Diagnostic Tests: MRI (Magnetic Resonance Imaging)

An MRI (magnetic resonance imaging) uses powerful magnetic and radio waves to view the internal organs or structure of the body.  MRI scans are used for diagnosing Multiple Sclerosis, tracking changes over time, and helping to determine treatment effectiveness. 

Magnetic resonance imaging (MRI) scans can detect patches of injured tissue (lesions) that suggest MS.  While this is the only test in which some Multiple Sclerosis lesions can be seen, it cannot be regarded as conclusive; because only lesions with are larger than 2mm register on MRI scans, and many other diseases can produce identical MRI images.  Nevertheless, together with supporting evidence from other diagnostic tests, medical history and neurological examination, the MRI is a very important diagnostic tool which can help confirm the MS diagnosis. 

Once diagnosed, periodic follow-up MRIs can be used to track the disease, and effectiveness of treatments by distinguishing new lesions from old ones, and by revealing increasing or decreasing numbers of lesions within the central nervous system over time.  Detecting lesions before further symptoms appear may allow a physician to initiate early treatment that may prove beneficial.  Many experts therefore, now advocate performing a brain MRI as soon as symptoms appear.  However, neither the rate nor the number of new or growing lesions necessarily predicts immediate onset or worsening of symptoms or the development of secondary progressive MS. 

MRIs are also helpful in determining brain volume.  As myelin, axons, oligodendrocytes, and neurons are destroyed, the brain begins to shrink.  Processing MRI images to determine brain volume may be a useful way to monitor progression and treatment effects.  MRI can also detect shrinkage in the spinal cord, which is proving to be a very strong marker of disease progression.  MRI’s can also help to measure severe disease progression by detecting the presence of so-called "black holes."  These are lesions in the brain that emit very low signals on an MRI scan.  Some evidence suggests that they may represent iron deposits in the brain. 

In an MRI scan, patients lie down on a padded examination table that moves into a doughnut-shaped magnet that is open on both ends.  The table moves into the magnet, and patients need to lie very still during the procedure. 

Some people feel very claustrophobic while in the MRI tube.  Persons suffering from claustrophobia should inform the doctor before scheduling the test.  Some facilities offer "open MRIs" which are not closed in like traditional ones.  If the "open" MRI is not an option claustrophobic patients may be given a mild sedative to relax them before beginning the MRI. 

There are no after effects from an MRI, and since it is not an invasive procedure there are no potential risks.  Though it is not painful in itself, some people may find it uncomfortable to lye still for long periods.  Depending on what body parts are being looked at, the test may take 30-90 minutes.