Case 5 Flashcards
How long do brain cells need to be deprived of oxygen before a person will lapse into unconsciousness? Why is this?
20 seconds as the affected neurons cease electrical activity.
How long does a brain cell need to be starved of oxygen before its cessation of electrical activity becomes permanent?
5 minutes.
What is the average blood flow to the brain?
about 50-55ml/100g of brain tissue per minute
At what level of blood flow does ischaemia start to take place in the brain? What percentage of normal blood flow is this?
below 30ml/100g of brain tissue (60% of normal)
At what level of blood flow does infarction start to take place in the brain?
below 20ml/100g of brain tissue.
As different parts of the brain are more active than others at different times how does the body accommodate for this?
Oxygen and blood is shunted around to areas and cells that need it most at a particular time.
What 2 values are vital for maintaining a constant blood flow?
Blood perfusion pressure and vascular resistance.
What are the two main groups of circulations that supply the brain?
The anterior and posterior.
What part of the brain does the anterior circulation supply?
The supratentorial structures (The cortex and diencephalon)
What are the supratentorial structures?
The cortex and diencephalon.
What part of the brain does the posterior circulation supply?
The cerebellum and brainstem.
What do the anterior and posterior circulations of the brain originate from?
The aortic arch.
Where does the posterior circuit enter the skull cavity?
The foramen magnum.
Where does the anterior circuit enter the skull cavity? What does it lie within?
The foramen lacerum, It lies within the cavernous sinus.
What proportion of the blood flow to the brain travels in the anterior circuit?
80%
What proportion of blood flow to the brain travels in the posterior circuit?
about 20%
What blood vessels is the anterior circulation of the brain derived from?
The internal carotid arteries
What course do the internal carotid arteries take when entering the skull what arteries do they arise from?
The internal carotid arise from the common corotid arteries and enter the brain cavity through the carotid canals in the petrosal and sphenoid bones of the skull to emerge on its interior surface via the foramen lacerum
What are the three main causes of stroke?
- Arterial embolism from a distant site (usually carotid, vertebral or basilar arteries)
- Arterial thrombosis causing occlusion in the atheromus carotid, vertebral or cerebral artery with subsequent brain infarct
- Haemorrhage into the brain (intracerebral or subarachnoid)
What are the two kinds haemorrhage that can lead to stroke?
intracerebral and subarachnoid
What type of haemorrhagic stroke is more common?
subarachnoid
What type of haemorrhagic stroke is more likely to lead to disabilty or death?
intracerebral
What is the term for a weakness of one side of the body?
Hemipariesis, or hemiplegia in its most severe form.
What are the two types of stroke? which is more common?
Stroke in evolution and completed stroke, completed stroke is more common.
What is the difference between a completed stroke and a stroke in evolution?
A completed stroke the infarct is completed whereas in a stroke in evolution the progression of neurological defects continues over 24-48 hours indicating an ongoing infarct.
What is the typical result from a middle cerebral artery thromboembolism?
Hemiplegia, because MCA supplies the cerebral cortex, including the motor areas.
What is aphasia?
An acquired language difficulty caused by damage to the brain.
How long do TIA’s last?
Can be from a few seconds to 24 Hours.
What is the first cranial nerve?
The olfactory nerve.
What number cranial nerve is the olfactory nerve?
I
Where does the olfactory nerve (I) originate from?
The anterior olfactory nucleus.
Where is the sensor for the olfactory nerve located?
The olfactory foramina of the ethmoid bone
What is the course of the olfactory nerve (I) olfactory foramina of the ethmoid bone?
It leaves the skull through one of many openings of the cribform plate of the ethmoid bone
What is the second cranial nerve?
The optic nerve
What number nerve is the optic nerve?
II
Why is the optic nerve considered part of the CNS?
As its fibers are mylinated by oligodenrocytes of the CNS rather than schwann cells.
What would a doctor test to screen for lesions of the second optic nerve?
Pupillary reflexes.
What is the third nerve?
The occulomotor nerve
What number nerve is the occulomotor nerve?
III
What is the 4th cranial nerve?
The trochlear nerve
What number nerve is the trochlear nerve?
IV
What is the 5th cranial nerve?
The trigemnal
What number nerve is the trigemnal nerve?
V
What is the 6th cranial nerve?
The abducens
What number nerve is the abducens?
VI
What is the seventh cranial nerve?
The facial
What number nerve is the facial nerve?
VII
What is the 8th cranial nerve?
The vestibulocochlear nerve
What number nerve is the vestibulocochlear nerve?
VIII
What is the 10th cranial nerve?
The vagus nerve
What number nerve is the vagus nerve?
X
What is the ninth cranial nerve?
The glossopharyngeal