of the many neurologic defects that can occur in the development of the nervous system, some of the most serious such as anencephaly, enchephalocele, and spinabifida, take place in the first two of gestation and represent defects in neural tube formation (dysraphia). Others, such as hydranencephaly and porencephaly, occur later and appear to be secondary to destructive processes of the brain after it has formed. Some defects are relatively benign.
Reasonably accurate in utero detection of many CNS malformations is now possible. Genetic counseling for parents with major neurologic abnormality is important, since the risk of subsequent child having such a defect is high. These parents also need psychologic help and support.
Anenchephaly is absence of the cerebral hemispheres. The absent brain is sometimes replaced with malformed cystic neural tissue which may either be exposed or covered with skin. Varying portions of the brainstem and spinal cord may be missing or malformed.
Encephalocele is a prostrusion of brain or heterotopic nervous tissue along with meninges through a skull defect, is associated with incomplete closure of the cranial vault or cranium bifidum. Enchephalocele usually occurs in the midline and is nasal or occipital but can be asymmetrically frontal or parietal. Small encephaloceles may resemble cephalhematomas. Most encephaloceles should be repaired, since even large ones may contain only heterotropic nerve tissue which can be removed without any residual functional disability. When the defect is associated with other serious malformations, the decision to repair may be more difficult. The hydrocephalus often associated with encephalocele requires definition by ventriculography.
Porencephaly is cerebral cysts or cavities involving cortical tissue, which usually penetrate the white matter and communicate with a ventricle, may occur prenatally or postnatal. The Porencephaly may be caused by a developmental anomaly or ischemia and resulting infarction. The ischemia may be due to birth trauma or vascular thromboses. Usually, the neurologic examination is abnormal and the transillumination
Hydranencephaly is an extreme form of porencephaly in which the cerebral hemispheres are almost totally absent. Usually, the cerebellum and brainstem are formed normally and the basal ganglia are intact. The meninges , bones, and skin over the cranial vault are normal. Neurologic examination in the newborn period may be normal or abnormal, but the infant fails to develop normally. Externally, the head appears to be normal. When it is transilluminated, however light shines completely through it.
Dandy-walker cysts are developmental malformations in which the outlets of the 4th ventricle do not open and the 4th ventricle itself becomes cystic.
Encephalocele is a prostrusion of brain or heterotopic nervous tissue along with meninges through a skull defect, is associated with incomplete closure of the cranial vault or cranium bifidum. Enchephalocele usually occurs in the midline and is nasal or occipital but can be asymmetrically frontal or parietal. Small encephaloceles may resemble cephalhematomas. Most encephaloceles should be repaired, since even large ones may contain only heterotropic nerve tissue which can be removed without any residual functional disability. When the defect is associated with other serious malformations, the decision to repair may be more difficult. The hydrocephalus often associated with encephalocele requires definition by ventriculography.
Porencephaly is cerebral cysts or cavities involving cortical tissue, which usually penetrate the white matter and communicate with a ventricle, may occur prenatally or postnatal. The Porencephaly may be caused by a developmental anomaly or ischemia and resulting infarction. The ischemia may be due to birth trauma or vascular thromboses. Usually, the neurologic examination is abnormal and the transillumination
Hydranencephaly is an extreme form of porencephaly in which the cerebral hemispheres are almost totally absent. Usually, the cerebellum and brainstem are formed normally and the basal ganglia are intact. The meninges , bones, and skin over the cranial vault are normal. Neurologic examination in the newborn period may be normal or abnormal, but the infant fails to develop normally. Externally, the head appears to be normal. When it is transilluminated, however light shines completely through it.
Dandy-walker cysts are developmental malformations in which the outlets of the 4th ventricle do not open and the 4th ventricle itself becomes cystic.
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