Space Occupying Lesions & Raised ICP

Question 1

Define hydrocephalus

Answer 1

Accumulation of excessive CSF within the ventricular system of the brain

Question 2

State three mechanisms of hydrocephalus

Answer 2

• overproduction of CSF (rare choroid plexus tumours)
• decreased resorption of CSF by arachnoid granules (arachnoiditis after haemorrhage/meningitis)
• obstruction of CSF flow (pus, tumour, congenital, SOL)

Question 3

Name two types of hydrocephalus

Answer 3

Communicating and non-communicating

Question 4

What is communicating hydrocephalus?

Answer 4

Obstruction to flow outside of the ventricular system e.g subarachnoid space or granulations

Question 5

What is non-communicating hydrocephalus?

Answer 5

Obstruction to flow occurs within the ventricular system

Question 6

When do cranial sutures close?

Answer 6

Between 2 and 3 years of age

Question 7

What happens if hydrocephalus occurs before cranial sutures close?

Answer 7

Cranial enlargement, increase in occipital- frontal circumference

Question 8

What happens if hydrocephalus occurs after cranial sutures close?

Answer 8

Expansion of ventricles, flattening of gyri and increased ICP

Question 9

What is ex vaco?

Answer 9

Loss of brain parenchyma, not due to an increase in pressure but expansion of CSF and ventricle e.g alzheimers, infarct

Question 10

What is normal ICP?

Answer 10

5-13mmHg

Question 11

What can cause increased ICP?

Answer 11

Increased CSF 
Focal lesions (SOL)
Diffuse lesion (oedema)
Increased venous volume 
Physiological (hypoxia, pain, hypercapnia)

Question 12

What are the effects of increased ICP?

Answer 12

Intracranial shifts and herniation 
Midline shift 
Distortion and pressure on cranial nerves and brain centres
Impaired blood flow 
Reduced consciousness

Question 13

Name four types of herniation

Answer 13

• subfalcine/cingulate
• tentorial/uncal
• cerebellar
• transcalvarial

Question 14

Describe subfalcine herniation

Answer 14

Displacement of cingulate gyrus under falx cerebri, anterior cerebral artery branches may be compressed- contralateral leg symptoms

Question 15

Describe tentorial herniation

Answer 15

Compression of ipsilateral third cranial nerve - pupillary dilatation, uncus of the temporal lobe is pushed against the midbrain

Question 16

Describe cerebellar/tonsillar herniation

Answer 16

Cerebellar tonsils are pushed through the foramen magnum, compresses vital respiratory centres and causes loss of consciousness

Question 17

Describe transcalvarial hernation

Answer 17

Associated with a defect in the dura/skull

Question 18

What are the clinical signs of increased ICP?

Answer 18

• papilloedema
• headache
• nausea/vomiting
• reduced consciousness
• neck stiffness

Question 19

How do brain tumours often present?

Answer 19

Focal symptoms, headache - retain CO2 during sleep, increase in bloodflow means it will be worse in the morning, seizures and increased ICP

Question 20

How do single abscesses in the brain arise?

Answer 20

Local extension - chronic otitis media, sinusitis, tooth infections
Direct implantation - skull fracture

Question 21

How do multiple brain abscesses arise?

Answer 21

Haemtogenous spread - IV drug use, respiratory/cardiac infections, congenital heart disease

Question 22

Where do brain abscesses often occur?

Answer 22

Grey/white matter boundary

Question 23

Describe the pathology of a brain abscess

Answer 23

Oedema, can cause midline shift, surrounding ischaemia and excitotoxic injury

Question 24

What does an abscess look like on imaging?

Answer 24

Central necrosis with oedematous fibrous capsule - ring enhancing lesion

Question 25

What are the organisms associated with brain abscesses?

Answer 25

Staph, strep (aerobic and anaerobic) | Immunocompromised - fungi and protozoa

Question 26

Name three types of skull fracture

Answer 26

Linear Compound Depressed

Question 27

Describe a linear skull fracture

Answer 27

Straight, sharp fracture line that may cross sutures, associated with haematoma - if it occurs at the squamous portion of temporal bone it can rupture the middle meningeal artery causing a subdural haematoma

Question 28

Describe a compound fracture

Answer 28

Full thickness scalp lacerations usually open - base of skull fractures are an example as paranasal sinus injury is presumed

Question 29

What are surface contusions?

Answer 29

Bruises due to damage of tissue, they predominate in cortices but can move into white matter

Question 30

What part of the skull is susceptible to contusions?

Answer 30

Under surface of temporal and frontal lobes due to sharp bony prominences

Question 31

Describe the difference between coup and contra coup

Answer 31

coup - side of impact | contra-coup - non-impact side may occur at the same time or as rebound

Question 32

What provokes diffuse axonal injury?

Answer 32

Rotational movement

Question 33

Where does diffuse axonal injury tend to occur?

Answer 33

- brainstem - corpus collosum - parasagittal area - interventricular septum - hippocampal formation

Question 34

What signs can be seen in axonal injury?

Answer 34

Microglia accumulation Shear strain and transection of axons Axonal bulging and blabbing

Question 35

Name types of secondary brain injury

Answer 35

- haematoma - reduced blood flow - hypoxia - excitotoxicity - oedema - raised ICP - infection - reduced auto regulation