The path to a diagnosis of multiple sclerosis can be a long and uncertain one. For some people, years may elapse between experiencing the first symptoms and receiving a definitive MS diagnosis. Waiting to see whether the disease flares or progresses after a first episode is an unfortunate aspect of the process for many people. Other conditions may be suspected or even misdiagnosed before a person is finally diagnosed with MS. Some people have multiple chronic conditions, making it difficult for doctors to identify which is causing MS-like damage.
How is MS diagnosed?
MS is very difficult to diagnose. There is no one conclusive test that proves MS. Instead, there are three main criteria, all of which must be present to diagnose MS:
Some people who have damage (also called a lesion) visible in scans in only one area of the CNS may be diagnosed with clinically isolated syndrome (CIS) if they have exhibited MS symptoms, or radiologically isolated syndrome (RIS) if they have a lesion but no MS symptoms. People with a diagnosis of CIS may be regularly checked for new lesions and may even be treated with disease-modifying therapy (DMT) to prevent progression, but they have not yet been diagnosed with MS.
Tests and what they show
Some tests can provide proof of MS-like damage, while others are performed to rule out other conditions.
The doctor will take a thorough history, asking about symptoms over time, family medical history, birthplace, and possible exposures to toxins or infections. A clear picture may emerge from the medical history that will help a doctor assess risk factors that may strengthen the suspicion of MS or rule out other conditions.
The doctor will carefully examine your eyes and reflexes for signs of nerve damage. You will be asked to move your arms and legs in specific ways to test for weakness or lack of coordination. The doctor will test for loss of sensation by touching various parts of your body with a vibrating tuning fork, or sharp or dull items. The neurological exam provides an objective assessment of signs and symptoms that may suggest MS or another condition.
Magnetic resonance imaging (MRI)
MRI is one of the most valuable tools used in studying MS, and a reliable source of criteria to diagnose MS. MRI uses a strong magnetic field and radio waves to measure the relative water content in the tissues of the CNS. Some types of MRI incorporate an intravenous injection of gadolinium. MRI scans provide the most detailed view of the CNS available with a noninvasive approach.
Getting an MRI should be painless, but the machine can be very loud. Wear earplugs to protect against ear damage. Be sure to report any metal content in your body – pacemaker devices, orthopedic hardware, shrapnel – to the doctor so they can ensure your safety during the procedure.
MRI scans can show the location, extent, and number of lesions on the brain, spinal cord, and optic nerves. Some types of MRI can differentiate between current inflammation, newer, growing lesions, and older sections of permanent damage. MRI can reveal “silent” damage to the CNS that is not causing symptoms.
Most MS diagnoses are based in part on MRI results over time. After a diagnosis of MS is made, most people continue to receive regular scans to track whether or how quickly the disease is progressing.
Evoked potentials (EP)
The evoked potentials (EP) test measures electrical activity in the brain in response to specific stimuli. During an EP test, wires are placed on the scalp in certain areas. The doctor or nurse will then provide stimuli such as light, sound, or physical sensations as the test records brain activity, checking for areas where electrical conduction is slower due to demyelination. EP tests are usually painless.
EP tests can help confirm MS by revealing the extent and location of lesions that do not produce symptoms and may not be detectable by other tests.
Cerebrospinal fluid (CSF) analysis
The CNS is bathed in a liquid called cerebrospinal fluid, or CSF. CSF cushions and protects the brain and spinal cord, circulates nutrients, and removes waste from the CNS. CSF analysis is a useful tool in diagnosing many neurological conditions.
CSF is collected via lumbar puncture, also called an LP or spinal tap. During a lumbar puncture, you will be asked to lie on your side with your knees pulled up to your chest to create space between vertebrae. The doctor or nurse will clean an area over the spine in your lower back and insert a hollow needle between two vertebrae into the spinal canal, the space where the spinal cord is located. They will draw out a small amount of CSF, then bandage the puncture site.
Lumbar puncture can be painful. Some people have headaches or backaches after the procedure. You may need to lie down for a while after the LP and avoid strenuous activities for the rest of the day.
In most people with MS, CSF analysis will show evidence of elevated levels of IgG antibodies and proteins called oligoclonal bands. In some people with MS, another type of protein created by the breakdown of myelin is also present. Finding these substances indicates an autoimmune condition, but is not conclusive for MS. CSF analysis alone does not constitute criteria to confirm or rule out a diagnosis of MS.
Ruling out other conditions
Dozens of other conditions can produce MS-like symptoms, and all of these must be ruled out in order to confirm MS. The process of ruling out similar conditions is referred to as differential diagnosis. To list just a few, conditions that may resemble MS may include brain tumors; nutritional deficiencies; structural damage to the brain or spinal cord; infections such as Lyme disease, syphilis, and HIV; autoimmune disorders such as lupus or Sjögren’s syndrome; and inherited conditions such as mitochondrial disease and leukodystrophies.
Your doctor may be able to rule many of these conditions quickly based on your medical and family history or simple blood tests. Other disorders may require time and repeated tests before they can be confirmed or ruled out. The presence of other diseases in addition to MS may complicate the differential diagnosis and eventually result in multiple diagnoses.
What is the prognosis for MS?
Multiple sclerosis is very rarely a fatal condition. For the most part, people with MS enjoy similar longevity as people without MS. On average, the lifespan of a person with MS is about seven years shorter than that of other people. Most people with MS die of the same conditions other people die of, such as cancer and heart disease. It is only in very rare, severe cases of MS with very rapid progression that MS is the cause of death.
There is no cure for MS, but it can be treated. In recent years, more than a dozen MS medications have been approved based on clinical evidence that they can reduce the number and intensity of MS flares and slow the progress of the disease.