Raised ICP

Question 1

What is the normal ICP?

Answer 1

5 to 15 mmHg

Question 2

What signs and symptoms are associated with raised ICP?

Answer 2

Headache 
Vomiting - N&V progresses to projectile 
Visual disturbance 
Reduced level of consciousness 
Evolving focal neurology 
Subtle personality change

Question 3

Describe the headache typically seen with raised ICP

Answer 3

Generalised ache
Worse on waking in morning - due to hypoventilation during sleeping hours
May wake patient from sleep
Aggravated on bending, stooping, lying down
Aggravated by coughing or sneezing (increasing intrathoracic pressure - preventing venous return from head)
Severity gradually progresses

Question 4

What visual disturbance is seen with raised ICP?

Answer 4

Blurring
Obscurations - transient blindness upon bending or posture change
Papilloedema
Retinal haemorrhage if rise has been rapid

Question 5

What is papilloedema?

Answer 5

Optic disc swelling due to raised ICP of any cause.

The optic nerve is part of the CNS - it has CSF around it, so raised ICP is transmitted to the nerve.

Question 6

Why is cranial nerve VI often affected?

Answer 6

Has a long course and runs close to the skull.

Innervates lateral rectus- abducts the eye

Question 7

What is a subfalcine herniation?

Answer 7

When the brain tissue is displaced under the falx cerebri

Question 8

What are some characteristics of a subfalcine herniation?

Answer 8

Most common type
May be asymptomatic
Symtoms: headache, contralateral leg weakness if anterior cerebral artery affected
Midline shift on CT

Question 9

What is an uncal herniation?

Answer 9

When the medial part of the temporal lobe is displaced across the tentorial opening

Question 10

As an uncal herniation progresses, it puts pressure on what part of the brainstem?

Answer 10

Midbrain

Function: eye movement and reflex responses to sound and vision
Projection fibres pass through

Contains CN III and IV nuclei

Question 11

What signs can be see with uncal herniation?

Answer 11

Damage to CNIII - ipsilateral dilated pupil
Compression of ipsilateral cerebral peduncle (contain sensory and motor tracts) - contralateral leg weakness
LOC

Signs may be false localising if midbrain pushing against opposite side of tentorium

Question 12

What is tonsillar herniation?

Answer 12

When the cerebellar tonsils herniate through the foremen magnum

Question 13

What symptoms and signs are associated with tonsillar herniation?

Answer 13

Compression of medulla - cardiac and respiratory dysfunction
LOC (RAS disturbance)
Lower CN dysfunction
Typically rapidly fatal

Question 14

If raised ICP is not treated and continues to rise, what reflex can occur?

Answer 14

Cushing’s reflex

Question 15

Why does Cushing’s reflex occur?

Answer 15

Last effort to perfuse the brain

Question 16

What is Cushing’s triad?

Answer 16

High BP
Bradycardia
Low respiratory rate

(Opposite to sepsis)

Question 17

Why do you get low respiratory rate in Cushing’s reflex?

Answer 17

Ischaemia to pons/ medulla damages respiratory centres

Question 18

Why do you get bradycardia in Cushing’s reflex?

Answer 18

Ischaemia at medulla causing sympathetic activation, which elevates BP and HR. Baroreceptors react to this causing bradycardia

Question 19

What are some causes of raised ICP?

Answer 19

Expanding mass:
Tumour - primary or mets 
Abscess 
Haemorrhage/ haematoma 
Cyst 

Cerebral oedema:
Meningitis 
Encephalitis 
Diffuse head injury 
Infarction 

Increased cerebral blood volume:
Venous outflow obstruction
Venous sinus thrombosis

Increased CSF:
Impaired absorption - hydrocephalus, benign intracranial hypertension
Excessive secretion - choroid plexus papilloma

Question 20

Does CSF contain a lot or a small amount of protein?

Answer 20

Small amount

Question 21

Compared to plasma, is CSF hyper or hypo osmolar?

Answer 21

Hyperosmolar (more sodium)

Question 22

What is raised ICP most commonly due to?

Answer 22

Trauma

Question 23

What is hydrocephalus?

Answer 23

An accumulation of CSF due to imbalance between production and absorption, causing enlargement of the brain ventricles

Question 24

What are the 2 classifications of hydrocephalus?

Answer 24

Non communicating/ obstructive - CSF obstructed within ventricles or between ventricles and subarachnoid space

Communicating - there is communication between ventricles and subarachnoid space, the problem lies outside ventricular system or too much CSF production.

Question 25

Obstructive hydrocephalus is most commonly due to aqueduct blockade. What can cause this?

Answer 25

Congenital or acquired e.g meningioma

Question 26

What is idiopathic intracranial hypertension?

Answer 26

Raised ICP without evidence of mass or hydrocephalus

Normal imaging results, but signs of raised ICP

Question 27

Who does idiopathic raised ICP normally affect?

Answer 27

Obese young women after weight gain

Question 28

What is a common presentation of idiopathic raised ICP?

Answer 28

Narrowed visual fields
Blurred vision
CN VI palsy 
Enlarged blind spot if papilloedema present 
Consciousness preserved and cognition

Question 29

How is idiopathic raised ICP treated?

Answer 29

Weight loss
CSF drainage (e.g therapeutic LP) and shunts
Carbonic anhydrase inhibitors

Question 30

What are the principles of management for raised ICP?

Answer 30

Shunts
Tumour resection
Diuretics while awaiting intervention

If cerebral oedema: mannitol, hypertonic saline, dexamethasone

Question 31

What test should be avoided?

Answer 31

LP avoid before imaging as risk of coning

Question 32

What imaging should be done?

Answer 32

CT +/- MRI

Question 33

Cerebral perfusion pressure=

Answer 33

Mean arterial pressure (MAP) - intracranial pressure

If intracranial pressure is high, the only way the body can compensate to increase CPP is by increasing MAP

(MAP= SPB+2(DBP) /3

A sympathetic reflex result I’m hypertension. A counter parasympathetic reflex occur by stimulation of the baroreceptors - bradycardia