13) Raised ICP

Question 1

Outline the values of Normal ICP

Answer 1

Adults = 5 - 15mmHg
Children = 5-7 mmHg
Term Infants = 1.5 - 6 mmHg
Rule of thumb >20 = Raised ICP

Question 2

What ICP determined by ?

Answer 2

> Volume of blood
Brain
CSF
all enclosed within a rigid skull

Question 3

Outline Monro - Kellie Doctrine

Answer 3

> Any increase in the volume of one of the intracranial constituents must be compensated by a decrease in the volume of another
- Compensation mechanism for an increase in pressure

Question 4

How is Cerebral Perfusion Pressure calculated.
> What compensatory mechanism occurs with :
- Increased CPP
- Decreased CPP

Answer 4

CPP = MAP - ICP
> Increased CPP => Vasoconstriction
> Decreased CPP => Vasodilation

Question 5

Describe Cushing’s Triad / Reflex

Answer 5

> Hypertension
Low RR
Bradycardia
- Raised ICP leads to reduced CPP
- Ischaemia of medulla leading to Sympathetic Activation (Na/K ATPase stops working leading to increased Na)
- Raises BP and Tachycardia
- Baroreceptors detects the raised BP -> Bradycardia
- Ischaemia at the medulla also affects respiratory centre causing a low RR

Question 6

What are the Signs and Symptoms of Raised ICP ?

Answer 6

> Headaches
- Worse in the morning, lying down increase venous pressure in the head, meaning more volume in the head and symptoms are worse
N+V
Visual disturbances
- Compression of the optic nerve seen in fundoscopy (Papilloedema)
Depression of Consciousness
Focal Neurological signs

Question 7

Outline the different types of Hernia

Answer 7

Subfalcine Herniation:
> Cingulate Gyrus moves underneath the Falx Cerebri into the other side
> Most common type and can present as Asymptomatic If Anterior Cerebral Artery is affected => Contra lateral Leg weakness

Uncal Herniation:
> Uncus of Temporal Lobe displaced under Tentorium Cerebelli
> Puts pressure on the mid brain which compresses the oculomotor (Ipsilateral) ; Cerebral Peduncles (Contralateral leg weakness)
> Decreased Consciousness

Tonsillar Herniation:
> Cerebellar Tonsils Herniate through Foramen Magnum
> This compresses Medulla and upper Spinal Cord
> Brainstem affected so CVS and Respiratory Centres
> Don’t do Lumbar puncture as this will cause Coning as the brain will be sucked down

Question 8

Outline the causes of raised ICP

> Too much Blood within Cerebral Vessels

Answer 8

Rarer
> Raised Arterial Pressure 
- Malignant Hypertension 
> Raised Venous Pressure 
- SVC Obstruction

Question 9

Outline the causes of raised ICP

> Haemorrhage

Answer 9

> Extra Dural 
> Sub Dural
> Sub Arachnoid 
> Haemorrhagic Stroke 
> Intraventricular Haemorrhage

Question 10

Outline the causes of raised ICP

> Too much CSF

Answer 10

Hydrocephalus
> Congenital
- Obstructive => Neural Tube, Aqueduct Stenosis
- Communicating (CSF drainage impaired) => increased CSF production; Decreased CSF absorption

> Acquired

• Meningitis
• Trauma
• Haemorrhage
• Tumours

Question 11

Outline the features of Hydrocephalus

• Clinical Signs
• Management

Answer 11

Clinical Signs
=> Bulging head with head circumference increased faster than expected
=> Sunsetting eyes due to direct compression of orbits as well as involvement of CN III

Management
> Acutely - tapping the fontanelle with a needle
> Medium - External Ventricular Drain
- Allows for continuous pressure monitoring
- Can at risk of infection due to direct communication between brain and outside world
> Long term - Ventricular Shunts
- Tube is placed from the ventricular system in the Peritoneum or Right Atrium

Question 12

Outline the causes of Raised ICP

> Too much Brain

Answer 12

> Cerebral Oedema

• Vasogenic
• Cytotoxic
• Osmotic
• Interstitial

Question 13

Outline the causes of Raised ICP

> Other

Answer 13

> Tumour 
> Cerebral Abscess 
> Idiopathic 
- Idiopathic intracranial hypertension 
=> Usually obese middle ages females, confirm with lumbar puncture

Question 14

Outline the management of raised ICP

Answer 14

Brain protection measures

• Airway and breathing
• Circulatory Support => Maintenance of MAP
• Sedation => Decrease metabolic demand and prevents cough shivering which may further increased ICP
• Head up tilt
• Temperature => Therapeutic hypothermia may be beneficial
• Anticonvulsants
• Nutrition and PPIs => Improve healing of injuries and prevent stomach ulcers due to increased Vagal activity

Other treatments
> Mannitol or Hyptonic Saline - Osmotic Diuresis
- Ventricular Drainage
- Decompressive Craniectomy as last resort