[MR imaging in mental retardation].
Mental retardation is considered idiopathic or not otherwise specified when no etiological diagnosis can be identified in spite of comprehensive history, physical examination and metabolic or genetic investigations. In such cases, brain MRI is indicated for patients with abnormal head size or shape, craniofacial malformation, somatic anomalies, neurocutaneous findings, seizures, focal neurological findings or behavioral and/or developmental problems. Brain anomalies are now considered a main category for the etiology of mental retardation. MRI evaluation should include axial images of the entire brain, sagittal images through the midline structures, and coronal images of the posterior fossa or entire brain. MRI allows detection of major and or minor cerebral anomalies or malformations, sometimes multiple. In the literature, the most frequently involved structures include: 1/ corpus callosum (hypoplasia, short corpus callosum and verticalized splenium), 2/ septum pellucidum (cavum septum pellucidum or cavum vergae), 3/ ventricles (ventriculomegaly), 4/ cerebral cortex (cortical dysplasia), 5/ cerebellum (hypoplasia), and 6/ extra-axial CSF spaces (enlargement). In our patient population, dysplasia involving the cerebellum and vermis have been identified, a finding that has not yet been described in the literature. MRI allows detection of multiple minor morphological anomalies. Most have classically been considered as normal variants but they may in fact be markers of cerebral dysgenesis and are currently the only anomaly detected in the work-up of patients with mental retardation. Their role in the pathogenesis of mental retardation is under evaluation.
Soto-Ares
G
G
Department of Neuroradiology, Hôpital Roger Salengro, CHRU Lille, France. gsotoares@chru-lille.fr
Joyes
B
B
Delmaire
C
C
Vallee
L
L
Pruvo
J P
JP
D000293:Adolescent; D001921:Brain / Q000473:pathology*; D002648:Child; D002675:Child, Preschool; D005260:Female; D006801:Humans; D007223:Infant; D008607:Intellectual Disability / Q000209:etiology / Q000473:pathology*; D008279:Magnetic Resonance Imaging; D008297:Male