Multiple sclerosis (MS) is a debilitating disease that most often affects women. The onset of MS usually occurs in the third or fourth decade of life. It involves episodic and localized autoimmune attacks on the myelin sheath of the central nervous system (CNS) neurons. As such, it is classified as a demyelinating disease.
The loss of myelin’s insulation slows conduction through the affected neurons, resulting in dysfunction. The clinical manifestation of the dysfunction depends on the location of the demyelination.
For example, if there is demyelination of an optic nerve, the patient may suffer unilateral visual loss. If demyelination occurs in the spinal cord, they may suffer paresis. If the demyelination occurs in Broca’s area (left frontal lobe), they may exhibit aphasia.
What is the pattern of disease in MS?
Symptoms of MS can be extremely varied, depending on where the areas of demyelination occur within the nervous system. Symptoms usually present as a rapidly progressive loss of a specific function followed by a gradual improvement. After a period of months to years, the patient will experience another attack. The pattern consisting of a loss of function followed by improvement repeats. Each attack tends to occur in another region of the nervous system.
The disease causes demyelination to occur in different areas at different points in time. The patient will experience an attack in one region of the CNS, recover to some degree, and then have another attack in a different location.
Multiple sclerosis can follow various patterns, but most commonly involves periods of disease activity known as relapsing periods and periods of disease quiescence known as remitting periods. In other words, MS is generally relapsing and remitting in nature. Attacks occur during the relapsing periods; improvements and neurological stability occur during the remitting periods.
During the remitting phases, signs and symptoms may go away altogether, or they may persist at a lower intensity. Over time, many patients with MS fall into a progressive variation of the disease where there is less improvement during remission periods and accumulating signs and symptoms from continued relapses.
When should you consider MS as a possible diagnosis?
A definitive diagnosis of MS—particularly early on—can be challenging. Clinical and paraclinical evidence, such as magnetic resonance imaging (MRI), evoked potentials, and lumbar punctures, are generally combined to build a case to explain the combination of multiple neurological syndromes occurring in different areas of the CNS at different times.
Signs and symptoms of MS
There are seven signs and symptoms that are common with MS:
- Regions of definitive sensory loss
- Visual disturbances (such as double vision or loss of vision)
- Definitive weakness (related to a specific region of the CNS)
- Hemiparesis or paraparesis
- Loss of coordination (such as ataxia or dysmetria)
- Bladder dysfunction
You should consider MS if any of these symptoms are present for more than 24 hours but eventually subside.
Differential diagnosis for MS
When you are considering MS as a diagnosis, many other differentials must be considered:
- Lyme disease
- Vitamin B12 deficiency
- Acute disseminated encephalomyelitis
- Cerebral vascular diseases
- Various tumors
- Human immunodeficiency virus (HIV)
- Mitochondrial diseases
- Transverse myelitis
- Paraneoplastic syndromes
- Cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL)
- CNS vasculitis
What should you do if you suspect MS?
If you suspect that your patient has MS, ask about a history of any previous neurological events involving flare-ups and remissions that affected other areas of the nervous system. In particular, the events should have occurred in totally different regions of the CNS with totally different symptoms. There should be a history of more than 30 days between separate neurological events.
Note that optic neuritis (unilateral, painful loss of vision in an eye) is often an early neurological manifestation of MS. As well, ask the patient if hot baths or showers make symptoms worse. Known as Uhthoff’s phenomenon, this is common in individuals with MS.
Perform a thorough neurological exam by looking for evidence of definitive neurological dysfunction elsewhere in the nervous system, in addition to dysfunction related to the current symptoms. For example, look for residual left hemiparesis in addition to the new symptom of acute visual acuity loss.
Additional testing for diagnosing MS
Magnetic resonance imaging
If you are concerned about MS in a patient who has sustained a new, isolated, neurological syndrome, order magnetic resonance imaging (MRI) of the brain with and without contrast. On a T2 MRI, look for scattered spots of high signal in the white matter. These spots may partially enhance, but they do not have to enhance on a post-contrast T1 MRI.
Keep in mind that these spots are not diagnostic for MS by themselves, nor are they conclusive for demyelination in the affected region. Multiple small areas of high signal in white matter regions (particularly near the ventricles) can add to the suspicion of MS, but in no way confirm the diagnosis.
A lumbar puncture is sometimes used to support the diagnosis of MS since certain laboratory parameters may be abnormal in these patients. But, there is currently no definitive biomarker for the disease.
There are five lumbar puncture findings that are typical of MS patients:
- Normal opening pressure
- Normal or mildly elevated cerebrospinal fluid (CSF) protein
- Elevated immunoglobulins
- Less than 20 mononuclear cells / µL
- The presence of oligoclonal bands
Oligoclonal bands on electrophoresis indicate concentrations of certain types of immunoglobulins that are not normally found in the CSF. These are not diagnostic for MS, but if elevated, are highly suggestive of a more aggressive progression of the disease.
The McDonald Criteria for diagnosing MS
A definitive diagnosis of MS is often made using the McDonald Criteria, which is a list of diagnostic criteria that is readily available online. The McDonald Criteria looks for evidence of CNS damage disseminated in time and space, combining clinical (history and findings of neurological deficits) and MRI evidence (CNS damage) to make the diagnosis.
Depending on the patient’s presentation, various combinations of evidence are used to make the diagnosis. In a recent revision of the McDonald Criteria, oligoclonal bands in the CSF was added as an indicator of ongoing CNS injury.
There you have it! Use the information here to help you evaluate the possibility of MS in your patient. Then, if you strongly suspect MS, seek neurology input for a definitive diagnosis.
That’s it for now. If you want to improve your understanding of key concepts in medicine, and improve your clinical skills, make sure to register for a free trial account, which will give you access to free videos and downloads. We’ll help you make the right decisions for yourself and your patients.
- 2017 McDonald MS Diagnostic Criteria. National Multiple Sclerosis Society. https://www.nationalmssociety.org/For-Professionals/Clinical-Care/Diagnosing-MS/Diagnosing-Criteria
- Louis, ED, Mayer, SA, and Rowland, LP. 2015. Merritt's Neurology. 13th Edition. North York: Wolters Kluwer.
- Luzzio, C, and Dangond, F. 2020. Multiple Sclerosis. Medscape Neurology. https://emedicine.medscape.com/article/1146199-overview
- Multiple Sclerosis Centers of Excellence. Kurtzke Expanded Disability Status Scale. U.S. Department of Veterans Affairs. https://www.va.gov/MS/Professionals/diagnosis/Kurtzke_Expanded_Disability_Status_Scale.asp
- Thompson, AJ, Banwell, BL, Barkhof, F, et al. 2018. Diagnosis of multiple sclerosis: 2017 revisions of the McDonald criteria. Lancet Neurol. 17: 162-173. PMID: 29275977