MAGNETIC-RESONANCE-IMAGING DEMONSTRATES INCOMPLETE MYELINATION IN 18Q- SYNDROME - EVIDENCE FOR MYELIN BASIC-PROTEIN HAPLOINSUFFICIENCY

Magnetic resonance imaging (MRI) and MRI relaxometry were used to inve stigate disturbed brain myelination in 18q- syndrome, a disorder chara cterized by mental retardation, dysmorphic features, and growth failur e, T1-weighted and dual spin-echo T2-weighted MR images were obtained, and T1 and T2 parametric image maps were created for 20 patients and 12 controls, MRI demonstrated abnormal brain white matter in all patie nts. White matter T1 and T2 relaxation times were significantly prolon ged in patients compared to controls at all ages studied, suggesting i ncomplete myelination. Chromosome analysis using fluorescence in situ hybridization techniques showed that all patients with abnormal MRI sc ans and prolonged white matter T1 and T2 relaxation times were missing one copy of the myelin basic protein (MBP) gene, The one patient with normal-appearing white matter and normal white matter T1 and T2 relax ation times possessed two copies of the MBP gene, MRI and molecular ge netic data suggest that incomplete cerebral myelination in 18q- is ass ociated with haploinsufficiency of the gene for MBP. (C) 1997 Wiley-Li ss, Inc.