Intraventricular hemorrhage (IVH) and germinal matrix hemorrhage in premature infants are common causes of hydrocephalus in the neonatal period. These types of hydrocephalus are identified as posthemorrhagic hydrocephalus (PHH), to distinguish them from other forms of hydrocephalus occurring in infancy. The cause of PHH is related bleeding within the germinal matrix (GM). The GM is thought to be a vascular watershed zone that is particularly vulnerable to ischemic, hypoxic and hypotensive events. The chance of developing PHH correlates with the severity of the IVH, although the exact pathogenesis is poorly defined. An early increase in ventricular size may signal an early failure of (CSF) absorption, but does not invariably lead to progressive hydrocephalus. Ventricular size can stabilize if the CSF production and absorption balances. With imaging, usually trans-fontanelle ultrasound (see Fig. 1), GM, and IVH are divided into four groups:

I. Subependymal location only

II. IVH without ventricular dilation

III. IVH with ventricular dilation

IV. IVH with extension into the brain parenchyma

Twenty to 50 percent of patients with IVH will develop progressive hydrocephalus. These patients usually have grade III or IV IVH; rarely will grade II IVH lead to hydrocephalus. This malabsorptive state is attributed to cellular debris and the breakdown products of blood inhibiting absorption of CSF in the arachnoid granulations and adhesive arachnoiditis.

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