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Study of Rare Brain Disorder Provides Clues to Dyslexia

Disconnection of cortical regions may lead to impaired reading fluency in periventricular nodular heterotopia

TUESDAY, Dec. 4 (HealthDay News) -- Individuals with the rare genetic brain malformation, periventricular nodular heterotopia (PNH), which is characterized by faulty neuronal migration and consequent abnormalities in white matter organization, share behavioral features with individuals with dyslexia, according to research published in the Dec. 4 issue of Neurology. The study authors postulate that structural brain changes may underlie the reading difficulties seen in PNH and propose that PNH might serve as a useful model in understanding dyslexia and other cognitive impairments.

Bernard S. Chang, M.D., of Beth Israel Deaconess Medical Center and Harvard Medical School in Boston, and colleagues performed neuropsychometric testing on 10 adults with periventricular nodular heterotopia, 10 adults with dyslexia, and 10 normal controls. MRI with diffusion tensor imaging was used in six heterotopia subjects to visualize white matter integrity and fiber tract organization.

Individuals with PNH and dyslexia had similar deficits in reading fluency, whereas dyslexic subjects had more pronounced phonological impairment than heterotopia subjects. Individuals with PNH undergoing MRI were noted to have focal disruptions in white matter microstructure and organization, and the level of white matter integrity corresponded to reading fluency.

"Our work, and that of others, supports the longstanding conception that developmental brain malformations can serve as an alternative model for our understanding of brain-behavior relationships, one that may be particularly relevant to the study of neurodevelopmental disabilities such as dyslexia," the authors write.

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