Is Magnetic Resonance Imaging (MRI) with or without contrast indicated for diagnosing stroke?

From the Guidelines

Magnetic Resonance Imaging (MRI) is indicated for diagnosing stroke, particularly in cases where further evaluation is needed beyond initial imaging studies. For acute stroke evaluation, non-contrast MRI is preferred, which typically includes diffusion-weighted imaging (DWI), T2-weighted imaging, and fluid-attenuated inversion recovery (FLAIR) sequences 1.

• The use of MRI without contrast is supported by its high sensitivity and specificity for diagnosing ischemic stroke in the first several hours after symptom onset 1.
• Additionally, MRI can identify arterial occlusions and noninvasively characterize ischemic pathology, making it a valuable tool in stroke diagnosis 1.
• However, in patients with renal insufficiency or x-ray contrast allergy, the combination of time-of-flight (TOF) magnetic resonance angiography (MRA) and DWI-MRI head without IV contrast can identify patients eligible for endovascular treatment (EVT) 6 to 24 hours without putting the patient at risk 1.
• Contrast-enhanced MRI may be considered in specific cases, such as suspected stroke of unknown origin or for evaluating vascular malformations, using a gadolinium-based contrast agent at a dose of 0.1 mmol/kg body weight 1.
• It is essential to exercise caution in patients with renal impairment and consider alternative imaging modalities if necessary 1.

From the Research

Diagnosis of Stroke using MRI

Magnetic Resonance Imaging (MRI) is a valuable tool in the diagnosis of stroke, with or without contrast. The following points highlight the indications and benefits of using MRI in stroke diagnosis:

• MRI sequences such as T1-weighted imaging (T1WI), T2-weighted imaging (T2WI), fluid-attenuated inversion recovery (FLAIR), diffusion-weighted imaging (DWI), and apparent diffusion coefficient (ADC) are essential for determining infarct location, volume, and age 2.
• Non-contrast MRI options are available and can be beneficial for patients with renal impairment or allergies to contrast agents 2.
• Advanced techniques like arterial spin labeling (ASL) can serve as a non-contrast alternative for mapping cerebral blood flow (CBF) and allowing for comparison between infarcted and healthy brain areas 2.
• DWI is more sensitive than conventional and contrast-enhanced MR imaging in detecting subacute ischemic lesions, especially in the first week of stroke and in patients with small lesions or preexisting ischemic cerebral damage 3.
• MRI can provide valuable insights for outcomes prognostication as well as stroke etiology, and can be used in conjunction with other imaging modalities such as CT angiography (CTA) and digital subtraction angiography (DSA) 4.

Comparison with other Imaging Modalities

The following points compare MRI with other imaging modalities in the diagnosis of stroke:

• Non-contrast head computed tomography (CT) is the most commonly used initial imaging tool to evaluate stroke, but MRI can provide more detailed information about tissue viability and fate 4.
• CT perfusion is widely used in endovascular therapy trials, but MRI can provide similar information without the need for contrast agents 4.
• MRI can be used to detect venous ischemic stroke, and may show different patterns of abnormalities compared to arterial ischemic stroke 5.

Clinical Implications

The following points highlight the clinical implications of using MRI in stroke diagnosis:

• MRI can help identify patients who are suitable for treatment with intravenous thrombolysis or other interventions 6.
• Advanced stroke imaging techniques such as CT and MR angiography and perfusion imaging can provide valuable information about the underlying cause of stroke and guide treatment decisions 6.
• A thorough understanding of the advantages and limitations of each MRI sequence is crucial for optimal implementation in diagnosis and treatment 2.