Diagnosis of MS
There is no simple test (such as a blood test) on which the diagnosis of MS can be based. When examining someone who might have MS, the neurologist will therefore start by looking for complaints that are typical of MS or for signs that show up on physical examination such as abnormal reflexes. The trouble is that many conditions associated with MS, such as blurred vision, tingling (‘pins and needles’) in the limbs, dizziness or fatigue, also occur in other diseases. If however the signs are typical of MS and occur in a series of attacks, there may be good reason to suspect the presence of MS.
If the neurologist suspects that someone has MS, the next step is usually to perform an MRI (‘magnetic resonance imaging’) scan of the brain and/or spinal cord of the person concerned. If MS is present, this may show up on the MRI scan. The evaluation of these scans must be carried out very carefully, because there are other diseases that may give rise to similar signs on the MRI scan.
The information the neurologist obtains from the pattern of complaints reported by the patient, the physical examination and the MRI scan is usually enough for a reliable diagnosis of MS to be made. In case of doubt, it may be necessary to perform a lumbar puncture, in which a small amount of the cerebrospinal fluid surrounding the brain and the spinal cord is sampled from the base of the spinal cord with the aid of a syringe with a thin needle. This fluid is then examined in the laboratory to see whether it contains any of the components of the immune system that are typically associated with MS or shows any other abnormal signs.
Depending on the precise nature of the complaints reported by the patient, his or her previous medical history and other factors, it may sometimes be necessary to carry out other tests such as blood tests.
International criteria for the diagnosis of MS have been drawn up to ensure that the diagnosis is made as reliably as possible. These are known as the McDonald criteria, after the British neurologist Professor W. Ian McDonald.
Since the diagnosis of MS has major consequences for the patient, and since it is not always easy to make, many neurologists suggest that their patients should get a second opinion from another neurologist – often one who has special experience in the diagnosis of MS. A second opinion is not always needed, however.