Download Posterior cerebral artery

Stroke
Stroke
is acute, focal brain dysfunction due to vascular
disease , is the third most common cause of death in
high-income countries after cancers and ischaemic
heart disease, and the most common cause of severe
physical disability. Stroke accounts for 11% of deaths
in England and Wales; About 750 000 new strokes
occur and about 150 000 people die from stroke in
the United States each year.Around half of all stroke
survivors are left dependent on others for everyday
activities: if a patient can return home, the burden on
carers is significant.One-quarter of all strokes occur in
people below the age of 65 years..
The underlying pathology responsible for the
persistent symptoms of stroke is either infarction or
haemorrhage.
Haemorrhage is subdivided according to location into
intracranial
haemorrhage
and
subarachnoid
haemorrhage,while infarction is caused by either
embolic (Sudden) or thrombotic (gradual)
The main arterial supply of the brain comes from the
internal carotid arteries, which supply the anterior
brain, and the vertebral and basilar arteries
(vertebrobasilar system), which provide the posterior
circulation. The anterior and middle cerebral arteries
supply the frontal and parietal lobes, while the
posterior cerebral artery supplies the occipital lobe.
The vertebral and basilar arteries perfuse the brain
stem and cerebellum; Communicating arteries
provide connections between the anterior and
posterior circulations and between left and right
hemispheres, creating protective anastomotic
connections that form the circle of Willis.
Three Stroke Types
Ischemic
Stroke
Intracerebral
Hemorrhage
Subarachnoid
Hemorrhage
Clot occluding
artery
85%
Bleeding
into brain
10%
Bleeding around
brain
5%
When infarction involves only a small volume of the
tissue (<1.5 cm in diameter on computerized
tomography [CT]) secondary to occlusion of a
penetrating artery, the resulting death of tissue is
known as a lacune or a lacunar infarct. The underlying
pathology responsible for lacunar infarction is often
referred to as small vessel disease. Lacunes are
generally found in subcortical white matter or the
basal ganglia. Larger infarcts usually involve a wedge
of both cortical and subcortical white matter and
result from occlusion of the trunk or branches of the
major cerebral arteries.
Vessel Stroke Syndromes
o
Middle cerebral artery (MCA):
–Arm>leg weakness
–Left (MCA) : Aphasia
–Right (MCA ) : Neglect
o
Anterior cerebral artery (ACA):
–Leg>arm weakness, Voluntary control of micturition may be
impaired
o
Posterior cerebral artery (PCA):
–Hemianopia
o Cerebellar arteries
--ipsilateral ataxia
o Brain stem vessels
Cross signs (ipsilateral cranial nerve plus contralateral
weakness or sensory loss) eg:
Posterior inferior cerebellar artery occlusion(PICA):
results in the lateral medullary (Wallenberg)
syndrome . This syndrome varies in its presentation
with the extent of infarction, but it can include
ipsilateral cerebellar ataxia, Horner syndrome, facial
sensory deficit and dysphagia ; contralateral impaired
pain and tempreture.The motor system is
characteristically spared because of its ventral
location in the brainstem.
Risk factors for stroke
Non modifiable risk factors
• Age
• Gender (male > female except at extremes of age)
• Race (Afro-Caribbean > Asian > European)
• Previous vascular event
Myocardial infarction
Stroke
Peripheral vascular disease
• Heredity
Modifiable risk factors
• hypertension
• smoking
• Hyperlipidaemia
• Diabetes mellitus
• Excessive alcohol intake
•Oral contraceptive pill
• Polycythaemia
• Heart disease
Atrial fibrillation
Congestive cardiac failure
•obesity
Differential diagnosis of stroke and TIA
• Brain tumours
•syncope
•Hypoglycaemia
• Migrainous aura
• Focal seizures
• Encephalitis
•Demylination disease eg : multiple sclerosis
• Conversion disorder
Several terms have been used to classify strokes,
often based on the duration and evolution of
symptoms
Transient ischaemic attack (TIA) describes a stroke
in which symptoms resolve within 24 hours.. The term
TIA also includes patients with amaurosis fugax,
usually due to a vascular occlusion in the retina most
likely due to caroted stenosis lead to transient foggy
scene in one eye .
Progressing stroke (or stroke in evolution) describes
a stroke in which the focal neurological deficit
worsens after the patient first presents. Such
worsening may be due to increasing volume of
infarction, haemorrhagic transformation or increasing
cerebral oedema.
Completed stroke describes a stroke in which the
focal deficit persists and is not progressing
Investigation of a patient with an acute stroke
Is it a vascular lesion? …… CT/MRI
Is there any cardiac source of embolism?..... (ECG)
& Echocardiogram
What is the underlying vascular disease?.... Duplex
ultrasound of carotids
What are the risk factors?..... Full blood count,lipid
profile & blood glucose
Management of acute stroke
Airway :Perform bedside swallow screen and keep
patient nil by mouth if swallowing unsafe or
aspiration occurs.
Breathing : Check respiratory rate and oxygen
saturation and give oxygen if saturation < 95%.
Circulation & BP: Unless there is heart or renal
failure, evidence of hypertensive encephalopathy or
aortic dissection, do not lower blood pressure in first
week as it may reduce cerebral perfusion. Blood
pressure after that should be controlled …
Penumbra
At the centre of an infarct the damage is most severe
but at the periphery collateral flow may allow
continued delivery of blood, although at a lower rate.
This zone may become dysfunctional secondary to
electrical failure although not dead and is referred to
as the ischaemic penumbra, Once blood flow falls
below the threshold for the maintenance of electrical
activity, neurological deficit develops. At this level of
blood flow the neurons are still viable; if the blood
flow increases again, function returns; However, if the
blood flow falls further, irreversible cell death occure.
Consensus exists that medications should be withheld
unless the systolic blood pressure is >220 mm Hg or
the diastolic blood pressure is >120 mm Hg in early
days unless there is contraindication to keep high BP
or we decide to give thrombolytic drug.
This high BP will help to reperfuse the penumbra and
keep it viable..
Penumbra
Core
Clot in Artery
Save the Penumbra
Normal
function
20
15
10
PENUMBRA
5
CORE
1
2
TIME (hours)
Neuronal
dysfunction
CBF
8-18
Neuronal
death
CBF
<8
3
CEREBRAL
BLOOD
FLOW
(ml/100g/min)
Nutrition & hydration : Assess nutritional status and
provide nutritional supplements if necessary, If
dysphagia persists for > 48 hrs, start feeding via a
nasogastric tube.hydration by iv fluid may need use
isotonic fluid eg:GS or NS avoid GW because it
exacerbate brain odema .
Blood glucose: Check blood glucose and treat when
levels are ≥ 11.1 mmol/L (200 mg/dL) (by insulin
infusion or glucose/potassium/insulin (GKI) ;Monitor
closely to avoid hypoglycaemia
Temperature: If pyrexic, investigate and treat
underlying cause ,Control with antipyretics, as raised
brain temperature may increase infarct volume.
Incontinence : Check for urinary retention; treat
Appropriately, Avoid urinary catheterisation unless
patient is in acute urinary retention or incontinence is
threatening.
Immediate medication include:
Thrombolysis
Intravenous thrombolysis with recombinant tissue
plasminogen activator (rt-PA, it should be given
within 4.5 hours of symptom onset to carefully
selected patients with inclusion and exclusion criteria.
Aspirin
In the absence of contraindications, aspirin (300 mg
daily) should be started immediately after an
ischaemic stroke unless rt-PA has been given, in which
case it should be withheld for at least 24 hours.
Aspirin reduces the risk of early recurrence and has a
small but clinically worthwhile effect on long-term
outcome.
Strategies for secondary prevention
Lifestyle modification
Patients with the relevant risk factors should be
strongly advised to stop smoking, eat healthily to
reach and maintain a normal weight, to take regular
exercise and reduce excessive alcohol consumption.
Lowering blood pressure
optimum targets: below 140/85 mmHg in general and
below 140/80 mmHg for patients with diabetes
,started with thiazide diuretic and then add an ACE
inhibitor, If further reduction in blood pressure is
required, calcium antagonists can be added
Antiplatelet drugs: Asprin 100 mg or clopidogril 75
mg or aspirin/dipyridamole
Lipid lowering agent :
Starting with a statin after ischaemic stroke
dramatically reduces the risk of recurrent stroke and
MI.
Anticoagulation:
Just in case of patients with cardio-embolic sources of
thrombus such as AF (atrial fibrillation )
anticogulation will be indicated .
Carotid endarterectomy:
Ischaemic stroke or TIA with Recently symptomatic
severe carotid stenosis
Control of blood glucose:
it is important to maintain HbAc1 levels at less than
7%.
Complications of acute stroke
Chest infection:Avoid aspiration (nil by mouth,
nasogastric tube, possible gastrostomy) treatment by
Antibiotics &Physiotherapy
Epileptic seizures:Maintain cerebral oxygenation
,Avoid metabolic disturbance treatment by
Anticonvulsants .
Deep venous thrombosis/ pulmonary embolism :
Maintain hydration ,Early mobilisation,Anti-embolism
Stockings or Heparin.
 Painful shoulder:Avoid traction injury
Shoulder/arm supports Physiotherapy, Local
corticosteroid injections may needed .
Pressure sores:Frequent turning, Monitor pressure
areas Avoid urinary damage to skin, Nursing care
And Pressure-relieving mattress.
Urinary infection:Avoid catheterisation
if possible Use penile sheath.. tratment by antibiotic.
Depression and anxiety:Maintain positive Attitude,
treatment by antidepressant.
Constipation: Appropriate aperients and diet