CT Head Flashcards
According to nice guidelines - within how many hours should a patient on anticoagulation who had a head injuries have a head CT?
8 hours
When was the FAST campaign launched?
2009 by PHE
What region do we scan during a head CT?
Base of skull to vertex
Which baseline do we use to position for a head CT?
Radiographic baseline
Which plane do we acquire head CT in?
What is the standard brain slice thickness?
Axial at 5mm slice thickness
What are the reconstructions during a CT head?
1.25 mm slices - soft tissue window
0.625 mm slices - Bone window
What is high density described as?
How does it appear on CT?
Hyperdense show bright
What is low density described as and how does it appear on CT?
Hypodense shows dark
what is the same density described as?
Isodense
What is infarction in the brain?
- sudden vascular insufficiency
- the development of ischaemia depends on the amount and duration of blood flow loss to the brain
- any cause of blood flow loss to the brain parenchyma can cause ischaemia
- can be transient or permanent
What are some of the causes of infarction?
- Thrombus
- Embolus - blood, air, fat
- Trauma - dissection
- Cardio-respiratory arrest
What are the clinical presentation of brain Infarction?
~ sudden onset
~ Painless
~ neurological deficits
~ may/ or not affect consciousness level
What are clinical factors that affect the risk of stroke?
AF
previous TIAs
Trauma
Side of neurological deficits
What is segmental infarction?
Occlusion of large vessels
What is a lacunar infarction?
Occlusion of small end vessels
What is a cortical infarction?
Focal areas affecting the cortex
What is a venous infarction?
Uncommon and most often associated with VST
What is involved in a multiple territory infarctions?
Infection, trauma, cardiac embolism etc
What are watershed infarctions?
AKA border zone infarct - occur at the border between cerebral vascular territories
What is a secondary infarction?
Vasospasm from haemorrhage
What key points does a request have to say for a radiographer to be able to vet the head CT?
? Stroke
Which side is affected
Onset time of symptoms
Why do we do a non-con head?
To exclude intracranial haemorrhage
To look for any early features of ischemia
To look for a dense vessel
To exclude other intracranial pathologies may be causing symptoms .
What region to we scan for a brain angiogram?
What are we looking for?
Aortic arch to vertex to look for occluded vessels
Not all blood clots can be seen on pre-contrast imaging
What is the flow rate of contrast for a brain angio?
5ml/sec through a green casual
Triggered using bolus tracking - contrast in the ascending aorta
What is the aim of delayed angiographic imaging?
To ascertain the extent of the impact and determine whether there is any salvageable brain. it is a key tool in the decision making process on whether to proceed with thrombolysis or thrombectomy.
It gives information about the patient’s collateral blood supply .
What does CT perfusion show?
It allows the core of the infarct (the part destined to never recover regardless of reperfusion) to be identified.
Along with the surrounding penumbra (the region which is ischaemic but is yet to become an infarct and can potentially be salvaged)
What are the treatments for acute ischemic stroke?
IV thrombolysis
Mechanical thrombectomy
What is the treatment window for thrombolysis?
Within 4 hours of symptom onset
What is the treatment window and scope of endovascular mechanical thrombectomy?
Used for patients with large artery occlusion up to 24 hours
What are the radiographic features of early infarction?
Early infarction (hyper acute phase) 0 -6 hours
~ subtle loss of grey/white matter differentiation
~ dense vessel sign
~ Insular ribbon sign (indicates acute MCA (middle Cerebral artery ) infarct)
What are the radiographic signs of Acute infarction?
Acute infarct 6 hours - 1 week
Hyper attenuation and swelling become more marked, resulting in mass effect
Swelling is as a result of cytotoxic oedema
What is Oedema?
Cells unable to maintain ATP dependent sodium/potassium, membrane pumps. When a cell bus comes ischaemic, these pumps fail to operate, drawing in extra cellular water, causing the cell to swell.
What are the radiographic signs of a sub-acute infarction?
Sub-acute infarction 7-10 days
Brain cells continue to swell - cytotoxic oedema becomes more marked
Can cause compression and shift of structures
What is the fogging effect?
Overtime, the swelling will start to subside
The phenomenon known as the fogging effect is where an initially hyperdense ischaemic area transiently becomes isodense to normal brain
This can mimic normal brain parachyma.
What are the radiographic signs of chronic infarction?
Chromic infarction = more than 3 weeks
- swelling subsides
- Gliosis sets in
- low density appearances with no mass effect
What is gliosis?
Occurs when your body creates more glial cells ( cels that support nerve cells)
These new glial cells can cause scars in the brain
This can lead to necrosis and other neurological symptoms
What are Lacunar infarctions caused by?
Occlusions of small penetrating end-arteries and must be smaller than 15 mm.
How do lacunar infarctions appear on CT?
In acute - appear as ill-defined hypodensities
Chronic lesions appear hypodense similar to CSF
What is a haemorrhagic transformation?
Haemorrhagic transformation is a complication of cerebral ischemic infarction and can significantly worsen prognosis.
Haemorrhagic infarction = petechial haemorrhages
Parenchyma haematoma
More frequency encountered in patients who receive anticoagulant therapy, and more common in those undergoing thrombolytic therapy.
What is laminar necrosis?
Cortical laminar necrosis is necrosis of neurons in the cortex of the brain in situations when the supply of oxygen and glucose is an adequate
Shows as gyriform, hypodensity .
What are the 2 categories of intracranial haemorrhage?
Extra axial haemorrhage
Intra axial haemorrhage
Which haemorrhages come under extra axial haemorrhage?
- Extradural
- subdural
- Subarachnoid
- Intraventricular
Which haemorrhages come within Intra axial haemorrhages?
- intraparechymal
- Contusions
What is a subdural haematoma?
AKA subdural haemorrhage
Collection of blood accumulating in the subdural space between the dura and arachnoid matter.
What is an extradural Haematoma?
A collection of blood that forms between the inner surface of the skull and outer layer of the dura.
They are usually associated with the history history of head trauma and frequently associated with skull fractures .
The source of the bleeding is usually arterial .
What is a subarachnoid haemorrhage?
Subarachnoid is a type of extra - axial haemorrhage
It’s where there is a presence of blood within the subarachnoid space.
When do subarachnoid haemorrhages occur?
They can be spontaneous due to a ruptured, aneurysm or arteriovenous malformation.
What are Haemorrhagic contusions?
Haemorrhagic contusions are common with significant head injuries.
They are usually characterised on CT as focal areas of high density within the brain parachyma.
How do intraparenchymal haemorrhages appear on CT?
What are some of the causes?
An area of hyper density within the brain parenchyma itself.
Can be caused by hypertension or trauma.
What does SOL stand for?
Space occupying lesion
How do mets appear within the brain?
- Often ring, enhancing lions
- Common site is the grey and white matter interface
- commonly assaulted with vasogenic (Perilesional) oedema
- Can be solitary or multiple.
What is a global hypoxic injury?
Global loss of grey/white matter differentiation.
Loss of sulcal definition, indication of cerebral swelling.
Seen in near drowning, asphyxia, cardiac/respiratory arrest.
How does hydrocephalus show on CT?
The dilation of the ventricular system with prominent temporal horns
Effacement surrounding sulci.
Transependymal oedema
Often treated with a shunt
