15.5.3 Raised Intracranial Pressure In Children

Question 1

Monro Kelli doctrine

Answer 1

Intact skull = sum of brain, blood & CSF is constant

• Skull is a rigid structure (except with open fontanelles)
• 3 components:
  ➡️Brain: 80% total volume, tissues and interstitial fluid
  ➡️Blood: 10% total volume = venous and arterial
  ➡️CSF: 10% total volume
  ➡️V intracranial = V brain + V CSF + V blood
• An increase in one component means compression of another.

Question 2

Brain cell types

Answer 2

• Neurons: Cell body, axons and dendrites Astrocytes/Pericytes
  • Support the neurons & other glial cells
• Endothelial cells
  • Forms the Blood Brain Barrier
• Oligodendrocytes
  • Myelin sheath around axons
• Microglia
  • Phagocytes, antigen-presenting cells, secrete cytokines

Question 3

CSF

Answer 3

• 10% of total volume
• Choroid plexus > 70% production
• Trans-ependymal shift from brain to ventricles ~30% (if you look at ventricle on scan and there is hypochephalis, the fluid shifts out; oedema around ventricles)
• Avg volume CSF children- 90ml (adult- 150ml)
• Rate of production: 500ml/d
• Increase in ICP
  ➡️Decreased production
  ➡️Increased absorption (up to 3X) arachnoid villae)

Question 4

Blood

Answer 4

• 10% of intracranial volume
• Delivered to the brain by Circle of Willis à course through subarachnoid space before entering brain
• Veins & sinuses drain into jugular veins
• Cerebral blood volume (CBV)
  ➡️Contributes to ICP
• Cerebral blood flow (CBF)
  ➡️Delivers nutrients to the brain

Question 5

Cerebral perfusion pressure

Answer 5

• Cerebral perfusion pressure = Systemic blood pressure - Intracranial pressure
• In intact brain there is auto-regulation
  ➡️Cerebral vessels dilate in response to low systemic blood pressure and constrict in response to higher pressures

Question 6

Complications of raised ICP

Answer 6

• Herniation
• Cerebral ischaemia (too little blood flow)
• Direct pressure effect - optic nerve damage

Why want to know this? Want to recognize clinical signs before it gets to point of decompensation

Question 7

Types ICP

Answer 7

SLIDE 12
But not that important

Question 8

Acute ⬆️ ICP

Answer 8

Infant
- Vomiting
- Irritability
- Bulging fontanelle
- Setting-sun sign
- Acute onset strabismus
- Signs of herniation
- Abducens (6th cranial nerve) palsy
- decerebration
- setting sun sign

Older child
- Depressed level of consciousness
- Vomiting
- Headache
- Acute onset strabismus (6th nerve palsy) -Hypertension/bradycardia
- Signs of herniation

Question 9

Clinical signs of herniation

Answer 9

• Depressed level of consciousness (only in this case you test the gag and corneal reflex)
• Pupils – unequal, non-reactive
• Absent oculocephalic (Doll’s eye) reflex
• Absent corneal & gag reflex
• Decerebration
• Neurogenic hyperventilation

Question 10

Chronic ⬆️ ICP

Answer 10

Infant
- NB Head circumference crossing centiles (good to see a pattern)
- Splayed sutures
- Delayed closure of fontanelles
- Prominent skull veins

Older child
➡️Headache (red flag signs for headaches)
➡️Sometimes increased head circumference
➡️NB papilloedema

Question 11

Causes of ⬆️ ICP

Answer 11

Cerebral oedema
- Vasogenic
➡️Increased capillary permeability - disruption blood brain barrier
➡️Tumors/abscesses/hemorrhage/trauma/ infection
- Cytotoxic
➡️Swelling of the neurons & failure ATPase Na+ channels
- Interstitial
➡️Flow of transependymal fluid impaired

CSF
- hydrocephalus

BLOOD
- perfusion swelling

OTHER
- tumour, bleeding, abscess, subdural effusion, empyema

Question 12

Meassuring ICP

Answer 12

LP
- Advantages and disadvantages

ICP monitors
- lumbar
- Intra-ventricular
- epidural (not into the ventricle)

Question 13

Lumbar puncture and ⬆️ ICP

Answer 13

• Only URGENT INDICATION for LP is to exclude meningitis
• LIFE-THREATENINGáICP(signsof herniation) is a CONTRA-INDICATION

Question 14

Neuroimaging

Answer 14

• Brain ultrasound in infants (open fontanelle)
• CT
• MRI