Ischemic Stroke Flashcards
What is a stroke?
An injury to the brain caused by interruption of its blood flow (ischemic), or by bleeding (hemorrhagic) into or around the brain.
What does a stroke produce?
Abrupt onset of focal neurologic deficits that frequently result in permanent disability or death.
What is a transient ischemic attack (TIA)?
The abrupt onset of focal neurological deficits that resolve within less than 1 hour.
Do TIAs warn for future stroke?
Yes
What are silent strokes?
Acute focal neurologic symptoms and signs that resolve completely but take longer than 1 hour do so.
Are silent strokes associated with detectable injury on MRI?
Yes
What is another name for a silent stroke?
Resolving ischemic neurologic deficits (RINDs)
Percentage of strokes that are hemorrhagic? Ischemic?
~20%
~80%
Types of hemorrhagic strokes?
Intracerebral - bleeding into the parenchyma of the brain
Subarachnoid - bleeding around the surface of the brain
Causes of ischemic stroke?
Athersclerotic occlusion of an intra- or extracerebral blood vessel
Embolus traveling to the brain from either the heart of a cerebral blood vessel
Disease of the lumen of small arterioles (Lacunar infarcts)
Cryptogenic - unknown cause
Non-modifiable stroke risk factors?
Age (doubles each decade > 55)
Gender (male 1.5 x risk of female)
Race (AA 2 x risk of EAs)
Family Hx (other genetic factors)
Modifiable stroke risk factors?
HTN DM Hyperlipidemia Smoking Carotid artery stenosis A-Fib Obesity Physical inactivity
What is the number one risk factor for stroke?
HTN
How does the stores of energy in the brain compare to the utilization of energy in the brain?
The stores of energy in the brain are very meager compared to the use of energy and thus ischemia and infarction occur rapidly with loss of blood supply to the brain.
What will accelerate and worsen brain injury?
Hyperthermia and hyperglycemia
How does hyperglycemia worsen brain injury?
The brain will continue to metabolize glucose via glycolytic pathways. This will lead to a high accumulation of lactic acid.
During an ischemic stroke, what is the central area with severe blood flow reduction called?
Ischemic Core
During an ischemic stroke, what is the peripheral areas with less severe ischemia called?
Ischemic penumbra
How long does it take tissue to die in the ischemic core? Ischemic penumbra?
< 1 hrs
~4-6 hrs
The cerebral blood flow (CBF) is proportionally related to what?
Mean arterial pressure (MAP) / cerebral vascular resistance (CVR)
At what levels in a normal individual are MAP and CBF virtually independent of each other? Chronic HTN pt?
55 mmHg - 155 mmHg
75 mmHg - 175 mmHg
What does severe hypotension lead to?
Reduced CBF and syncope
What does severe acute HTN lead to?
Raised CBF and hypertensive encephalopathy
What must you be careful of doing in a person with chronic HTN?
Lowering the blood pressure too fast leading to syncope.
Neurologic signs and symptoms produced by a stroke?
Weakness or paralysis Loss of sensation Loss of vision in one eye of field Difficulty in talking or in understanding what is being said Clumsiness of lack of balance
What is loss of vision in one eye called?
Amaurosis fugax
If a stroke is in which vessels is it considered an anterior circulation stroke?
Internal carotid (ICA) Middle cerebral (MCA) Anterior cerebral (ACA) Any of their branches
If a stroke is in which vessels is it considered a posterior circulation stroke?
Posterior cerebral (PCA) Vertebral (VA) Superior cerebellar (SCA) Anterior inferior cerebellar (AICA) Posterior inferior cerebellar (PICA) Any of their branches
A stroke is considered large vessel if?
It occurs in any of the main branches
A stroke is considered small vessel if?
It occurs in any of the penetrating branches off of the main arteries
A disruption of what blood supply will result in Lateral medullary syndrome (Wallenberg syndrome)?
Vertebral Artery
Posterior inferior Cerebellar Artery
Major symptoms of Wallenberg syndrome?
Loss of pain and temperature from the face - ipsilaterally and the body - contralaterally
What causes the ipsilateral loss of pain and temperature of the face in Wallenberg syndrome?
Lesion of the spinal trigeminal tract and nucleus
What causes the contralateral loss of pain and temp of the body in Wallenberg syndrome?
Lesion of the spinothamalic tract
What are some other symptoms in which a Wallenberg syndrome patient might present with?
Ptosis (drooping eyelid), miosis (small pupil), anhidrosis (loss of sweating), dysarthria (trouble speaking), dysphagia (trouble swallowing), and gait ataxia –> all ipsilateral
What is the cause of the ptosis in Wallenberg syndrome?
Loss of sympathetic innervation to the superior tarsal muscle
What is the cause of the miosis in Wallenberg syndrome?
Loss of sympathetic innervation to the pupillodilator muscle in the eye
What is the cause of the anhidrosis in Wallenberg syndrome?
Loss of sympathetic innervation to sweat glands
What is the cause of the dysarthria and dysphagia in Wallenberg syndrome?
Lesion to the nucleus ambiguus
Occlusion of what vessels will lead to Medial Pontine syndrome?
Paramedian branches of the basilar artery.
Symptoms associated with Medial Pontine Syndrome?
Contralateral - hemiparesis, ataxia, discriminative touch, vibration, and conscious proprioception, may include pain/temp
Both - horizontal gaze palsy, internal strabismus of the affected eye ( deviation toward the nose)
Ipsilateral - (depends on the level of the lesion) facial weakness
What causes the contralateral hemiparesis in MPS?
Lesion to the corticospinal tract rostral to the pyramidal decusation
What causes the contralateral ataxia in MPS?
Lesion of the pontine nuclei and transverse fibers in the basal pons that arise from the pontine nuclei and cross to enter the contralateral cerebellum
What causes the contralateral loss of discriminative touch, vibration, and proprioception in MPS?
Lesion of the medial lemiscus
What causes the gaze palsies seen in MPS?
Damage to the paramedian pontine reticular formation, the medial longitudinal fasciculus, and abducens nerve
Occlusion of what vessels will cause Central Midbrain Syndrome (Benedikt Syndrome)?
Posterior cerebral artery
How does a patient present in Benedikt Syndrome?
Ipsilateral - Eye is abducted and rotated down, and dilated
Contralateral - Tremor and ataxia, loss of discriminative touch, vibration, and proprioception
What causes the ipsilateral eye problems in Benedikt syndrome?
CN III palsy as well as an affected Edinger-Westphal Nucleus
What causes the contralateral tremor and ataxia in Benedikt Syndrome?
Lesion to the red nucleus
What causes the contralateral loss of discriminative vibration, and proprioception in Bendikt syndrome?
Lesion to the medial lemniscus
What are possible signs and symptoms of an anterior circulation stroke?
Ipsilateral blindness or contralateral inferior quadrantanopsia (anopia affecting a quarter of the field of vision)
Contralateral gaze paresis
Contralateral mono/hemiparesis and/or mono/hemisensory deficit
Aphasia in the dominant hemisphere or neglect in the nondominant hemisphere
What are possible signs and symptoms of a posterior circulation stroke?
Unilateral, bilateral, or crossed (face/body) weakness or sensory deficits
Contralateral homonymous hemianopsia or superior quadrantanopsia
Vertigo, nausea/vomiting, gait ataxia, diplopia, dysphagia, Horner’s syndrome
Altered consciousness and amnesia
What are lacunar strokes?
Small areas of ischemic necrosis caused by occlusion of small, penetrating arteries
Lacunar Syndromes?
Pure hemiparesis
Pure hemisensory deficit
Ataxia hemiparesis
Dysarthria-clumsy hand syndrome
Common sites of atherothrombosis/atheroemboli?
Origins of carotid and vertebral arteris
Bifurcations of common carotid arteries
Internal carotid arteries at the carotid siphon and at branch points of middle and anterior cerebral arteries
M1 segment of the middle cerebral arteries
Basilar artery
Pathogenesis of lacunar stroke?
Microatheroma
Microemboli
Lipohyalinosis
Fibrinoid necrosis
What is lipohyalinosis and fibrinoid necrosis?
Histological transformation that occurs in the smooth muscle and intima of small penetrating cerebral vessels as a consequence of chronic HTN.
Common causes of cardiogenic emboli?
Arrhythmia (A-Fib) Valvular Heart Dz (Mitral stenosis, bacterial endocarditis, prosthetic heart valves) Mural Thrombus (MI)
Uncommon causes of cardigenic emboli?
Atrial myxoma Valvular Heart DZ (Mitral Valve prolapse, marantic endocarditis) Mural Thrombus (cardimyopathy)
Pts with CNS vasculitis present how?
Multifocally reflecting multiple small and medium-sized vessel occlusions
Causes of CNS vasculitis?
Collagen Vascular Dzs (Lupus - most common)
Giant Cell Arteritis ( >55 yrs) [responds well to corticosteroids]
Infectious vasculitis
