What is periodic limb movement disorder?
Periodic limb movement disorder (PLMD) involves repetitive
episodes of muscle movements that usually occur in the legs. The movements are
described as a jerking motion or an upward flexing of the feet. The movements
happen about every 20 to 40 seconds and occur in clusters lasting from minutes
to a few hours.
PLMD is considered a sleep disorder when these movements disrupt
sleep and lead to daytime effects such as sleepiness. Most children and
adolescents with PLMD are unaware that these movements are taking place.
Many children and adolescents with PLMD may also experience
restless legs syndrome – – another movement disorder in which the child or
adolescent reports an uncomfortable sensation and irresistible urge to move his
or her legs when awake. This urge usually happens in the evenings around
bedtime but can occur at other times when the legs have been inactive, such as
when sitting still for a long period of time (eg, during long car rides or while
watching a movie).
What causes PLMD?
The exact cause of this disorder is not known. Scientists think
PLMD may be related to a low iron level or problems with limb nerve conduction
due to diabetes or kidney disease. Though not necessarily a cause, the following
are all thought to "influence" or increase the risk of PLMD:
- Restless legs syndrome
- Caffeine
- Side effects of some medications including antidepressants (eg,
tricyclic antidepressants and SSRIs [selective serotonin reuptake
inhibitors]), dopamine-receptor antagonists (eg, some anti-nausea drugs),
lithium and some anticonvulsants
- Other sleep disorders such as narcolepsy (a sleep disorder involving
overpowering urge to sleep during waking hours) and sleep-related eating
disorder.
- Neurodevelopmental and genetic disorders, including attention deficit
hyperactivity disorder (ADHD) and William’s syndrome
- Spinal cord injury/spinal cord tumor
What are the signs and symptoms of PLMD?
Symptoms of PLMD include:
- Leg movements. Repetitive leg movements in one or both legs are the
classic sign of PLMD. Remember, though, that the child or adolescent
experiencing PLMD may be unaware of his or her leg movements since they
occur during sleep.
- Sleep disruption/restless sleep. The frequent leg movements cause
disturbed sleep and multiple awakenings. These awakenings are brief and
termed "arousals." They can be easily missed by the onlooker but captured on
a sleep test by EEG (brain wave) analysis.
- Daytime sleepiness, behavior and school performance problems. The
sleep disruption may cause daytime drowsiness. Many times, children will not
appear sleepy but rather they may manifest this as irritability,
hyperactivity, and impulsivity.