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N361: Pathophysiology II > Module 11 - Herniation Syndrome > Flashcards

Module 11 - Herniation Syndrome Flashcards

1
Q

Normal ICP{

A

5-15 mmHg`

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2
Q

The head is a confined cavity with a non expandable skull, what are the 3 compatments that make up the volume?

A

10% - Blood volume

10% CSF

80% Brain tissue

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3
Q

Monroe Kellie Hypothesis

A

change in volume of one compartment can be compensated for by a change in one or both of the other two compartments

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4
Q

What two compartments are most able to compensate for changes in ICP?

A

CSF or Blood Volume

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5
Q

What can increase CSF

A

excessive production

decreased absorption

obstructed circulation

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6
Q

What can decrease CSF

A

translocation to the spinal subarachnoid space (basal cisterna)

or

Increased reabsorption

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7
Q

What can increase Blood Volume (BV)

A

vasodilation of cerebral blood vessels

OR

obstruction of venous outflow

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8
Q

What can decrease Blood volume

A

low pressure venous system has limited buffering capacity (since blood likes to go high to low)

blood flow control by autoregulatory mechanisms (hyperventilation to decrease PCO2 which leads to vasoconstriction (which can lower blood volume)) - but vasoconstriction is temporary before compensation through vasodilation

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9
Q

Effects of Increased ICP

A

obstructs cerebral blood flow (cannot go high to low or it cant flow at all)

destroys brain cells

displaces brain tissue (herniation)

damages delicate brain structures

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10
Q

Cerebral Compliance

A

as cerebral volume increases from brain tumor, cerebral edema, and hematoma there is some compliance in pressure to allow change in volume

Change in volume / Change in Pressure!!!

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11
Q

Pressure-Volume Curve

A

once compensatory mechanisms are exceeded, even small changes in volume cause dramatic increases in pressure in the brain

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12
Q

Cerebral perfusion pressure

A

70-100 mmHg

CPP = MABP - ICP

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13
Q

Brain ischemia occurs in CPP is…

A

<50-70 mmHg

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14
Q

If ICP is greater than or equal to MABP, what happens?

A

there is a very low pressure so inadequate tissue perfusion, cellular hypoxia, and neuronal death occur

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15
Q

Stages of Intracranial HTN

A

Stage 1 - Compensation

Stage 2 - Increased ICP

Stage 3 - Decompensation

Stage 4 - Herniation or Loss of CPP

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16
Q

Stage 1: Compensation

A

occurs on a normal basis

increased volume in one compartment –> decrease in one or both of other compartment volumes

ICP remains near normal

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17
Q

Stage 2: Increased ICP

A

Brain responds by constricting cerebral arteries to reduce pressure but results in hypoxia and hypercarbia and deterioration of brain function

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18
Q

Stage 3: Decompensation

A

cerebral arteries respond to hypoxia and hypercarbia with reflex dilation –> this increases Blood volume –> this further increases ICP

Small changes in intracranial volume at this point results in large changes in pressure

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19
Q

Stage 4: Herniation or Loss of CPP

A

Swelling and pressure lead to herniation

if ICP = MABP (or higher than) means there is no cerebral perfusion

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20
Q

The earliest and most reliable sign of increased ICP is…

A

decrease in level of consciousness

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21
Q

Cushing Reflex

A

CNS ischemic response triggered by ischemia of vasomotor center in the brain

Rarer nowadays because of ICP monitoring

Late indicator of Increased ICP

A last ditch effort

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22
Q

What are the three responses in the Cushing Triad/Reflex

A
  1. Increased MABP (body trying to perfuse brain)
  2. Widening Pulse Pressure (systolic - diastolic because diastolic gets very high)
  3. Reflex Bradycardia (baroreceptors in carotids tell vasomotor center to tell vagus center to slow heart to decrease ICP and prevent herniation)
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23
Q

What does it mean by the Cushing Reflex being a Last Ditch effort?

A

it is a last ditch effort to maintain cerebral circulation (and regulate BP)

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24
Q

Brain Septae

A

protects against excessive brain tissue movement

help divide the brain and keep things where they should be

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25
Q

Falx Cerebri

A

sickle shaped brain septae

separates the two hemispheres of the brain (left and right)

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26
Q

Tentorium Cerebelli

A

divides the cranial cavity into anterior and posterior fossae (front and back)

Divides the brain from the cerebellum

brain septae

27
Q

Incisura or Tentorial Notch

A

Large semicircular opening in the midbrain that occupies the anterior portion

28
Q

Supra means…

A

tissue above the temporium

29
Q

Infra means…

A

tissue below the temporium

30
Q

Brain Herniation

A

displacement of brain tissue under the falx cerebri
or through the tentorial notch or incisura of the tentorium cerebelli

31
Q

Herniation Syndromes

A

based on the area of the brain that has herniated and structure under which it has been pushed

32
Q

Supratentorial herniation

A

Above the cerebellum and above the tentorium

Has different syndromes and they each have distinguishing features in early phases

33
Q

What are the different Supratentorial Herniation Syndromes

A

Cingulate or Across the Falx Cerebri

Uncal or lateral

Central or Transtentorial

34
Q

Common element between supratentorial herniation syndromes?

A

compression of the vasculature and CSF flow

35
Q

All supratentorial syndromes have distinguishing features early on but ..

A

the clinical signs become more similar as the compression of the pons and medulla continues and pressure builds

36
Q

What happens at the maximum point of ICP in supratentorial herniations?

A

The only place brain will be able to go is through the foramen magnum causing brain stem herniation, medullary herniation and compression and death

37
Q

Cingulate Herniation

A

Type of Supratentorial herniation syndrome

Displacement of the cingulate gyrus and hemisphere beneath the sharp edges of the falx cerebri to the opposite side of the brain (so this is a herniation to opposite hemisphere - left or right)

Displacement compresses local blood supply and brain tissue –> this causes ischemia and edema –> this leads to increased ICP

38
Q

Key S/S of Cingulate Herniation

A

Leg weakness can be seen - early sign

can progress to leg paralysis

The top of the brian is where the motor strip is so there would be consequences of motor activity

39
Q

Uncal Herniation

A

Subtype of transtentorial herniation

A lateral mass pushes brain tissue centrally and forces medial aspect of the temporal lobe (containing the uncas and hippocampus gyrus) under the edges of the tentorial incisura and into the posterior fossa

40
Q

Uncus

A

innermost part of temporal lobe

Increased ICP makes it move towaad the tentorium and put pressure on the brain stem

This especially happens on the mid brain

Also it puts pressure on CN III which controls pupil dilation which means there are eye issues

41
Q

What are the CNIII (oculomotor) nerve and posterior cerebral artery caught between in uncal herniation?

A

the uncas and tentorium

42
Q

Earliest sign of Uncal Herniation

A

Ipsilateral pupillary dilation from CNIII entrapment (same side)

Consciousness may not be affected, but deterioration proceeds rapidly

43
Q

What are motor changes like in Uncal Herniation

A

ipsilateral changes in motor strength and coordination of voluntary movements d/t compression of descending motor pathways - HEMIPARESIS

occurs same side as herniation because its before the cross at medulla oblongata

44
Q

Two Big Signs of Uncal Herniation are…

A

Ipsilateral pupillary dilation

ipsilateral motor changes

45
Q

What are some late signs of Uncal herniation?

A

Bilateral positive Babinski sign and respiratory changes (Cheyne strokes, ataxic patterns)

Decorticate and Decerebrate Posturing

Dilated, Fixed pupils, flaccidity, and repsiratory arrest

46
Q

Central Herniation

A

Downward displacement of cerebral hemispheres, basal ganglia, and midbrain through the tentorial incisura

Herniation is downward

47
Q

What is different between Central and Uncal Herniation

A

Central is just downward moving but Uncal is in and down

48
Q

What is the earliest sign of central herniation

A

Clouding/decrease in level of consciousness because of pressure on the RAS system for wakefulness

They may be confused and this is a sign of decreased LOC

49
Q

Other Early signs of Central herniation

A

Clouding of Consciousness

Bilateral small pupils (2mm) with full range of constriction

Motor responses to pain that are purposeful or semi purposeful (localizing) and often asymmetric

50
Q

Late signs of Central Herniation

A

Painful stimulation –> decorticate posturing which may be asymmetric

Waxing and waning of respirations with periods of apnea (Cheyne Stokes)

51
Q

What are some late signs of midbrain involvement in a central herniation?

A

Fixed and mid-sized (5 mm) pupils, reflex adduction is impaired

Pain –> cerebrate posturing

Respirations –> neurogenic hyperventilation (40 bpm)

52
Q

What are some late signs of Pons and Medullary involvement in Central herniation?

A

pupils –> fixed, midsize with loss of reflex eye adduction

Pain –> no motor response or only leg flexion occurs

53
Q

Decorticate Posturing comes from damage where

A

to cortical structures in the anterior frontal area

54
Q

Decerebrate posturing comes from damage where

A

to central structures like the midbrain

55
Q

What is worse, decerebrate or decorticate posturing

A

decerebrate - damage occurred to more central structures that do automatic function

56
Q

Infratentorial Herniation

A

Herniation that starts bellow the tentorial incisura and tentorium cerebelli – can go up through the incisura or down below the foramen magnum opening to the spine

Results from increased pressure in the infratentorial compartment

Tends to progress rapidly and can cause death

57
Q

Infratentorial Herniations are more likely to involve what?

A

Lower brain stem centers that control vital cardiopulmonary functions

58
Q

How can infratentorial herniations move?

A
  1. Superiorly (Upward) through the tentorial incisura
  2. Inferiorly (Downward) through the foramen magnum
59
Q

Superiorly Moving Infratentorial herniation leads to …

A

upward movement through the incisura –> blockage of aqueduct of sylvius –> hydrocephalus –> coma

60
Q

Inferiorly Moving Infratentorial herniation leads to …

A

downward movement through the foramen magnum –> cardiac or resp arrest

61
Q

What can happen if there is a pre existing increased ICP and a lumbar puncture is done?

A

Downward herniation can occur when pressure is released causing cardiac or respiratory arrest

62
Q

A cingulate herniation looks like what?

A

herniation of brain tissue from right to left or left to right under the falx cerebri

63
Q

An uncal herniation looks like what?

A

movement over and down toward the incisura

64
Q

What does a transtensorial/downward herniation look like?

A

downward across the tentorium and pushes the tentorium

N361: Pathophysiology II (20 decks)

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