Multiple sclerosis shares symptoms with other diseases, which sometimes makes it difficult to diagnose.
It can be difficult for doctors to make a multiple sclerosis diagnosis because there are many other conditions with similar symptoms. Additionally, there are no specific tests for multiple sclerosis (MS) so the diagnosis ultimately relies on a combination of a physical examination, radiological studies and laboratory studies. Despite these challenges, approximately 10,000 Americans are diagnosed each year, according to the National Institute of Neurological Disorders and Stroke.
Multiple sclerosis is characterized by a partial or complete loss of the sheath, known as myelin, which surrounds and protects nerve fibers. This can cause a wide range of symptoms in many different parts of the body and is one of the reasons that a standard set of criteria has been established to aid in the diagnosis of MS. One of the goals of any diagnostic procedure should be to determine if the symptoms meet these criteria.
According to the Medical University of South Carolina, an MS diagnosis currently relies upon the following two criteria:
There are several ways a doctor can access the likelihood of MS during a physical exam:
According to the National Multiple Sclerosis Society, magnetic resonance imaging (MRI) is the best technology for detecting MS plaques, also known as lesions. It can also distinguish between new and old lesions. However, there are also other diseases that cause similar lesions in the central nervous system and a normal MRI does not rule out MS. An MRI does not initially show brain lesions in 5 percent of confirmed MS cases, although a diagnosis of MS becomes less likely the longer a patient goes without an MRI showing any lesions.
A spinal tap, evoked potential test and blood tests are useful in diagnosing MS. A spinal tap removes a small amount of cerebrospinal fluid (CSF) from the spinal canal for analysis. This may show an abnormal level of white blood cells or proteins and can also be used to eliminate other possible diagnoses, such as chronic infections. The CSF exam must be evaluated in combination with the physical exam and MRI results. An evoked potential test can measure the electrical signals transmitted by the brain in response to visual stimuli, or electrical impulses applied to the arms or legs. Blood tests may also be used to exclude other diseases with symptoms similar to MS, such as a vitamin B-12 deficiency, lupus and other collagen vascular diseases, HIV and syphilis.