Raised Intracranial Pressure

Question 1

State the intracranial pressure ranges in adults, children, and infants.

Answer 1

Adults = 5-15mmHg
Children = 5-7mmHg
Infants = 1.5-6mmHg

Question 2

What is intracranial pressure?

Answer 2

A measure of the pressure of the brain tissue and CSF that cushions and surrounds the brain and spinal cord.

Question 3

What intracranial pressure is considered to be raised?

Answer 3

Anything above 20mmHg

Question 4

What are the 4 major causes of raised ICP?

Answer 4

1. Too much blood
2. Too much CSF
3. Too much brain
4. Other

Question 5

Why is the ICP in infants similar to atmospheric pressure?

Answer 5

1.5 - 6mmHg
Similar because the infant skull has unfused fontanelles which do not allow for significant pressure gradients to be established. These fontanelles are why, raised ICP in infants is generally better tolerated than in adults.

Question 6

Give examples of conditions in which too much blood in the brain can lead to raised ICP.

Answer 6

1. Haemmorhage - subdural, extradural, haemmorhagic stroke.
2. Malignant hypertension
3. Venous obstruction

Question 7

Give examples of conditions in which too much CSF can lead to raised ICP.

Answer 7

Hydrocephalus - caused by congenital obstruction to CSF flow e.g. neural tube defects like spina bifida, aqueductal stenosis, or communicating hydrocephalus (increased production of CSF / decreased absorption)

Question 8

Give examples of conditions in which too much brain can lead to raised ICP

Answer 8

Anything that results in cerebral oedema.

1. Vasogenic - vasoactive substances break down tight junctions of BBB.
2. Cytotoxic - trauma can lead to toxins entering brain and the retention of Na+ and H2O.
3. Osmotic - SIADH / excessive water intake reduces osmolality in the serum/ peripheries causing water to move into the brain.
4. Interstitial - trauma can disrupt the BBB allows CSF to leak into the interstitial spaces.

Question 9

The presence of what can lead to raised ICP?

Answer 9

Tumours

Abscesses

Question 10

How babies with raised ICP present and why?

Answer 10

Commonly present with:

1. Sunsetting eyes = damage to cranial nerves or pressure of CSF pushing eyes down.
2. Enlarging head = unfused fontanelles allow the head to grow without a significant increase in pressure.

Question 11

How might congenital hydrocephalus be treated?

Answer 11

Initially by tapping/ draining the fontanelle.
External ventricular drains can be used for short to medium term drainage
Ventricular shunts can be used as a more permanent treatment, but most need to be adjusted as the infant grows.

Question 12

What does the Monroe-Kellie Doctrine state?

Answer 12

Any increase in the volume of one of the cranial constituents (venous volume, arterial volume, brain, and CSF) must be compensated for by a decrease in the volume of another constituent.

Question 13

Cerebral perfusion pressure = Mean arterial pressure - intracranial pressure.

What are the normal ranges for the factors involved in this equation?

Answer 13

MAP = 65-110mmHg
ICP = 5-15mmHg
CPP = >70mmHg

Question 14

Describe the process of cerebral autoregulation.

Answer 14

The process of autoregulation maintains cerebral blood flow (CBF) when CPP is between 50-150mmHg.
It does so by vasodilating to maximise perfusion at lower CPPs, and vasoconstricting to prevent over-perfusion at higher CPPs.
Outside of this range, cerebral blood flow becomes pressure dependent, as the brain has already maximally constricted or dilated its blood vessels.

Question 15

Give an example where impaired autoregulation can lead to hypoperfusion of the brain.

Answer 15

If there is a mass within the brain (tumour) which raises the intracranial pressure, this might reduce the brains blood vessels ability to vasodilate. Consequently at points where CPP is lower than the brain needs, the vessels cannot vasodilate to maximise perfusion, and as such the brain experiences hypoperfusion.

Question 16

What is Cushing’s Triad?

Answer 16

The body’s response to raised ICP.

1) MAP and SBP increase.
2) Reduced HR (Baroreceptors in the carotid sinus detect this increase in BP, and so act to reduce CO and thus SV)
3) Irregular breathing is the last change and occurs due to compression of the medulla in the brainstem.

(2+3 can both be caused by compression of the cardio-respiratory centres in the brainstem)

Question 17

In what situation do Cushing’s ulcers arise? What treatment must you prescribe to manage this?

Answer 17

Increased ICP caused overstimulation of the vagus nerve. This acts on the stomach, causing it to produce too much gastric acid.
Treatment invovles a PPI, or H2-antagonist.

Question 18

Name three types of herniation and where they occur.

Answer 18

Tonsillar (cerebellar) herniation = ‘coning’ where the cerebellar tonsils herniate through foramen magnum.
Subfalcine (cingulate) herniation = herniation under the falx cerebri.
Uncal herniation = herniation of the uncus of the temporal lobe through the tentorial notch)

Question 19

List the 7 early signs of raised ICP.

Answer 19

Headache
Nausea and vomiting
Confusion
Difficulty concentrating / drowsiness
Double vision 
Focal neurological signs
Seizures

Question 20

What tests and investigations would you perform if you suspected raised ICP?

Answer 20

Imaging- CT/ MRI
Examination - full neurological and cranial nerve exam

If after trauma….

1. Perform ABCDE assessment
2. CT head and cervical spine (bleeds, oedema, bony cervical injury)
3. CT chest, abdomen, pelvis (pneumothorax, rib fractures, free intraperitoneal blood/air)
4. Plain X-ray of both lower limbs (femoral shaft fractures- hypovolaemia)

Question 21

What is sciwora? Who does it present in?

Answer 21

Damage to the spinal cord without damage to the vertebral column / bones.
Occurs in younger people.

Question 22

How could a patient present with brain injury to both sides of their brain?

Answer 22

‘Coup contra coup’ injury. Initial traumatic impact leads to damage on the side of the injury, but as the brain recoils back the other way, it hits the other side of the skull, and also sustains injury as the head is shaken.

Question 23

What is Idiopathic intracranial hypertension?

Answer 23

Usually seen in obese females. Symptoms resemble that of a brain tumour. Diagnosed with a lumbar puncture at high opening pressure (>25cmH2O)
Condition improves with weight loss and BP control.

Question 24

List 7 measures enlisted in the management of raised ICP that help protect the brain.

Answer 24

1. Airway control and ventilation
2. Circulatory support (maintain MAP to allow adequate CPP)
3. Sedation, analgesia, and paralysis (decrease metabolic demand, prevent coughing, shivering…)
4. Head up (15-30 degrees) to improve venous drainage, and take off C-spine collar as this can obstruct venous flow.
5. Temperature - avoid high temps as this increases metabolic demand
6. Anticonvulsants - prevent seizures
7. PPIs + nutrition - prevents ulcers and improves wound healing.