Holoprosencephaly
Regarding holoprosencephaly, the phrase “Face predicts brain” is apt. It is a spectrum of congenital structural forebrain anomalies and is the commonest malformation involving face and brain together. Its hallmark is monoventricle with non-cleaved frontal lobes. Also there is non-cleavage of diencephalon, and at times basal ganglia and thalami . Sylvian fissures are displaced anteriorly, resulting in increased sylvian angle (angle formed by lines drawn tangentially through the sylvian fissures). Radiography reveals hypotelorism and fused metopic suture.
It is a spectrum with three forms, alobar, semilobar and lobar . Alobar variety (Figure A), which is the most severe form, is characterized by monoventricle with “horseshoe” brain, fused thalami and basal ganglia, and absence of septum pellucidum, corpus callosum, falx cerebri and interhemispheric fissure, in association with severe craniofacial anomalies. In semilobar holoprosencephaly (Figure B) facial anomalies are variable, rudimentary occipital horns of lateral ventricles are present and falx is partially present. Lobar form, which is the least severe form, has squared-off frontal horns, well formed falx, separated thalami and only some anteroinferior fusion of hemispheres. Septum pellucidum is absent in all three forms. Holoprosencephaly may be associated with cyclops with ethmocephaly, dorsal brain cyst or olfactory nerve hypoplasia. Extracranial anomalies such as polydactyly, renal dysplasia, omphalocele and hydrops may be associated. Myelination may be delayed.
Figure : Holoprosencephaly. A, Axial CT image showing alobar holoprosencephaly. Note the fused thalami (Arrows), monoventricle with absence of septum pellucidum and absence of interhemispheric fissure and falx. B, Axial CT of semilobar holoprosencephaly. Note single large ventricle, absence of septum pellucidum and rudimentary interhemispheric fissure (Arrow).
Regarding holoprosencephaly, the phrase “Face predicts brain” is apt. It is a spectrum of congenital structural forebrain anomalies and is the commonest malformation involving face and brain together. Its hallmark is monoventricle with non-cleaved frontal lobes. Also there is non-cleavage of diencephalon, and at times basal ganglia and thalami . Sylvian fissures are displaced anteriorly, resulting in increased sylvian angle (angle formed by lines drawn tangentially through the sylvian fissures). Radiography reveals hypotelorism and fused metopic suture.
It is a spectrum with three forms, alobar, semilobar and lobar . Alobar variety (Figure A), which is the most severe form, is characterized by monoventricle with “horseshoe” brain, fused thalami and basal ganglia, and absence of septum pellucidum, corpus callosum, falx cerebri and interhemispheric fissure, in association with severe craniofacial anomalies. In semilobar holoprosencephaly (Figure B) facial anomalies are variable, rudimentary occipital horns of lateral ventricles are present and falx is partially present. Lobar form, which is the least severe form, has squared-off frontal horns, well formed falx, separated thalami and only some anteroinferior fusion of hemispheres. Septum pellucidum is absent in all three forms. Holoprosencephaly may be associated with cyclops with ethmocephaly, dorsal brain cyst or olfactory nerve hypoplasia. Extracranial anomalies such as polydactyly, renal dysplasia, omphalocele and hydrops may be associated. Myelination may be delayed.
Figure : Holoprosencephaly. A, Axial CT image showing alobar holoprosencephaly. Note the fused thalami (Arrows), monoventricle with absence of septum pellucidum and absence of interhemispheric fissure and falx. B, Axial CT of semilobar holoprosencephaly. Note single large ventricle, absence of septum pellucidum and rudimentary interhemispheric fissure (Arrow).
(A)
(B)Reference:The Internet Journal of Radiology™ ISSN: 1528-8404
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