Stroke and acute neurological diagnoses Flashcards
Sparing of the forehead indicates which motor neuron issue?
Why is this
The lower motor neurons innervating the bottom half of the face receive innervation from upper motor neurons originating on the contralateral side
The lower motor neurons innervating the top half of the face receive innervation from upper motor neurons originating on both the ipsilateral and the contralateral side (i.e. they have dual innervation)
Thus, in a stroke (affecting the upper motor neurons), the top half of the face will be spared, because the stroke will only affect one side of the brain, but the lower motor neurons for the top half of the face receive dual innervation, so they will still receive innervation from the upper motor neuron not affected by the stroke
HOWEVER,
In Bell’s palsy, there is a disease of the LOWER motor neuron so although both the ipsilateral and contralateral supply to the lower motor neuron is fine, the damage to the lower motor neuron itself means that the muscles in the top half of the face will be paralysed
What is bell’s phenomenon
Bell’s phenomenon (also known as the palpebral oculogyric reflex) is a medical sign that allows observers to notice an upward and outward movement of the eye, when an attempt is made to close the eyes.
The upward movement of the eye is present in the majority of the population, and is a defensive mechanism.
The phenomenon is named after the Scottish anatomist, surgeon, and physiologist Charles Bell. Bell’s phenomenon is a normal defense reflex present in about 75% of the population, resulting in elevation of the globes when blinking or when threatened (e.g. when an attempt is made to touch a patient’s cornea).
It becomes noticeable only when the orbicularis oculi muscle becomes weak as in, for example, bilateral facial palsy associated with Guillain–Barré syndrome or in bell’s palsy`
What is bright on a CT scan
Blood, contrast, bone, calcium and meta
What is dark on CT scan
Air, CSF/H2O, oedema
Bright on CT in the lateral ventricles?
Might be calcium in the choroid plexus
What is the problem with haemorrhage
Increasing displaced blood causes pressure
Blood itself is irritating to brain tissue, causing it to swell
Causes of intra-cerebral haemorrhage
Hypertension
Rupture of aneurysm or AVM (ESPECIALLY in young)
Haemorrhagic necrosis (e.g. tumour, infection)
Venous out flow obstruction
Trauma
Altered haemostasis
How can infection lead to haemorrhage
Patients with IE have vegetations growing on their heart valves.
This can displace and go into the arteries of the brain, and start damaging the vessels.
This can lead to a myocotic aneurysm , which can rupture.
What might happen to brain parenchyma on CT during ischaemic stroke and why
It might become hypoattenuated, or translucent, showing it is less dense.
This happens because when brain cells are deprived of sufficient oxygen, a biochemical cascade is initiated, involving several pathways known as the ischaemic cascade, leading toward cells death.
It involves loss of plasma membrane function and membrane integrity and the cells swell and can burst. This causes them to become less dense so the affected brain areas look almost like CSF. This is called liquifactive necrosis.
After necrosis/apoptosis, inflammation occurs before repair and remodelling occurs (angiogenesis and neurogenesis).
Causes of ischaemic stroke
Small vessel disease (25%)
Large vessel atherosclerosis (20%)
Cardio-embolic (20%)
But most common cause (30%) is not known!
What is a panumbra
When an artery is blocked in the brain, the immediate area around the artery has infarcted brain tissue and is completely deprived of oxygen
There is then a region of brain around the outside of the infarcted area that is semi-deprived of oxygen, and is vulnerable. This is called panumbra
Examples of large artery atherosclerosis as cause of ischaemic stroke
What are the risk factors
Investigations
What is the management
Intracranial stenosis
Carotid stenosis
Aortic arch plaque
HT DM Smoling Chol BMI
CAD, FHx, Age
Modify the first set of risk factors, and give antiplatelet!
Note that usually the thombi that form embolise and block a smaller artery upstream, rather than causing occlusion in situ (this is in contrast to coronary arteries with myocardial infarction)
Do a duplex because you can offer carotid endarterectomy if carotid artery is severely stenosed.
Examples of cardioembolic causes of ischaemic stroke
What are the risk factors- risk score
Investigations
What is the management
- Atrial fibrillation and paroxysmal AF
- Valve disease
- Ventricular thrombi
*PAF is an episode of AF that terminates spontaneously or with intervention in less than seven days
CHADSVASc score:
- Congestive heart failure
- Hypertension
- Age (2) >75yrs
- Diabetes mellitus
- Stroke or TIA in the past (2)
- Vascular disease
- Age>65
- Sex: female
Management is oral anticoagulants like warfarin, and DOACs (apixaban, dabigatran).
Note that ONLY warfarin should be used if the cause of AF is valvular heart disease e.g. in mitral valve stenosis
Biggest risk factor for stroke
AF
