At this time, there are no symptoms, physical findings or laboratory tests that can, by themselves, determine if a person has MS. Several strategies are used to determine if a person meets the long-established criteria for a diagnosis of MS, and to rule out other possible causes of whatever symptoms the person is experiencing. These strategies include a careful medical history (.pdf), a neurologic exam and various tests including magnetic resonance imaging (MRI), evoked potentials (EP) and spinal fluid analysis.
Criteria for a diagnosis of MS
In order to make a diagnosis of MS, the physician must:
Find evidence of damage in at least two separate areas of the central nervous system (CNS), which includes the brain, spinal cord and optic nerves AND
Find evidence that the damage occurred at least one month apart AND
Rule out all other possible diagnoses
The Revised McDonald Criteria, published In 2010 by the International Panel on the Diagnosis of Multiple Sclerosis, include specific guidelines for using MRI, visual evoked potentials (VEP) and cerebrospinal fluid analysis to speed the diagnostic process. These tests can be used to look for a second area of damage in a person who has experienced only one attack (also called a relapse or an exacerbation) of MS-like symptoms — referred to as clinically-isolated syndrome (CIS). A person with CIS may or may not go on to develop MS.
Tools for making a diagnosis
The physician performs a variety of tests to evaluate mental, emotional and language functions, movement and coordination, balance, vision, and the other four senses. In many instances, the person’s medical history and neurologic exam provide enough evidence to meet the diagnostic criteria. While there is no definitive blood test for MS, blood tests can rule out other conditions that cause symptoms similar to those of MS, including Lyme disease, a group of diseases known as collagen-vascular diseases, certain rare hereditary disorders, and AIDS. Other tests (described below) are used to confirm the MS diagnosis or provide additional evidence if it’s necessary.
Other conditions cause demyelination
Although MS is the most common, other conditions can damage myelin in the CNS, including viral infections, side effects from high exposure to certain toxic materials, severe vitamin B12 deficiency, autoimmune conditions that lead to inflammation of blood vessels (the "collagen-vascular diseases"), and some rare hereditary disorders.
Demyelination of the peripheral nervous system (the nerves outside the brain and spinal cord) occurs in Guillain-Barré Syndrome. After some injuries, the myelin sheath in the peripheral nervous system regenerates, bringing recovery of function.
Some demyelinating conditions are self-limiting, while others may be progressive. Careful (and sometimes repetitive) examinations may be needed to establish an exact diagnosis among the possible causes of neurologic symptoms.