Intracranial vascular disease

Stroke and transient ischaemic attacks

The management of these conditions consumes about 5% of health service hospital costs within the UK. Stroke is not a diagnosis as such but is merely a description of a symptom complex ending in a cerebral infarct or haemorrhage as a result of a variety of vascular diseases.

A transient ischaemic attack (TIA) is an sudden onset episode of focal neurological deficit due to inadequate blood supply to the brain which resolves within 24 h and leaves no residual deficit. The majority occur in the internal carotid artery territory, although they can occur in the vertebrobasilar territory as well. Following TIA 5-10% of patients will have a stroke in each year after the event, the risk is highest in the first few days and weeks. Most TIAs are embolic and due to disease in the carotid arteries or heart. Such patients require urgent investigation of the heart by electrocardiogram and, possibly echocardiography of the carotid arteries by Doppler/duplex ultrasound and of the brain by CT scanning. If there is a carotid stenosis of >70%, then consideration needs to be given to carotid endarterectomy.

Of strokes, 85% are due to thromboembolic disease and 15% to haemorrhage (5% secondary to subarachnoid haemorrhage and 10% to intracerebral haemorrhage); the clinical distinction between occlusive and haemorrhagic stroke is often extremely difficult and CT scanning is required. The vast majority of strokes are treated medically but intracra-nial aneurysms, arteriovenous malformations and a small number of intracranial haemorrhages without obvious structural abnormality are treated surgically.

The risk factors for stroke include increasing systemic hypertension, cardiac disease, diabetes mellitus, and smoking. Hypertension is the most important risk factor and lowering blood pressures to the norm corrected for the patient's age is essential; in the non-urgent surgical case, referral should be made to a physician and surgery delayed until the blood pressure is controlled; in the emergency case it is essential to discuss the problem with the anaesthetist who will try and stabilize the situation during induction and maintenance of anaesthesia, although it must also be appreciated that sudden lowering of blood pressure can be dangerous.

Intracranial haemorrhage

Spontaneous intracranial haemorrhage may occur within the brain substance or subarachnoid space, and less commonly in the subdural space. The commonest cause is rupture of an intracranial aneurysm; rarer causes are rupture of a cerebral arteriovenous malformation, haemorrhage from a neoplasm or a bleeding diathesis (most commonly iatro-genically induced by the anticoagulant warfarin, Fig. 21.16).

The patient complains of a sudden very severe headache the like of which they have never experienced before. They may then lose consciousness (coma-producing haemorrhage) or remain unwell without going into coma (non-coma producing); approximately 20% die immediately or very soon after the haemorrhage. The survivors develop meningism due to the blood passing into the spinal subarachnoid space; meningism causes painful stiffness of the neck and lumbar region, which worsens with movement, and must not be confused with spinal pathology (see Chapter 20). Patients may develop neurological deficit either from the site of the aneurysm (e.g. a 3rd nerve palsy from an aneurysm of the internal carotid artery) or from ischaemia resulting from spasm of the major vessels and/or narrowing or occlusion of more distal vessels within the cerebral substance.

The diagnosis of a subarachnoid haemorrhage (SAH) is confirmed by the finding of blood on CT brain scan provided the scan is completed within 48 h of the ictus. If the scan is negative then a lumbar puncture is indicated but this is best left to

Figure 21.16. CT scan of a 30-year-old woman on uncontrolled warfarin. Note the large frontal spontaneous intra-cerebral haematoma (arrow).

Figure 21.17. Digital subtraction angiogram anterior projection in 40-year-old woman with subarachnoid haemorrhage showing an aneurysm of bifurcation of internal carotid artery (large arrow) and posterior communicating aneurysm (small arrow).

Figure 21.16. CT scan of a 30-year-old woman on uncontrolled warfarin. Note the large frontal spontaneous intra-cerebral haematoma (arrow).

longer than 6h after the ictus if the patient's condition allows, SAH is confirmed by the finding of uniformal blood staining or xanthochromia. Thereafter, referral should be made to a neurosurgeon who will then obtain cerebral angiography of all four major vessels (both internal carotid and both vertebral arteries) to ascertain the cause of the haemorrhage.

Aneurysms are true aneurysms. They are nearly always situated at junctions of the major vessels of the circle of Willis, most commonly the anterior communicating complex, the internal carotid close to the junction with the posterior communicating artery and the trifurcation of the middle cerebral artery (Figs 21.17 and 21.18). If they occur in the young, they are thought to be congenital and they may also be familial. The majority occur from 40 years onwards and in these are thought to arise from a slight pre-existing weakness of the arterial wall which is then further weakened by atheroma and/or systemic hypertension. Once rupture has occurred, there is a propensity for further rupture and treatment is directed towards early obliteration of the aneurysm by inserting coils inside the aneurysmal sac and inducing clotting by interventional radiology or if this is not possible by craniotomy and placing of a spring clip across the neck thus excluding the aneurysm from the circulation.

Arteriovenous malformations (AVM) can occur anywhere in the cerebral substance. The majority are mainly capillary in structure and they all have arteriovenous shunts leading in some to increasing demands for blood and as a result further enlargement (Fig. 21.19). They cause problems in three main ways: haemorrhage, epilepsy and cerebral steal whereby blood is diverted from normal areas of brain to feed the AVM and thus causes neurological deficits. There is

Figure 21.17. Digital subtraction angiogram anterior projection in 40-year-old woman with subarachnoid haemorrhage showing an aneurysm of bifurcation of internal carotid artery (large arrow) and posterior communicating aneurysm (small arrow).

Figure 21.18. As for Fig. 21.17 but lateral projection.

usually no normal neural tissue within an AVM and treatment is by surgical excision, embolization by interventional radiology and/or stereotactic radiosurgery.

Occasionally, intracranial haematomas without an obvious structural aetiology require evacuation; this particularly applies to haematomas of the cerebellum. The patient on warfarin presents particular problems and haemorrhage

Figure 21.19. Lateral digital subtraction angiogram of a 38-year-old woman with subarachnoid and intra-cerebral haemorrhage showing arteriovenous malformation (large arrow). Note the enlarged feeding artery (smallest arrow) and cerebral steal with filling of contralateral artery (middle sized arrow).

Blood Pressure Health

Blood Pressure Health

Your heart pumps blood throughout your body using a network of tubing called arteries and capillaries which return the blood back to your heart via your veins. Blood pressure is the force of the blood pushing against the walls of your arteries as your heart beats.Learn more...

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