Extracranial cerebrovascular disease Flashcards
Describe the posterior circulation of the brain
Two vertebral arteries originate from the first part of the subclavian arteries. These join intra-cranially to form the basilar artery and supply the posterior cerebral circulation. This is the main blood supply to the brain stem, cerebellum and posterior cerebrum
Describe the anterior circulation of the brain
Both internal carotid arteries arise from the carotid bifurcation in the neck. Intra-cranially the internal carotid arteries form the middle cerebral arteries
Definition of a stroke
- Acute focal ischaemia or infarction of the brain secondary to vascular insufficiency
- Symptoms exceeding more than 24 hrs or lead to death
Definition of transient ischaemic attack
- Temporary focal ischaemia of the brain secondary to vascular insufficiency with symptoms lasting less than 24 hours
- Majority of TIAs last less than 10 mintutes
Definition of amaurosis fugax
- ‘Fleeting blindness’ Temporary retinal artery ischaemia
- Symptoms described as curtain coming down over the eye
What are the two main types of strokes
- Ischaemic (80 percent)
- Hemorrhagic (15-20%)
Causes of ischaemic strokes
- Embolisation or occlusion of an artery that supplies the brain - 25 %
- Atherosclerosis of large arteries (75% of ischaemic strokes)
- Small vessel occlusion (usually secondary to hypertension) - 10%
Causes of haemorrhagic stroke
- Primary intracranial haemorrhage
- Subarachnoid haemorrhage
List possible extracranial arterial pathology that may affect brain perfusion
- Atherosclerosis
- Fibromuscular dysplasia
- Aneurysms
- Dissection
- Arteritis (Giant cell and Takayasu’s)
- Carotid body tumours
What are the two theories of how atherosclerosis at the carotid bifurcation may lead to strokes and TIAs
- Embolic theory: Embolisation of atherosclerotic or thrombotic material to the brain. Likelihood of embolisation or occlusion of the ICA increases with degree of stenosis
- Haemodynamic theory: Tight stenosis or occlusion of the ICA and incomplete collateral circulation leads to risk of cerebral hypoperfusion that can result in a TIA or stroke
Bruits in the neck may indicate carotid artery disease; what are the differentials for bruit in the neck
Need to distinguish bruits that originate from the carotids and those radiating from the heart or great vessels
Clinical presentation of symptomatic extracranial cerebrovascular disease (Excluding when the verterbrobasilar system is involved)
- Symptoms may be transient (TIA or amaurosis fugax) or more permanent (stroke)
- Focal or global
- Anterior or posterior circulation affected
- Motor and sensory symptoms are usually focal and involve the contralateral limbs
- Dysphasia and contralateral cranial nerve palsies
What are the symptoms if the vertebrobasilar system is involved
-Symptoms may be less specific and may include limb weakness, bilateral visual disturbance (blurring, graying, double vision), ataxia, dizziness, vertigo or bradycardia, drop attacks, numbness or tingling and slurred or loss of speech
What symptoms are more associated with intracranial haemorrhage or space-occupying lesion
Headache and loss of consciousness
General medical evaluation of a patient presenting with neurological symptoms
- Blood pressure
- ECG
- Renal function, lipid and glucose levels
- Coagulopathy screening when appropriate
First line diagnostic test to evaluate the carotid arteries?
Duplex doppler
Imaging used to identify intracranial haemorrhage or space-occupying lesions
CT angiogram or MRI
What are the parameters of the ABCD2 stroke risk score
- Age: greater than or equal to 60 = 1
- Blood pressure: SBP >=140 / DBP>=90 = 1
- Clinical features: focal weakness (=2) or speech impairment without local weakness (=1)
- Duration of symptoms: >= 60 mins (=2); <=59 mins (=1)
- Diabetes = 1
What is the risk of another CVA at two days in a patient with an ABCD2 score of 6-7; and what should happen to these patients
- 8.7 % risk
- They should get urgent carotid duplex and possible intervention if warranted
When should DSA be done?
- Ultrasound findings uncertain
- Aortic arch and other branch vessels need to be assessed for the planning of carotid artery stenting
which risk factors should be controlled as part of the treatment of extracranial carotid artery disease
- Hypertension
- Diabetes
- Cholesterol
- Smoking cessation
- Aspirin is also administered to reduce the risk of future TIAs
How should patients with a focal neurological event within the last 6 months with a residual ICA stenosis of more than 70 % be treated?
Carotid endarterectomy
What should one consider before offering surgery to an asymptomatic patient with high grade ICA stenosis
-Patient’s fitness and life expectancy (>5years) and surgical complication risks (<3%)
Steps in a carotid endarterectomy
- Carotid bifurcation exposed (longitudinal incision made along medial border of sternocleidomastoid)
- Internal jugular vein mobilized laterally to enter the carotid sheath
- Dissection continued proximally to expose the carotid bulb, internal and external carotid arteries
- Systemic heparin given
- Assess stump pressure
- Longitudinal ateriotomy is made from common carotid to internal carotid across the stenotic lesion
- Diseased intima and proximal media are then carefully removed from the remainder of the vessel wall
- Arteriotomy is then sutured closed using a prothetic Dacron or vein patch
- Platysma and skin are closed after haemostasis has been achieved
