10.1 Anatomy And Physiology Of Stroke Flashcards
What is the definition of a stroke?
An acute focal injury of the CNS due to a vascular pathology causing a sudden neurological deficit. Causes include cerebral infarction, intracerebral hemorrage (ICH), and subarachnoid hemorrhage (SAH). Symptoms and signs last longer than 24 hours.
What is the definition of a TIA?
a transient episode of neurological dysfunction caused by focal brain, spinal cord, or retinal ischemia, without acute infarction
What are the most common causes of stroke?
Ischaemic (85%) - thromboembolism Haemorrhagic (10%) - intracerebral - subarachnoid Other (5%) - dissection - venous sinus thrombosis - hypoxia brain injury
In a younger patient, what are the most likely causes of a stroke?
Vasculitis (autoimmune disease that causes inflammation and narrowing of blood vessels)
Thrombophilia (imbalance in naturally occurring blood-clotting proteins, or clotting factors)
Subarachnoid haemorrhage
Venous sinus thrombosis
Carotid artery dissection
In an older/elderly patient, what are the most likely causes of a stroke?
Thrombosis in situ Athero-thromboembolism Heart emboli CNS bleed Sudden blood pressure drop of more than 40mmHg Vasculitis Venous sinus thrombosis
What are the risk factors of stroke?
Hypertension Smoking Diabetes mellitus Heart disease (fibrillation/valvular/ischaemic) Peripheral arterial disease Post-TIA (high early risk of stroke) Carotid artery occlusion: carotid bruit Polycythemia Vera COCP Hyperlipidaemia Excess alcohol Clotting disorders.
What signs occurs in an infarct of the anterior cerebral artery?
Affects the medial areas of the primary motor and sensory cortex. Similar distribution of motor and sensory deficit in the contralateral lower limb.
Paracentral lobules may be affected in anterior cerebral stroke causing urinary incontinence
May have corpus callosum issues. Results in split brain syndrome or alien hand syndrome.
Frontal lobe features such as personality / apraxia changes.
What are the signs and symptoms of a proximal middle cerebral artery infarct?
Main trunk occlusion associated with mortality.
Contralateral full hemiparesis (face, arm and leg) as internal. capsule affected
Initial flaccid hemiparesis followed by spastic hemiparesis due to spinal shock
Lateral primary sensory cortex = Contralateral sensory loss in upper limb and face, could involve larger areas f the sensory components in the internal capsule are affected
Destruction of the superior and inferior optic radiations as they pass through the parietal and temporal lobes = Contralateral homonomous hemianopia
If left sided stroke and affecting Broca’s and wernickes area = aphasia / speech problems.
If lesion affects right parietal lobe = Neglect on left hand side
Why is proximal MCA occlusion not uncommon?
As the MCA is a continuation of the internal Carotid and therefore atherosclerosis emboli can easily enter from the internal carotid artery.
What is anosognosia?
literally does not acknowledge that they have had a stroke or neurological deficit, so will confabulate to explain disability.
What is tactile extinction?
if touch each side simultaneously doesn’t feel the affected side.
The failure to detect a stimulus only in the presence of another stimulus to certain parts of the body-is a well-known clinical sign of parietal lobe disease.
What are the manifestations of lenticulostriate arteries strokes?
Often destruction of internal capsule/ basal capsule.
Small deficits in motor or sensory function.
What are the manifestations of a distal MCA occlusion affecting the MCA superior division?
Supplies lateral frontal lobe - Primary motor cortex and Broca’s area if on left side.
Contralateral face and arm weakness
If on left side then may have Broca’s aphasia / expressive aphasia
What are the manifestation of a distal MCA occlusion affecting the inferior division of the MCA?
Supplies the lateral parietal lobe and the superior temporal lobe.
Have problems with the sensory cortex and wernickes area
May have problems with one or both optic radiations
Contralateral sensory problems
Wernickes aphasia/ fluent aphasia
Problems with vision - non macular sparing homonomous hemianopia or a quadrantopia.
What are the manifestations of a posterior cerebral artery occlusion?
Supplies the thalamus, midbrain and occipital lobe.
Contralateral homonomous hemianopia that is MACULA SPARING
As sensory pathways travel through the thalamus may get contralateral sensory loss.
What are the manifestations of cerebellar artery occlusions?
Ipsilateral DANISH symptoms / cerebellar deficit
nausea, vomiting, headache, vertigo
Ipsilateral Horners syndrome - affecting sympathetics running laterally from the brainstem
Contralateral sensory signs - sensory fibres run more laterally in the brain stem and contralateral as post-decussation
