abstract

\s=b\ Objective.\p=m-\Todevelop quantitative methods for identifying cerebral anomalies on magnetic resonance images of subjects with language disorders and other learning disabilities. Design.\p=m-\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.Settings.\p=m-\Hospitalpediatric neurology clinic and private reading clinic.Patients and Other Participants.\p=m-\Volunteers: individuals with dyslexia (seven male and two female, aged 15 to 65 years) from professional families; unaffected first-and second\x=req-\ 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).Interventions.\p=m-\Gradient echo three-dimensional scan in Seimens 1-Tesla Magnetom; 128 1.25-mm consecutive sagittal images.Main Outcome Measures.\p=m-\(1) Average length of the tem-poral (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 asym-metry=(T-P)/[(T+P)/2]; and (4) qualitative assessment of gyral variants in the parietotemporal operculum.Results.\p=m-\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.\p=m-\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.Early investigators believed that neuroanatomical cor-

Abnormal asymmetry in language association cortex in autism

“…Prior MRI studies of subjects with SLI have reported abnormal hemispheric asymmetries in language cortex–related measures compared with controls,27, 28, 31, 32, 49 consistent with our study findings in autism. Furthermore, the language abnormalities observed in autism share many features with those observed in SLI, and these disorders may be co‐occurring or overlapping in many respects 18, 50.…”

Abnormal asymmetry in language association cortex in autism

“…Prior MRI studies of subjects with SLI have reported abnormal hemispheric asymmetries in language cortex–related measures compared with controls,27, 28, 31, 32, 49 consistent with our study findings in autism. Furthermore, the language abnormalities observed in autism share many features with those observed in SLI, and these disorders may be co‐occurring or overlapping in many respects 18, 50.…”

Sulcal/Gyral Pattern Morphology of the Perisylvian Language Region in Developmental Dyslexia

“…This finding runs counter to the findings reported by and Leonard et al (1993) in which dyslexic populations had a greater incidence of Type III sulcal arrangement in the left hemisphere. However, this may be due to differences in diagnostic criteria between this study and previous studies.…”

Gyral morphology in the posterior Sylvian region in families affected by developmental language disorder

“…As was previously reported by Leonard et al (1993), we found a greater proportion of Type III Sylvian fissure morphology among the subjects with impaired language skills and their first-degree relatives than in control subjects. That this anomalous morphological type was not limited to the impaired members of these families was not entirely unexpected.…”

Abnormal asymmetry in language association cortex in autism

“…Prior MRI studies of subjects with SLI have reported abnormal hemispheric asymmetries in language cortex–related measures compared with controls,27, 28, 31, 32, 49 consistent with our study findings in autism. Furthermore, the language abnormalities observed in autism share many features with those observed in SLI, and these disorders may be co‐occurring or overlapping in many respects 18, 50.…”

Sulcal/Gyral Pattern Morphology of the Perisylvian Language Region in Developmental Dyslexia

“…This finding runs counter to the findings reported by and Leonard et al (1993) in which dyslexic populations had a greater incidence of Type III sulcal arrangement in the left hemisphere. However, this may be due to differences in diagnostic criteria between this study and previous studies.…”

Gyral morphology in the posterior Sylvian region in families affected by developmental language disorder

“…As was previously reported by Leonard et al (1993), we found a greater proportion of Type III Sylvian fissure morphology among the subjects with impaired language skills and their first-degree relatives than in control subjects. That this anomalous morphological type was not limited to the impaired members of these families was not entirely unexpected.…”

Abnormal asymmetry in language association cortex in autism

“…Prior MRI studies of subjects with SLI have reported abnormal hemispheric asymmetries in language cortex–related measures compared with controls,27, 28, 31, 32, 49 consistent with our study findings in autism. Furthermore, the language abnormalities observed in autism share many features with those observed in SLI, and these disorders may be co‐occurring or overlapping in many respects 18, 50.…”

Sulcal/Gyral Pattern Morphology of the Perisylvian Language Region in Developmental Dyslexia

“…This finding runs counter to the findings reported by and Leonard et al (1993) in which dyslexic populations had a greater incidence of Type III sulcal arrangement in the left hemisphere. However, this may be due to differences in diagnostic criteria between this study and previous studies.…”

Gyral morphology in the posterior Sylvian region in families affected by developmental language disorder

“…As was previously reported by Leonard et al (1993), we found a greater proportion of Type III Sylvian fissure morphology among the subjects with impaired language skills and their first-degree relatives than in control subjects. That this anomalous morphological type was not limited to the impaired members of these families was not entirely unexpected.…”