Transcript for Stroke
A stroke is a when there’s a sudden focal neurological deficit due to a part of the brain losing its blood supply.
There are two types of strokes - ischemic strokes and hemorrhagic strokes.
The majority are ischemic strokes and there are three types: thrombotic, embolic, and hypoxic strokes.
Thrombotic strokes are caused by local arterial obstruction due to inflammatory diseases like atherosclerosis, and non-inflammatory diseases like fibromuscular dysplasia.
Thrombotic strokes affect large vessels like the internal carotid artery, as well as small vessels like the penetrating arteries that branch off of the basilar artery.
When they affect these small arteries they’re called lacunar strokes, and they typically cause symptoms like hemiparesis, ataxia, dysarthria, and numbness in the contralateral face, arm, and leg.
An embolic stroke is when the blood vessel is blocked by an embolus.
If it arises from the heart, it’s called cardioembolic, and that usually occurs in the setting of atrial fibrillation.
That’s because in atrial fibrillation, blood stagnates in the atria and can become clotted.
That clot can then travel up to the blood vessels supplying the brain.
Alternatively, an embolus might dislodge from a thrombus or atherosclerotic plaque in the carotid artery, and that results in a thromboembolic or atheroembolic stroke.
It enters the left atrium, and from there it can head off to the blood vessels supplying the brain.
Finally, there’s a hypoxic stroke which is sometimes called a hypoxic ischemic injury, which develops when there’s systemic hypoperfusion or hypoxemia.
This commonly occurs in infants due to ischemia during birth, but can also be due to things like septic shock or drowning.
Now, the minority of strokes are hemorrhagic strokes, where a blood vessel breaks and blood spills out, forming a hematoma that compresses and damages surrounding brain tissue.
An intracerebral hemorrhage is when the bleeding occurs in the brain itself, and is usually caused by hypertension.
A subarachnoid hemorrhage is when the bleeding occurs between the pia mater and arachnoid mater of the meninges and is most often caused by a ruptured aneurysm.
Patients with stroke typically have a focal neurological deficit which corresponds to the region of the brain that’s affected, which is why the symptoms often suggest the location of the stroke.
For example, an anterior cerebral artery stroke affects the feet and legs.
Whereas, the middle cerebral artery stroke affects the hands, arms, face, and the language centers in the dominant hemisphere, including Broca’s and Wernicke's area.
Finally, a posterior cerebral artery stroke primarily affects the visual cortex, which affects a person’s ability to see clearly.
Now in any of these body regions, both motor and sensory fibers may be affected.
When motor pathways are damaged, flaccid paralysis develops almost immediately. And then over the following days to weeks, there’s spastic paralysis and hyperreflexia due to the hyperexcitable stretch reflex.
When sensory pathways are damaged, there’s numbness as well as reduced pain and vibration sensation.
Both motor and sensory symptoms usually happen on the side that’s contralateral from the stroke, except in rare cases of brain stem stroke, where both sides are affected.
When a person comes into the Emergency Department with focal neurologic deficit the first thing to do is to assess the airway, breathing and circulation, especially if the patient is unconscious. Sometimes, intubation might be needed, especially if the there is decreased respiration and muscular airway obstruction.
Hypoxic patients should be given supplemental oxygen and have monitors to ensure that their oxygen saturation remains above 94 percent.
If a stroke is suspected, it’s important to check glucose levels, and the following blood tests: CBC to check the platelet count, PT, PTT, INR, and fibrinogen.
Cardiac monitors and an ECG should also be utilized to look for arrhythmias like atrial fibrillation.
Stroke therapy is extremely time sensitive, so it’s best not to wait for the results of the tests unless thrombocytopenia or anticoagulant use is suspected - because of the risk of bleeding.
Patients with complicated migraine will present with preceding aura, usually a strange light or smell, headache, and they’ll have a history of these events.
Patients with generalized seizures usually have a postictal period, which may include weakness of one side of the body which can mimic a stroke. This is referred to as Todd’s paralysis.
Patients with brain tumors will often have a gradual progression of symptoms and can also have seizures.
Usually, the symptoms of stroke occur suddenly, and progressively worsen over minutes to hours.
In particular, a subarachnoid hemorrhage classically presents with “the worst headache of a person’s life”.
Next up, a full neurological examination, using the NIH stroke scale, can help assess the severity of the stroke.
Points are given for any deficits in 11 specific categories, with a maximum score of 42.
The 11 categories are level of consciousness, horizontal eye movement, visual field test, facial palsy, motor arm function, motor leg function, limb ataxia, sensory deficits, language skills, speech, and extinction and inattention.
In addition, some specific physical exam maneuvers include checking the pulse in the neck, arms, and legs to check for irregularities, because that might suggest a cardiac cause.
In addition, the neck and retro orbital regions should be auscultated for vascular bruits, because that can suggest carotid artery occlusions.
Next, a noncontrast computed tomography, or CT scan, is done to help differentiate between an ischemic and hemorrhagic stroke.
Contrast should be avoided to prevent mistaking contrast for blood.
Blood on the CT shows up as white, or hyperdense, and indicates a hemorrhagic stroke.
The absence of blood indicates an ischemic stroke.
An MRI is more sensitive than CT for detecting both ischemic and hemorrhagic stroke, but a CT is usually safer and easier to obtain acutely, so it’s usually the imaging method of choice.
Small subarachnoid hemorrhages can be missed on the CT, due to the small amount of blood, so if it’s suspected, a lumbar puncture can be done to look for red blood cells in the cerebrospinal fluid.
If the blood has been in the CSF for a few days, then the CSF may appear yellowish due to the heme getting metabolized into bilirubin - this is called xanthochromia.
If there’s a hemorrhagic stroke from severe hypertension, there’s usually a homogenous-appearing hematoma on CT.
Alternatively, if there was recent head trauma, then blood might appear in a pattern consistent with the injury.
In an ischemic stroke, the treatment of choice is thrombolysis with recombinant tissue plasminogen activator - or rtPA.
The ischemia is most severe in the core of the ischemic area, where the cells die first, and slightly less severe in the surrounding penumbra which gets collateral blood from other blood vessels.