From the Guidelines
Computed Tomography (CT) of the brain is indicated for several clinical scenarios where rapid assessment of intracranial pathology is needed, including trauma with suspected intracranial injury, especially in patients with Glasgow Coma Scale (GCS) score below 15 or with risk factors identified by the Canadian CT Head Rule or the New Orleans Criteria, as supported by the most recent evidence from 1 and 1. The primary indications for CT brain include:
- Trauma with suspected intracranial injury
- Sudden severe headache suggesting subarachnoid hemorrhage
- New focal neurological deficits
- Seizures without a known cause
- Altered mental status
- Signs of increased intracranial pressure
- Suspected stroke (within 24 hours of symptom onset)
- Monitoring of known brain lesions such as tumors, abscesses, or hydrocephalus For stroke assessment, the National Institutes of Health Stroke Scale (NIHSS) helps determine severity, while the ASPECTS score evaluates early ischemic changes on CT. The Wells score may guide imaging decisions for suspected venous sinus thrombosis. CT brain is preferred as the initial imaging modality because it is widely available, fast (taking only minutes to complete), effectively detects acute hemorrhage and major structural abnormalities, and can be performed on patients with metallic implants or devices that would contraindicate MRI, as noted in 1 and 1. However, MRI provides superior soft tissue contrast and may be more appropriate for certain conditions like demyelinating diseases or subtle brain abnormalities, as discussed in 1. Some scores that may guide the use of CT brain include:
- Glasgow Coma Scale (GCS)
- Canadian CT Head Rule
- New Orleans Criteria
- National Institutes of Health Stroke Scale (NIHSS)
- ASPECTS score
- Wells score
- Marshall score
- Rotterdam score
- Neuro-Imaging Radiological Interpretation System
From the Research
Indications for CT Brain
The following are indications for CT brain:
- Head trauma patients with a Glasgow Coma Scale (GCS) score less than 15, as 41.0% of patients with GCS 15 had abnormal CT scan findings 2
- Patients with mild head trauma who meet the criteria of standardized guidelines, as the overuse of brain CT scans can lead to unnecessary radiation exposure and financial burden on healthcare systems 3
- Older adult patients with minor head injury who have high-risk mechanisms of injury, vomiting, witnessed loss of consciousness, or anterograde amnesia, as these factors are significantly associated with traumatic head findings on CT 4
- Patients with moderate and severe head injuries who have clinical deterioration unexplained by ICP changes alone, as follow-up CT scans may provide additional information and help identify complications 5
Scoring Systems
The following scoring systems are used to assess the severity of head injury:
- Glasgow Coma Scale (GCS), which categorizes head injury as mild (GCS 13-15), moderate (GCS 9-12), or severe (GCS <8) 2, 4, 5
- Computed Tomography of the Head for the patients at Advanced age (CTHEAD), which is a clinical prediction rule developed to risk-stratify older adult patients with minor head injury and avoid unnecessary CT head imaging 4
CT Brain Findings
The following CT brain findings are associated with head trauma:
- Abnormal CT findings, which were present in 54.5% of head trauma patients, with 77.1% categorized as mild head injury, 11.0% as moderate head injury, and 11.9% as severe head injury 2
- Acute traumatic lesions, which were present in 9.1% of older adult patients with minor head injury, and were associated with high-risk mechanisms of injury, vomiting, witnessed loss of consciousness, and anterograde amnesia 4
- Complications, such as hemodynamic instability, increased intracranial pressure, desaturation, and agitation, which occurred in 16.9% of follow-up CT scans in patients with moderate and severe head injuries 5