Is A Sleep Study Needed to Diagnose Restless Legs Syndrome?

It’s common that people complaining of the symptoms of restless legs syndrome (RLS) are simply prescribed a drug or supplement (vitamin or mineral) treatment to address their situation.

But you might be curious: Could a sleep study identify RLS?

Or maybe the better question is this one: Should a sleep study be used to diagnose RLS?

Movement disorders of sleep

RLS belongs to a larger diagnostic category known as “movement disorders of sleep.” The American Academy of Sleep Medicine (AASM) recognizes five different disorders within this category:¹

Restless legs syndrome

The legs, as described, feel “restless” during periods of stillness, most noticeably at bedtime. The sensations can be slight—a need to move the legs—or profound—burning, buzzing, itching, twitching, kicking. Even though RLS doesn’t technically happen during sleep, it qualifies as a sleep disorder because it prevents sleep onset and can severely disrupt sleep in the middle of the night.

Note: RLS may also be experienced during the day, making it also a general movement disorder unrelated to sleep.

Periodic limb movement disorder

Also known as periodic limb movement disorder, PLMD describes activity in which the legs (and sometimes the arms) move during periods of sleep in distinct patterns. The movements may present as kicking of the feet, pointing and flexing of the toes, or whole limb movements following a distinct “choreography.” People with PLMD may not realize they have this without learning of it through complaints from their bed partners.

Interestingly, 80 percent of people with RLS also experience PLMs.² PLMs, or periodic leg movements, can also occur without fulfilling a full-blown diagnosis of PLMD. PLMs describe all leg movements occurring during sleep. They’re often explained by other reasons (such as awakening from apneas or as a medication side effect).

Nocturnal leg cramps

These may occur for any number of reasons, such as vitamin or mineral deficiencies or a preexisting neurological condition. However, anyone who’s ever experienced even a single “charleyhorse” in the middle of the night can quickly relate to how much these movements—and the movements needed to find relief—can disrupt sleep.

Sleep rhythmic movement disorder

While this happens mostly in children, it can happen to anyone. Body rocking, headbanging, or head rolling describe repetitive movements that can occur at bedtime while drowsy or while fully asleep. These self-soothing behaviors are considered normal unless they disrupt sleep. Then, they qualify as movement disorders of sleep.

Bruxism

You know it as tooth grinding or jaw clenching. Some folks wear bite guards for this. If you’ve ever been told by a dentist you have distinct tooth wear, this may be why. For some, bruxism’s intensity can create a distinct (and unpleasant) noise that keeps others awake. It occurs most often during earlier, lighter stages of sleep.

Can a sleep study identify RLS?

Of course, it can. (This is true for all movement disorders of sleep.) People who experience RLS go to great lengths to describe their subjective experiences. Generally, doctors use this self-reported information to proceed accordingly.

If a patient goes into the clinic for a sleep study to investigate other sleep problems, the test can confirm RLS more objectively. Among all the sensors placed on the body for the test, the long leg “leads” attached to the calf muscles can confirm squirmy leg movement throughout the study. This information is then batched with other information gathered from:

• Electrodes affixed to the scalp to identify sleep stages, and
• belts and breathing measures used to highlight potential sleep breathing disruptions

Together, this data “draws a picture” of your sleep for the sleep doctor, revealing when leg movements are—or aren’t—caused by apneas, seizures, or other culprits.

It’s worth noting here that a home sleep apnea test (HSAT) can’t diagnose RLS. An HSAT’s key test targets are blood oxygen, heart rate, airflow, and respiratory patterns. HSATs don’t measure leg movements.

Should people undergo a sleep study to diagnose RLS?

The sheer cost and undertaking of an overnight sleep study make this unlikely.

Most doctors review medical history, consider current medication use, and ask questions about family history and the severity of daytime sleepiness. They may also ask a patient to keep a sleep diary to capture the length of RLS episodes. In some cases, a blood draw can identify an easily corrected deficiency causing the RLS.³

However, if the doctor suspects something beyond RLS, they may order a test to achieve a differential diagnosis.  Other conditions to rule out include:

• Parasomnias (sleepwalking, REM sleep behavior disorder)
• Sleep apnea
• Neurological concerns (epilepsy, Parkinson’s disease)
• Drug-related side effects

The chances are good, however, that most people complaining of RLS won't need a sleep study.