Subdural hemorrhage, which now occurs less often because of improved obstetric techniques, results from tears in the falx, tentorium, or bridging veins. Such tears are most common in infants of primiparas, in large infants, or after difficult deliveries. All these conditions can produce unusual pressures on blood vessels inside the skull. The presenting finding may be seizures, a rapidly enlarging head, or an abnormal neurologic examination with hypotonia, a poor Moro reflex, or extensive retinal hemorrhages. Hemorrhages occur most often in premature infants, are often bilateral, and usually arise in the germinal matrix, which lies on the lateral wall of the lateral ventricles.
Most bleeding episodes are subependymal or intraventricular and involve a small amount of blood.
In severe hemorrhage, there may be bleeding into the parenchyma or a cast of the ventricular system with large amounts of blood in the cisterna magna and basal cisterns. Hypoxia-ischemia often precedes intraventricular and subarachnoid bleeding. Hypoxia-ischemia damages the capillary endothelium, impairs cerebral vascular autoregulation, and can increase cerebral blood flow and venous pressure, all of which make hemorrhage more likely. Most intraventricular hemorrhages are asymptomatic, but larger hemorrhages may cause apnea, cyanosis, or a sudden collapse. Cranial ultrasound and CT can detect blood and are useful.