Is it MS or ALS? The Differences Between the Symptoms

Similarities and Differences Between Multiple Sclerosis and Lou Gehrig's Disease

Older Black woman rubbing her hands
Getty Images/Jose Luis Pelaez Inc

Because the list of possible symptoms is so long and varied, it is inevitable that there will be some overlap between some multiple sclerosis symptoms and many other diseases and disorders, especially neurological ones. Amyotrophic lateral sclerosis (ALS), also known as Lou Gehrig's disease, is no exception. However, distinct differences in the symptoms of MS and ALS become evident to health care professionals fairly quickly.

The Primary Difference Between MS and ALS

One huge difference in the presentation of these two neurological diseases is that the symptoms of ALS all involve nerves that control voluntary muscle movement, whereas the nerves affected in MS affect both voluntary and involuntary muscle movement. That said, there is more to the story.

Initial Symptoms of ALS and MS

Muscle weakness on one side of their body is the first symptom for 80% of people with ALS. This is usually in the hands (such as trouble writing or picking up tiny objects), shoulder (such as difficulty lifting arms above the head to do tasks like combing their hair or reaching for an object), or feet/legs (usually seen as "foot drop" or difficulty climbing stairs). The other initial ALS symptoms usually involve trouble speaking (dysarthria) or swallowing (dysphagia).

In contrast, the first symptoms usually experienced by people with multiple sclerosis (MS) are often paresthesias (numbness or tingling in extremities) or optic neuritis.

Of course, any of the symptoms of MS can show up first; these two are just the most common.

Similarities (and Differences) in Symptoms of ALS and MS

While the initial presentations of these diseases are different, they share symptoms that are similar, but also subtly different, which include:

Muscle Weakness in Arms and Legs: People with ALS will experience a decline in the strength and ability to use the muscles in their arms and legs.

The muscles actually atrophy, making it difficult to walk — eventually, an assistive device (walker, wheelchair or scooter) will be needed by everyone with ALS. While many people with MS certainly do experience problems walking, this is not universal.

Speech Difficulties: Dysarthria is the most common speech disorder experienced by people with ALS and by people with MS. They may speak slowly, softly, in strange rhythms, or slur their words. Although this can make it difficult to understand their speech, the meaning of what they are saying is normal. In people with ALS, the dysarthria tends to get progressively worse, whereas in MS, it is usually intermittent. In addition, it is usually more severe in people with ALS.

People with MS often have additional symptoms that interfere with communication, such as dysphasia, which are problems understanding or communicating spoken or written words. These are one type of MS-related cognitive dysfunction. People with ALS typically do not experience these types of symptoms.

Although some people with ALS do experience some cognitive dysfunction, these symptoms are usually more subtle.

Read more about cognitive dysfunction that can occur with multiple sclerosis.

Swallowing Problems: People with ALS also commonly experience dysphagia, which means they have difficulty swallowing. This will often progress to the point that a feeding tube or other means of feeding will need to be introduced. While people with MS may also have this symptom, it is usually much less severe and people may not be aware of it, besides occasional swallowing problems that feel like gagging or coughing when eating.

Read more about swallowing problems with multiple sclerosis.

Breathing Problems: When the muscles controlling respiration begin to atrophy, the person with ALS begins to experience problems breathing, as they simply cannot take enough air into their lungs. At some point, many people with ALS will use a device to help them breathe, often starting with noninvasive ventilation — wearing a mask that delivers oxygen. 

Breathing problems also occur in people with MS, but usually not to the same extent — it is extremely rare for MS-related respiratory problems to require breathing assistance. It has been shown that lung function is lower than normal in most people with MS, but most people do not notice it or are only bothered by shortness of breath upon exertion, like when climbing stairs or moving quickly.

Read more about respiratory problems in people with multiple sclerosis.

ALS and MS Symptom Differences

Vision: In ALS, people lose control of voluntary muscle movement, but usually retain the ability to see. In MS, vision can be affected by optic neuritis or nystagmus.

Read more about Optic Neuritis as a Symptom of Multiple Sclerosis and what Nystagmus is.

Sensory Symptoms: Some people with ALS report tingling, also known as paresthesia; however, this is not a common symptom and it usually goes away.

Sensory symptoms are much, much more common in people with MS, as people with MS often experience a range of unpleasant sensory symptoms, such as paresthesias and pain.

Read more about these symptoms:

Bladder and Bowel Symptoms: It is estimated that over 90% of people with MS experience bladder dysfunction, including incontinence, at some point. People with ALS usually do not experience urinary incontinence; however, it is fairly common. Both people with MS and ALS experience constipation, but people with MS are more likely to experience bowel incontinence (diarrhea) than people with ALS.

Read more about these symptoms:

Bottom Line

Because nerves controlling many bodily functions (voluntary and involuntary) are affected in MS, some symptoms of MS and ALS are similar — often rare symptoms of MS are common symptoms of ALS.

If you have a strange symptom that has you worried or impacts your life in a negative way, talk to your neurologist. He or she will probably reassure you that it is just another unpredictable, funky "MS thing" or tell you that there is no connection, but it is nothing to worry about (which usually annoys me).

However, if you are really concerned, your doc can evaluate you to rule out other diseases.

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