Periodic Limb Movement Disorder
Periodic Limb Movement Disorder
Periodic limb movement disorder (PLMD), also called nocturnal myoclonus, is the sudden, involuntary jerking of a muscle or group of muscles in the arms or legs.
In its simplest form, PLMD consists of a muscle twitch followed by relaxation . An example of PLMD is the jerks or “sleep starts” that some people experience while drifting off to sleep. Periodic limb movements in sleep are repetitive movements, most typically in the lower limbs, that occur about every 20–40 seconds. These movements occur as brief muscle twitches, jerking movements, or an upward flexing of the feet. They cluster into episodes lasting anywhere from a few minutes to several hours. PLMD is similar to restless legs syndrome (RLS) but is classified as a separate disorder. Approximately 80% of people with RLS have PLMD, though most people with PLMD do not experience RLS. Restless legs syndrome (RLS) is a neurological disorder characterized by unpleasant sensations in the legs and an uncontrollable urge to move when at rest in an effort to relieve these feelings. RLS sensations are often described by people as burning, creeping, tugging, or like insects crawling inside the legs. Often called paresthesias (abnormal sensations) or dysesthesias (unpleasant abnormal sensations), the sensations range in severity from uncomfortable to annoying to painful.
The incidence of PLMD increases with age. It is estimated to occur in 5% of people age 30 to 50 and in 44% of people over the age of 65. As many as 12.2%of patients suffering from insomnia and 3.5% of patients suffering from excessive daytime sleepiness may experience PLMD. Approximately 80% of people with RLS have PLMD, though most people with PLMD do not experience RLS. Men and women are equally affected by PLMD.
Causes and symptoms
The exact cause of PLMD is unknown. Some researchers suggest PLMD is caused by reactions in the brain, while others suggest it might originate in the spinal cord. It may also be associated with circulatory problems . PLMD is often seen in patients with kidney disease, metabolic disorders, rheumatoid arthritis , pregnancy, or circulatory problems. A person with PLMD is usually unaware of the repetitive motion or the accompanying brief awakenings that disrupt sleep. Thus, people who have PLMD usually complain of difficulty in falling asleep, staying asleep, or staying awake during the day. They may also note restless sleep, hot or cold feet, or hair wearing off their legs. Bed partners often report being kicked, fighting for bed covers, or being awakened by the movements. Limb movements can be severe enough to wake an individual from sleep, making it difficult to stay asleep for a significant duration and leading to excessive sleepiness during the day. Many patients who suffer from excessive daytime sleepiness do not know they are being aroused from sleep by periodic limb movements because they do not actually wake up. Rather, they will feel as though they have not slept well. These arousals can occur anywhere from five times an hour up to more than 50 times an hour, depending on the severity of movement.
Periodic limb movement disorder appears to be related to the following factors or conditions, although researchers do not yet know if any of these factors actually cause PLMD:
- People with low iron levels or anemia may be prone to developing PLMD. Once iron levels or anemia is corrected, patients may see a reduction in symptoms.
- Chronic diseases such as kidney failure, diabetes, Parkinson's disease, and peripheral neuropathy are associated with PLMD. Treating the underlying condition often provides relief from PLMD symptoms.
- Certain medications—such as anti-nausea drugs (prochlorperazine or metoclopramide), anti-seizure drugs (phenytoin or droperidol), anti-psychotic drugs (haloperidol or phenothiazine derivatives), and some cold and allergy medications—may aggravate symptoms. Patients can talk with their physicians about the possibility of changing medications.
QUESTIONS TO ASK YOUR DOCTOR
- How does PLMD differ from restless legs syndrome?
- What treatment options do I have?
- If I don't receive treatment, will my symptoms worsen?
- Is PLMD an indication that other diseases or disorders are present?
- Are there any new treatments in development that may be available soon?
In most cases, the cause of PLMD is unknown (idiopathic). A family history of the condition is seen in approximately 50 percent of such cases, suggesting a genetic form of the disorder. To diagnose PLMD, leg movements are recorded during sleep. Sensors placed over the calf muscle record the number of leg movements during each hour of sleep. This is called the periodic limb movement index. If this index is greater than or equal to five, which means leg movements occurred at least five times an hour, then the diagnosis of PLMD is made. Despite these efforts to establish standard criteria, the clinical diagnosis of PLMD is difficult to make. Physicians must rely largely on patients' descriptions of symptoms and information from their medical history, including past medical problems, family history, and current medications. Patients may be asked about frequency, duration, and intensity of symptoms as well as their tendency toward daytime sleep patterns and sleepiness, disturbance of sleep, or daytime function. If a patient's history is suggestive of PLMD, laboratory tests may be performed to rule out other conditions and support the diagnosis of PLMD. Blood tests to exclude anemia , decreased iron stores, diabetes, and kidney dysfunction should be performed.
Generally, there are three classes of drugs that are used to treat PLMD and RLS. These are benzodiazepines , Parkinson drugs, and narcotics. Medical treatment of PLMD often significantly reduces or eliminates the symptoms of these disorders,
though not always. There is no cure for PLMD, and medical treatment must be continued to provide relief. Clonazepam is the most commonly employed benzodiazepine treatment. It is effective in many cases, but not all, and it usually causes drowsiness or sedation. Sometimes, clonazepam allows the patient a better, more restful night's sleep without affecting the occurrence of limb movement. Patients with PLMD may have other sleep disorders , such as obstructive sleep apnea, which the use of clonazepam could worsen. The drugs used to treat Parkinson's disease are also very effective against PLMD. These include, L-dopa/carbidopa, bromocriptine (which suppresses the excretion of prolactin), pergolide, selegiline, and ropinirole (Requip). If either benzodiazepines or Parkinson's medications do not relieve symptoms, then narcotics, such as codeine, oxycodone, methadone, and propoxyphene are sometimes used.
Idiopathic —Describes a disease or disorder that has no known cause.
Neurological —Referring to the structure and function of the nervous system.
Nocturnal —Occurring at night.
Restless legs syndrome —A neurological disorder characterized by unpleasant sensations in the legs and an uncontrollable urge to move when at rest in an effort to relieve these feelings.
Rheumatoid arthritis —A chronic disease of joints that causes stiffness, swelling, weakness, loss of mobility, and leads to damage and eventual destruction of the joints.
Sleep apnea —A temporary cessation of breathing during sleep.
There is no known connection between PLMD and diet or nutrition . Vitamin and mineral supplements have shown to have some success in treating PLMD. However, this treatment has not been proven clinically. Vitamin E may alleviate PLMD symptoms if poor peripheral circulation is the cause.
There is no known therapy associated with periodic limb movement disorder.
PLMD is generally a lifelong condition for which there is no cure. Symptoms may gradually worsen with age, though more slowly for those with the idiopathic form of PLMD than for patients who also suffer from an associated medical condition. Nevertheless, current therapies can control the disorder, minimizing symptoms and increasing periods of restful sleep. In addition, some patients have remissions, periods in which symptoms decrease or disappear for days, weeks, or months, although symptoms usually eventually reappear. A diagnosis of PLMD does not indicate the onset of any other neurological disease.
For those with mild to moderate symptoms, prevention is key, and many physicians suggest certain lifestyle changes and activities to reduce or eliminate symptoms. Decreased use of caffeine , alcohol, and tobacco may provide some relief, in addition to significant general health benefits. Physicians may suggest that certain individuals take supplements to correct deficiencies in iron, folate, and magnesium. Studies also have shown that maintaining a regular sleep pattern can reduce symptoms. Some individuals, finding that PLMD symptoms are minimized in the early morning, change their sleep patterns. Others have found that a program of regular, moderate exercise helps them sleep better; on the other hand, excessive exercise has been reported by some patients to aggravate PLMD symptoms. Taking a hot bath, massaging the legs, or using a heating pad or ice pack can help relieve or prevent symptoms in some patients.
If the care giver is the sleeping partner of the person with PLMD, they may be the first to notice symptoms. Bed partners may be awakened by restlessness or limb movement by their partner. When symptoms of PLMD are noticed, the care giver should encourage their partner to seek medical attention for diagnosis and treatment.
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Canadian Neurological Sciences Federation, 7015 Macleod Trail S.W., Suite 709, Calgary, AB, Canada, T2H 2K6, (403) 229-9544, (403) 229-1661, info@cnsfederation. org, http://www.ccns.org.
Ken R. Wells