How is Multiple Sclerosis diagnosed?
Due to the wide range of symptoms it causes- sometimes similar to other conditions- and the multiple ways in which they can present, Multiple Sclerosis (MS) may be difficult to diagnose. Therefore, several strategies need to be used by doctors to determine if a patient meets the criteria for an MS diagnosis and discard other conditions [1-2].
Multiple Sclerosis diagnosis is based on a clinical evaluation to fully document the symptoms (e.g. difficulty controlling the bladder, tingly sensations, double vision, etc.) and signs (e.g. hyperactive reflexes, incoordination, weakness of specific muscles, abnormal eye movements, etc.) of the disease .
MS diagnosis requires the presence of two distinct episodes of symptoms- lasting at least 24 hours and separated by one or more months- and two or more signs evident on the neurological examination and involving two or more separate parts of the brain and spinal cord [1-2].
If there are fewer than two abnormal signs on the neurologic exam, diagnostic tests can facilitate Multiple Sclerosis diagnosis. Mostly, no single test can definitely prove that a patient has MS after a first episode of symptoms or in the very early stages of the disease. Nevertheless, some tests that could help to diagnose the disease include [1-2]:
To rule out other conditions causing similar symptoms, such as AIDS or Lyme disease.
Magnetic resonance imaging (MRI)
A technique using a powerful magnetic field and radio waves to obtain cross-sectional images of the brain and spinal cord where small areas of inflammation and scarring in the brain, which occur in MS, could be detected.
It should be noted that, even though MRI scans can be helpful in MS diagnosing, they are not always conclusive, especially in the early stages of the disease. Therefore, they should always be considered together with the symptoms and physical evaluation.
Evoked potentials: test that measures the electrical response of the central nervous system (CNS) to a stimulus (e.g. checkerboard pattern of light and dark squares alternated on a television monitor for visual evoked potential, click sounds applied through earphones for brain stem auditory evoked potentials, etc.) using electrodes applied to the scalp. A slowing or abnormal pattern in the electrical impulses in certain nerves suggests a nerve malfunction probably due to myelin damage. In about 70-90% of patients clinically diagnosed with Multiple Sclerosis, these tests are abnormal. Evoked potentials often detect other abnormalities not apparent on neurological examination. Moreover, as these tests measure function within the brain or spinal cord, they complement the information about the brain structure provided by MRI.
Lumbar puncture: analysis of a sample of cerebrospinal fluid (CSF, liquid that cushions the brain and spinal cord) to evaluate abnormalities occurring in patients with MS. CSF is removed by inserting a needle, under local anesthetic, into the lower part of the back. These CSF alterations, detected in 80-90% of MS patients, include an increase in the number of cells and proteins of the immune system (immunoglobulins), suggesting an inflammation or an intense immune response. This test is useful to diagnose patients experiencing a slowly progressive decline in function with no exacerbation (i.e. patients with primary progressive MS) in absence of abnormalities on the brain MRI scans. Evaluation of the spinal fluid may also help to exclude infections difficult to distinguish from Multiple Sclerosis.
1. In: http://www.nationalmssociety.org/What-is-MS. Accessed 25/01/2017.
2. Rolak LA. Multiple Sclerosis: It’s Not The Disease You Thought It Was. Clin Med Res. 2003; 1(1): 57-60.