Question: What tests are used to diagnose multiple sclerosis?
The diagnosis of multiple sclerosis remains a clinical one. That is, there should be two neurological or visual events associated with symptoms and objective clinical evidence lasting more than 24 hours, separated by time (greater than 30 days between events), and separated by space (involvement of different areas of the central nervous system, brain or spinal cord). However, we rely heavily on laboratory data, particularly the MRI scan and cerebrospinal fluid analysis. The MRI scan shows plaques that are seen as hypertense or bright spots. Certain characteristics make them very suggestive of MS. Subequent follow-up MRI scan findings can help fulfill the criteria of separation in time and space. The brain is the most common scan ordered although spinal cord scans are frequently done. The cerebrospinal fluid if positive helps confirm the diagnosis. We look for oligoclonal bands that are immunoglobulins (protein fragments) that are elevated in a high percentage of MS patients. The IgG (immunoglobulin) index is also often elevated.
Less commonly used are visual evoked potentials that are abnormal if a patient has had a MS lesion in the anterior optic nerve pathway even if the individual never had visual symptoms. Also available is a specific blood test showing positive for a disease related to MS called neuromyelitis optica (Devic's disease). Additionally, various blood studies are ordered that rule out diseases that mimic MS such as connective diseases, B12 deficiency and sarcoid among others. Our ability to diagnose MS has been greatly enhanced by all these tests but at times the diagnosis remains in doubt and we rely on time (hence close clinical follow-up) for a diagnosis to declare itself.
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