ALS vs MS: Know The Difference

I was diagnosed with multiple sclerosis in my early twenties. It didn’t take long for me to realize that a lot of people, particularly in my own age group, had no idea what MS entailed. Once my diagnosis was official, I gathered some buddies together over a few beers to break the news.

A lot of people get MS and ALS confused

After the shocked expressions, misty eyes, and hugs, we settled in for some drinking and some discussion about my new condition. After a while, one of my good friends commented to me “I know you man, I bet the fact that it’s named after a Yankee is eating at you some, at least it’s not named for someone from the Mets.”

Mind you, I grew up in a suburb of Philadelphia, where we are pretty fanatical about our sports teams. I respond with “yea...wait, what?” To which he replied, “you know, the Lou Gehrig’s jawn”. I then explained that was ALS and I had MS. My friend’s confusion really isn’t that strange, a lot of people get MS and ALS confused, and rightly so, as there are some similarities between the two. I thought I’d take a moment and talk about the similarities and differences between these two diseases.

An overview of MS

Because you are visiting an MS website, I’m going to assume you have a little knowledge about multiple sclerosis. MS is an autoimmune and neurodegenerative disease that causes your immune system to attack the insulative layer (known as myelin) that surrounds the nerves in your body.

When this layer of insulation is damaged, signals from our brain to other parts of our body may not get to where they are supposed to go, or they may arrive late. That myelin layer is critical in how efficiently those electrical signals travel along the nerves. This is similar to a phone charging cord that has some of the wire damaged: it’ll still charge, if it’s in just the right spot, otherwise, it may charge slower or it may not charge at all.

MS is usually characterized by the scarring/hardening it causes along the nerves in your brain and spine. That scarring/hardening is where we get the word “sclerosis”. MS can cause a wide range of symptoms including spasms, fatigue, muscle weakness, trouble walking, cognitive dysfunction, pain, and many more, which you probably already know.

While MS can affect your ability to move, it can also impact your senses, bladder control, speech, emotions, and mental health. MS is unpredictable and can vary widely from person to person. Some people may only ever have minor symptoms, while others may progress quickly and severely. MS is rarely a death sentence, however, it has been known to happen. MS is more common in women than men.

A look at ALS

Amyotrophic Lateral Sclerosis, ALS, or sometimes referred to as Lou Gehrig's disease is a progressive neurodegenerative disease that affects the nerve cells in the brain and the spinal cord. You’ll notice some similarities with MS in that it affects the brain and spinal cord. You’ll even notice the word “sclerosis” again.

Like MS, there is some scarring/hardening around the nerve cells with ALS. Early on in MS, some symptoms may also be the same, like muscle weakness, fatigue, spasms, and trouble walking. There are big differences though. While MS attacks the insulation around the nerves, ALS breaks down the actual nerve cells, specifically those known as motor neurons.

These nerve cells are responsible for movement in your arms, legs, face, and even your diaphragm (which is critical to breathing). The myelin layer hardens once those nerve cells are destroyed. While that myelin layer is still hardened, there’s a huge difference between MS and ALS, because, in MS, the nerve cells are still intact, they simply aren’t as effective at conducting signals because of the damage to myelin. With ALS, the nerve cells are destroyed, making communication between the brain and the affected areas of the body impossible.

ALS is extremely progressive, leading people to rapidly deteriorate and become completely debilitated and paralyzed; while that can happen with MS, that is the exception, not the norm. ALS will eventually cause patients to be unable to swallow or breathe on their own.1 ALS is so progressive that most patients are given a time from between three to five years before they pass due to complications with this disease.2 ALS is more common in men than women.

Let's break these two conditions down.

With so many similarities, particularly early on, how do doctors tell them apart? Early on, it often becomes a case of trying to rule out one condition versus the other. Here are some diagnostic methods and the differences in how ALS and MS present.

Type of symptoms

While some symptoms are similar, others only belong to MS. ALS really only has symptoms that affect movement, so, for example, if someone experiences vision-related issues, then they know it’s more likely that MS is the cause and not ALS.


MRIs are a very good tool for determining the difference between ALS/MS as that hardening/scarring will show up early on in MS, whereas in ALS, that won’t be apparent until after the nerve is already dead. So if someone is having symptoms that are common between the two diseases, an MRI is a good way of eliminating ALS.

Electromyography or EMG

This test measures how fast your nerves conduct electricity. If ALS is the cause, doctors will see patterns on an EMG that indicate that.

Nerve conduction study

A test where they measure the ability and velocity of the nerves to conduct signals.4  If ALS is considered the culprit, they will run these tests on upper and lower limbs to see if there is a problem with the nerves. Electrical shocks are sent through the nerves and the responses are recorded. This test is focused particularly on muscles that involve movement, so while some patterns may point to ALS, they may not rule out MS. 5

Evoked potentials

An evoked potential test is extremely similar to a nerve conduction study, wherein the clinician is looking at how the nerves conduct electricity. The big difference here is that it is looking at sensory nerves. Instead of shocks being sent through, sensory stimuli like sounds or images are used to trigger a response. The results of this test are a good way to determine MS vs ALS because these areas would not be affected by ALS.

Lumbar puncture (spinal tap)

A lumbar puncture (spinal tap) is another good tool in determining the difference between MS vs ALS as the results can indicate whether the cause is an inflammatory condition like MS, and subsequently rule out ALS.

Feel free to share your own research and insight into these two conditions in the comments. I'm eager to hear about your experience.

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This article represents the opinions, thoughts, and experiences of the author; none of this content has been paid for by any advertiser. The team does not recommend or endorse any products or treatments discussed herein. Learn more about how we maintain editorial integrity here.

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