Radiology Resident Case of the Week
Clinical Sx:
Premature infant born with encephalocoele
Etiology/Pathophysiology
Failure of cleavage of the rostral prosencephalon into both telencephalon and diencephalon, and into cerebral hemispheres.
Pathology:
There is a spectrum of holoprosencephaly depending on the extent of failure of differentiation and cleavage in the developing fetus. Alobar holoprosencephaly is characterized by fused thalami, monoventricle, absence of the falx and interhemispheric fissure, and a dorsal cyst. It is associated with cyclopia, hypotelorism and midline defects. In semilobar holoprosencephaly a portion of the interhemispheric fissure remains intact and the thalami are not completely fused. There may be extensions of the monoventricle that resemble occipital or temporal horns of the lateral ventricles. Lobar holoprosencephaly may resemble patients with septo-optic dysplasia as there is nearly complete cleavage into cerebral hemispheres and there is no septum pellucidum. There may be a dysplastic anterior falx or frontal horns.
Holoprosencephaly is associated with several chromosomal abnormalities (trisomy 13 and 15, and others), and fetal infections and exposures.
Miscellaneous
Imaging
1) Monoventricle
2) Fused thalami
3) No interhemispheric fissure
4) Large dorsal cyst which extends through the sagittal suture to form a large rostral encephalocoele
5) Right intraventricular hemorrhage with blood CSF layer
posteriorly in the monoventricle
6) Absence of gyri (possibly due to prematurity rather that
true lissencephaly)
DDX
Key references
Barkovich, A. James. Pediatric Neuroimaging. New York: Raven Press, 1990. pp. 102-6.
Castillo, Mauricio & Mukherji, Suresh K. Imaging of the Pediatric Head, Neck, and Spine. New York: Lippincott-Raven Publishers, 1996. pp.33-36
ACR Code
Keywords:
holoprosencephaly