Download 1)Transtentorial herniation

13/5/2014
Pathology #25
Sara Al_Tally
This lecture will be about the central nervous system, mainly about surgical condition; including
trauma, emergency states and needs surgical intervention, and usually all surgical conditions have
acute onset.
First, we are going to talk about cerebral edema:
edema means accumulation of fluids outside the tissue, and they are two types at the microscopic
level ;
1) Vasogenic edema which means: accumulation of fluids between the neurons
2)Cytotoxic edema: the accumulation within the cells.
The vasogenic type is because of a problem in the BBB; so that the fluids go out from the blood to
the brain (vasogenic)----> from the vesicles. and it occurs when there is a disruption in the normal
BBB.
**what conditions can cause this disruption?
its caused by something physical; Trauma, Tumors, or infections
and all these cause disruption and the brain gets enlarged at the same side and it's called edema.
The cytotoxic means that the cells are swollen and contain extra fluids, and it usually occurs in
ischemia; as you remember in the basic pathology that the first sign of ischemia is the swelling of
the cells.
the vasogenic edema mainly affects the white matter and caused by the disruption of the blood
brain barrier, the fluid shifts from the blood to between the cells while the cells are still
intact.(between the neurons) and the site is usually localized.
but there is generalized cyotoxic edema it occurs in late cerebral ischemia, the ischemia kills all the
cells when its global , in the whole brain which means there is no blood reaching the blood. then
relative ischemia occurs and the BBB dies. And the generalized vasogenic edema occurs.
this type( generalized) usually present in patients having generalized shock either cardiogeneic or
septic and they'll have swollen brain all over.
In the cytotoxic edema the brain looks swollen, soft and there is loss of function in the affected
area.
Cytotoxic edema :
usually in the early ischemia, or early cell injury. The first sign is swollen cells, swollen neurons.
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13/5/2014
Pathology #25
Sara Al_Tally
Now we'll talk about other diseases related to the CSF circulation:
the normal circulation is when the CSF goes out of the ventricles and it moves all over to the laterals
then the thirds and fourths and then to the spinal cord then it goes back to the brain and drains out
from the subarachnoid between the brain and the meninges .
So any disruption in this root or obstruction the CSF will accumulate and so enlarges the ventricles
on the expense of the brain, and this condition is called HYDROCEPHALOUS
*Hydrocephalous: means accumulation of fluids in the ventricles on the expense of the brain as we
said, and it exerts pressure on the brain's parenchyma itself.
this condition usually occurs in children, newborns mainly. note that in newborns the sutures of the
skull are not closed yet so its expandable, and sometimes when there is congenital anomaly; there is
obstruction of this circulation the baby's head becomes very enlarged, and it's commonly seen in
the clinical practice.
**what is the difference between hydrocephalous and edema?!
edema is in the brain's parenchyma itself and the hydrocephalous is in the ventricles; which are
empty (free space) containing fluids that can be enlarged and the brain becomes compressed and
will have impaired function.
Types of hydrocephalous:
1) Non Communicating Hydrocephalous:
*most common
* from the name the ventricles or these spaces are obstructed, not opened to each other (no
communication between them).
*Results either from Tumors: a tumor compresses and closes canal
or a congenital anomaly; which is called stenosis aqueduct of sylvius.
this duct is the duct which joins the third ventricle with the fourth one, so sometimes the baby is
born with this duct being absent or fully obstructed (stenosis) and this baby is born with a very large
head due to hydrocephalous.
* the non-communicating is always because of a physical obstruction of the ventricles.
slide #8: this is how it clinically appears
in the CT scan you can see the enlarged ventricles , they are expanded making one mass ,
and the right is separated from the left.
*** how to know is it communicating or non-communicating?!
- we look at the subarachnoid which is the last part of the circulation , it must be small and when
it's small then its non-communicating.
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13/5/2014
Pathology #25
Sara Al_Tally
2)Communicating Hydrocephalous:
* Its very rare
* communicating means the whole root is enlarged, there is no physical obstruction
*Causes:
-increased production: the CSF is produced in large amounts so it enlarges the path of the CSF.
they are rare cases where there is a brain tumor within the same ventricle, functioning tumors
which produce large amounts of CSF.
The whole root becomes enlarged, and the subarachnoid space is also enlarged
-the second condition is the obstruction in the subarachnoid space (final drainage).
usually occurs as a complication of severe meningitis; because the subarachnoid is between the
brain and the meninges .
generalized meningitis----> Fibrosis----> Adhesion-----> then it closes : so the CSF continues flowing
until reaching there and it cannot be drained out the brain. so communicating type occurs
*** note that in the communication there is no physical obstruction in the root.
either excess production, or impaired drainage.
3) Brain Herniation:
the brain is the most soft organ in the body and the most confined one within the skull, so
that any physical abnormality causes a damage in the brain.
herniation of the brain results of the brain to exert pressure on its own both parts especially
the compressed one are very impaired.
so its the displacement of the brain from its normal position to another site "herniation",
due to increased pressure.
**what can cause physical displacement?
trauma, tumors, hemorrhage: the blood accumulates as a mass and pushes the brain.
The normal space is very confined, very limited; any movement of the brain will be on the
expense of the brain itself in another site. And the herniated part is the most affected one
not the pushed part of the brain, but the one compressd(last part) .
We have three types of hernia:
1)Transtentorial herniation:
*tentorium: its normally the part of the meninges which seperates cerebrum from
cerebellum.
tentorial herniation means that the upper part is moving downward.
it occurs when having supratentorial mass, like a mass in the cerebrum itself pushing the
whole cerebrum downward. the most common is the subdural hematoma
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13/5/2014
Pathology #25
Sara Al_Tally
we have other types of hematoma but this one is Subdural and its caused by trauma.
the hamatoma enlarges and pushes the brain downward, so the cerebrum moves downward
crossing the tentorium.
slide#16: the middle arrow points at the tongue which represents transtentorial herniation.
and it pushes the midbrain underneath, and gives complications as:
1) medical duret (duret hemorrhage): brainstem damage, hemorrhage in the brainstem because of
tentorial herniation. can be lethal, the brainstem is a vital organ.
2)Third cranial nerve (occulomotor) is affected as it passes from that area, so the pupil becomes
enlarged.
3) compression of the posterior cerebral artery that goes to the posterior circulation .
and as we have the occipital area posteriorly so the vision is also impaired, so overall they will have
blindness, dilated pupils and duret hemorrhage .
2) Subfalcine herniation:
falx: is the part of the meninges which seperates the right from the left in the cerebrum itself
so subfalcine herniation: is moving a part from right to the left and vice versa.
And the most common cause is hemorrhage that is caused by stroke, non traumatic.
slide#16: you can see the compressing from the right to the left, and this gyrus is called cingulate
gyrus; and so it has another name which is cingular herniation
structures affected:
1) Anterior cerebral artery; which goes to the anterior circulation and it can be lethal
frontal or parietal lobe results in Cingular herniation under the falx can injure the ant. cerebral
artery and results in ischemia and death.
note that : transtentorial; downward movement ( vertical) , spratentorial mass, may produce
herniation to the lower part of the cerebrum and it results in compression of the third cranial nerve
produces dilation of the pupils fixed in the ipsilateral side ( on the same side)
and compression of the post. cerebral artery results in ischemia of the visual cortex that results in
blindness.
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13/5/2014
Pathology #25
Sara Al_Tally
3) Tonsillar herniation
the most severe one, the whole brain is compressed downward, the whole cerebellum itself goes
downward, the tonsils of the cerebellum is moving downward (tonsillar)
cerebellum goes down to the cerebellum magnum which is the base of the brain and compresses
the midbrain; and its the most critical and significant complication becuase it compresses the
midbrain directly
go back to slide #16
now the stroke:
cerebrovascular accidents : CVA
vascular diseases that result in ischemia of the brain CVA, when its acute we call it a stroke.
like any part in the body it can result from thrombosis, embolism or vascular rupture
vascular rupture: results in ischemia and mass because of the hemorrhage.
Global Cerebral Ischemia:
global means that the blood isnt reaching the brain at all, generalized reduction in cerebral
perfusion, usually from a cardiogenic origin ; the heart isnt pumping or its pumping and there is no
blood, when the B.P is low 50mm systolic.
it can also result from a cardiac arrest ; severe hypotension because of bleeding.
there are 2 types:
1> mild global ischemia: minor form, very common has another name "vasovagal attack"
sympathetic chain is not working well either because of stress, low sleep hours, fasting
pulling of the blood downward occurs , he will have dizziness, visual blurring, and then fall down
what to do ? lye him flat and raise his legs.
2> severe global ischemia:
because of cardiac arrest or severe hypotension
**complication: generalized edema( early stage ) then the damage occurs,
results in persistent vegetative state; only vital functions no motor and sensory
functions, the person becomes like plants taht live on basic thing; he dosnt move or feel.
all the cortex is damaged. awake but not aware.
sometimes the damage reaches a part of the midbrain, and its the brain death stage where the
respiratory function is impaired , but still having residual functions. these patients live on
ventilators.
and the electroencephalogram EEG appears a straight line; no charge in the neurons.
but the heart is pumping normally.
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13/5/2014
Pathology #25
Sara Al_Tally
3) Focal cerebral ischemia:
it results from thrombosis embolism or hemorrhage; 2/3 thromboembolism 1/3 hemorrhage
the hemorrhage is more signifivant because it results in a mass also.
the affected site in these cases gives the clinical situation.
it depends on the site whether significant or not and on the size, and these factors determine the
tissue results.
we have collateral circulation which means if a vessel was obstructed the collateral can compensate
in that particular area (they are spared).
but we have locations with one single artery , and here the patient simply dies
*collaterals in the brain are called circle of willis; where you have single vessel with multiples arising
from it , usually supplies the cortex not the deep gray matter. so usually the cortex is spared and the
more significant case is the ischemia in the arteries supplying the deep sites.
so if the thrombus or embolus occurred on circle of willis then its mild ( white matter ischemia)
which is less significant than the gray matter (gray matter is more serious)
In thrombosis; a thrombus is enlarged and results in ischemia and the most common sites are both
the anterior and the posterior arteries going to the brain (carotid taht can be palpated and basillar
artery that cannot be palpated)respectively.
but the most common is the internal carotid artery for thrombus formation.
In embolism, the most common site is from the heart itself, and the most common cause is atrial
fibrillation ; a type of arrhythmia : the atria is not moving well and this abnormal movement result in
an abnormal movement of the blood and this increases the incidence of formation of thrombus in
the atria and then it reaches the brain as embolus
The middle cerebral artery is the most affected in embolism. it goes vertically to the cortex.
results in hemiplegia usually contralateral , ataxia (impaired balance) , loss of sensation motor and
sensory; (aphasia) and sometimes blindness.
Intracranial Hemorrhage:
less common, the most common cause is hypertension which is very common in population
and so the most common cause of death after MI is the Stroke.
commonly it causes intracranial hemorrhage; the same artery ruptures and bleeds and
results in a mass(hematoma) and ischemia.
so hypertension is the most common caus of non-traumatic intracranial hemorrhage.
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13/5/2014
Pathology #25
Sara Al_Tally
Subarachnoid hemorrhage:
its located outside the brain itself , beneath the subarachnoid not like the stroke; there the bleeding
is within the brain
it occurs as a developmental disease, not congenital; through developing defectives occur.
saccular aneurysm develops, small arteries in the subarachnoid space undergo dilations and
swellings in the vessel wall.
It can affect anybody; however sometimes there is family history of this disease, but usually with
unknown risk factors.
the patient has aneurysm, and the vessel might rupture and so causes sudden bleeding in the brain,
in only 1/3 of cases its associated with increased intracranial pressure. and 2/3 without problems or
symptoms suddenly the vessel ruptures and bleeding occurs.
symptoms:
-Severe Headache: because its near the meninges. that has sensory function
-Rapidly loses consciousness : if not had a spontaneous surgical drainage , the will die or develop
complications.
50% mortality, critical situation
sometimes there is recurrent bleeding; a sac ruptures and the bleeding makes compression
but there is a chance for another bleeding (high chance)
the most common site is the anterior circulation of the brain.
-Has an association with polycystic kidney disease-
Vascular malformation:
this one is congenital, arteriovenous malformation, the baby is born with a structurally abnormal
vessels( neither an artery nor a vessel) and they form a mass like a tumor but its congenital and not
growing and it can rupture and cause bleeding, it might remain asymptomatic during childhood and
begin to show symptoms with age or it can show in the early childhood.
we call it vascular or arteriovenous malformation.
it forms a mass so it causes seizures and epilipsy, or it can rupture and cause intracranial or
subarachnoid hemorrhage.
In trauma the doctor talked about situation and wants from us to know breifly about them.
1) contusions: results from blunt trauma , when the head strikes against a solid part
the first part which had the strike is called "coup "
and the affected part in the other site is called counter coup
it can cause damage and hematoma.
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13/5/2014
Pathology #25
Sara Al_Tally
the most common parts are the frontal and temporal.
2)Laceration: results from sharp trauma, and cases deep damage but focal .
includes fracture of the skull and vascular damage.
3)Diffuse axonal injury: special situation when there is angular acceleration, the movement of the
brain with an angle; so the brain twists axon itself, the axons become damaged.
commonly in car accidents.
symptoms are not clear patients have loss of consciousness and then the damage occur.
4) concussion : the least one, loss of function without abnormality ,anatomy is normal bit there is
focal loss of function , usually they have dysfunction ; all the brain stops functioning including
respiration. but its temporary.
no physical damage, the common thing is that they have amnesia and cannot remember what
happened
we talked about non traumatic hematoma now we will talk about the traumatic ones
1) Epidural :
above, between the skull and meninges. its more serious because its arterial
an emergency condition, usually a trauma in the temporal part and its very common in sports
compression of beneath occur which is the middle meningeal artery, bleeding between the skull and
meninges happen. it expands rapidly and can kill the patient after 30 min of trauma the patient
loses consciousness and then if not treated he might die.
2)Subdural:
beneath, between the dura and the brain.
the veins beneath the dura are torn, common in elderly as their vessels are weak and any minor
trauma can cause.
but occur gradually, not like epidural, normal development is within two days ; it might be
asymptomatic and then the symptoms appear , its diagnosed by a radiograph.
it can also occur in kids, newborns .
Good Luck
Sara Al_Tally
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