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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 1).

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.

Figure 2

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

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

Head CT slices are oriented obliquely, parallel to the base ...

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