2005-10-24-11 Heron Werner, MD*, Pedro Daltro, MD*, Dorothy Bulas, MD# * Clínica de Diagnóstico por Imagem (CDPI) & Instituto Fernandes Figueira (IFF) – FIOCRUZ – Rio de Janeiro – Brazil
# Professor of Radiology and Pediatrics – Children"s National Medical Center – George Washington University Medical Center – 111 Michigan Ave, NW, Washington D.C. 20010

There have been reports of sporadic cases of holoprosencephaly recognized by MRI. This is a pathology with precocious origin (during the organogenesis of the brain, that originates from a cleavage failure of the primitive prosencephalon. Its incidence is of around 1 out of 10.000 births (Sanders, 1996). According to its level of severity, holoprosencephaly is classified in alobar, semilobar and lobar (Table 1). Despite few accounts in literature, MRI does seem to be beneficial to characterizing an intrauterine lobar holoprosencephaly, enabling a more precise differential evaluation with agenesis of the corpus callosum and Dandy-Walker deformity (Girard, 1993; Lair-Milar, 1997).

Fetuses with holoprosencephaly of both the alobar and semilobar types tend to die at birth. Survival relates to the most mild forms of the disorder, including the lobar type, and is associated with mental retardation.

Findings Alobar Semilobar Lobar
Craniofacial anomaly Severe Variable Mild or absent
Ventricles Mono ventricle Rudimentary occipital horns Frontal horns with either a rectangular aspect
Pellucid septum Absent Absent Absent
Falx cerebri Absent Partial Well developed
Inter hemispheric fissure Absent Partial Present; some anteroinferior fusion
Thalamus, basal ganglia Fused Partial Separated

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