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| Holoprosencephaly |
| Etiology •Usually associated with trisomy 13 or 18. •May be associated with other abnormal chromosome abnormalities or occasionally with normal chromosomes. •Arises early in gestational life causing lack of cleavage of hemispheres. |
| Pathogenesis •Arises in the first few weeks of intrauterine life when the brain does not cleave into hemispheres. •Usually associated with chromosomal defects., |
| Epidemiology •Seen in l in 13,000 births •Usually sporadic. |
| General Gross Description •Facial abnormalities range from the cyclops with one central abnormal eye, a proboscis above it, and an abnormal mouth to close set eyes with no nose and an abnormal mouth often with cleft lip and palate •Brain abnormalities range from a central ventricle with fused hemispheres or almost no hemispheres and fused basal ganglia and thalamus to absence of the olfactory bulbs and tracts only. •The severity of the facial abnormalities reflects the the severity of the brain abnormalities to a certain extent. |
| General Microscopic Description •In severe holoprosencephaly, the cortex is not well organized and there are cerebral and cerebral heterotopias. •The white matter is thinned. •About the brainstem, astrocytes have migrated into the leptomeninges. |
| Clinical Correlation •Most severely affected infants are born dead or live only a few days. •Less severely affected infants may live several months or years with marked homeostatic abnormalities such as markedly unstable body temperature and blood pressure. •Least severely affected infants may live a normal life span with lack of smell and variable degrees of mental retardation. |
| References • Cotran RS, Kumar V, Robbins SL: Robbins Pathologic Basis of Disease. 5th ed. Philadelphia, W.B. Saunders, 1994, pp. 1302. • Poirer J et.al. Manual of basic neuropathology. Philadelphia: Saunders, 1990, pp. 199. |
| Holoprosencephaly |
| Synopsis by: M. L. Grunnet M.D. (TX2000M20100)[27] |
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