Porth's Essentials of Pathophysiology, 4e

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Disorders of Brain Function

C h a p t e r 3 7

Anterior

Sagittal sinus

Severance of bridging veins

Subdural hematoma

Epidural hematoma

Dura

Outer membrane

Bridging vein

Subdural hematoma Inner membrane

Arachnoid

after injury. Symptoms of chronic subdural hematoma may not arise until several weeks after the injury. Acute subdural hematomas progress rapidly and have a high mortality rate because of the severe secondary injuries related to edema and increased ICP. The high mortality rate has been associated with uncontrolled ICP increase, loss of consciousness, decerebrate postur- ing (see Fig. 37-4B), and delay in surgical removal of the hematoma. The clinical picture is similar to that of epidural hematoma, except that there usually is no lucid interval. By contrast, in subacute subdural hematoma, there may be a period of improvement in the level of consciousness and neurologic symptoms, only to be fol- lowed by deterioration if the hematoma is not removed. Symptoms of chronic subdural hematoma develop weeks after a head injury, so much later that the person may not remember having had a head injury. Chronic subdural hematoma is more common in older persons because brain atrophy causes the brain to shrink away from the dura and stretch fragile bridging veins. When these veins rupture, there is slow seepage of blood into the subdural space. Fibroblastic activity causes the hematoma to become encapsulated. The sanguinous (blood fluid) in this encapsulated mass, with its high concentration of osmotically-active particles, draws fluid from the surrounding subarachnoid space, causing the hematoma to expand and exert pressure on the sur- rounding brain tissue. In some instances, the clinical pic- ture is less defined, with the most prominent symptom being a decreasing level of consciousness, as manifested by drowsiness, confusion, headache, and apathy Traumatic Intracerebral Hematomas. Traumatic intracerebral hematomas may be single or multiple. They can occur in any lobe of the brain but are most com- mon in the frontal or temporal lobes, related to the bony prominences on the inner skull surface (Fig. 37-9). They may occur in association with the severe motion that the brain undergoes during head injury, or a contusion can coalesce into a hematoma. Intracerebral hematomas occur more frequently in older persons and alcoholics, whose cerebral vessels are more friable. FIGURE 37-8. Mechanism of bleeding in subdural hematoma. (FromTrojanowski JQ.The central nervous system. In: Rubin E, Gorstein F, Rubin R, et al; eds. Rubin’s Pathology: Clinicopathologic Foundations of Medicine. 4th ed. Philadelphia, PA: Lippincott Williams &Wilkins; 2005:1430. Courtesy of Dmitri Karetnikov, artist.)

Intracerebral hematoma

Posterior

FIGURE 37-7. Location of epidural, subdural, and intracerebral hematomas.

there are focal symptoms related to the area of the brain involved. These symptoms can include ipsilateral pupil dilation and contralateral (opposite side) hemiparesis from uncal herniation. If the hematoma is not removed, the condition progresses, with increased ICP, tentorial herniation, and death. The prognosis is excellent, how- ever, if the hematoma is removed before loss of con- sciousness occurs. Subdural Hematoma. A subdural hematoma develops in the area between the dura and the arachnoid (sub- dural space) and usually is the result of a tear in the small bridging veins that connect veins on the surface of the cortex to dural sinuses. The bridging veins pass from the pial vessels through the CSF-filled subarach- noid space, penetrate the arachnoid and the dura, and empty into the intradural sinuses. 1,4,7 These veins are readily snapped in head injury when the brain moves suddenly in relation to the cranium (Fig. 37-8). Bleeding can occur between the dura and arachnoid (i.e., sub- dural hematoma) or into the CSF-filled subarachnoid space (i.e., subarachnoid hematoma). The venous source of bleeding in a subdural hema- toma develops more slowly than the arterial bleeding in an epidural hematoma. Subdural hematomas are clas- sified as acute, subacute, or chronic. This classification system is based on the approximate time before the appearance of symptoms. Symptoms of acute hematoma are seen within 24 hours of the injury, whereas subacute hematoma does not produce symptoms until 2 to 10 days