Diagnosing Multiple Sclerosis

MS is a clinical diagnosis—there is no one test that will confirm diagnosis. Rather, diagnosing MS is a combination of clinical assessment and results from additional testing. For MS, these additional tests include evoked potentials, MRI, and lumbar puncture.

Evoked Potentials

Evoked potential tests measure electrical activity in certain areas of the brain in response to stimulation of specific sensory nerve pathways. These tests are often used to help make a diagnosis of MS, because they can indicate dysfunction along these pathways that is too subtle to be noticed by the person or to show up on neurologic examination. In people with MS, dysfunction is caused by the destruction of myelin—the fatty sheath that surrounds and protects nerve fibers in the central nervous system. Demyelination causes the nerve impulses to be slowed, garbled, or halted altogether, producing the symptoms of MS.

In order to measure evoked potentials, wires are placed on the scalp over the areas of the brain being tested. The examiner then provides specific types of stimulation, and records the person’s responses. Evoked potential testing is harmless, painless, and very sensitive in detecting lesions—or damaged areas.

Three Main Types of Evoked Potential Tests

1. Visual Evoked Potentials (VEP): The patient sits before a screen on which an alternating checkerboard pattern is displayed.
2. Brainstem Auditory Evoked Potentials (BAEP): The patient hears a series of clicks in each ear.
3. Sensory Evoked Potentials (SEP): Short electrical impulses are administered to an arm or leg.

It usually takes about two hours to do all three types of evoked potentials. A neurologist or neurophysiologist interprets the results.

While evoked potentials are used to help make a diagnosis of MS, other conditions also produce abnormal results, so the tests are not specific for MS. The information the tests provide needs to be considered along with other laboratory and clinical information before a diagnosis of MS can be made.

MRI

Magnetic resonance imaging (MRI) uses computer technology to produce very sharp images of selected body parts without using x-rays by relying on radiofrequency waves and strong magnetic fields. Your physician may order an MRI of the brain, cervical, or thoracic region in order to further evaluate your condition. MRI is the preferred method of imaging to help establish a diagnosis of MS. Demyelination, or the destruction of myelin (the fatty sheath that surrounds and protects nerve fibers), causes nerve impulses to be slowed or halted and produces the symptoms of MS.

Lumbar Puncture

Lumbar Puncture (LP), also known as a spinal tap, evaluates the cerebral spinal fluid (CSF), which is a clear, colorless liquid that bathes the central nervous system. While the primary function of CSF is to cushion the brain within the skull and serve as a shock absorber for the central nervous system, CSF also circulates nutrients and chemicals filtered from the blood and removes waste products from the brain. Examining the fluid can be useful in diagnosing many diseases of the nervous system, including MS. CSF is obtained by doing a lumbar puncture.

The CSF of people with MS may contain elevated levels of IgG antibodies, as well as a specific group of proteins called oligoclonal bands. Occasionally there are also certain proteins that are the breakdown products of myelin. These findings indicate an abnormal autoimmune response within the central nervous system, meaning that the body is producing an immune response against itself.