Multiple sclerosis (MS) is an unpredictable disease that comes in several distinct forms. The four main types of multiple sclerosis are clinically isolated syndrome (CIS), relapsing-remitting MS (RRMS), secondary progressive MS (SPMS), and primary progressive MS (PPMS). Other classifications exist as well for rarer forms of the disease.
This article will look at how MS is diagnosed, expand on the different types and how each one progresses, and explain what the outlook is like for the different types of MS.
How Is MS Diagnosed?
MS is difficult to diagnose. Each case involves a unique set of symptoms that may be similar to a host of other illnesses.
It is an autoimmune disease. The immune system mastakes myelin, a coating on your nerves, for a dangerous invader, like a virus. It then attacks and tries to destroy it. The attack leads to damage—called demyelination—and inflammation in the central nervous system (CNS, brain and spinal nerves), which leads to lesions. Lesions cause MS symptoms.
They’re also part of the diagnostic process. Under guidelines called the McDonald criteria, MS is diagnosed if you have:1
Two lesions in different parts of the CNS
Damage of various ages
No evidence of another condition that could be responsible
To determine if you meet the criteria, healthcare providers use:
Neurological exam: This checks your coordination, strength, reflexes, and nerve function through various exercises.2
Evoked potentials testing: Electrodes on your scalp track how your nerves respond to different stimuli, such as flashing lights and physical sensation.3
Magnetic resonance imaging (MRI): Magnetic waves produce detailed images of your brain and spinal cord. An injected contrast material lights up lesions.4
Lumbar puncture (spinal tap): Cerebrospinal fluid is removed from your spinal column and examined in the lab for oligoclonal bands, which are proteins related to inflammation in the CNS.5 Cerebrospinal fluid is a watery liquid that flows in and around your brain and spinal cord. It cushions these delicate structures to protect them from injury, removes waste from the CNS, and helps the CNS work properly.
Your doctor may also order bloodwork, imaging, and other tests depending on specific symptoms to rule out other conditions.
Recap
MS is an autoimmune condition that's hard to diagnose. Healthcare providers use neurological exams, nerve testing, an MRI, a lumbar puncture, and other tools to reach a diagnosis.
Types of MS
The four main forms of MS were defined in 1996 by the National Multiple Sclerosis Society. The organization based its on survey responses from specialists in MS treatment and research.
Based on new knowledge from research, the definitions were updated in 2013. The diagnostic criteria continue to be refined as well. The most recent update was in 2017.
Clinically Isolated Syndrome
Clinically isolated syndrome is somewhat of a “pre-MS” diagnosis. CIS is diagnosed if you have:
A single episode of MS-like symptoms that lasts for 24 hours or longer
Symptoms not related to an infection, fever, or another illness
Symptoms caused by CNS inflammation or demyelination (myelin loss)
Some people with CIS never have another attack. If an MRI doesn’t find a lesion, you have a low likelihood of developing MS. However, if an MRI does detect an MS-like lesion, you’re very likely to eventually have more episodes and be diagnosed with relapsing-remitting MS.
The 2017 diagnostic guidelines update allows CIS to be diagnosed as MS if there’s evidence of prior lesions, which may not have caused symptoms. This allows for earlier diagnosis and treatment, which may delay the onset of full-blown MS.
In-Depth: Clinically Isolated Syndrome
Relapsing-Remitting MS
Relapsing-remitting MS is the most common type. About 80%–85% of MS cases are initially diagnosed as RRMS.6
This type features clearly defined attacks (relapses) or new or worsening neurological symptoms separated by remissions—periods of partial or complete recovery.
Symptoms may all disappear during remissions, or some may continue while others recede. The disease doesn’t have any apparent worsening during remissions.
In-Depth: Relapsing-Remitting MS
Secondary Progressive MS
Some people with RRMS will eventually transition to this more severe type. Secondary progressive MS gets progressively worse, regardless of remissions.
Some people with SPMS continue to have relapses and remissions, but not all do. And the remissions tend to include more symptoms than in RRMS.
If RRMS isn’t treated, about 50% of the time it’ll progress to SPMS within a decade.6
In-Depth: Secondary Progressive MS
Primary Progressive MS
PPMS involves steadily worsening disease and two additional criteria from the following:
A brain lesion typical of MS
Two or more similar lesions in the spinal cord
Evidence of immune system activity in the CNS, including oligoclonal bands and an elevated IgG index
PPMS generally involves more spinal cord lesions and fewer brain lesions than RRMS.
Compared with White people, Black people with MS appear to have a more severe disease course and lab results that reveal a worse prognosis. Researchers have called for further investigation into this to help guide treatment and meet the special needs Black people may have.8
Other Types of MS
Some forms of MS are rare, and some are even controversial. They include:6
Progressive-relapsing MS: This type steadily worsens from onset but with symptom flares and possibly remissions. This being used less as more is learned about the disease.
Fulminate, malignant, or Marburg MS: This type is rapidly progressive, with severe relapses in the first five years. People with this type of MS may need more aggressive treatment than other types.
Inactive or benign MS: In this type, the condition changes very little or not at all for 15 years. However, it may become active again later. This is a controversial diagnosis, and the definition isn’t universally agreed upon, with some experts not believing in it.
Burned-out MS: This is a controversial term for MS with progression that slows significantly later in life and is considered inactive.
Radiologically isolated syndrome (RIS): This is another possible “pre-MS” diagnosis. It's used when an MRI shows evidence of MS lesions, but the person has had no symptoms. More than half of people with RIS will develop MS in the following decade.9
Recap
CIS is often a pre-MS diagnosis. It can be diagnosed after just one episode. RRMS is the most common type and includes symptoms that come and go. It sometimes transitions to SPMS, which is steadily more disabling and may include milder relapses. PPMS is steadily disabling from the beginning. Other types of MS are rare or controversial.
Facts About MS Progression
MS is an unpredictable disease. No one can say for sure how severe your symptoms will become or how quickly the disease will progress.
As your MS progresses, your healthcare providers may talk about where you fall on the Expanded Disability Status Scale (EDSS). The EDSS goes from 0 to 10 in 0.5-unit increments. Higher numbers mean greater disability. A score of 10 means the person died from MS.
EDSS Scores Level of Disability
0-4.5 Able to walk without aid
5-9.5 Require mobility aids to walk
The EDSS evaluates you based on MS-related impairment in eight functional systems. Each functional system is a network of neurons in the brain that’s associated with certain tasks.
The functional systems include:10
Muscle weakness, difficulty moving limbs
Poor balance and coordination, tremor, loss of control of bodily movement
Problems with speech, swallowing, and abnormal eye movements (nystagmus)
Numbness or reduced sensation
Bowel and bladder dysfunction
Vision problems
Thinking and memory deficits
With modern diagnostics and treatments, most people never reach the higher scores. In one large study, 51% of people scored 5 or lower, and 88% had a score of 7 or lower.11
To put that in perspective:12
A score of 5 means disability is severe enough that you can’t perform full daily activities or work a full day without special provisions; you can walk without aid or rest for 200 meters.
A score of 7 means that you are restricted to a wheelchair, but you can get yourself in and out of the chair and wheel yourself around.
Only 12% of people with MS progress beyond this to the point of needing to be pushed in a wheelchair, being confined to bed, being totally dependent on others for care, or dying from MS.11 Advancements in treatments and diagnostics will likely keep more people out of the higher numbers in the future.
Recap
The progression of MS is unpredictable. The Expanded Disability Status Scale is used to rate levels of disability. Thanks to modern treatments, most people never reach the highest levels.
Outlook by Type of MS
Clinically Isolated Syndrome
If you have CIS, one of three things can happen:
It remains an isolated incident and you never develop MS.
You develop RRMS.
You develop RRMS that progresses to SPMS.
A 2018 study using a model to simulate the course of CIS looked at rates of transition from one stage to the next in 10-year increments. At 10 years post-CIS diagnosis:13
Almost 36% hadn’t had a second episode.
About 48% had developed RRMS.
About 15% had progressed to SPMS.
At 50 years post-CIS diagnosis:13
Only 0.5% had never had a second episode.
About 12% had RRMS.
Nearly 70% had SPMS.
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Relapsing-Remitting MS
RRMS is most often diagnosed in people between 20 and 40 years old. The transition to SPMS generally happens at least 10 years after diagnosis.
The most common symptoms of RRMS include:
Fatigue
Numbness
Vision problems
Muscle spasticity or stiffness
Bowel and bladder problems
Cognitive problems affecting learning, memory, and information processing
RRMS is less likely than progressive forms to cause problems with walking.
According to a 2017 study, the life expectancy of someone with RRMS is between six and seven years shorter than that of the general population.14 However, that number may shrink due to newer treatments and improved diagnostics.15
Secondary Progressive MS
Once you’ve progressed to SPMS, you may or may not continue to have relapses. In people who don’t, it’s because the disease process changes. Instead of being primarily driven by inflammation, as RRMS is, it becomes more about progressive nerve damage.16
About 50% of people diagnosed with RRMS transitioned to SPMS in the first 10 years. That number jumped to 90% in 25 years. Many experts believe newer medications will help lower those numbers, but it’s too soon to tell.16
More than two-thirds of people with SPMS retain the ability to walk. But some may need an assistive device like a cane or walker.17
Recent studies haven’t looked at the life expectancy for people with SPMS. Most sources estimate it at between seven and 14 years less than the general population.18
Primary Progressive MS
Symptoms of PPMS tend to be associated with movement more often than the other types. This is because of progressive degeneration of the spinal cord, also called progressive myelopathy.
That can cause:
Clumsiness and lack of muscle coordination
A spastic gait (how a person walks), with legs that stiffen and jerk
Weakness or immobility on one side of the body
Impaired sexual, bowel, and bladder function
The 2017 study estimated that life expectancy for someone with PPMS is about six years less than for someone with RRMS and about 13 years less than the general population. Again, newer drugs may significantly change this number in the future.15
Factors Affecting Prognosis
Factors that can suggest you may have a faster disease progression include:18
Being over age 40 at symptom onset
Having more than two attacks in the first two years
Having early symptoms that affect urinary control, mobility, or mental function
Having early symptoms in several areas of your body
Having frequent relapses
Having many lesions in the brain or brainstem at diagnosis
Scoring higher than 1.5 on the EDSS after your second relapse
Recap
Your outlook depends on what type of MS you have. Most cases of CIS eventually progress to RRMS and possibly SPMS. RRMS generally transitions to SPMS after at least a decade. About two-thirds of people with SPMS retain the ability to walk, some with mobility aids. PPMS involves more spinal cord degeneration and movement problems.
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