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Overview
Computed tomography Head (CT-Head) is a radiological examination of the brain and surrounding structures.
Indications
The primary purpose of a CT-Head is to evaluate for neurosurgical and medical emergencies, including haemorrhage, midline shift, hydrocephalus, herniation, infarction.
Common indications for CT-Head include:
Acute head trauma as per NICE Guidelines
Altered Glasgow Coma Score (GCS) with specific concerns regarding:
Intracranial haemorrhage,
Space occupying lesion
Intracranial infection
Infarct
Coagulopathy
Raised intracranial pressure (ICP)
Haemorrhage/Thrombosis:
Intracranial haemorrhage
Ischaemic stroke / Transient ischaemic attack
Dural venous sinus thrombosis
Suspected subarachnoid haemorrhage
Suspected meningitis/encephalitis
First presentation of seizures
Non-cranial indications:
Skull lesions
General principles
Patient: Confirm patient name, hospital number, date of birth.
Scan: Check scan date & time acquired.
Reference: Previous scans if available.
Check all planes: axial, coronal, sagittal.
Check all windows: brain & bone.
Inspect for haemorrhage
Acute haemorrhage/haematoma can be categorised by location:
Extra-axial: Extradural, subdural
Extradural: Hyperdense acute blood. Lentiform shape, limited by the suture lines.
Subdural: Mixed hyperdense acute blood with hypodense chronic blood (depending on age). Crescenteric in shape. Crosses suture lines.
Intra-axial: subarachnoid, intracerebral
Subarachnoid: sometimes sutble, hyperdense blood in/around the basal cisterns and subarachnoid space. Check the posterior horns for intraventricular extension. Can be graded using the modified Fisher scale.
Intracerebral: Hyperdense acute blood within the brain parenchyma and can extend into ventricles. Common locations include basal ganglia and cerebellar (hypertension), or frontal/occipital in trauma.
Extradural haematoma
Acute Subdural haematoma
Chronic subdural haematoma
Subarachnoid haemorrhage (Grade 3)
Subarachnoid haemorrhage with intraventricular extension (Grade 4)
Intraparenchymal haemorrhage
Inspect for MIDline shift
Tumors, hemorrhages, and abscesses may cause shift of midline structures due to the mass effect on the brain parenchyma.
Midline shift can be measured in milimiters. The midline is the line between the anterior and posterior attachments of the falx cerebri.
Midline
Acute subdural haematoma causing midline shift
Other sites of abnormal shift include:
Subfalcine: Beneath falx cerebri
Uncal: Inferomedial displacement of uncus
Transcalvarial: Brain shift through calvarium
Transtentorial: Superior or inferior to tentorium
Tonsilar: Downward displacement of cerebellar tonsils into foramne magnum
Inspect THE VENTRICLES
Hydrocephalus is the abnormal accumulation of CSF in the ventricles.
Hydrocephalus can be obstructive or non-obstructive.
Features of acute obstructive hydrocephalus:
CSF cannot pass through the ventricular system, causing dilation proximal to obstruction.
Lateral ventricles: enlarged temporal horns and transependymal oedema.
Third ventricle: bowing of lateral walls and floor.
Fourth ventricle: enlarged fourth suggests obstruction at foramina of Luschka or Magendie.
Can be caused by a phsyical stenosis (e.g. at various foramina) or pathological - i.e. obstruction secondary to mass effect from tumour/haemorrhage/infarct
Features of non-obstructive (communicating) hydrocephalus:
Passage of CSF through ventricular system is unimpeded.
Can be caused by subarachnoid haemorrhage, infection, leptomeningeal infiltration, normal pressure hydrocephalus.
Assess for ventricular effacement: compression of a ventricular space, usually secondary to haemorrhage/oedema/space occupying lesion.
Obstructive hydrocephalus
Obstructive hydrocephalus with dilated temporal horns and fourth ventricle
Obstructive hydrocephalus secondary to medulloblastoma compressing CSF outflow (MRI-T1)
Inspect The brain
Inspect the brain parenchyma for sulcal effacement and grey-white matter differentiation
Sulcal effacement: Loss of normal sucli in the brain - associated with raised intracranial pressure.
Grey-white matter differentiation: Loss of differnetiation suggests oedema usually secondary to an underlying pathology
Inspect The ISCHAEMIA/Stroke
The goals of CT in the acute setting for assessing for ischaemia include:
Rule out haemorrhage or other thromboylisis contraindications
Identify early ischaemia
Exclude mimic pathologies (e.g. tumour)
A hyperdense MCA (shown below) indicates a large thrombus within the vessel.
An ischaemic stroke may vary on imaging depending on age (hyperacute, acute, subacute, chronic).
MCA Infarct
Hyperdense R MCA - Acute
Other key findings
Pneumocephalus: air within the cranium.
Inspect the bone for fractures and overlying soft tissue for injury.
References
Extradural haematoma: Case courtesy of UoE Radiology, Radiopaedia.org, rID: 34072Chronic subdural haematoma: Case courtesy of Tariq Walizai, Radiopaedia.org, rID: 98023Subarachnoid haemorrhage (Grade 3): Case courtesy of David Cuete, Radiopaedia.org, rID: 22770Subarachnoid haemorrhage with intraventricular extension (Grade 4): Case courtesy of David Cuete, Radiopaedia.org, rID: 25683Intraparenchymal haemorrhage: Case courtesy of Mark Rodrigues, Radiopaedia.org, rID: 58350Midline CT: Case courtesy of David Cuete, Radiopaedia.org, rID: 23768Acute subdural haematoma with midline shift: adapted from Case courtesy of Frank Gaillard, Radiopaedia.org, rID: 35891Obstructive hydrocephalus: Case courtesy of Paul Simkin, Radiopaedia.org, rID: 30453Obstructive hydrocephalus with dilated temporal horns and fourth ventricle: Case courtesy of Frank Gaillard, Radiopaedia.org, rID: 5050Obstructive hydrocephalus secondary to medulloblastoma compressing CSF outflow (MRI-T1): Case courtesy of Ahmed Abdrabou, Radiopaedia.org, rID: 22688MCA Infarct: Case courtesy of David Cuete, Radiopaedia.org, rID: 35732Hyperdense R MCA - Acute: Case courtesy of David Cuete, Radiopaedia.org, rID: 35427
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