Magnetic resonance imaging evaluation of delayed myelination in Down syndrome: a case report and review of the literature.

Magnetic resonance imaging has been found to be useful in assessing brain myelination and provides information on brain maturation. The normal pattern of brain myelination conforms to a fixed sequence, with good pathologic and MRI correlation. Neuropathologic analysis of myelination has shown delayed central myelination in Down syndrome. Delayed myelination on MRI in Down syndrome has not previously been reported. We report a case of Down syndrome with a significant delay in myelination as demonstrated on MRI. This 18-month-old infant had brain myelination equivalent to that expected for an 11-month-old infant. To determine the relative incidence, extent of delayed myelination, and time for recovery to full myelination in Down syndrome, more cases require examination and assessment. Magnetic resonance imaging has the advantage of serial assessment of myelination during brain maturation.