Intracranial Hemorrhage · 481 11

Further causes of cerebellar hemorrhage include the rupture of an arteriovenous malformation or aneurysm, and bleeding into a tumor (usually a metastasis).

Subarachnoid Hemorrhage

Aneurysms

The most common cause of spontaneous subarachnoid hemorrhage is the rupture of an aneurysm of one of the arteries of the base of the brain. There are different types of aneurysms.

Saccular (“berry”) aneurysms are found at points of bifurcation of the intracranial arteries. They form on the basis of a prior lesion of the vessel wall, which is either a (usually congenital) structural defect, or an injury due to hypertension. The common sites of saccular aneurysms are the anterior communicating artery (40%), the bifurcation of the middle cerebral artery in the sylvian fissure (20%), the lateral wall of the internal carotid artery (at the origin of the ophthalmic or posterior communicating artery, 30%), and the basilar tip (10%) (Fig. 11.31). Aneurysms at other sites, such as the origin of

Fig. 11.31 Common sites of intracranial aneurysms

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11 482 · 11 Blood Supply and Vascular Disorders of the Central Nervous System

the PICA, the P2 segment of the posterior cerebral artery, or the pericallosal segment of the anterior cerebral artery, are rare. Aneurysms can produce neurological deficits by pressing on neighboring structures even before they rupture. For example, an aneurysm of the posterior communicating artery can compress the oculomotor nerve, causing a third nerve palsy (the patient complains of diplopia).

Fusiform aneurysms. An elongated (“spindle-shaped”) enlargement of a vessel is called a fusiform aneurysm. Such aneurysms preferentially involve the intracranial segment of the internal carotid artery, the main trunk of the middle cerebral artery, and the basilar artery. They are usually caused by atherosclerosis and/or hypertension, and they are only rarely a source of hemorrhage. Large fusiform aneurysms of the basilar artery can compress the brainstem. Slow flow inside a fusiform aneurysm can promote intra-aneurysmal clot formation, particularly at the sides, with subsequent embolic stroke or cut-off of perforating vessels by the direct extension of thrombus. These aneurysms usually cannot be treated neurosurgically, because they are elongated enlargements of normal vessels, rather than pathological structures (like saccular aneurysms) making no contribution to the cerebral blood supply.

Mycotic aneurysms. Aneurysmal dilatations of intracranial blood vessels are sometimes the result of sepsis with bacterially induced damage to the vascular wall. Unlike saccular and fusiform aneurysms, these mycotic aneurysms are preferentially found on small arteries of the brain. The treatment consists of treatment of the underlying infection. Mycotic aneurysms sometimes regress spontaneously; they very rarely cause subarachnoid hemorrhage.

Case Presentation 9: Multiple Unruptured Aneurysms

This previously healthy 43-year-old mechanic was briefly unconscious after an automobile accident (front-end collision) and was taken to the hospital for observation. A CT scan of the head was performed to rule out intracranial injury. The noncontrast images revealed no hemorrhage or other abnormality, but the contrastenhanced images revealed a possible aneurysm of the right middle cerebral artery as an incidental finding. This was followed up by cerebral angiography, which confirmed the presence of an aneurysm at the bifurcation of the

right middle cerebral artery, as well as further aneurysms of the left internal carotid artery and the tip of the basilar artery (Fig. 11.32a). The MCA and ICA aneurysms were clipped in an open neurosurgical operation. The basilar tip aneurysm, however, was not amenable to surgical treatment with an acceptably low risk. Instead, it was treated with an interventional neuroradiological procedure: a microcatheter was inserted into it under angiographic control, and its lumen was filled with metal coils (Fig. 11.32b).

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Intracranial Hemorrhage · 483 11

a

b

Fig. 11.32 Basilar tip aneurysm. Intra-arterial digital subtraction angiography before (a) and after (b) the aneurysm was filled with coils. The basilar tip aneurysm is well seen on the angiogram; it is narrower at its base (neck). Coiling excludes the aneurysm from the circulation. (Images courtesy of PD Dr. Skalej and Dr. Siekmann, Tübingen.)

Acute Nontraumatic Subarachnoid Hemorrhage

Nontraumatic subarachnoid hemorrhage (SAH) is usually caused by the spontaneous rupture of a saccular aneurysm, with escape of blood into the subarachnoid space.

Manifestations. The leading symptom of a subarachnoid hemorrhage is a sudden, very intense headache (“the worst headache of my life”). Meningeal irritation by subarachnoid blood causes nuchal rigidity (differential diagnosis: meningitis). Consciousness may be impaired immediately or within the first few hours. Cranial nerve palsies and focal neurological signs may be present, depending on the site and extent of the hemorrhage. The grading scheme proposed by Hunt and Hess in 1968 is still useful in clinical practice, as it gives a rough indication of the patient’s prognosis (Table 11.2).

Diagnostic evaluation. CT sensitively detects acute subarachnoid hemorrhage (Fig. 11.33);yet,thelongertheintervalbetweentheacuteeventandtheCTscan, the more likely it is that the scan will be negative. If SAH is suspected despite a negative CT scan, a lumbar puncture must be performed. This will enable the direct demonstration of blood or siderophages in the cerebrospinal fluid.

OnceSAHhasbeendiagnosed,thesourceofbleedingmustbeidentified.This canonlybedonereliablybyintra-arterialdigitalsubtractionangiography,which

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Fig. 11.33 Acute subarachnoid hemorrhage. The basal cisterns are filled with hyperdense (bright) blood. The temporal horns of the lateral ventricles are dilated because of an obstruction of CSF outflow (hydrocephalus). Because there is no blood in the ventricles, the internal CSF spaces are dark, while the external CSF spaces are bright.

should, however, be performed only if the patient is a candidate for a surgical proceduretocliptheaneurysmortocloseitwiththemethodsofinterventional neuroradiology (see below). DSA reliably demonstrates the presence of an aneurysm and illustrates its spatial relationship to the neighboring vessels. All four great vessels supplying the brain are studied with contrast medium, because about 20% of patients with aneurysms have more than one aneurysm.

Treatment. Aneurysms can be treated with a neurosurgical operation in which the neck of the aneurysm is closed with a metal clip. The aneurysm is thereby permanently excluded from the circulation, so that it cannot bleed again. This form of treatment is definitive, but the disadvantage is that it requires operative opening of the skull (craniotomy) and neurosurgical manipulations around the base of the brain that may cause further complications. Surgery should be performed in the first 72 hours after subarachnoid hemorrhage, i.e., before the period of greatest risk for the development of vasospasm (see

Table 11.2 Grading of Subarachnoid Hemorrhage According to Hunt and Hess

Grade

Clinical features

1Asymptomatic or mild headache and meningeal irritation

2Moderate or severe headache (worst headache of life), meningismus, cranial nerve deficits (abducens palsy is common)

3Drowsiness, confusion, mild focal neurological signs

4Stupor, severe neurological deficits (e. g., hemiparesis), autonomic manifestations

5Coma, decerebration

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Intracranial Hemorrhage · 485 11

below). Early surgery has been shown to improve the prognosis of patients who present with SAH in Hunt and Hess grades 1, 2, or 3. It is the most important form of treatment for the prevention of rebleeding.

An alternative, less invasive form of treatment is the filling of the aneurysm with metal coils (“coiling,” a procedure belonging to the field of interventional neuroradiology). The coils are delivered from the tip of a specialized angiographic catheter, which is inserted transfemorally and advanced to the level of the aneurysm. Coiling obviates the need for craniotomy, but it may not be an equally reliable method of permanently obliterating the aneurysm.

Clinical course, prognosis, and complications. Subarachnoid hemorrhage usually stops spontaneously, probably because it is tamponaded by the rising intracranial pressure. Only patients in whom the aneurysm has stopped bleeding survive to be transported to the hospital; the prehospitalization lethality of aneurysmal SAH is approximately 35%.

After the acute event, the patient faces the risk of three potentially fatal complications:

Hydrocephalus

Vasospasm

Rebleeding

Hydrocephalus (impaired CSF circulation and/or resorption), if it develops, appears very rapidly after the initial SAH. The resulting intracranial hypertension often impairs the patient’s consciousness and may also cause focal neurological deficits. Hydrocephalus can be effectively treated by external ventricular drainage. Lumbar drainage is less commonly used.

Vasospasm occurs a few days later, presumably through the effect of vasoactive substances contained in the extravasated subarachnoid blood. The risk of vasospasm can be reduced by the removal of as much subarachnoid blood as

Case Presentation 10: Acute Subarachnoid Hemorrhage due to Aneurysmal Rupture

This previously healthy 46-year-old man suddenly experienced the worst headache of his life, combined with profound anxiety and a sense of impending doom. He also complained of double vision, particularly on looking to the right. The physician who admitted him to the hospital examined him neurologically and found a stiff neck and a right partial third cranial nerve palsy, but no other neurological deficits.

The presumptive diagnosis of acute subarachnoid hemorrhage was confirmed by CT scan and lumbar puncture. The patient was stable enough to be considered a candidate for surgery, and cerebral angiography was therefore performed at once, revealing an aneurysm of the internal carotid artery arising at the origin of the posterior communicating artery (Fig. 11.34a). This aneurysm proved to be

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amenable to treatment by interventional neuroradiological methods: immediately after the lesion was identified by angiography, a microcatheter was introduced into it under angiographic guidance, and its lumen was filled with platinum coils (Fig. 11.34b, c).

Because coiling does not immediately reduce the volume of the aneurysm, immediate improvement of the cranial nerve palsy was not expected. In the further course, however, the aneurysm may shrink, leading to symptomatic improvement. This took six weeks in the present case.

a

b

c

Fig. 11.34 Acute nontraumatic subarachnoid hemorrhage due to rupture of an aneurysm of the internal carotid artery at the origin of the posterior communicating artery. a Conventional angiography, lateral view. The internal carotid artery aneurysm is seen at the origin of the posterior communicating artery. b The aneurysm has been excluded from the circulation by coiling. The metal coils strongly absorb x-rays and therefore appear dark in the nonsubtracted images. c The coils are barely seen in the subtracted image, but the dome of the aneurysm is clearly no longer filled with blood. (Images courtesy of MD Dr. Skalej and Dr. Siekmann, Tübingen).

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