Raised Intracranial Pressure

Question 1

What is normal ICP?

Answer 1

5-15 mmHg

Question 2

How is ICP regulated?

Answer 2

Vasoconstriction
Vasodilation- in response to low cerebral pH
Movement of CSF and venous volume out of the cranial cavity.

Question 3

What is the pathophysiology of raised ICP?

Answer 3

Reduction of blood supply to brain cells (eg compression by intracranial tumour)

This causes failure of Na K ATPase so cell depolarises and calcium enters. This leads to the process of oncosis.

This leads to cytotoxic cellular oedema

Which leads to further swelling and compression

Question 4

What are the signs and symptoms of a raised ICP?

Answer 4

Headache- generalised ache, worst in mornings, aggravated by bending, coughing or sneezing. Severity gradually progresses.

Vomiting- nausea and vomiting progresses to projectile vomiting

Visual disturbance- blurring, obscurations, papilloedema, retinal haemorrhage, CN6 palsy.

Depression of conscious level

Question 5

What signs and symptoms might you expect from a subfalcine herniation?

Answer 5

Headache

Contralateral leg weakness as anterior cerebral artery can be affected

Question 6

What signs and symptoms might you expect from an uncal herniation?

Answer 6

Ipsilateral CN 3 lesion- leads to ipsilateral dilated pupil

Compression of cerebral peduncle leads to contralateral leg weakness

Decreased level of consciousness.

Question 7

What signs and symptoms might you expect from a tonsillar herniation?

Answer 7

Compression of medulla and spinal cord leads to cardiac and respiratory dysfunction.
Decreased level of consciousness.

Question 8

What is cushings reflex?

Answer 8

If raised ICP is not treated and continues to rise
Is a last ditch attempt to perfuse the brain

Characterised by:
High BP
Bradycardia
Low resp rate

Question 9

What is the mechanism behind cushings reflex?

Answer 9

Ischaemia at medulla—> sympathetic activation—> rise in blood pressure+ tachycardia—> baroreceptor reflex= brady cardia.

Ischaemia at pons/medulla at respiratory centre= low respiratory rate

Question 10

What are the 4 major divisions of causes of raised intracranial pressure?

Answer 10

Increased cerebral blood volume- eg venous outflow obstruction, venous sinus thrombosis

Cerebral oedema- meningitis, encephalitis, diffuse head injury, infarction

Increased CSF- impaired absorption- hydrocephalus, benign intracranial hypertension, or excessive secretion eg choroid plexus papilloma.

Expanding mass- abcess, tumour, haemorrhage.

Question 11

What does normal CSF contain?

Answer 11

Normal CSF is clear and colourless and contains very little protein, little immunoglobulin and only 1-5 cells per ml. It is hyperosmolar compared to plasma.

Question 12

What is the prevalence of hydrocephalus?

Answer 12

1 in 1000 births

Question 13

What are the two types of hydrocephalus?

Answer 13

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

Communicating- problem lies outside of ventricular system eg reduced absorption or blockage of venous drainage/ increased CSF production.

Question 14

What are the most common brain tumours in children?

Answer 14

Astrocytomas

Medulloblastomas

Question 15

What are the most common brain tumours in adults?

Answer 15

Gliomas, meningiomas, metastases

Question 16

From which organs do brain tumours commonly come from?

Answer 16

Lung, breast and kidneys.

Question 17

What is idiopathic intracranial hypertension?

Answer 17

Raised ICP without evidence of hydrocephalus or mass lesion.

Normal investigations include imaging of brain

Usually found in obese young women after weight gain

Treatment options include weight loss, carbonic anhydrase inhibitors, CSF drainage and shunts.

Question 18

What is the management of raised ICP?

Answer 18

Treat the cause:
Venous outflow obstruction- anticoagulation, stenting
Cerebral oedema- mannitol, hypertonic saline
Increased CSF- shunts
Expanding mass- surgical resection

Question 19

How do you tell if someone has RICP?

What is the acute management of raised intracranial pressure?

Answer 19

Reduced GCS
Bradycardia, hypertension, reduced respiratory rate
Focal neurological signs
Seizures
Abnormal posture
Unequal, dilated pupils
Papilloedema

If yes to any of these—> do not perform lumbar puncture. NBM.
ABC and oxygen
Measure glucose
Give mannitol bolus
Treat shock
Call anaesthetist and contact PICU
Intubate and ventilate to control PaCO2
Urinary catheter and monitor output. NG tube.