Five Major Categories of Hemorrhagic Disease: Treatment of Specific Underlying Mechanisms

Hemorrhagic cerebrovascular disorders cause 15% to 20% of all strokes. These conditions can be divided into five subgroups on the basis of the location of the primary hemorrhage: (from superficial to deep) epidural, subdural, subarachnoid, intracerebral, and intraventricular hemorrhage (see Fig. 1-1 and Table 8-2).

The clinical features of hemorrhagic cerebrovascular disease vary, depending on the site and the size of the hemorrhage, and occasionally may not be clinically distinguishable from other types of stroke. Computed tomography (CT) or magnetic resonance imaging (MRI) allows precise differentiation and localization of brain hemorrhage and also helps to determine the extent of damage.

When performed, cerebral arteriography may show an avascular mass in the region of hemorrhage. Deterioration of a patient with hemorrhagic stroke is usually attributed to rebleeding (most commonly with saccular aneurysms and arteriovenous malformations [AVMs]); progressive cerebral edema; or other systemic causes such as heart, renal, or hepatic failure, serious cardiac arrhythmias, recurrent cardiac emboli, acute myocardial infarction, pneumonia, pulmonary embolism, septicemia, drug effects, or electrolyte disturbances such as hyponatremia (associated with salt-wasting syndrome or inappropriate antidiuretic hormone syndrome).

EPIDURAL HEMATOMA

Epidural hematoma is a collection of blood between the skull and dura and commonly results from a parietal or temporal skull fracture with laceration of the middle meningeal artery and, occasionally, from a dural sinus tear. Because the dura becomes adherent to the skull with age, epidural hematoma rarely occurs in the elderly. A lucid interval, of several minutes to a few hours, followed by increasing severity of headache associated with nausea, vomiting, progressive impairment of consciousness, and contralateral hemiparesis is the classic clinical course. Pupillary dilation on the side of the hematoma is often an indication of transtentorial herniation. In this situation, the head injury and the hemorrhage are ipsilateral to the dilated pupil in 90% of patients, and the pulse is often less than 60 beats per minute, with a concomitant increase in systolic blood pressure (BP).

Radiography of the skull may reveal a fracture line that crosses the groove associated with the middle meningeal artery. CT or MRI reveals a lenticular-shaped (biconvex; Fig. 17-1) or, rarely, a crescent-shaped clot with a smooth inner margin,
and cerebral arteriography shows inward displacement of the surface arteries. Lumbar puncture may precipitate transtentorial herniation and is contraindicated in this setting. Early diagnosis and immediate neurosurgical consultation may be lifesaving. Treatment typically involves placement of several burr holes, evacuation of the hematoma, and identification and ligation of the bleeding vessel.

FIGURE 17-1. Computed tomography scan of the head without contrast: lenticular-shaped clot consistent with an epidural hematoma (arrows).

SUBDURAL HEMATOMA

Subdural hematoma occurs 10 times more often than epidural hematoma. Subdural hematoma results from head trauma with a tear in a vein as it crosses the subdural space. Because the blood is collected between the dura and the underlying brain, nonfocal neurologic symptoms such as headache, nausea, vomiting, and altered consciousness are often more prominent than focal or lateralizing signs. Symptoms may fluctuate and, when focal, may (rarely) resemble transient ischemic attacks. A lucid interval between the trauma and comatose state is usually absent or brief. CT or MRI (Fig. 17-2) demonstrates a crescent-shaped (or, less common, lenticular-shaped) high-intensity mass consistent with hemorrhage, typically located over one or both (10% of cases) hemispheres. At 1 to 3 weeks after the appearance of subdural blood, the lesion changes from hyperdense to isodense on CT and thereafter becomes hypodense.

Depending on the interval between the head injury and the onset of symptoms, subdural hematomas may be acute (within 24 hours), subacute (1-14 days), or chronic (>14 days). Acute or subacute subdural hematoma may be unilateral or bilateral and frequently results from a severe, high-speed head injury. A combination of subdural hematoma, cerebral contusion, and laceration is common. Urgent surgical treatment with placement of burr holes and evacuation of the subdural hematoma is often indicated to prevent the development of deep coma.

FIGURE 17-2. Magnetic resonance imaging scan of the head: high-intensity mass consistent with a subdural hematoma (arrows).

In contrast to acute or subacute subdural hematoma, chronic subdural hematoma usually results from a less severe head injury, which may have been trivial or even forgotten. A gradual drift into drowsiness, inattentiveness, incoherence of thinking, confusion, stupor, and coma may be associated with increasing headache and, rarely, a seizure. Mental deterioration may be prominent, resembling dementia, brain tumor, drug intoxication, or depressive illness. Focal signs may include ipsilateral dilated pupil and hemiparesis, which may be contralateral, ipsilateral, or both. In infants and children, vomiting and seizures are prominent manifestations of chronic subdural hematoma. In these age groups, retinal hemorrhage in association with subdural hematoma may be manifestation of the so-called shaken infant syndrome.

Patients who have small, chronic subdural hematomas without severe or progressive deficit and in whom follow-up with serial neurologic examination and CT is possible can be managed conservatively. In cases of chronic subdural hematoma with severe or progressive deficit, surgical treatment is generally recommended.

SUBARACHNOID HEMORRHAGE

Subarachnoid hemorrhage (SAH) causes 5% to 10% of all strokes, affecting females more often than males (1.5-2:1). The disorder usually presents with the very sudden onset of a new, severe headache, which is commonly associated with vomiting and follows a rapid alteration of the level of consciousness, including unconsciousness with recovery in a few minutes. Primary SAH (excluding trauma) may be caused by a ruptured intracranial saccular aneurysm (˜75%-80% of all cases); AVM (˜5% of all cases); or other conditions, including mycotic, atherosclerotic, traumatic, dissecting, or neoplastic aneurysms or vasculitis (˜5% of all cases). SAH is of unknown cause in approximately 10% to 15% of all cases (see Table 8-2).

Intracranial Aneurysm

The most common cause of primary SAH is a ruptured intracranial aneurysm (Fig. 17-3). Saccular or berry aneurysms represent 80% to 90% of all intracranial
aneurysms and normally appear as small, rounded, berry-like arterial outpouchings, but other shapes (sessile, pedunculated, and multilobed) are also seen. The size of saccular aneurysms ranges from 2 mm to several centimeters in diameter, and most lesions are between 2 and 10 mm in greatest diameter.

FIGURE 17-3. Cerebral arteriogram: basilar caput saccular aneurysm.

Intracranial aneurysms usually go undetected until rupture results in a clinical picture of SAH, intracerebral hemorrhage (ICH), or both. The clinical features that are associated with SAH and ICH are described in detail in Chapters 14 and 15. In some instances, however, the aneurysm is diagnosed before rupture on the basis of SAH related to a separate aneurysm or clinical signs and symptoms unrelated to intracranial hemorrhage, including cranial nerve compression, compression of other central nervous system (CNS) structures, seizures, focal headaches, and cerebral ischemic events that result from embolism of thrombus within large aneurysms. Alternatively, the diagnosis may be fortuitous after CT, MRI, or cerebral arteriographic studies that are performed for an unrelated disorder.

On the basis of existing evidence, it appears that most aneurysms probably form over a relatively short time (hours, days, or weeks) and attain a size allowed by the limits of elasticity in the elastic components of the walls of the aneurysm. At that point, either the aneurysm ruptures or, if the limits of elasticity are not exceeded and the aneurysm maintains itself intact, the walls undergo a process of compensatory hardening, similar to the process in other vascular walls that are subjected to arterial BPs, in which excessive amounts of collagen are formed. The
tensile strength of collagen is several hundred times that of elastic fibers. With this added tensile strength, which continues to accumulate over time, the likelihood of rupture decreases unless the aneurysm is large at the time it initially stabilizes. Aneurysms that are 7 to 10 mm or more in size at the time of initial stabilization are much more likely to undergo subsequent growth and rupture, because the stress on the wall increases with the square of the diameter of the aneurysm. Therefore, it follows that the critical size for aneurysm rupture is lower if rupture occurs at the time of or soon after formation, as appears to be the case for most aneurysms that rupture. The mean size of aneurysms that are discovered after rupture is approximately 7.5 mm; the mean size of aneurysms discovered before rupture, which then go on to rupture, is approximately 20 mm.

It is important to recognize that ruptured and unruptured intracranial aneurysms constitute distinctly different clinical entities and need to be considered and managed as such. A more thorough discussion of the treatment of patients with unruptured intracranial aneurysms can be found in Chapter 29.

Intracranial aneurysms are typically located at large artery bifurcations involving the circle of Willis and its major branches (Fig. 17-4): internal carotid-posterior communicating artery junction, approximately 30%; anterior communicating artery, 30%; proximal middle cerebral artery, 20% to 25%; and posterior circulation, 10% to 15% among patients with aneurysms that are discovered subsequent to rupture. The locations of unruptured intracranial aneurysms (discovered before rupture) differ somewhat (Fig. 17-4): internal carotid-posterior communicating junction, approximately 45%; anterior communicating artery, 10% to 15%; proximal middle cerebral artery, 30% to 35%; and posterior circulation, 5% to 10%.

Intracranial aneurysms are rare in childhood, and the incidence of aneurysmal SAH is higher in women than in men (ratio, ˜3:2). Approximately 20% to 30% of patients with saccular aneurysms have a family history of SAH or intracranial aneurysm, and 20% to 25% of patients have multiple aneurysms.

The pathogenesis of intracranial saccular aneurysms is controversial and may be multifactorial. There is convincing evidence that these are not congenital
lesions but, rather, that they develop with increasing age. This possibility, however, does not preclude a genetic predisposition for these lesions to develop. Cigarette smoking, female gender, and hypertension appear to be associated with the development of unruptured intracranial aneurysms. Various other environmental factors (use of oral contraceptives, use of stimulant drugs, physical stress, and heavy alcohol consumption) may also have some role in the pathogenesis of ruptured and/or unruptured intracranial aneurysms. Medical conditions that have been associated with intracranial aneurysm include autosomal dominant polycystic kidney disease, intracranial AVM, coarctation of the aorta, Marfan syndrome, type IV Ehlers-Danlos syndrome, hereditary hemorrhagic telangiectasia, fibromuscular dysplasia, bicuspid aortic valve, pseudoxanthoma elasticum, moyamoya disease, neurofibromatosis, pheochromocytoma, Klinefelter syndrome, microcephalic osteodysplastic primordial dwarfism, and pituitary tumors.

FIGURE 17-4. Most common sites of ruptured and unruptured (in parentheses) saccular aneurysms.

Several large autopsy studies have shown a wide range in overall frequency (0.2%-9.9%) of intracranial aneurysms in the general population. More recent prospective MRI, angiographic, and autopsy studies suggest an overall frequency of approximately 2% to 4%. The incidence of aneurysmal SAH increases progressively with age, and the average annual incidence is approximately 6 to 10 per 100,000 population per year. These data suggest that most intracranial aneurysms never rupture.

Approximately 5% of all cerebral aneurysms are cerebral mycotic aneurysms. They commonly result from infected arterial emboli, primarily as a complication of acute or subacute bacterial endocarditis, and lead to septic degeneration of the elastic lamina and the muscular coats of the arterial wall. The most common sites of mycotic aneurysm formation are the distal middle cerebral artery branches, as seen in 2% of cases of bacterial endocarditis. The lesions often resolve with antibiotic treatment, although some symptomatic lesions require surgical clipping.

Dissecting and traumatic intracranial aneurysms are rare. The clinical presentation of dissecting intracranial aneurysms in a relatively young patient may consist of a focal and severe headache followed by progressive stroke, brain edema, and death. Typically, traumatic intracranial aneurysms develop after neck or head trauma (penetrating trauma, bony fractures) and occur most commonly in the internal carotid, middle cerebral, and anterior cerebral arteries.

Neoplastic cerebral aneurysms may be caused by arterial emboli from a cardiac (atrial) myxoma. Cerebral arteriography shows irregular filling defects in major and minor cerebral arterial branches, fusiform and saccular aneurysms, and arterial occlusions. Systemic emboli often occur.

Nonsaccular (fusiform) intracranial aneurysms may develop in patients with widespread atherosclerosis and hypertension and affect primarily the basilar, internal carotid, middle cerebral, and anterior cerebral arteries. Radiographic abnormalities include tortuosity, widening, and elongation of the affected arteries. Other terms such as dolichoectasia, ectasia, aneurysmal malformation, atherosclerotic aneurysm, and cirsoid aneurysm have also been applied to this category of lesions. In contrast to saccular or mycotic aneurysms, these aneurysms uncommonly present with SAH, but they may cause cerebral ischemia or mass effect. They typically are treated conservatively, although antiplatelet agents or even anticoagulants may be needed if thromboembolic events from the fusiform aneurysm occur. Endovascular or surgical management may be needed in patients with hemorrhage, recurrent cerebral ischemia despite medical management, or progressive symptoms because of aneurysmal compression.

Early investigation and treatment of intracranial aneurysms are important, particularly when the aneurysm has produced intracranial hemorrhage (see Appendix E-4). Even in pregnant patients, radiologic and therapeutic or surgical procedures should not be delayed or avoided, although special shielding during radiography is required (see Chapter 22). The clinical decisions that are involved in managing these patients vary with the type of aneurysm, but in patients who present with SAH, CT should be performed as soon as possible. CT may confirm the presence of subarachnoid blood, detect associated ICH and intraventricular hemorrhage, and, in some instances, demonstrate the aneurysm. If CT is nondiagnostic, then lumbar puncture may confirm the diagnosis of SAH (see Chapter 14). CT angiography may reveal the aneurysm, particularly if it is greater than 3 mm in maximal diameter.

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