Should an MRI brain be performed with or without contrast?

MRI Brain: With or Without Contrast?

For most clinical indications, MRI brain should be performed WITHOUT contrast initially, with contrast reserved for specific scenarios where tumor, infection, inflammation, or vascular pathology is suspected. 1

Initial Imaging Approach by Clinical Scenario

New-Onset Seizures (Non-Traumatic)

• MRI brain WITHOUT IV contrast is usually appropriate as the initial study 1
• Noncontrast imaging adequately identifies structural lesions that are potentially resectable and defines the epileptogenic zone 1
• 20-40% of patients with epilepsy have no clear lesion on MRI, but noncontrast sequences are sufficient for initial assessment 1

Altered Mental Status/Delirium

• CT head WITHOUT IV contrast is the first-line test in acute/emergent settings for rapid assessment 1
• MRI brain WITHOUT IV contrast is appropriate as a second-line test when CT is unrevealing and occult pathology is suspected 1
• MRI without and with contrast should be reserved for cases where intracranial infection, tumor, or inflammatory lesions are specifically suspected 1

Ataxia (Non-Traumatic)

• MRI brain WITHOUT AND WITH IV contrast is the preferred modality for comprehensive posterior fossa evaluation 1
• Contrast is particularly important because ataxia can result from masses, inflammatory processes, or vascular lesions that require contrast enhancement for proper characterization 1

New-Onset Psychosis

• Neuroimaging is not always required unless the clinical picture is unclear, presentation is atypical, or abnormal examination findings are present 1
• When imaging is indicated, CT head WITHOUT contrast, MRI WITHOUT contrast, or MRI WITHOUT AND WITH contrast are all reasonable alternatives 1
• The American Psychiatric Association suggests MRI is preferred over CT, and contrast may provide helpful information when the clinical picture is unclear 1

When Contrast IS Essential

Suspected Brain Tumors

• MRI brain WITHOUT AND WITH IV contrast is mandatory for pretreatment evaluation of suspected intraaxial or extraaxial tumors 1, 2
• Contrast enhancement is crucial because both primary and metastatic brain tumors have leaky vasculature best demonstrated on postcontrast T1 imaging 1, 2
• MRI WITHOUT contrast alone is insufficient to adequately delineate tumor extent or differentiate residual/recurrent enhancing tumor 1

Brain Metastases Screening

• MRI brain WITHOUT AND WITH IV contrast is recommended for secondary screening in patients with systemic malignancy 1, 2
• Contrast is essential for detecting small metastatic lesions that may not be visible on noncontrast sequences 2

Posttreatment Tumor Surveillance

• MRI brain WITHOUT AND WITH IV contrast is essential for detecting recurrence or progression 1, 2
• Noncontrast MRI alone cannot distinguish residual/recurrent enhancing tumor from treatment effects 1

Suspected Infection/Inflammation

• MRI WITHOUT AND WITH IV contrast should be performed when intracranial infection, encephalitis, or inflammatory pathologies are suspected 1
• Contrast enhancement helps identify areas of blood-brain barrier breakdown characteristic of these conditions 3

Clinical Decision Algorithm

Step 1: Determine the clinical indication

• Seizure, altered mental status, ataxia, psychosis, or suspected mass lesion 1

Step 2: Assess urgency and available resources

• In emergent situations, CT without contrast is faster and more readily available 1
• In non-emergent settings, MRI provides superior tissue characterization 1

Step 3: Decide on contrast based on suspected pathology

• NO contrast needed: Structural epilepsy evaluation, initial delirium workup, routine follow-up of stable conditions 1
• Contrast REQUIRED: Suspected tumor (primary or metastatic), infection, inflammation, vascular malformation, or when initial noncontrast imaging shows a focal lesion requiring characterization 1, 2, 3

Step 4: Consider patient-specific factors

• Renal function (for gadolinium administration) 3
• History of malignancy (lower threshold for contrast) 1
• Immunocompromised status (consider infection, use contrast) 1

Common Pitfalls and Caveats

Overuse of Contrast

• Routine use of contrast for all brain MRIs increases cost, scan time, and patient burden without clear benefit in many scenarios 4
• Fixed-interval imaging of gliomas and early postoperative MRI are examples where contrast may have uncertain survival benefits 4

Underuse of Contrast

• Never perform MRI without contrast alone when evaluating known or suspected brain tumors—this is insufficient for proper assessment 1, 2
• In patients with known malignancy presenting with neurological symptoms, contrast should be strongly considered even if initial clinical suspicion is low 1

Interpretation Challenges

• Pseudoprogression can mimic tumor progression on conventional MRI and typically occurs 3-6 months post-radiotherapy 1, 2
• Enhancement is not reliable in patients receiving bevacizumab therapy 1, 2
• Conventional MRI has modest sensitivity (68%) and specificity (77%) for differentiating progressive disease from treatment effects 1, 2

Special Populations

• In pediatric patients, reducing gadolinium exposure is particularly important due to repeated imaging needs and longer life expectancy 4
• Half-dose gadolinium protocols may be considered for glioma surveillance in select cases 4