Raised ICP

Question 1

What is the normal intracranial pressure

Answer 1

0-10mmHg

Question 2

What processes regulate ICP

Answer 2

Autoregulation:
vasoconstriction
Vasodilation

Chemoregulation:
Vasodilation in response to low pH

Question 3

What compensatory processes maintain ICP

Answer 3

Reduced venous blood volume

Reduced CSF volume

Question 4

Why do we need compensatory processes

Answer 4

Cranium is an inextensible cavity containing brain+blood+CSF
Increased volume of one structure causes decreased volume of another
Venous blood/CSF needs to be reduced to maintain ICP and blood supply

Question 5

What is the pathophysiology of raised ICP

Answer 5

RICP causes compression of cerebral arteries
Reduced blood supply
Hypoxia + inhibit Na/K ATPase
Increased intracellular Na
Cellular oedema 
Further RICP and compression

Question 6

What are the clinical features of RICP

Answer 6

Headache
Reduced consciousness level 
N+V
Visual disturbance
Double vision 
Cushings reflex

Question 7

What is the characteristic headache in RICP

Answer 7

Generalised
Worse in mornings (sleep+hypoventilation causes vasodilation)
Worse on bending, coughing (obstruct SVC)

Question 8

Why do you get N+V in RICP

Answer 8

Stimulate Area Postrema - vomiting centre

With compression of medulla

Question 9

What visual disturbance do you get

Answer 9

Blurry vision
Transient blindness on bending
Papilloedema

Question 10

Why do you get double vision

Answer 10

Compression of CN VI on petrous part of temporal bone with downward displacement of brainstem
False localising sign

Question 11

Why do you get altered conscious level

Answer 11

Compression of midbrain and depression of reticular formation

Question 12

What is Cushing’s reflex

Answer 12

Physiological response to RICP that leads to triad of: Hypertension + Bradycardia + Respiratory depression

Question 13

What are the stages of cushings reflex

Answer 13

Hypertension - cerebral ischaemia activations SNS
Bradycardia - increased aBP activates baroreceptors
Respiratory depression - RICP causes herniation and compression of brainstem

Question 14

What are causes of RICP

Answer 14

Blood volume: venous obstruction, venous sinus thrombosis

CSF: hydrocephalus, choroid plexus papilloma

Brain: meningitis, encephalitis, diffuse brain injury, infarction

SOL: tumour, abscess, haematoma

idiopathic intracranial hypertension

Question 15

What is idiopathic intracranial hypertension

When does it typically occur

Answer 15

RICP in absence of evidence of hydrocephalus of mass lesions

In obese young women after weight gain

Question 16

What are causes of hydrocephalus

What are the findings on CT

Answer 16

Communicating: post SAH, Post meningitis
All ventricles equally enlarged

Non-communicating: congenital atresia, stenosis, tumour
Third ventricle enlarged, fourth ventricle normal

Question 17

What are the steps in acute management of RICP

Answer 17

1. Recognise signs:
   Reduced GCS, focal neurological sign, Papilloedema (late), htn+bradycardia, seizures
2. Do NOT perform lumbar puncture
3. Stabilise patient:
   ABC + O2, mannitol or 3% saline, treat shock, anaesthetist to intubate + ventilate
4. Neurointensive care:
   Elevate head, sedation, prevent hyperthermia, consider CT

Question 18

How do you manage RICP caused by increased blood volume

Answer 18

Anticoagulation

Tenting of venous sinus

Question 19

How do you manage RICP caused by cerebral oedema

Answer 19

Treat cause: antibiotics, alteplase

Mannitol / 3% Saline: fluid shift from interstitium into vessels

Question 20

How to you manage RICP caused by hydrocephalus

Answer 20

Ventriculoperitoneal shunt
Tumour resection
Diuretics: furosemide, carbonic anhydrase inhibitor

Question 21

How do you manage RICP caused by SOL

Answer 21

Surgical resection - craniotomy

Abscess drainage