stroke and cerebrovascular disease

21
STROKE AND CEREBROVASCULAR DISEASE Stroke is the 2nd common cause of death (9%) and a major cause of disability. The annual death rate is about 200 per 100 000 (12% of all deaths). Rates are higher in Asian and black African populations than in Caucasians. Stroke is uncommon below the age of 40 and commoner in males. The death rate following stroke is 20-25%. Hypertension is the most treatable stroke risk factor; stroke is decreasing in the 40-60 age groups because hypertension is treated. Thromboembolic infarction (80%), cerebral and cerebellar hemorrhage (10%) and subarachnoid hemorrhage (SAH) (about 5%) are the main causes; arterial dissection and arteriovenous malformations also contribute. Definitions Stroke. Is defined as a syndrome of rapid onset of cerebral deficit (usually focal) lasting >24 hours or leading to death, with no cause apparent other than a vascular one. Completed stroke : the deficit has become maximal, usually within 6 hours. Stroke-in-evolution describes progression during the first 24 hours. Minor stroke. Patients recover without significant deficit, usually within a week. Transient ischemic attack (TIA) means a sudden focal deficit lasting from seconds to 24 hours with complete recovery). TIAs have a tendency to recur, and may herald thromboembolic stroke. Pathophysiology Completed stroke This is caused by: Arterial embolism from a distant site. Arterial thrombosis . Hemorrhage (intracranial or SAH). Less commonly, other processes cause stroke: venous infarction carotid or vertebral artery dissection polycythemia and hyperviscosity syndromes

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Page 1: Stroke and Cerebrovascular Disease

STROKE AND CEREBROVASCULAR DISEASE Stroke is the 2nd common cause of death (9%) and a major cause of disability. The annual death rate is about 200 per 100 000 (12% of all deaths). Rates are higher in Asian and black African populations than in Caucasians. Stroke is uncommon below the age of 40 and commoner in males. The death rate following stroke is 20-25%. Hypertension is the most treatable stroke risk factor; stroke is decreasing in the 40-60 age groups because hypertension is treated. Thromboembolic infarction (80%), cerebral and cerebellar hemorrhage (10%) and subarachnoid hemorrhage (SAH) (about 5%) are the main causes; arterial dissection and arteriovenous malformations also contribute.

Definitions

Stroke. Is defined as a syndrome of rapid onset of cerebral deficit (usually focal) lasting >24 hours or leading to death, with no cause apparent other than a vascular one.

Completed stroke : the deficit has become maximal, usually within 6 hours. Stroke-in-evolution describes progression during the first 24 hours. Minor stroke. Patients recover without significant deficit, usually within a

week. Transient ischemic attack (TIA) means a sudden focal deficit lasting from

seconds to 24 hours with complete recovery). TIAs have a tendency to recur, and may herald thromboembolic stroke.

Pathophysiology

Completed stroke

This is caused by:

Arterial embolism from a distant site. Arterial thrombosis . Hemorrhage (intracranial or SAH).

Less commonly, other processes cause stroke:

venous infarction carotid or vertebral artery dissection polycythemia and hyperviscosity syndromes fat and air embolism . multiple sclerosis . Mass lesions .

Transient ischemic attacks

TIAs are usually the result of microemboli. TIAs may be caused by a fall in cerebral perfusion (e.g. a cardiac dysrhythmia, postural hypotension or decreased flow

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through atheromatous arteries). Infarction is usually averted by autoregulation (p. 1127). Rarely, tumors and subdural hematomas cause episodes indistinguishable from thromboembolic TIAs: a clinical TIA is thus not a reliable indicator of thromboembolism. Principal sources of emboli are cardiac thrombi and atheromatous plaques/thrombi within the great vessels, carotid and vertebral systems. Cardiac thrombi (mural and valvular) follow atrial fibrillation, often secondary to valvular disease, or myocardial infarction. Polycythemia is also a cause. Thromboembolism from sources outside the brain generates 80% of TIAs and also 70% of strokes. Carotid and vertebral artery dissection Dissection accounts for around 20% of strokes below age 40 and is sometimes a sequel of head or neck trauma. Stroke, TIA or sudden headache/migraine-like symptoms occur, sometimes with neck pain at the site of dissection. Risk factors and prevention

Low-dose aspirin is used in primary prevention in men and women with a 10-year risk of coronary heart disease greater than 10%. For brain hemorrhage, hypertension, bleeding disorders, anticoagulants and antiplatelet drugs, pre-existing cerebral aneurysms and AVMs are risk factors.

Table 21-25. Factors reducing stroke risk  Reduction in stroke risk

Risk factorActionInfarctionHaemorrhageSAH

HypertensionTreat and monitor++++Probable

SmokingStop+++Probable

LifestyleMore active+00

AlcoholModerate intake+00

High cholesterolStatins, diet+00

Raised hematocritReduce+00

Atrial fibrillationAnticoagulate+Increases risk slightly0

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ObesityWeight reductionProbableProbable0

DiabetesGood controlProbable00

Severe carotid stenosisSurgery++00

Sleep apneaTreat+00

++: Major correlation with reduced stroke risk, +: moderate correlation, SAH: subarachnoid hemorrhage.

Rarer risk factors and other causes of stroke

1. Thrombocythemia and thrombophilia (protein C deficiency, factor V Leiden) predispose to cerebral venous thrombosis.

2. Anti-cardiolipin and lupus anticoagulant antibodies (antiphospholipid syndrome predispose to arterial thrombotic strokes in young patients.

3. Endocarditis.4. Low-dose estrogen-containing OCPs do not increase stroke risk significantly

in healthy women but probably do so with other risk factors, e.g. uncontrolled hypertension or smoking.

5. Migraine.6. Vasculitis (polyarteritis, (SLE), GCA, and granulomatous CNS angiitis).7. Amyloidosis can present as recurrent cerebral hemorrhage.8. Hyperhomocysteinemia predisposes to thrombotic strokes. Folic acid therapy

does not reduce the incidence.9. Neurosyphilis, mitochondrial disease.10. Drugs of abuse e.g. cocaine, cold remedies containing vasoconstrictors.11. Cox-2 inhibitors

Vascular anatomy

The circle of Willis is supplied by the two internal carotid arteries and by the basilar. Stenosis and plaques proximal to the circle of Willis are seen typically at four extracranial sites :

1. origin of common carotid artery (1)2. origin of internal carotid artery (2)3. origin of vertebral artery (3)

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4. Subclavian artery (4) and carotid artery syphon - within the cavernous sinus.

Autoregulation Usually, constant cerebral blood flow (CBF) is maintained at mean arterial blood pressures between 60 and 120 mmHg, smooth muscle in small arteries responding directly to changes in pressure. CBF is normally independent of perfusion pressure, i.e. there is autoregulation.

In disease, CBF autoregulation can fail. Contributory causes are:

severe hypotension with S BP <75 mmHg severe hypertension with S BP >180 mmHg increase in blood viscosity, e.g. polycythemia raised ICP Increase in arterial PCO2 and/or fall in arterial PO2.

CLINICAL SYNDROMESTransient ischemic attacks (TIAs) The most common features are Hemiparesis and aphasia, others are:

Amaurosis fugax

This is a sudden transient loss of vision in one eye. When due to the passage of emboli through the retinal arteries it is often the first clinical evidence of internal carotid artery stenosis - and forerunner of a hemiparesis. Amaurosis fugax also occurs as a benign event in migraine.

Transient global amnesia Episodes of amnesia/confusion lasting several hours, occurring principally in people over 65 and followed by complete recovery, are presumed to be due to posterior circulation ischemia. The exact cause is unknown. Episodes rarely recur and there is little evidence that they are actually thromboembolic. Clinical findings in TIA

Table 21-26. Features of transient ischaemic attacksAnterior circulationPosterior circulationCarotid systemVertebrobasilar systemAmaurosis fugaxDiplopia, vertigo, vomitingAphasiaChoking and dysarthriaHemiparesisAtaxiaHemisensory lossHemisensory lossHemianopic visual lossHemianopic visual loss Bilateral visual loss Tetraparesis Loss of consciousness (rare) Transient global amnesia (possibly)

. Consciousness is usually preserved in TIA. There may be clinical evidence of a source of embolus, e.g.:

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carotid arterial bruit (stenosis) atrial fibrillation or other dysrhythmia valvular heart disease/endocarditis recent myocardial infarction Difference between right and left brachial BP.

An underlying condition may be evident:

atheroma Hypertension, postural hypotension. bradycardia or low cardiac output diabetes mellitus rarely, arteritis, polycythaemia, neurosyphilis, HIV Antiphospholipid syndrome.

Differential diagnosis

TIAs can be distinguished from other transient episodes: Mass lesions: occasionally give identical features to TIAs. Focal epilepsy is usually recognized by its positive features (e.g. limb jerking

and loss of consciousness) and progression over minutes. In a TIA, involuntary limb movements do occur occasionally; deficit is usually instantaneous.

A focal prodrome in migraine sometimes causes diagnostic difficulty. Headache, common but not invariable in migraine, is rare in TIA. Typical migrainous visual disturbances are not seen in TIA.

Prognosis Prospective studies show that 5 years after a single thromboembolic TIA:

30% have had a stroke, a third of these in the first year 15% have suffered a myocardial infarct.

TIAs in the anterior cerebral circulation carry a more serious prognosis than those in the posterior circulation.Cerebral infarction

Following vessel occlusion brain ischaemia occurs, followed by infarction. The infarcted region is surrounded by a swollen area which does not function but is structurally intact. This is the ischaemic penumbra, which is detected on MRI and can regain function with neurological recovery. Within the ischaemic area, hypoxia leads to neuronal damage. There is a fall in ATP with release of glutamate, which opens calcium channels with release of free radicals. These alterations lead to inflammatory damage, necrosis and apoptotic cell death. Clinical features

The stroke most typically seen is caused by infarction in the internal capsule following thromboembolism in a middle cerebral artery branch. A similar picture is

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caused by internal carotid occlusion .Limb weakness on the opposite side to the infarct develops over seconds, minutes or hours. There is a contralateral hemiplegia or hemiparesis with facial weakness. Aphasia is usual when the dominant hemisphere is affected. Weak limbs are at first flaccid and areflexic. Headache is unusual. Consciousness is usually preserved. Exceptionally, an epileptic seizure occurs at the onset. After a variable interval, usually several days, reflexes return, becoming exaggerated. An extensor plantar response appears. Weakness is maximal at first; recovery occurs gradually over days, weeks or many months. Brainstem infarction

The lateral medullary syndrome (thrombosis of posterior inferior cerebellar artery (PICA) or its branches, and Wallenberg's syndrome) is a common example of brainstem infarction presenting as acute vertigo with cerebellar and other signs. It can follow vertebral artery thromboembolism or dissection.

Coma follows damage to the brainstem reticular activating system. The locked-in syndrome is caused by upper brainstem infarction. Pseudobulbar palsy can follow lower brainstem infarction.

Table 21-27. Features of brainstem infarctionClinical featureStructure involvedHemiparesis or tetraparesisCorticospinal tractsSensory lossMedial lemniscus and spinothalamic

tractsDiplopiaOculomotor systemFacial numbnessVth nerve nucleiFacial weaknessVIIth nerve nucleusNystagmus, vertigoVestibular connectionsDysphagia, dysarthriaIXth and Xth nerve nucleiDysarthria, ataxia, hiccups, vomitingBrainstem and cerebellar connectionsHorner's syndromeSympathetic fibresComa, altered consciousnessReticular formation

Table 21-28. Clinical signs in the lateral medullary syndrome (PICA thrombosis)IpsilateralContralateralFacial numbness (Vth)Spinothalamic sensory lossDiplopia (VIth)Hemiparesis (mild, unusual)Nystagmus Ataxia (cerebellar) Horner's syndrome IXth and Xth nerve lesions 

Other patterns of infarction

1. Lacunar infarction

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Lacunes are small (<1.5 cm3) infarcts seen on MRI or at autopsy. Hypertension is commonly present. Lacunar infarction is often symptomless.

2. Hypertensive encephalopathy

This is due to cerebral oedema, causing severe headaches, nausea and vomiting. Agitation, confusion, fits and coma occur if the hypertension is not treated. Papilloedema develops, either due to ischaemic optic neuropathy or following the brain swelling due to multiple acute infarcts. MRI shows oedematous white matter in the parieto-occipital regions.

3. Multi-infarct dementia (vascular dementia)

Multiple lacunes or larger infarcts cause generalized intellectual loss seen with advanced cerebrovascular disease. In the late stages, there is dementia, pseudobulbar palsy and a shuffling gait (small steps), sometimes called atherosclerotic parkinsonism. Binswanger's disease is a term for widespread low attenuation in cerebral white matter, usually with dementia, TIAs and stroke episodes in hypertensive patients (the changes being seen on imaging/autopsy).

4. Visual cortex infarction(Anton's syndrome) PCA infarction or infarction of the MCA macular branch causes combinations of hemianopic visual loss and cortical blindness.

5. Weber's syndrome is due to a unilateral infarct in the midbrain, there are

Ipsilateral IIIrd nerve palsy with contralateral hemiplegia. Paralysis of upward gaze is usually present.

6. Watershed (borderzone) infarction

Cortical infarcts, often multiple, follow prolonged periods of low perfusion (e.g. hypotension after massive myocardial infarction or cardiac bypass surgery) between areas supplied by the anterior, middle and posterior cerebral arteries. Cortical visual loss, memory loss and intellectual impairment are typical. In some cases a vegetative state or minimal conscious state follows.

Acute stroke: immediate care, and thrombolysis

Paramedics and members of the public are encouraged to make the diagnosis of stroke on a simple history and examination - FAST:

Face - sudden weakness of the face Arm - sudden weakness of one or both arms Speech - difficulty speaking, slurred speech Time - the sooner treatment can be started, the better

The benefit of thrombolysis is shown on CT perfusion scans and decreases with time,

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even within the time window of 4.5 hours. Every minute counts. If thrombolysis is not given, aspirin 300 mg daily should be given as soon as a diagnosis of ischaemic stroke or thromboembolic TIA is confirmed, reducing to 75 mg after several days. Following thrombolysis aspirin should not be started until 24-48 hours later.

Investigations

The purpose of investigations in stroke is:

to confirm the clinical diagnosis and distinguish between haemorrhage and thromboembolic infarction

to look for underlying causes and to direct therapy To exclude other causes, e.g. tumour.

Sources of embolus should be sought (e.g. carotid bruit, atrial fibrillation, valve lesion, evidence of endocarditis, previous emboli or TIA) and hypertension/postural hypotension assessed. Brachial BP should be measured on each side; >20 mmHg differences are suggestive of subclavian artery stenosis.

Table 21-29. Thrombolysis in acute ischaemic strokeEligibilityAge ≥ 18 yearsClinical diagnosis of acute ischaemic strokeAssessed by experienced teamMeasurable neurological deficitBlood tests: results availableCT or MRI consistent with acute ischaemic strokeTiming of onset well establishedThrombolysis should commence as soon as possible and up to 4.5 hours after acute strokeExclusion criteriaHistoricalStroke or head trauma within the prior 3 monthsAny prior history of intracranial haemorrhageMajor surgery within 14 daysGastrointestinal or genitourinary bleeding within the previous 21 daysMyocardial infarction in the prior 3 monthsArterial puncture at a non-compressible site within 7 daysLumbar puncture within 7 daysClinicalRapidly improving stroke syndromeMinor and isolated neurological signsSeizure at the onset of stroke if the residual impairments are due to Postictal phenomenaSymptoms suggestive of subarachnoid haemorrhage, even if the CT is normalAcute MI or post-MI pericarditisPersistent systolic BP > 185, diastolic BP > 110 mmHg, or requiring aggressive therapy to control BP

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Pregnancy or lactationActive bleeding or acute trauma (fracture)LaboratoryPlatelets < 100 000/mm3

Serum glucose < 2.8 mmol/L or > 22.2 mmol/LINR > 1.7 if on warfarinElevated partial thromboplastin time if on heparinDose of i.v. alteplase (tissue plasminogen activator)Total dose 0.9 mg/kg (maximum 90 mg)10% of total dose by initial i.v. bolus over 1 minuteRemainder infused i.v. over 60 minutes

Imaging in acute stroke

CT and MRI:

Non-contrast CT will demonstrate haemorrhage immediately but cerebral infarction is often not detected or only subtle changes are seen initially.MRI shows changes early in infarction and a later MRI shows the full extent of the damaged area or penumbra.

Diffusion-weighted MRI (DWI) can detect cerebral infarction immediately but is as accurate as CT for the detection of haemorrhage.

Box 21.1 Stroke: further investigation and management

Further investigations

Routine bloods (for ESR, polycythaemia, infection, vasculitis, thrombophilia, syphilitic serology, clotting studies, autoantibodies, lipids)

Chest X-ray ECG Carotid Doppler studies MR angiography, if appropriate

Further management

Drugs for hypertension, heart disease, diabetes, other medical conditions

Other antiplatelet agents, e.g. dipyridamole Question of endarterectomy Question of anticoagulation. Speech therapy, dysphagia care, physiotherapy, occupational

therapy Specific issues, e.g. epilepsy, pain, incontinence Preparations for future care

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CT is still more widely available than MRI and should be performed if MRI is unavailable so that there is no delay in giving thrombolysis for cerebral infarction.

More detailed studies involving perfusion-weighted images and diffusion-weighted MRI will differentiate the infarct core and the penumbral area which is potentially recoverable.

Treatment of acute stroke

. Thrombolysis has been shown to improve outcome and should be used immediately if there are no contraindications. In a massive middle cerebral artery infarct, hemispheric swelling occurs with oedema. Decompressive hemicraniectomy reduces the intracranial pressure and the mortality but extensive neurological deficits remain.

Later investigations MR angiography (MRA) or CT angiography

is valuable in anterior circulation TIAs to confirm surgically accessible arterial stenoses, mainly internal carotid stenosis. If ultrasound suggests carotid stenosis, normotensive patients with TIA or stroke in the anterior circulation should have vascular imaging.

Box 21.2 Stroke: immediate management1. Admit to multidisciplinary stroke unit2. General medical measures

o Airway: confirm patency and monitoro Continue care of the unconscious or stuporose patiento Oxygen by masko Monitor BPo Look for source of embolio Assess swallowing

3. Is thrombolysis appropriate?If so immediate brain imaging is essential.

4. Brain imagingCT should always be available. This will indicate haemorrhage, other pathology and sometimes infarction. MR is better overall, if immediately available

5. Cerebral infarctionIf CT excludes haemorrhage, give immediate thrombolyte therapy. Aspirin, 300 mg/day is given if thrombolytic therapy is contraindicated

6. Cerebral haemorrhageIf CT shows haemorrhage, give no drugs that could interfere with clotting. Neurosurgery may occasionally be needed

Carotid Doppler and duplex scanning.

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This screen for carotid (and vertebral) stenosis and occlusion: in skilled hands they demonstrate accurately the degree of internal carotid stenosis.

Long-term management

Medical therapy

Risk factors should be identified and addressed.

1. Antihypertensive therapy

Control of high blood pressure is the major factor in primary and secondary stroke prevention. Transient hypertension, often seen following stroke, usually does not require treatment provided diastolic pressure does not rise >100 mmHg. Sustained severe hypertension needs treatment; BP should be lowered slowly to avoid any sudden fall in perfusion.

2. Antiplatelet therapy

Long-term soluble aspirin (75 mg daily) reduces the incidence of further infarction following thromboembolic TIA or stroke. Aspirin inhibits cyclo-oxygenase, which converts arachidonic acid to prostaglandins and thromboxanes; predominant therapeutic effects are reduction of platelet aggregation. Clopidogrel and dipyridamole are also used. Combined aspirin 75 mg daily and dipyridamole 200 mg twice daily possibly provide optimal prophylaxis against further thromboembolic stroke or TIA.

3. Anticoagulants

Heparin and warfarin should be given when there is atrial fibrillation, other paroxysmal dysrhythmias, cardiac valve lesions (uninfected) or cardiomyopathies. Brain haemorrhage must be excluded by CT/MRI. Patients must be aware of the small risk of cerebral (and other) haemorrhage. Anticoagulants are potentially dangerous in the two weeks following infarction because of the risk of provoking cerebral haemorrhage.

4. Other measures

Polycythaemia and any clotting abnormalities should be treated. Statin therapy should be given for all.

5. Surgical approaches

Internal carotid endarterectomy

Surgery is usually recommended in TIA or stroke patients with internal carotid artery stenosis >70%. Successful surgery reduces the risk of further TIA/stroke by around 75%. Endarterectomy has a mortality around 3%, and a similar risk of stroke. PCTA (stenting) is an alternative. The value of surgery for asymptomatic carotid stenosis is

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debatable.

Stroke in the elderly

Table 21-30. Anticoagulants and stroke preventionIndicationCommentValvular heart diseaseHeparin/warfarin of benefit in chronic rheumatic heart disease,

particularly mitral stenosisRecent MI

  Intracardiac thrombus

Heparin/warfarin if there is evidence of Intracardiac thrombus

  Atrial fibrillationAnticoagulants long term reduce stroke incidence in atrial fibrillation

Acute internal carotid artery thrombusAcute basilar artery thrombusInternal carotid artery dissectionExtracranial vertebral artery dissection

Anticoagulants reserved for imaging-confirmed cases of arterial thrombosis or dissection. They have not been shown to be beneficial in stroke prevention after thromboembolism from carotid or vertebrobasilar sources

Prothrombic states, e.g. protein C deficiency

Consider anticoagulation, in consultation with haematologist

Recurrent TIAs or stroke on full antiplatelet therapy

If no remediable cause, a trial of anticoagulants may be justified

Cerebral venous thrombosis including sinus thrombosis

Benefits of anticoagulation outweigh risks of haemorrhage

Whilst in the elderly the yield of investigation in stroke diminishes, age is no barrier to recovery; elderly patients benefit the most from good rehabilitation. Consider social isolation, pre-existing cognitive impairment, nutrition, skin and sphincter care, and reassess swallowing. Carotid endarterectomy over 75 years carries little more risk than in younger cases.

Rehabilitation: multidisciplinary approach

Of particular value in the first few weeks after stroke to relieve spasticity, prevent contractures and teach patients to use walking aids. Baclofen and/or botulinum toxin are sometimes helpful in the management of severe spasticity.

.

Prognosis

About 25% of patients die within 2 years of a stroke, nearly 10% within the first month. This early mortality is higher following intracranial haemorrhage than

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thromboembolic infarction. Poor outcome is likely when there is coma, a defect in conjugate gaze and hemiplegia.

Recurrent strokes are common (10% in the first year) and many patients die subsequently from MI. Of initial stroke survivors, some 30-40% remains alive at 3 years.

Intracranial haemorrhage

This comprises:

intracerebral and cerebellar haemorrhage subarachnoid haemorrhage Subdural and extradural haemorrhage/haematoma.

Intracerebral haemorrhage

Etiology

Causes approximately 10% of strokes. Rupture of microaneurysms (Charcot-Bouchard aneurysms, 0.8-1.0 mm diameter) and degeneration of small deep penetrating arteries are the principal pathology. Such haemorrhage is usually massive, often fatal, and occurs in chronic hypertension and at well-defined sites - basal ganglia, pons, cerebellum and subcortical white matter.

In normotensive patients, particularly over 60 years, lobar intracerebral haemorrhage occurs in the cerebral cortex. Cerebral amyloid angiopathy (rare) is the cause in some of these haemorrhages, and the tendency to rebleed is associated with particular apolipoprotein E genotypes.

Recognition

Intracerebral haemorrhage tends to be dramatic with severe headache. It is more likely to lead to coma than thromboembolism.

Brain haemorrhage is seen on CT imaging immediately as intraparenchymal, intraventricular or subarachnoid blood. Routine MRI may not identify an acute small haemorrhage correctly in the first few hours but MRI diffusion weighted (MRI DW) is as good as CT.

Management: haemorrhagic stroke

The principles are those for cerebral infarction. The immediate prognosis is less good. Antiplatelet drugs and, of course, anticoagulants are contraindicated. Control of hypertension is vital. Urgent neurosurgical clot evacuation is occasionally necessary when there is deepening coma and coning (particularly in cerebellar haemorrhage).

Cerebellar haemorrhage

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There is headache, often followed by stupor/coma and signs of cerebellar/brainstem origin (e.g. nystagmus, ocular palsies). Gaze deviates towards the haemorrhage. Skew deviation may develop. Cerebellar haemorrhage sometimes causes acute hydrocephalus, a potential surgical emergency.

Subarachnoid haemorrhage (SAH)

Of dramatic onset. SAH accounts for some 5% of strokes and has an annual incidence of 6 per 100 000.

Causes

The causes of SAH are shown in Table 21.31; it is unusual to find any contributing disease.

Saccular aneurysms develop within the circle of Willis and adjacent arteries. Common sites are at arterial junctions:

between posterior communicating and internal carotid artery - posterior communicating artery aneurysm( is the commonest cause of a painful IIIrd nerve palsy)

between anterior communicating and anterior cerebral artery - anterior communicating and anterior cerebral artery aneurysm

At the trifurcation or a bifurcation of the middle cerebral artery - middle cerebral artery aneurysm.

Other aneurysm sites are on the basilar, PICA, intracavernous internal carotid and ophthalmic arteries. Saccular aneurysms are an incidental finding in 1% of autopsies and can be multiple.

Aneurysms cause symptoms either by spontaneous rupture, when there is usually no preceding history, or by direct pressure on surrounding structures.

Arteriovenous malformation (AVM)

AVMs are collections of arteries and veins of developmental origin. An AVM may also cause epilepsy, often focal. Once an AVM has ruptured, the tendency is to rebleed - 10% will then do so annually.

Cavernous haemangiomas (cavernomas) are common (<0.5% of population) and consist of collections of capillary vessels; they are frequently symptomless and seen incidentally on imaging. Rarely cavernomas cause seizures or bleed; exceptionally they cause sudden death from massive haemorrhage. Surgery is rarely appropriate.

Table 21-31. Underlying causes of subarachnoid haemorrhageSaccular (berry) aneurysms70%Arteriovenous malformation (AVM)10%No arterial lesion found15%Rare associations (< 5%) 

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Bleeding disorders Mycotic aneurysms - endocarditis Acute bacterial meningitis Tumours, e.g. metastatic melanoma, oligodendroglioma Arteritis (e.g. SLE) Spinal AVM → spinal SAH Coarctation of the aorta Marfan's, Ehlers-Danlos syndrome Polycystic kidneys 

Clinical features of subarachnoid haemorrhage

There is a sudden devastating headache, often occipital. usually followed by vomiting , coma and death. SAH is a possible diagnosis in any sudden headache.

Following major SAH there is neck stiffness and a positive Kernig's sign. Papilloedema is sometimes present, with retinal and/or subhyaloid haemorrhage . Minor bleeds cause few signs, but almost invariably headache.

Investigations

CT imaging is the immediate investigation needed. LP is not necessary if SAH is confirmed by CT. CSF becomes yellow (xanthochromic) several hours after SAH. Visual inspection of supernatant CSF is usually sufficiently reliable for diagnosis. Spectrophotometry to estimate bilirubin in the CSF released from lysed cells is used to define SAH with certainty. MR angiography is usually performed in all potentially fit for surgery, i.e. generally below 65 years and awake. In some, no aneurysm or source of bleeding is found, despite a definite SAH.

Differential diagnosis

From migraine. Thunderclap headache is used (confusingly) to describe either SAH or a sudden (benign) headache for which no cause is ever found. Acute bacterial meningitis occasionally when a meningeal microabscess ruptures or at the onset. Cervical arterial dissection can present with a sudden headache.

Complications

Obstructive hydrocephalus, seen on CT. Shunting may be necessary. Arterial spasm (visible on angiography and a cause of coma or hemiparesis) is a serious complication of SAH and a poor prognostic feature.

Management

Immediate treatment is bed rest and supportive measures. Hypertension control. Dexamethasone to reduce cerebral oedema; it also is believed to stabilize the blood-brain barrier. Nimodipine, a calcium-channel blocker, reduces mortality.

Nearly half of cases are die before reaching hospital. Of the remainder, a further 10-20% rebleeds and dies within several weeks.

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Subdural and extradural bleeding

These conditions can cause death following head injuries unless treated promptly.

Subdural haematoma (SDH)

This follows rupture of a vein. Usually following a head injury, sometimes trivial. The interval between injury and symptoms can be days, or extend to weeks or months. Chronic, apparently spontaneous SDH is common in the elderly, and also occurs with anticoagulants.

Headache, drowsiness and confusion are common; symptoms are indolent and can fluctuate. Focal deficits develop. Epilepsy occasionally occurs. Stupor, coma and coning may follow.

Extradural haemorrhage (EDH)

Typically follows a linear skull vault fracture tearing a branch of the middle meningeal artery. Extradural blood accumulates rapidly over minutes or hours. A characteristic picture is of a head injury with a brief duration of unconsciousness, followed by improvement (the lucid interval). The patient then becomes stuporose, with an ipsilateral dilated pupil and contralateral hemiparesis, with rapid transtentorial coning. Bilateral fixed dilated pupils, tetraplegia and respiratory arrest follow. An acute progressive SDH presents similarly.

Management

Needs immediate imaging. CT is the mostly used. MRI is more sensitive for the detection of small hematomas. T1 weighted MRI shows bright images due to the presence of methaemoglobin.

EDHs require urgent neurosurgery: if N/A drainage through skull burr-holes has been lifesaving.

Subdural bleeding usually needs less immediate attention. Even large collections can resolve spontaneously without drainage. Serial imaging is needed to assess progress.

CORTICAL VENOUS THROMBOSIS AND DURAL VENOUS SINUS THROMBOSIS (intracranial venous thrombosis)

Are usually (>50%) associated with a pro-thrombotic risk factor, e.g. OCPs, pregnancy, genetic or acquired pro-thrombotic states, dehydration and head injury. Infection, e.g. from a paranasal sinus, may be present. Venous thromboses can also arise spontaneously.

Cortical venous thrombosis

Can leads to headache, focal signs and/or epilepsy, often with fever.

Dural venous sinus thromboses

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Cavernous sinus thrombosis causes ocular pain, fever, proptosis and chemosis. External and internal ophthalmoplegia with papilloedema develops.

Sagittal and lateral sinus thrombosis cause raised ICP with headache, fever, papilloedema and often epilepsy.

Management

MRI, MRA and MRV show occluded sinuses and/or veins. Treatment is with heparin followed by warfarin for 6 months. Anticonvulsants are given if necessary.