Data Interptretation: CT Head

Question 1

Which 3 details should you confirm before interpreting a CT head?

Answer 1

1. Patient details
2. Date and time of CT head
3. If previous CT heads are available for comparison

Question 2

In what order should you interpret a CT head?

Answer 2

Blood Can Be Very Bad:

B: Blood

C: Cisterns

B: Brain

V: Ventricles

B: Bone

Question 3

If you identify an obvious abnormality on a CT head, how should you then interpret the scan?

Answer 3

Comment on any obvious abnormalities then go through Blood Can Be Very Bad approach

Question 4

In CT head interpretation, what does ‘Blood’ refer to, and what are the 5 main findings?

Answer 4

Areas of haemorrhage:

Extradural haematoma

Subdural haematoma

Subarachnoid haemorrhage

Intraparenchymal blood

Intraventricular blood

Question 5

What is extradural haemorrhage, and what does it look like on CT head?

Answer 5

Extradural/epidural haemorrhage: Blood collection between skull and dura mater (outer lining of brain)

CT finding: Hyperdense biconvex (lens-shaped/lemon) lesion with well-defined borders, between skull and dura mater

Question 6

What is subdural haemorrhage, and what does it look like on CT head?

Answer 6

Subdural haematoma: Blood collection between dura mater and arachnoid mater

CT finding: Hyperdense crescent-shaped (banana) lesion with well-defined borders, located between dura mater (outer lining of brain) and arachnoid mater (middle lining of brain)

Question 7

What are the main differences between an extradural haematoma and a subdural haemtoma?

Answer 7

1. Extradural haematoma is between skull and dura mater, but subdural haematoma is between dura mater and arachnoid mater
2. Extradural haematoma develops quickly due to collection of arterial blood, due to precipitating skull fracture which damages middle meningeal artery (major artery supplying dura mater)
3. Subdural haematoma develops slowly due to collection of venous blood, due to tearing of bridging veins in subdural space
4. Extradural haematoma looks lens-shaped on CT but Subdural haematoma looks crescent-shaped

Question 8

What is subarachnoid haemorrhage, and what does it look like on CT head?

Answer 8

Subarachnoid haemorrhage: Blood collection between arachnoid mater (middle lining of brain) and pia mater (inner lining of brain), in the subarachnoid space (CSF, cisterns, fissures/sulci)

CT finding: Hyperdense lesions in CSF-filled areas eg. Sulci (grooves), cisterns (outpouchings of subarachnoid space)

Question 9

What are the 2 types of intracerebral haemorrhage that are found on CT head?

Answer 9

Intraparenchymal haemorrhage

Intraventricular haemorrhage

Question 10

What is Intraparenchymal haemorrhage, and what does it look like on CT head?

Answer 10

Intraparenchymal haemorrhage: Blood collection in brain tissue

CT finding: Hyperdense lesions in cerebral hemispheres/brainstem/cerebellum/basal ganglia

Question 11

What is Intraventricular haemorrhage, and what does it look like on CT head?

Answer 11

Intraventricular haemorrhage: Blood collection in ventricles

CT finding: Hyperdense lesion in ventricle

Question 12

In CT head interpretation, what does ‘Can’ refer to, and what are the 4 main findings?

Answer 12

Can: Cisterns

1. Ambient cistern effacement/blood/asymmetry
2. Suprasellar cistern effacement/blood/asymmetry
3. Quadrigeminal cistern effacement/blood/asymmetry
4. Sylvian cistern effacement/blood/asymmetry

Question 13

What is cistern effacement, and what does it look like on CT head?

Answer 13

Cistern effacement: Compression or obliteration of cisterns, caused by surrounding lesions eg. Tumour, haematoma

Question 14

What is a cistern, and how many are there on a CT head?

Answer 14

Cisterns: Outpouchings in subarachnoid space, due to uneven distance between pia mater and arachnoid mater

1. Ambient cistern: Ring surrounding midbrain
2. Suprasellar cistern: Pentagon-shaped
3. Quadrigeminal cistern: Smile-shaped
4. Sylvian cistern: Upper outer corners

Question 15

In CT head interpretation, what does ‘Be’ refer to and what are the main findings?

Answer 15

Brain

1. Sulcal effacement
2. Grey-white matter differentiation
3. Midline shift
4. Hyperdensities or hypodensities
5. Pneumocephalus

Question 16

What does sulcal effacement look like on a CT head, and what conditions does it indicate?

Answer 16

Sulcal effacement: Loss of normal, symmetrical gyral-sulcal pattern of brain tissue

Indicates increased intracranial pressure

Question 17

How can you identify grey-white matter differentiation on CT head, and what does loss of it indicate?

Answer 17

Normal grey-white matter differentiation: Grey matter looks hyperdense (lighter) and white matter looks hypodense (darker), due to grey matter having cell bodies and dendrites but white matter has myelinated axons

Loss indicates cerebral oedema secondary to infarction (ischameic stroke), hypoxic brain injury, tumour, cerebral abcess or rupturedd cerebralal aneurysmsm

Question 18

What does midline shift look like on CT head, and what conditions does it indicate?

Answer 18

CT finding: Brian tissue displaced across midline so structures look wavy

Indicates increased intracranial pressure secondary to traumatic brain injury, stroke, tumour, haematoma

Question 19

Give 4 examples of hypodense foci on CT head, within the brain tissue?

Answer 19

Oedema

Pneumocephalus (air)

Infarction (ischaemic stroke)

Hypodense vessel sign: Focal area of decreased density in a blood vessel usually due to fat embolus

Question 20

Give 4 examples of hyperdense foci on CT head, within the brain tissue?

Answer 20

Blood (haematoma or haemorrhagic stroke)

Thrombus

Calcification

Hyperdense vessel sign: Focal area of hyperdensity within a blood vessel due to an acute thrombus

Question 21

In CT head interpretation what does the ‘Very’ refer to, and what are the main 4 findings?

Answer 21

Ventricles

1. Ventricular effacement
2. Ventricle shift
3. Hydrocephalus
4. Blood and choroid plexus

Question 22

What does ventricular effacement look like on CT head, and what conditions does it indicate?

Answer 22

Ventricle looks thinner and smaller, instead of normal wide sickle-shape

Indicates increased intracranial pressure secondary to cerebral odema released from tumour, ischaemic stroke OR haemorrhaging

Question 23

What is hydrocephalus, and what does it look like on CT head?

Answer 23

Hydrocephalus: Abnormal accumulation of CSF in brain ventricles and spinal cord

CT finding: Ventricles look swollen with loss of sharp points, with dark colour (hypodense due to fluid accumulation)

Question 24

Which conditions cause hydrocephalus?

Answer 24

Blockage in CSF flow: Spina bifida, tumour, traumatic brain injury, meningitis

Impaired CSF absorption: Stroke, medications

Question 25

How can you tell if there is blood in the ventricles on a CT head, and which conditions can cause this?

Answer 25

Ventricle appear hyperdense, due to blood collection, and hyperdensity pools due to blood being denser than CSF Indicates intraventricular haemorrhage

Question 26

What is the choroid plexus, and why is it important to consider when assessing for intravascular haemorrhage?

Answer 26

Choroid plexus: Network of cells in ventricle that produces CSF As age increases the choroid plexus calcifies, which can be mistaken for blood on CT head

Question 27

In CT head interpretation, how do you tell the difference between calcification and blood?

Answer 27

Compare the colour of the hyperdense area to the skull bone colour 1. Same colour (pure white) as skull bone: Hyperdense area is calcification 2. Darker colour (light grey): Hyperdense area is blood

Question 28

In CT head interpretation, what does 'Bad' refer to and what are the 4 main findings?

Answer 28

Bone: Any skull fractures 1. Linear fracture 2. Depressed fracture 3. Diastatic fracture 4. Basilar fracture

Question 29

What is a linear skull fracture, and what does it look like on CT head?

Answer 29

Linear skull fracture: Straight, non-displaced break in skull bone Usually causes minimal brain damage CT finding: Thin line interrupting the cortical outline of skull bone

Question 30

What is a depressed skull fracture, and what does it look like on CT head?

Answer 30

Depressed skull fracture: Skull bone is pushed inward, towards the brain, due to a head injury Urgent neurosurgery needed if bone fragment is compressing brain CT finding: Bony fragment is displaced inwardly, can also look like a curve

Question 31

What is a diastatic skull fracture, and what does it look like on CT head?

Answer 31

Diastatic skull fracture: Along the suture lines of the skull, the areas where the skull bones connect CT: Thin break in bone at suture lines

Question 32

What is a basilar skull fracture?

Answer 32

Basilar skull fracture: Fracture at base of skull (supports bottom of brain), caused by blunt force trauma