Computed tomography (CT) is the most useful neuroimaging study
in emergency medicine practice because it readily detects acute
blood collections and intracranial lesions causing mass effect. These
are the most important immediate considerations in patients presenting
with head trauma, headache, or stroke.
MRI is superior for imaging parenchymal abnormalities and has
replaced CT in most nonemergency neurodiagnosis.
MRI produces images in the sagittal and coronal planes and can better
depict the anatomic characteristics of intracranial lesions. In
addition, MR images are not degraded by bone artifacts that hamper
visualization of the posterior fossa and brainstem on CT (Figure
Many intracranial lesions produce CT findings that are easy to
identify (Figure 2). A rudimentary approach to
CT interpretation uses symmetry in comparing the right and left
sides of the brain, locates the midline, and notes any midline shift.
A CT that is easy to interpret.
Acute epidural hematoma in an 11-month-old child who fell from
the height of a chair.
However, to detect more subtle abnormalities, as well as to confirm
that a CT scan is normal, a methodical approach to CT interpretation
is necessary. This depends on knowledge of normal CT anatomy as
well as the CT manifestations of various intracranial disorders.
Using a systematic approach, each
CT slice is examined individually looking for specific anatomical
landmarks (Table 1). If a lesion is found, on adjacent CT slices
are then examined to determine its extent.
Table 1 Systematic Approach to Head CT Interpretation |Favorite Table|Download (.pdf)
Table 1 Systematic Approach to Head CT Interpretation
and right sides of the cranium|
|Midline—Look for midline shift|
|Cross-sectional anatomy—Review anatomical landmarks for
|Brain tissue—Gray matter, white
matter, intracerebral lesions|
basal cisterns, cortical sulci, and fissures|
|Skull and soft tissues—Scalp swelling, fractures, sinuses, orbits|
for blood collections adjacent to the skull|
|Bone windows—Skull, orbits
and sinuses, intracranial air|
CT interpretation also entails a complementery targeted approach in which specific
abnormalities related to the patient’s clinical presentation
are sought, for instance head trauma, headache or an acute focal
neurological deficit (Table 2).
Table 2 Targeted Approach to CT Interpretation |Favorite Table|Download (.pdf)
Table 2 Targeted Approach to CT Interpretation
|Trauma—Blood (extra-axial, intraparenchymal), cerebral edema,
fractures, pneumocephalus, scalp swelling, coup, and contra-coup injuries|
|Headache—Blood in the
basilar cisterns (SAH), masses, hydrocephalus, cerebral venous sinuses thrombosis, paranasal sinusitis|
of neurological deficit for blood, edema, or masses |