CT head

Question 1

What are some common indications for CT head?

Answer 1

acute stroke (identify haemorrhage stroke or other pathology eg. space occupying lesion)
trauma (identify intracranial haemorrhage and fractures)
abnormal neurological signs/symptoms (identify space-occupying lesions)

Question 2

What colour is acute haemorrhage on CT?

Answer 2

Bright (white)

Question 3

What happens to blood in a CT image as it gets older?

Answer 3

Blood becomes less dense, gets darker (attenuation drops)

becomes similar colour to CSF

Question 4

What are the two main types of haemorrhage?

Answer 4

Intra-axial (within brain parenchyma)
Extra-axial (within space between skull and brain)
OR BOTH

Question 5

What can cause intra-axial haemorrhage?

Answer 5

haemorrhage stroke
bleed in to underlying lesion (eg. tumour or vascular malformation)
trauma
venous sinus thrombosis

Question 6

What are the different types of extra-axial haemorrhages?

Answer 6

subarachnoid
subdural
extra/epidural haemorrhages

Question 7

Intra-axial haemorrhage:
site
clinical presentation
causes
CT features

Answer 7

site: brain parenchyma

clinical presentation: headache, LOC, features of space-occupying lesion eg. seizures/vomiting/focal neurological deficit

causes: haemorrhage stroke, bleed in to underlying tumour, trauma

CT features: high attenuation in brain parenchyma

Question 8

acute subarachnoid haemorrhage:
site
clinical presentation
causes
CT features

Answer 8

site: between pia mater and arachnoid mater

clinical presentation: sudden onset, SEVERE headache, seizures, focal neurology, vomiting, neck stiffness

Causes: rupture aneurysm (90%), trauma, vascular malformation, extension of intraparenchymal haemorrhage, idiopathic

CT features: High attenuation in subarachnoid space (CSF spaces, cisterns around circle of willis/brainstem, sulk and ventricles)
hydrocephalus
CT angiogram often shows aneurysm

Question 9

Acute subdural:
site
clinical presentation
causes
CT features

Answer 9

site: between arachnoid mater and dura mater

Clinical presentation: gradual onset, headache, confusion, seizures, focal neurology

Causes: traumatic rupture of bridging veins
(commenest in neonates, infants and elderly)

CT features: high attenuation present-shaped collection over brain surface
Resultant mass effect - midline shift, effacement of adjacent ventricle/CSF space, herniation

Question 10

Acute extra-dural:
site
clinical presentation
causes
CT features

Answer 10

site: between dura mater and skull

Clinical presentation: headache, focal neurology, LOC, initial lucent period

Causes: traumatic arterial bleed (most common in middle meningeal artery in temporal region)

CT features: High attenuation biconvex collection overlying the brain
Frequently associated with skull fractures
Resultant mass effect

Question 11

How can a CT be used to assess ischaemic stroke?

Answer 11

In the acute stage, useful to rule out haemorrhage (or mass)
CT findings of ischaemic stroke not usually visible until about 6 hours after event started
(ischaemic stroke diagnosis made on clinical Hx and rule-out of haemorrhage)

Question 12

What is the most common cause of space-occupying lesions in brain? Other than the mass itself on the scan, what else might you see?

Answer 12

metastases

low attenuation oedema surrounding brain tumours

Question 13

What can cause mass effect in the brain?

Answer 13

space-occupying lesion
haemorrhage
localised oedema
general cerebral oedema (secondary to prolonged hypoxia)

Question 14

What might you see on a CT that indicates mass effect?

Answer 14

effacement of normal CSF spaces (ventricles, sulci)
midline shift
herniation (eg. cerebellar tonsils herniation)