Estimated reading time: 6 minutes
Medically reviewed and verified by Kate Burke, MD, MHA
Multiple sclerosis (MS) is an autoimmune disease that affects the central nervous system (CNS). In the United Sates alone, almost 1 million people were diagnosed with the condition in 2019. In MS, the body’s immune system attacks nerve fibers, disrupting their ability to send signals. This can lead to a wide range of symptoms, like muscle weakness, trouble walking, fatigue, vision problems, and cognitive issues. MS mostly affects women and is commonly diagnosed between the ages of 20 and 40, but it can happen at any age. The exact cause is unknown! Researchers think that genetic and environmental factors, as well as potential viral infections, may contribute. There are several categories of MS based on its clinical presentation, progression, and the presence or absence of disease activity. The classification of MS phenotypes helps guide diagnosis, prognosis, and treatment decisions.
Here is a breakdown from PatientsLikeMe.
The Central Nervous System
The CNS is our information processing center. It is made of two parts: the brain and the spinal cord. The brain controls thoughts, movements, emotions, and body functions like breathing and heart rate. It processes information and sends commands to different parts of the body. The spinal cord is the communication highway, relaying messages between the brain and the rest of the body. It allows for movement, sensation, and reflexes to function. Bones, membranes, and cerebrospinal fluid protect both the brain and spinal cord.
How MS Affects the Nervous System
The nervous system is a complex network that controls every function in the human body. MS disrupts the nervous system’s ability to send signals efficiently by attacking a part of the body called the myelin sheath. The myelin sheath is a fatty layer that wraps around our nerve cells. It lets electrical impulses travel along the nerves. Without this protective layer, nerve signals slow down or become completely blocked. This leads to impaired movement, sensation, and coordination.
The Different Categories of MS
MS can live in the body in a few different forms. Each of them affects you in unique ways! There are three main types to know.
Relapsing-Remitting MS (RRMS)
RRMS is the most common form, affecting about 85% of all people with the condition. It is called relapsing-remitting because people with RRMS have episodes where symptoms get worse (relapsing) followed by periods where the symptoms improve (remitting). The severity of these relapses can vary. Eventually, some might transition to another form of MS called secondary-progressive MS over time.
Secondary-Progressive MS (SPMS)
SPMS is a phase of MS that follows an initial relapsing remitting course of RRMS. SPMS can be further categorized into active (with relapses or MRI activity) and non-active (without relapses or MRI activity) forms. This distinction is crucial for treatment decisions, as active SPMS may respond to disease-modifying therapies, whereas non-active SPMS typically may not.
Some common symptoms of SPMS are bowel and bladder issues, difficulty walking, fatigue, numbness, issues with learning or memory, and vision problems.
Primary-Progressive MS (PPMS)
PPMS affects between 10-15% of all patients with the condition. Like SPMS, this form is progressive, meaning it gets worse over time. There are a few key differences. The first is that SPMS develops after someone has RRMS, while PPMS is an initial diagnosis. Usually, people with PPMS also do not have distinct periods of relapses or remissions. Their symptoms just get progressively worse over time. This can happen quickly or slowly depending on the person. PPMS also has two types, active and non-active.
On the whole, doctors generally diagnose PPMS later than SPMS and leads to worse symptoms. People affected tend to experience issues with balance, mood changes, muscle weakness, tremors, cognition and vision. Difficulty walking is more common, as spinal cord lesions are found more often in PPMS than brain lesions. Of note, PRMS (Progressive-Relapsing MS) was initially defined as a progressive disease from onset with clear acute relapses, with or without full recovery, and periods between relapses characterized by continuing progression. However, the term PRMS has been largely eliminated in recent classifications. The 2013 revision by an international consensus group recommended dropping the term PRMS and reclassifying these patients under PPMS if they exhibit relapses or under secondary progressive MS (SPMS) if they initially had a relapsing-remitting course.
Related Conditions
Two additional syndromes are also included in the MS classification scheme because they may represent early stages of the disease spectrum and are critical for early diagnosis and intervention.
- Clinically Isolated Syndrome (CIS): CIS is when a person has a single episode of neurological symptoms lasting at least 24 hours that could be MS but does not meet the criteria for an official diagnosis. MS has multiple episodes, so a single event does not qualify someone for a diagnosis.
- Radiologically Isolated Syndrome (RIS): Here, a person might not have any symptoms! However, an MRI of the brain and spinal cord identifies an MS type lesion before the MS is clinically apparent. Close monitoring and early intervention may prevent or delay the onset of clinical symptoms. Two years after an initial MRI scan, doctors diagnose about one third of patients with RIS with MS.
MS and its forms are complex because of how varied the symptoms are and how hard it is to diagnose. Understanding the different types and how they impact the nervous system can help you make better decisions about your health! There is ongoing research and regular advancements in treatment. People living with MS today have more options than ever to manage their symptoms and live a fulfilling life.
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