ICP and brain herniation

Question 1

what components of the brain contribute to intracranial pressure

Answer 1

• CSF (10%)
• brain tissue (78%)
• intravascular blood (12%)

Question 2

what is the phenomenon when all three factors that contribute to ICP are in equilibrium

Answer 2

Monroe Kellie doctrine

Question 3

what is the normal range for ICP

Answer 3

5 to 15 mmHg

Question 4

when do we consider ICP to be elevated

Answer 4

when it is above 20mmHg

Question 5

what 6 factors influence ICP

Answer 5

arterial pressure
venous pressure
intra-abdominal and intra-thoracic pressure
posture
temperature
blood gases

Question 6

what are the compensatory adaptations for change in ICP

Answer 6

change in CSF volume
change in intracranial blood volume
change in tissue brain volume

Question 7

what affects compensation of ICP

Answer 7

if the volume increases continues and ICP increases further then there will be decompensation

Question 8

what is cerebral blood flow and how is it divided

Answer 8

the amount of blood in milliliters that passes through 100g of brain tissue per minute

about 50ml/min per 100g of white matter
about 170ml/min per 100g of grey matter

Question 9

what factors of BP need to be satisfied for the brain to get its nutrients

Answer 9

Mean Arterial pressure needs to be higher than ICP

Question 10

what is cerebral perfusion pressure (CPP)

Answer 10

the pressure needed to overcome the ICP in order to deliver O2 and nutrients to the brain

Question 11

how do you calculate CPP

Answer 11

CPP = MAP - ICP

Question 12

what happens when CPP is less than 50mmHg

Answer 12

brain ischaemia

Question 13

what happens when CPP is less than 30mmHg

Answer 13

brain death

Question 14

what is the normal CPP

Answer 14

88mmHg

Question 15

what factors regulate CBF

Answer 15

autoregulation
metabolic regulation

Question 16

what happens with autoregulation

Answer 16

blood vessel diameter changes in order to ensure consistent CBF
and this is only effective if MAP is between 70 and 150. when its outside those ranges the Pa02 levels gets affected

Question 17

what metabolic factors get regulated

Answer 17

PCO2
PO2
Acidosis

Question 18

what are the causes of increased ICP

Answer 18

mass lesions
cerebral oedema
head injury
brain inflammation
metabolic insult

Question 19

what happens in the event of sustained increase in ICP

Answer 19

brain compression and brain herniation

Question 20

what are the 6 types of brain herniation

Answer 20

upward herniation
central herniation
tonsilar herniation
subfalcine herniation
transtentorial herniation
transcalvarial herniation

Question 21

what happens in subfalcine herniation

Answer 21

Ipsilateral cingulate gyrus gets pushed beneath falx cerebri and this causes infarction of distal territory of ACA

Question 22

what happens in transtentorial herniation

Answer 22

ipsilateral medial temporal lobe is squeezed under and across tentorium cerebelli

this causes compression of CN3, compression of cerebral aqueduct which will cause hydrocephalus

the infarction is on the temporal or occipital lobe

Question 23

where do you find a kernohans notch

Answer 23

transtentorial herniation

Question 24

what happens in central herniation

Answer 24

the thalamu and hypothalamus and the medial parts of the temporal lobe are forced though the tentorial notch

this will destruction of chiasmatic cistern and this will cause pin point pupils and duret haemorrhages

Question 25

what happens in tonsilar herniation

Answer 25

= infratentorial mass forces cerebellar tonsils through foramen magnum

compression of the brainstem leading to coma and death

compression of PICA and vertebral arteries causing ischaemia of brainstem. tonsils and lower cerebellum

Question 26

what happens with upward herniation

Answer 26

infratentorial mass compresses the brain stem causing displacement of the brainstem and the cerebellum

this ultimately results to occlusion of PCA and SCA leading territorial infarct

cerebrum pushes cerebral aqueduct causing hydrocephalus

Question 27

what happens in transcalvarial herniation

Answer 27

displacement of the brain through the defects in the skull