Diagnosing multiple sclerosis (MS) requires a thorough process that mainly relies on ruling out other neurological conditions through many tests. This process is known as differential diagnosis.
Several conditions have symptoms similar to MS. Lupus erythematosus is an autoimmune disease that causes inflammation and can damage the central nervous system. Vitamin B12 deficiency leads to a demyelinating condition that mimics MS.
People with vitamin D deficiency can present with symptoms similar to MS, such as fatigue and muscle weakness. Similarly, Lyme disease is an infection-based condition that causes numbness or tingling in the hands, arms, feet, and legs, and can appear similar to MS. Neuromyelitis optica is an autoimmune disease that shares many symptoms with MS, making it difficult to distinguish between the two conditions.
Your health care team will work to rule out these and other conditions during the diagnosis process.
To diagnose MS, a person must meet certain criteria, and other conditions must be ruled out. These are known as the McDonald Criteria, which were updated in 2017. The McDonald Criteria consider the clinical presentation of MS attacks and lesions alongside other evidence, such as MRI evidence of lesions.
MS can be confirmed without additional information in cases when someone has had at least two MS attacks and has clinical evidence of two or more lesions involving the central nervous system — or clinical evidence of one lesion and historical evidence of a previous attack.
In other cases when a person has had fewer MS attacks or doesn’t have clinical evidence of lesions, then MRI evidence or evidence of substances in the spinal fluid may be needed to confirm MS.
Read more about the full McDonald Criteria.
MS is typically diagnosed by a doctor who specializes in brain diseases and disorders, known as a neurologist. There is no single test that can give a definitive MS diagnosis — your neurologist will perform a series of tests to look for signs of MS while ruling out other diseases and disorders.
Your neurologist will begin by taking a detailed medical history, which includes asking about your family history of MS and your symptoms (what kind, how severe they are, and how often they occur). If a parent or sibling has had MS, you are at a higher risk for developing it.
Next, the neurologist will perform a thorough neurological exam that tests many abilities that may be affected by MS. These tests will help your neurologist determine the extent of potential damage to the brain and spinal cord from MS.
Blood tests are used to look for specific biomarkers of MS and also to rule out other diseases. Some conditions can be ruled out using specific criteria:
Magnetic resonance imaging (MRI) is an imaging method that creates detailed pictures of the body’s organs and tissues. It is one of the most useful methods for diagnosing MS because it allows neurologists to see changes to the brain and spinal cord. MRI scans will show sclerosis (MS lesions) on the white matter of the brain and changes to other parts of the brain. It can also identify atrophy or loss of brain or spinal cord volume.
A lumbar puncture (also called a spinal tap) is used to examine the cerebrospinal fluid (CSF) surrounding the brain and spinal cord. Your neurologist will do this to look for signs of inflammation, infection, and more. It is used to diagnose several conditions, including cancer, meningitis, bleeding in the brain, and MS. Overall, this is a useful method during the MS diagnostic process, but it is not considered necessary to perform in all cases.
In this test, the lower back near the spine is numbed with a local anesthetic, and a hollow needle is inserted between two vertebrae to remove CSF. The fluid is then analyzed for different components that may point to which disease you have.
One example of these is oligoclonal bands, which are antibodies that are created when inflammation is present in the central nervous system. Oligoclonal bands are often used to support an MS diagnosis, but they can also appear in other diseases or conditions, such as lupus erythematosus, stroke, Lyme disease, lymphomas, and HIV infection. Your neurologist will need to perform other tests to make a definitive MS diagnosis.
Read more about lumbar punctures and MS.
The brain communicates with the nervous system by producing electrical signals that stimulate different nerve pathways. Evoked potential tests may be used to diagnose a neurological disease that causes nerve damage, such as MS. However, other diseases that affect nerve pathways may also provide similar results on evoked potential tests. Your neurologist will use this test in combination with others to come to a diagnosis.
Electrodes attached to wires are placed on the scalp to measure how quickly electrical signals travel through the body to the brain. Many different kinds of evoked potential tests measure visual and auditory signaling. Other tests stimulate nerves in different parts of the body (the wrist and ankle, for example) to see how quickly these signals travel from distant parts of the body to the brain.
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