Are Nightly Leg Movements Caused by MS...or RLS? |

If you’ve already gone through the complex protocols that lead to an MS diagnosis, you know that an MS specialist is looking for a lot of things.

First, they attempt to identify MS-specific symptoms. You’re asked to rate pain and fatigue, to describe your concerns about balance, function, memory, speech, and other unusual sensations that concern you.

They also review the results of a good number of tests to rule out possible “mimic” disorders such as lupus, vitamin B-12 deficiency, Lyme disease, and other neurological conditions which share many of the same symptoms.

They may also test for other “non-mimic” conditions which may coexist alongside a potential MS diagnosis (this is what they mean by comorbid conditions). These could be concerns like rheumatoid arthritis, carpal tunnel syndrome, or neurological disorders like Parkinson’s disease.

It can be impossible to really know which test is being used to identify which problem (MS? Mimic? Non-MS mimic?).

One thing that you may—or may not—have been tested for are sleep disorders. In fact, you may not have been asked anything at all about your sleep health.

Recent research suggests that it might be time to include surveys about sleep health in those diagnostic tests, as disorders of sleep may be symptomatic of MS, potential mimics, or comorbid conditions.

In particular, data from study results published last spring (April 2019, Neurología) show a meaningful connection between restless legs syndrome (RLS) and MS.¹

What is restless legs syndrome (RLS)?

Restless legs syndrome describes unpleasant sensations in the legs, with an irresistible need to move them.

RLS can happen at any time of day, but is particularly disruptive in the evening as it can often kick in right before or at bedtime.

Nighttime RLS can cause significant discomfort and anxiety and may cause delays in falling asleep or insomnia as a result.

People with untreated RLS also experience excessive daytime sleepiness caused by ongoing sleep loss.

Could RLS be a symptom of MS?

It’s possible. RLS is a neurological problem which might fall into the same category as muscle spasticity when it comes to describing MS symptoms.

The National Sleep Foundation reports that previous research shows that 51 percent of people with MS also meet the diagnostic criteria for RLS based on neurological exam and medical history. RLS is also shown to be associated with higher probability for MS-related disability.²

The difficulty in knowing the different between an MS-related nocturnal leg cramp and RLS might be best resolved through a sleep study.

Could RLS be an MS “mimic”?

It’s not likely, as RLS does not have other key symptoms that are unique to MS, such as muscle spasticity in other parts of the body, speech issues, or memory problems.³

Could RLS be an MS comorbidity?

Should you have both MS and RLS, it’s unlikely they exist independently of one another, given the findings from the National Sleep Foundation noted earlier.

Also, the Neurología study mentioned earlier showed that for those they studied who had both MS and RLS, who had experienced a recent relapse, showed a much higher risk for anxiety, depression, and nerve pain.¹ They also suffered poor measures of sleep quality, fatigue, daytime sleepiness, and quality of life when compared to those people with MS who did not experience RLS.

The researchers concluded that “RLS should be considered in the neurological evaluation of patients with MS; early diagnosis and treatment would improve the quality of life of patients with MS presenting RLS.”

What about other sleep disorders?

Other sleep disorders which can be linked—either as a symptom, a potential mimic, or comorbidity—include:

Sleep apnea
Narcolepsy
Insomnia
Circadian rhythm disorder
Idiopathic hypersomnia

Given these links, it’s not a bad idea to discuss any sleep problems you might have with your MS specialist. They may not have asked about sleep before, but could be inspired to refer you to a sleep lab to identify and treat any related issues. After all, good sleep is critical for disease management and healing.⁴