DELAYED MYELINATION IN INFANTS AND YOUNG-CHILDREN - RADIOGRAPHIC AND CLINICAL CORRELATES

Magnetic resonance imaging (MRI) is the best method for assessing myel ination in infants and young children. Although delayed myelination is a common neuroradiologic diagnosis, there are few or no data regardin g the reliability of this diagnosis or radiographic and clinical findi ngs in cohorts of such patients. We evaluated the cranial MRI scans of 109 patients from age 0 to 36 months, without knowledge of any patien t's age or previous clinical or radiologic diagnosis. For each cranial MRI, seven neuroradiologic landmarks were evaluated and established c riteria used to assess the state of myelination. We found that in 12 o f 109 patients, delayed myelination was misdiagnosed, whereas the diag nosis of delayed myelination was missed in four other patients. Lack o f familiarity with the myelination milestones of infancy was the most common reason for a misdiagnosis of delayed myelination. Failure to re cognize delayed myelination was due to a failure to appreciate the for ceps minor as a landmark. Overall, the diagnosis of delayed myelinatio n was inaccurately applied or missed in 15% of the patients in this se ries. Of the 14 patients identified as having delayed myelination, 10 had other central nervous system structural abnormalities seen on MRI, most commonly cortical atrophy. Developmental delay was the most comm on clinical correlate of delayed myelination and was documented in 12 of the 14 patients. To increase the reliability of neuroradiologic ass essments in young children, we propose that central nervous system mye lin maturation be evaluated and expressed as a myelination age equival ent, analogous to the assessment of pediatric bone age using conventio nal radiographs. Further, prospective studies of infants and young chi ldren with delayed myelination are needed to learn the full clinical s pectrum of this common neuroradiologic diagnosis.