Raised ICP

Question 1

What is normal ICP?

Answer 1

5-15 mm Hg

Question 2

How is ICP regulated?

Answer 2

Autoregulation = vasoconstriction, vasodilation

Chemo-regulation = vasodilation in response to low cerebral pH

Question 3

When a mass is present intracranially how do constituents change?

Answer 3

Venous volume lost

CSF lost

Question 4

Outline the pathophysiology of brain injury

Answer 4

Reduction of blood to the brain = lowers oxygen = Na/K ATPase stopes working = more salt inside cell = more oedema = burst = cytotoxic cellular oedema = further swelling and compression = further reduction of blood supply

Question 5

Outline the signs and symptoms of raised ICP

Answer 5

Headache

Vomiting

Visual disturbances

Depression of conscious level

Infants = slowing increasing head size

Herniation syndrome

Question 6

Outline the pathophysiology of a headache in RICP

Answer 6

Worse lying down = higher pressure inside the head

Breath slower when sleeping = accumulation of CO2 = vasodilation = more volume inside the head = more symptoms

Compress SVC = stagnate return of venous blood back to heart from head = more blood volume inside head

Question 7

What causes vomiting in RICP?

Answer 7

Ishcmeia

Starts with nausea, can get projectile vomiting

Question 8

Outline the causes of visual disturbances in RICP

Answer 8

Compression of optic nerve

Transient blindness = increased pressure = compression

Retinal haemorrhages

Question 9

Why does conscious level fluctuate during RICP?

Answer 9

Ischaemia of reticular formation

Question 10

How does the optic nerve change in response to RICP

Answer 10

Swelling of the optic disk = papillodema (optic disk swelling secondary to RICP)

Compression of the arteries

Question 11

What is a false localising sign

Answer 11

Sign that is pointing to the wrong area

CN6 runs so close to the skull CN6 palsy is the first sign of RICP

Question 12

What is one of the first signs of RICP?

Answer 12

CN6 palsy

Question 13

Outline herniation syndromes

Answer 13

Subfalcine herniation = cingulate gyrus across midline - contralateral leg weakness if anterior cerebral A affected

Uncal herniation = uncus displaced across tentorial opening – puts pressure on midbrain, compression of CN 3 (dilated pupil)/cerebral peduncle (leg weakness)

Tonsillar herniation = herniate through foramen magnum – compression of medulla and upper spinal cord, cardiac/resp dysfunction, decreased consciousness

Question 14

Outline the cushings reflex

Answer 14

In response to long term RICP

Triad = 1) high BP, 2) bradycardia, 3) low resp rate

Mechanism = Ischaemia at medulla –> sympathetic activation –> Rise in blood pressure + tachycardia. Baroreceptors react –> bradycardia. Ischaemia at pons/medulla at resp centres –> low resp rate.

Question 15

What are the causes of RICP?

Answer 15

1) increased cerebral blood vol = venous outflow obstruction, venous sinus thrombosis
2) increased CSF = choroid plexus papilloma (excessive secretion), hydrocephalus (impaired absorption)
3) cerebral oedema = meningitis, encephalitis, diffuse head injury, infarction
4) space occupying lesion = abscess, tumour, haemorrhage

Question 16

Discuss CSF

Answer 16

Clear

Hyperosmolar compared to plasma

Production = choroid plexus cells

Filtering = arachnoid vili in dural sinuses

Through aperture to subarachnoid space bathing

Question 17

Discuss hydrocephalus

Answer 17

Accumulation of CSF is thought to be due to an imbalance between production and absorption of CSF with subsequent enlargement of brain ventricles

Obstructive = within/between ventricles, congenital or acquired

Communicating = problem outside the ventricular system, mostly post-meningitits, block arachnoid villi

Question 18

Discuss how brain tumours can cause RICP

Answer 18

Tend to be midline or posterior

Children = astrocytomas

Adults = gliomas, meningiomas, mets from lung/breast/kidney

Question 19

Outline Idiopathic intracranial hypertension

Answer 19

RICP without evidence of hydrocephalus or mass lesion

All scans normal

Usually obese young women after weight gain

Question 20

Outline the principles of management regarding raised ICP

Answer 20

Increased cerebral blood vol = anticoag, tenting venous sinuses

Increased CSF = shunts, tumour resection, diuretics

Cerebral oedema = treat cause, mannitol, hypertonic saline

Space occupying lesion = surgical resection, steriods

Question 21

What is the acute management of RICP?

Answer 21

NO lumbar puncture, nil by mouth

ABC and oxygen

Glucose – rule out other causes

Mannitol (osmotic diuretic)