What is periodic limb movement disorder (PLMD)?
Periodic limb movement disorder (PLMD) is a condition that was
formerly called sleep myoclonus or nocturnal myoclonus. It
isdescribed as repetitive limb movements that occur during
sleep and cause sleep disruption. The limb movements usually
involve the lower extremities, consisting of extension of the big
toe and flexion of the ankle, the knee, and the hip. In some
patients, the limb movements can occur in the upper extremities as
well.
The limb movements occur most frequently in light non-REM sleep.
The repetitive movements are separated by fairly regular intervals
of 5 to 90 seconds. There can be significant night-to-night
variability to the frequency of limb movements.
What causes PLMD?
The exact cause of PLMD is unknown. However, several medications
are known to make PLMD worse. These medications include some
antidepressants, antihistamines, and some antipsychotics.
Many individuals have periodic limb movements in sleep (PLMS).
This is observed in about 80 percent of patients with restless legs
syndrome (RLS). PLMS can occur in over 30 percent of people aged 65
and older and can be asymptomatic. PLMS are very common in patients
with narcolepsy,REM behavior disorder, and Parkinson's
disease.
True PLMD -- the diagnosis of which requires periodic limb
movements in sleep that disrupt sleep and are not accounted for by
another primary sleep disorder including RLS -- is uncommon.
What are some of the symptoms of PLMD?
Most patients are actually not aware of the involuntary limb
movements. The limb jerksare more oftenreported by bed
partners. Patientsexperience frequent awakenings from sleep,
non-restorative sleep, daytime fatigue, and/or daytime
sleepiness.
How do I know if I have PLMD?
The diagnosis is based on the clinical history as well as an
overnight polysomnogram (PSG).This is a test that records
sleep and the bioelectrical signals coming from the body during
sleep. A thorough neurological examination should be performed.
Respiratory monitoring during the PSG allows one to rule out the
presence of sleep disordered breathing as a cause for the disrupted
sleep and excessive muscle activity. Occasionally, additional sleep
laboratory testing is useful. Blood work may be ordered to check on
iron status, folic acid, vitamin B12, thyroid function, and
magnesium levels.
Who gets PLMD?
PLMD has been less extensively studied than RLS. The exact
prevalence is unknown. It can occur at any age; however, the
prevalence does increase with increasing age. Unlike RLS, PLMD does
not appear to be related to gender.
As with RLS, some medical conditions are associated with PLMD.
These include uremia, diabetes, iron deficiency, and spinal cord
injury.
How is PLMD treated?
First,certain products and medications should be
avoided.Caffeine often intensifies PLMD symptoms.
Caffeine-containing products such as chocolate, coffee, tea, and
soft drinks should be avoided. Also, many antidepressants can cause
a worsening of PLMD in many patients and should be reviewed,
discussed and replaced by your doctor.
Generally, there are several classes of drugs that are used to
treat PLMD. These include the Parkinson's disease drugs,
anticonvulsant medications, benzodiazepines, and narcotics. Current
treatment recommendations consider the anti-Parkinson's
medications as a first line of defense. Medical treatment of PLMD
often significantly reduces or eliminates the symptoms of these
disorders. There is no cure for PLMD and medical treatment must be
continued to provide relief.