Can any stroke be detected with MRI?

The MRI has a great resolving power, so that even small strokes can be detected. Nevertheless, there are tiny strokes and even bleedings that escape the MRI. If MRI is used as an imaging technique in the acute phase of an ischemic stroke, it should be noted that in about 20 to 35% of patients no diffusion disturbance (disturbance of substance transport) can be measured in the MRI.

This concerns so-called clinically manifest ischemias and non-transitory ischemic attacks. In this case the clinical findings and not the result of the imaging are decisive. A lack of detection in the MRI is no reason to doubt the well-founded clinical diagnosis of a stroke. There is also no reason to change the treatment guidelines. Therefore, the outcome of these patients is not affected.

MRI or CT of the head – Which is better?

There is no general answer to this question. Each method has its advantages & disadvantages. MRI is superior to CT in the detection of ischemia (reduced blood flow).

It can detect them earlier and already at a smaller size. In addition, it is more reliable than CT in detecting ischemia in certain areas of the brain, e.g. the brain stem. MRI provides better information about the cause of the infarction and shows a clear superiority in the detection of stroke mimics (other causes that cause stroke-like symptoms).

Disadvantages of MRI include the long duration of the examination, the high costs, the more difficult monitoring of critically ill patients and the delays in diagnosis. These include, for example, patients with pacemakers or other metallic implants, even though this does not usually describe a contraindication to an MRI examination nowadays. Despite the considerable number of advantages of MRI mentioned above, CT is considered the most important examination in the diagnosis of a stroke.

According to the guidelines, a native CT should exclude intracranial (in the skull) bleeding.In purely clinical terms, it is not possible to distinguish this from an ischemic stroke with sufficient reliability. However, intracranial hemorrhage is a contraindication against the initiation of intravenous lysis therapy, as used in ischemic stroke. The decisive advantage of CT compared to MRI is the significantly lower effort or shorter duration of the examination, which is particularly important in an emergency situation. In addition, the radiation dose has become so low with the new computed tomographs that radiation exposure, at least in emergency diagnostics, is no longer an argument against CT.