Subarachnoid hemorrhage refers to blood between the arachnoid layer and the piamater. Unlike epidural and subdural hematomas, the blood in the subarachnoid hemorrhages gets into the sulci and fissures of the CNS. Subarachnoid hemorrhages are very common in the neonatal period. Subarachnoid hemorrhages are usually asymptomatic but they may be associated with paroxysmal clinical events, decreased limb movements or facial weakness. Subarachnoid hemorrhages often occur after vaginal delivery. Extensive subarachnoid hemorrhages probably warrant a coagulation work-up. Subarachnoid hemorrhages do not require any treatment. More about... 53
INTRA-AXIAL HEMORRHAGES AND HEMATOMAS
Intra-axial hemorrhages or hematomas may involve the brain (Figure 251.1) or the spinal cord. Intracranial intra-axial hemorrhages or hematomas may be localized to the parenchyma, ventricles, and choroid plexus. Intra-axial spinal cord hemorrhages are very rare.
Parenchymal hemorrhages have very different presentations in premature and full-term neonates. Parenchymal hemorrhages occur more often in premature than in full-term neonates.
Parenchymal hemorrhage in premature neonates
most common site of parenchymal bleeding in the premature neonate
is the germinal matrix. The germinal matrix is in the subventricular
area. The germinal matrix is what is left of the germinal layer after
the pluripotential cells stop dividing and producing neurons and glia
cells. The germinal matrix is prone to bleeds because as the pluripotential
cells of the germinal matrix disappear, so does the vasculature, and
in the process of disappearing the vessels walls become fragile.
Ganglionic germinal matrix is the most common site for germinal matrix hemorrhage after about 32 weeks gestation. The ganglionic germinal matrix is localized adjacent to the head of the caudate nucleus. The ganglionic germinal matrix is the most frequent site of bleeding because the venous blood flow at the level of the ganglionic germinal matrix makes a U-turn (Figure 251 B, 2), producing an area of high mechanical stress in the venous vessel wall.
Figure 251.3.— Schematic representation of the brain (Gestational age: 34-38 weeks) demonstarting angles on an axial cut (B-B: sagittal) and (C-C: coronal). The ventricles are represented in blue; the choroid plexus in pink. 1: medullary veins; 2: terminal vein; 3: internal cerebral vein; 4: vein of Galen; 5: straight sinus; 6: thalamostriate vein; 7: choroidal vein; 8: Heubner's artery; 9: striated branches of the middle cerebral aftery; 10: frontal poles; 11: frontal horn of the left lateral ventricle; 12: germinal matrix; 13: foramen of Monro; 14: third ventricle; 15: occipital poles.
This high pressure venous system renders the capillary-venous junction vulnerable to ischemic reperfusion injury. Germinal matrix hemorrhages occur when a vulnerable capillary-venous system junction in the mechanically stressed venous walls is further stressed by events that cause an increase in venous pressure. Pneumothorax is a frequent cause of increased cerebral venous pressure and often leads to germinal matrix hemorrhage.