From the Guidelines
Neuroimaging is indicated in patients with delirium when there are specific clinical indicators suggesting an underlying structural brain abnormality, such as new focal neurological signs, history of recent head trauma, fever with signs of meningitis, decreased level of consciousness, or when delirium occurs in a patient without known risk factors or predisposing conditions. Brain imaging, typically CT or MRI, is recommended in these cases to identify potential treatable conditions like subdural hematomas, strokes, or space-occupying lesions that require specific interventions beyond standard delirium management 1. The choice between CT and MRI depends on availability and clinical context; CT is often used initially due to faster acquisition and better tolerance, while MRI provides superior detail for certain conditions like small vessel disease or subtle structural changes 1.
Some key factors that increase the likelihood of finding abnormal brain imaging in patients with delirium include:
- New focal neurological signs
- History of recent head trauma
- Fever with signs of meningitis
- Decreased level of consciousness
- History of falls with possible head injury
- First-onset seizures
- Delirium persisting despite addressing obvious precipitating factors
The rationale for selective imaging is that most delirium cases have identifiable medical causes that don't require neuroimaging, and routine imaging in all delirium patients has low diagnostic yield 1. However, when structural brain pathology is suspected as the underlying cause, prompt imaging can identify treatable conditions that require specific interventions beyond standard delirium management. MRI may be helpful for further evaluation of an abnormality detected on noncontrast CT in the workup of new onset delirium, such as space-occupying lesions or infection 1.
In patients with new onset delirium, the reported yield of brain MRI is very low in the absence of a focal neurologic deficit or history of recent falls 1. Therefore, neuroimaging should be used judiciously, taking into account the patient's clinical presentation and risk factors, to minimize unnecessary testing and optimize patient outcomes.
From the Research
Indications for Neuroimaging in Delirium
Neuroimaging is indicated in patients with delirium in certain situations, including:
- New neurological deficits 2
- Recent falls history 2
- Decline in conscious level 2
- Acute or subacute infarct, haemorrhage, abscess, neoplasm, vasculitis, posterior reversible encephalopathy syndrome, encephalitis, acute demyelination, or fat embolism 3
Diagnostic Yield of Neuroimaging
The diagnostic yield of head computed tomography (CT) in determining the cause of delirium is low, with yields ranging from 2.7% to 14.5% 2, 4. However, neuroimaging can provide valuable information in certain cases, such as:
- Identifying intracranial pathology accountable for the cause of delirium 2
- Detecting structural brain changes, such as impaired white matter integrity, brain atrophy, ischemic lesions, edema, and inflammation 5
Factors Influencing the Use of Neuroimaging
The use of neuroimaging in delirium is influenced by various factors, including:
- Patient age, with younger patients more likely to have MRI compared to CT brain scan 3
- Admission to a neurology unit, with patients admitted to these units more likely to have cerebral imaging 3
- Clinical predictors, such as new neurological deficits, recent falls history, and decline in conscious level 2