Magnetic resonance imaging ( MRI) is the safest, most thorough and most cost-effective way to evaluate most patients with known or suspected disease or damage to the central nervous systemthe brain and spinal cord.
According to neuroradiologist Douglas J. Quint, however, the circumstances under which MRI should be used on an emergency basis are less defined.
The timing of emergency MR imaging has significant implications for patient care, equipment availability and staffing, says Quint, professor of neuroradiology and magnetic resonance imaging. So it is important to identify those clinical situations when an emergency MR evaluation is justified. Inappropriate emergency use of such a limited, expensive resource can be wasteful. Or worse, it can delay treatment of patients with true emergency conditions who could best benefit from such evaluation.
Quints proposed indications for emergency use of magnetic resonance imaging were published in the Feb. 16 issue of the Journal of the American Medical Association. According to Quint, decreasing the inappropriate use of MRI will keep the equipment available for emergencies that require immediate MRI evaluation before treatment can be initiated. It also will decrease instances of patients having scheduled appointments delayed or cancelled by emergency studies.
Some medical conditions require immediate MRI evaluation, since emergency therapy can change the outcome for the patient. For example, if a physician suspects new spinal cord compression from disease or injury, an emergency MRI evaluation is necessary.
In a patient with risk factors for disease in the spine who is losing the ability to walk, an emergency search for spinal cord compression with MRI is crucial. If treated for spinal cord compression before they lose the ability to walk, most patients will be able to walk after treatment, Quint says. However, if a spinal cord compression patient loses the ability to walk, the chances of that patient walking again after therapy are small. Since spinal cord compression, usually due to cancer, can result in loss of ability to walk over hours, it is crucial that MRI be available to evaluate these patients on an emergency basis.
Quint also recommends emergency MRI for evaluation of suspected arterial dissections of blood vessels to the brain and also for suspected acute clotting of major veins that drain the brain.
In the past, evaluation of these disorders required invasive, dangerous and expensive angiography, he says. However, essentially non-invasive, extremely safe MRI can now be used to detect these disease processes in many patients. Timely diagnosis of these disorders with subsequent initiation of appropriate therapy can affect ultimate patient outcome.
Quint includes several conditions in a second category that might occasionally require emergency MR evaluation. These include some infections of the brain like meningoencephalitis, and some non-infectious inflammatory processes of the brain, such as lupus vasculitis or SLE.
However, he cautions such emergency MRI evaluations should only be considered if the results will change patient management. For example, he explains that many patients with suspected acute brain infections will still be treated for a brain infection, even if the emergency brain MRI is negative.
In the near future, Quint believes that emergency MRI will be the imaging study of choice to acutely evaluate patients with a suspected stroke and determine which patients should be treated aggressively, as opposed to patients who do not need and might be harmed by aggressive therapy.
Physicians now have a therapy that can change the course of a stroke if given in a timely manner, Quint says. Some of the newest MRI scan techniques may be able to help identify which patients would be most likely to benefit from this therapy.
While MRI is recognized as the best test for evaluating the vast majority of brain and spinal canal pathology, Quint says that other technology is best for certain conditions.
In an emergency setting, CAT scanning remains best for identifying fractures of the head or spine, searching for acute bleeding in the head and for acute intracranial mass effects, which would require acute treatment, he says. Currently, CAT scanning is the standard test for identifying which patients with symptoms of an acute stroke should be treated aggressively, but in the near future, MRI will have a role in evaluation of patients with stroke symptoms.
Quint added that chronic headaches or chronic low back pain are not indications for emergency MRI. Confusion following a traumatic event, such as a car accident, is not an indication for an emergency MRI, if a head CT scan is negative.