Radiographic evaluation

CT scans in trauma

General information

Non-contrast CT scan of the head is enough for trauma or with a new neurologic deficit.

Enhanced CT or MRI not required emergently but indicated in the following

Suspected ischemic stroke
Significant brain edema on non-contrast CT suggesting a neoplasm that cannot be demonstrated without contrast

CT findings in trauma

Blood (hemorrhages or hematomas):

Extra-axial blood: surgical lesions are usually ≥ 1cm maximal thickness

EDH:

Biconvex
Due to arterial (venous - less common) bleeding.
May cross dural barriers (unlike SDH) such as falx, tentorium

SDH:

Crescentic
Due to venous bleeding.
May cover larger surface area than EDH

Dural adherence to inner table limits extension of EDH).

Chronology of SDH:

Acute= high density,
Subacute ≈ isodense,
Chronic ≈ low density

SAH:

tSAH

Most common cause of SAH.
High density spread thinly over convexity and filling sulci or basal cisterns.

sSAH (spontaneous)

Blood is thickest near the circle of Willis
However, when the history of trauma is not clear, a CTA (or arteriogram) may be indicated to R/O a ruptured aneurysm (that might have precipitated the trauma in some cases)

ICH:

Increased density in brain parenchyma

Hemorrhagic contusion:

“Fluffy” inhomogeneous high-density areas within brain parenchyma, usually adjacent to bony prominences (frontal and occipital poles, sphenoid wing).
Less well-defined than primary ICH

IVH:

Present in ≈ 10% of severe head injuries.
Associated with poor outcome

May be a marker for severe injury rather than the cause of the poor outcome.

Use of intraventricular rt-PA has been reported for treatment

Hydrocephalus:

Enlarged ventricles may sometimes develop following trauma

Cerebral swelling:

Obliteration of basal cisterns

Compression of ventricles and sulci…

Evidence of cerebral anoxia:

Loss of gray-white interface

Signs of swelling

Skull fractures (best appreciated using bone windows):

Basal skull fractures (including temporal bone fracture)

Orbital blow-out fracture

Calvarial fracture (CT may miss some linear nondisplaced skull fractures)

Linear vs. stellate
Open vs. Closed
Diastatic (separation of sutures)
Depressed vs. nondepressed:

CT helps assess need for surgery

Ischemic infarction:

Findings are usually minimal or subtle if< 24 hrs since stroke

DWI MRI is the test of choice

Pneumocephalus:

Indicate skull fracture (basal or open convexity)

Shift of midline structures

Due to extra- or intra-axial hematomas or asymmetric cerebral edema

Can be associated with altered levels of consciousness

CT classification of TBI

Marshall classification-1992

Category	Description	Mortality
I - diffuse injury	- No visible pathology	6.4%
II - diffuse injury	- MLSᵃ of 0 to 5 mm - Basal cisterns remain visible - No high or mixed density lesions ≥ 25 cm³ estimated volumeᵇ, may include bone fragments & foreign bodies	11%
III - diffuse injury (swelling)	- MLS 0 to 5 mm - Basal cisterns compressed or completely effacedᶜ - No high or mixed density lesions ≥ 25 cm³	29%
IV - diffuse injury (shift)	- MLS > 5 mm - No high or mixed density lesions ≥ 25 cm³	44%
V - evacuated mass lesion	- Any lesion evacuated surgically	30%
VI - non-evacuated mass lesion	- High or mixed density lesions ≥ 25 cm³ - Not surgically evacuated	34%

ᵃ"MLS" = midline shift
ᵇto estimate volume of mass on CT
ᶜto assess the basal cisterns

6 categories of severity of TBI based on a non-contrast head CT with binary assessments for presence or absence of:

Intracranial abnormalities
CT evidence of increased ICP as demonstrated by

Midline shift (MLS) > 5mm and/or
Compression of basal cisterns

Presence or absence of mass lesions (contusions/hemorrhages)
Planned evacuation of mass lesions

The Marshall score was devised for descriptive purposes, and while it has subsequently been shown to correlate with outcome parameters, including mortality, outcome prediction is stronger with the specific CT findings identified by recursive partitioning analysis in the “Rotterdam score”

Rotterdam CT score of traumatic brain injury

Based on a non-contrast head CT obtained within 4 hours of injury.

Classification

Basal cisterns:

Normal: 0
Compressed: 1
Absent: 2

Midline shift

No shift or <= 5 mm: 0
Shift > 5 mm: 1

Epidural mass lesion

Present: 0
Absent : 1

Intraventricular blood or traumatic SAH

Absent: 0
Present: 1

Prognosis In adults the mortality at six months increases with the score

Score 1: 0%
Score 2: 7%
Score 3: 16%
Score 4: 26%
Score 5: 53%
Score 6: 61%

Better than marshal classification

Marshall struggles to classify patients who have injuries of multiple types

There is evidence that the worst CT scan obtained during the admission has greater predictive value.

Indications for initial brain CT

Presence of any moderate or high risk criteria which include:

GCS≤ 14,
Unresponsiveness,
Focal deficit
Amnesia for injury
Altered mental status (including those who are significantly inebriated)
Deteriorating neuro status
Signs of basal or calvarial skull fracture

Assessment prior to general anaesthesia for other procedures

During which neurologic exam cannot be followed in order to detect delayed deterioration

Follow-up CT

Routine follow-up CT (when there is no indication for urgent follow-up CT):

Repeat head CT at 24 hours for patients who are clinically stable but had findings on initial head CT of: traumatic SAH, small SDH or EDH, intraparenchymal contusions
For patients with severe head injuries:

For stable patients, follow-up CTs are usually obtained

Between day 3 to 5 (some recommend at 24 hrs also) AND
Between day 10 to 14

Routine follow-up CT several hours after the “time zero” CT (i.e., initial CT done within hours of the trauma) to rule out

Delayed EDH
SDH
Traumatic contusions

For patients with mild to moderate head injuries:

For those with an abnormal initial CT, the CT scan is usually repeated prior to discharge
Stable patients with mild head injury and normal initial CT do not require follow-up CT

Urgent follow-up CT:

Performed for neurological deterioration (loss of 2 or more points on the GCS, development of hemiparesis or new pupillary asymmetry), persistent vomiting, worsening H/A, seizures or unexplained rise in intracranial pressure (ICP) in patients with an ICP monitor.

Spine films

Cervical spine: must be cleared radiographically from the cranio-cervical junction down through and including the C7–1 junction.

Spinal injury precautions (cervical collar…) are continued until the C-spine is cleared.

Skull X-rays

A skull fracture increases the probability of a surgical intracranial injury (ICI)

In a comatose patient it is a 20-fold increase
In a conscious patient it is a 400-fold increase).

Significant ICI can occur with a normal skull X-ray (SXR)

SXR was normal in 75% of minor head injury patients found to have intracranial lesions on CT, attesting to the insensitivity of SXRs).
SXRs affect management of only 0.4–2% of patients in most reports.

An SXR may be helpful in the following:

In patients with moderate risk for intracranial injury by detecting an unsuspected depressed skull fracture (however, most of these patients will get a CT scan, which obviates the need for SXR)
If a CT scan cannot be obtained, an SXR may identify significant findings such as pineal shift, pneumocephalus, air-fluid levels in the air sinuses, skull fracture (depressed or linear)… (however, sensitivity for detecting ICI is very low)
With penetrating injuries: helps in visualization of some metallic objects

MRI scans

Usually not appropriate for acute head injuries.

Due to

Longer acquisition time,
Less access to patients during study
Increased difficulty in supporting patients (requires special non-magnetic ventilators, cannot use most IV pumps…),
MRI is less sensitive than CT for detecting acute blood.

There were no surgical lesions demonstrated on MRI that were not evident on CT in one study.

MRI may be helpful later after the patient is stabilized, e.g. to evaluate brainstem injuries, small white matter changes, e.g. punctate hemorrhages in the corpus callosum seen in diffuse axonal injury…

Spinal MRI is indicated in patients with spinal cord injuries.

Rapid sequence MRI may be useful for follow-up in paediatrics to minimize radiation exposure.

Arteriogram (Cerebral arteriogram):

Useful with non missile penetrating trauma.

Transcranial near Infrared spectroscopy (NIRS) - infrascanner 2000

Scan depth: 3.5cm in adults and children

Mechanisms

Scan 4 (frontal, temporal, parietal, occipital) symmetrical points of each side of head (all together 8 points)
The scanner will tell you the difference in light absorption (haematoma will absorb more of the infra red Light therefore giving you a difference in infra light absorption between the two side)
Able to give you relative volume of blood in brain

Accuracy: in patients with epidural, subdural and intracerebral hematoma. Sensitivity: 88%, specificity 90.7%

Robertson et al 2010 journal of neurotrauma

Cannot use over large wound

Cannot detect small haematoma (>3.5ml haematoma can be detected)

Cannot detect deep haematoma (>3.5cm deep)

Can get false positive over subgaleal hematoma