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
What number nerve is the glossopharyngeal
IX
What is the eleventh cranial nerve?
The accessory nerve (XI)
What number cranial nerve is the accessory nerve?
XI
What number cranial nerve is the hypoglossal?
XII
What is the 12th cranial nerve?
The hypoglossal.
What are the roles of the oculomotor (III) nerve?
Control of eye movements, constriction of the pupil and keeping the eyelids open.
What are the two nuclei of the oculomotor (III) nerve?
The oculomotor nucleus and the edinger westphal nucleus.
How might a doctor test the occulomotor (III) nerve? What other two nerves would be tested at the same time?
The patient would be asked to to hold their head still and follow with their eyes a pen light or finger being moved in H pattern. This nerve is tested at the same time as the trochlear nerve (IV) and the abducens nerve (VI)
What type of nerve is the trochlear nerve (IV)?
motor nerve (somatic efferent nerve)
What does the trochlear nerve (IV) innervate?
It innervates the superior oblique muscles of the eye.
What are some of the unique features of the trochlear nerve?
- smallest number of axons,
- greatest intracranial length
- exits from the dorsal aspect of the midbrain
- the only cranial nerve that decussates before innervating its target
When do the majority of cranial nerve fibres decussate what is the one exception to this?
The majority of cranial nerves decussate after innervating their targets the trochlear nerve is the exception as it decussates before its target.
Where does the trochlear nerve (IV) leave the midbrain?
The dorsal aspect of the midbrain, caudal to the inferior colliculus.
Where does the the trochlear nerve (IV) enter the eye?
Through the superior orbital fissure where it innervates the superior oblique muscle.
What is the largest cranial nerve?
The trigemnal (V)
Where do the three branches of the trigeminal nerve (V) converge? What is the alternate name for this?
The trigeminal ganglion, also known as the semilunar ganglion
What is the trigeminal/semilunar ganglion the cranial equivalent for of the spinal nerves?
The dorsal root ganglion.
Where are the cell bodies of the motor fibers of the trigeminal nerve (V) found?
The trigeminal motor nucleus located deep within the pons.
What nerves, apart from sensory axons of the trigemnal nerve, terminate in the trigeminal/semilunar ganglion? What does this mean is contained within the trigeminal/semilunar ganglion?
sensory fibers of the facial (VII), glossopharyngeal (IX) and vagus (X) nerves, this means that an entire sensory map of the face is contained within the trigeminal nucleus.
What is the function of the abducens nerve (VI)?
to control the movement of the lateral rectus muscle of the eye.
Where does the abducens nerve (VI) leave the brainstem?
The junction between the pons and medulla medial to the facial nerve (VII).
pontomedullary junction.
Once the abducens leaves the brainstem (pontomedullary junction) it enters the subarachnoid space, what does it run between while it passes through the subarachnoid space?
The pons and the clivus
What artery does the abducens nerve run alongside after it enters the cavernous sinus?
The internal carotid
Where does the abducens (VI) nerve make a sharp turn what does it enter after it has made this turn?
The tip of the petrous temporal bone it enters the cavernous sinus once it has made this turn.
Once the abducens nerve (VI) has passed through the dura matter what does it pass between on its way to the tip of the petrous part of the temporal bone?
The dura matter and the skull
Where does the abducens nerve (VI) enter the orbit through?
The superior orbital fissure
Which cranial nerve can be selectively damaged by a fracture of the petrous temporal bone?
The abducens nerve (VI)
Where is the abducens nucleus?
In the pons at the base of the fourth ventricle at the level of the facial colliculus.
What is a test for the abducens nerve?
Hold an object in front of the patient and ask them to follow it with their eyes if they cannot abduct their eye their is likely an abnormality
Where does the facial nerve enter the the brainstem?
The ventrolateral aspect of the caudal pons at the pontomedullary junction. this region is called the pontomedullary angle
The facial nerve (VII) splits into two roots what is the difference between the two?
The lateral root contains sensory and parasympathetic fibers whereas the more medial roots contains motor fibers.
Where do the cell bodies of the primary afferents of the facial nerves lie within?
the geniculate ganglion within the facial canal of the petrous temporal bone.
Where do the central processes of the taste fibres terminate?
the rostral part of the nucleus solitarius of the medulla.
Where do the motor fibres of the facial nerve (VII) originate?
The caudal pontine tegmentum, in the facial motor nucleus.
Where do the preganglionic parasympathetic fibres of the facial nerve originate from?
Superior salivatory nucleus
what is the sensory root of the facial nerve (VII) known as?
Nervus intermedius.
what do the postganglionic parasympathetic fibres from the facial nerve (VII) innervate?
The submandibular and sublingual salivary glands.
What portion of the tongue does the facial nerve (VII) innervate in respect to taste?
anterior 2/3
What differs in upper motor neuron lesions and lower motor neuron lesions of the face?
With an upper motor neuron lesion only the lower side of the face on the opposite side to the lesion will be effected whereas in lower motor neuron lesions there will be upper and lower facial weakness the same side as the lesion.
Where does the vestibulocochlear nerve (VIII) enter the brainstem?
The cerebellopontine angle.
What nuclei does the vestibular nucleus connect with to help co-ordinate eye movements?
The abducens (VI), the trochlear (IV) and occulomotor (III) nerves.
Is the glossopharyngeal (IX) nerve a predominately sensory or motor nerve?
Mostly sensory but contains preganglionic parasympathetic and some motor fibers.
What gland does the glossopharyngeal nerve innervate?
Parotid salivary gland
Where does the Glossopharyngeal (IX) nerve link to the brainstem?
Lateral to the olive in the rostral medulla.
Where does the glossopharyngeal (IX) nerve carry sensation from?
- Oropharynx tastebuds
- Posterior 1/3 tongue
- Eustation tube and middle ear
- Chemoreceptors and baroreceptors in carotid body and sinus
Where do taste fibres from the glossopharyngeal nerve (IX) terminate?
nucleus ambiguus
Where does the Vagus (X) nerve attach to the brainstem?
Lateral aspect of the medulla immediately caudal to the glossopharyngeal nerve (IX)
Where do the sensory afferent nerve fibres of the Vagus nerve (X) carry information from?
- Pharynx, larynx, oesophagus
- tympanic membrane, external acoustic meatus and part of the concha of the external ear,
- chemoreceptors in aortic bodies and baroreceptors in the aortic arch
- distributed through the thoracic and abdominal viscera
Where do the motor fibers of the vagus nerve (X) arise from?
Nucleus ambiguus
What are the muscles innervated by the motor aspects of the vagus nerve (X) responsible for?
speech and swallowing
What are the three signs of someone with a Vagus nerve lesion?
- Difficulty swallowing
- lose the gag reflex
- their uvula would be deviated away from the side of the lesion.
What type of nerve is the accessory nerve (XI)?
Purely motor.
Which cranial nerve allows a person to shrug their shoulders?
The accessory nerve (XI)
What are the two parts of the accessory nerve (XI)
The cranial and spinal
Where does the cranial aspect of the accessory nerve (XI) emerge from the spinal cord? where do these fibres have their origins?
It emerges from the lateral aspect of the medulla, The fibres from it originate from the caudal part of the nucleus ambiguus.
What does the cranial aspect of the accessory nerve fuse with at the level of the jugular foramen?
The vagus nerve (X)
Where does the the spinal aspect of the accessory nerve arise from where does it leave the spinal cord?
It arises from motor neurons located in the ventral horn of the spinal grey matter at C1-C5 and leave the cord via a series of rootlets at the lateral aspects of the cord.
Where does the spinal aspect of the accessory nerve enter and leave the skull?
Enters at the foramen magnum and leaves via the jugular foramen
What type of nerve is the hypoglossal nerve (XII) ?
Purely motor
How would you test the hypoglossal nerve?
Ask a patient to stick their tongue out straight if it deviates to one side then that side most likely has a hypoglossal lesion.
What area is most commonly effected by the infarct of a stroke?
The internal capsule
What artery is typically occluded in a stroke where the infarct occurs in the internal capsule?
The middle cerebral artery or sometimes by internal carotid occlusion.
What is noticeable about reflexes when they return after a stroke?
They are exaggerated.
What kind of stroke would someone with atrial fibrillation be predisposed to?
An embolic stroke
Attention to what is critical to a dysphagia team?
The ability of the stroke patient to swallow and to their airway.
What is an endarterectomy when is it recommended in stroke patients with an internal carotid artery stenosis?
An endarterectomy is a surgery to remove a plaque from the inside of an artery in the case of an internal carotid artery stenosis an endarterectomy is seen as appropriate when the occlusion is over 70%
What is the common name for percutaneous transluminal angioplasty?
Stenting.
Why is the restoration of blood flow to the brain after a stroke so important besides causing more ischemic infarct?
When parts of the brain die they release inflamtory mediators that cause damage to adjacent area increasing the blow flow stops other areas from dying releasing more mediators.
What is physiotherapy particularly useful for alleviating in stroke?
spasticity and helps them to use working aids.
What proportion of stroke patients die within two years of their stroke?
25%
How many stroke survivors remain alive after 3 year?
30-40%
What are the two main areas where neurogenesis occurs in adulthood?
The subventricular zone and the subgranular zone
Where is the subventricular zone involved in neurogenesis? where do new nerve cells move from here and via what?
lining the lateral ventricles these new cells migrate o the olfactory bulb via the rostral migratory stream.
Where is the subgranular zone involved in neurogenesis?
it is part of the dentate gyrus of the hippocampus
What are the two main types of memory?
Declarative and procedural
Which type of memory is easier to acquire but also easier to lose?
Declarative
Which type of memory is harder to acquire and is more associated with motor acts?
Procedural
Where is the hippocampus in the brain?
The most medial part of the temporal lobe
What type of memory is unaffected by hippocampal lesions?
procedural memories.
What does the internal capsule divide?
The caudate nucleus and thalamus from the lenticular nucleus
