Restless Legs Syndrome (RLS) and Periodic Limb Movement Disorder (PLMD) are two common physical sleep disorders, affecting tens of millions of people. Both conditions lead to movement of the legs. Neither condition has a full explanation for why it occurs. Yet, both conditions are adequately treated with low doses of specialized medications.
RLS is the condition in which:
While lying or sitting, uncomfortable or difficult to describe sensations occur in the back of the calves (or other spots on the leg or arms), so unpleasant you notice an urge to move your body
Movement of the legs, arms or body eliminates the feeling
The sensation returns when you stop moving
The sensation intensifies during the evening or bedtime.
The feelings prevent sleep or make it difficult to stay asleep.
So RLS is a waking condition. It occurs prior to sleep; whereas…
PLMD is a sleeping condition in which:
Legs jerk or twitch rhythmically (periodically) during the night
The leg jerk may be small and barely noticeable, occurring in the ankle or involving dramatic motions in the whole body.
Each movements lasts a few seconds or less
The movements occur in repeating cycles, say once every 30 seconds, with cycles usually ranging in the 30 to 90 second time frame.
The movement may or may not provoke an arousal, that is, speeding up the brain waves while you’re sleeping.
The impact of PLMD on sleep is controversial, but it produces enough disruption in some sleep-disordered breathing (SDB) patients to prevent CPAP use, and it may disrupt sleep in patients without SDB.
If you have RLS, there’s a high chance you have PLMD during sleep. Those with PLMD have a 50% chance of also suffering RLS.
Both conditions are quite real. At their worst, RLS drives a person into a state of mental instability, because it is so harrowing to not know what’s going on or how to stop it. RLS is easily missed, because so few physicians are aware of it, and patients think it a weird complaint. The patient endures it for years and compensates in various ways. The most disabling problem is staying up later and later, so total sleep declines.
Many with RLS use drugs or alcohol to sleep, which often compounds the problem. Many physicians have prescribed sedatives or antidepressants for these patients without ever “hearing” about the leg movement part of the sleep complaint. Sedatives are fairly weak treatments for RLS in comparison to well-researched treatments. Antidepressants produce or aggravate RLS or PLMD symptoms.
Leg Jerks and Sleep-Disordered Breathing
The great controversy about RLS and PLMD is their relationship to SDB. Many patients with RLS and PLMD also suffer from SDB, especially upper airway resistance events. In sleep studies in some of these patients, recent research shows that the movement occurred at the end of a UARS event. Remarkably, when these patients received PAP therapy, their leg jerks decreased as air pressure normalized breathing.
These SDB findings indicate some people’s conditions mimic but are not true leg movement disorders. This conundrum requires patience to sort out at a sleep center. If we see PLMD in an SDB patient, we are reluctant to treat the legs until we’ve treated the breathing. But, if the patient also complains of RLS, then the leg jerks are more suspicious. Then we could start medication before the first night of PAP therapy, so that when next tested in the lab, we determine whether the drug decreased leg jerks. Usually, if the patient reports the drug decreased RLS, the sleep test confirms the leg jerks decreased, too.
The most important consideration in SDB cases is whether RLS or PLMD interfere with PAP therapy. In those with clear-cut cases of restless legs or leg jerks, then the proper medication transforms their use of PAP therapy. You will be surprised to know which medication achieves these dramatic results, and you already know it is not sedatives.
Fortunately, a single drug from several choices treats either or both RLS or PLMD. In severe cases, a patient may use two medications or alternate drugs. The list of available drugs is growing longer with increasing research and interest in movement disorders.
The most tested and established medications include:
Vitamin and mineral effects are implicated in RLS or PLMD:
Iron storage, measured by Ferritin levels, are low in some patients
Magnesium supplements have been tested with mixed results.