Topics Discussed: cerebrospinal fluid; cerebrospinal fluid circulation; communicating hydrocephalus; congenital hydrocephalus; fetal ventriculomegaly; hydrocephalus; hydrocephalus, posthemorrhagic; neurology; obstructive hydrocephalus; spina bifida.
Excerpt:"I. Definition. Hydrocephalus is dilation of the cerebral ventricular system secondary to an accumulation of cerebral spinal fluid (CSF) and a disturbance in CSF circulation. It is usually associated with increased intracranial pressure (ICP) and an enlarging head. The measurable occipital-frontal head circumference (OFC) may exceed the growth percentiles for gestational age or chronological age. Typically, an OFC of >2 standard deviations of normal is consistent with macrocephaly due to hydrocephalus. Occasionally hydrocephalus may be present with normal head size but with marked ventricular dilation.
CSF is produced largely from the choroid plexus of each ventricle throughout the cerebral ventricular system. Approximately 80% is choroid plexus in origin, and the remainder is contributed from the substance of the brain and spinal cord. CSF flows posterior from the lateral ventricles through the third ventricle into the aqueduct of Sylvius and through to the fourth ventricle. It ultimately reaches the subarachnoid space by way of the foramina of Magendie and Luschka. CSF enters the venous circulation by way of the absorptive arachnoid villi that line the superior sagittal sinus. Any disturbance of the flow or absorption of CSF leads to accumulation and hydrocephalus. Two mechanisms exist to explain pathologic CSF accumulation:
- A. Noncommunicating hydrocephalus is the result of obstruction anywhere along the ventricular CSF..."
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