Periodic Limb Movement Disorder (PLMD) is a movement disorder that occurs during sleep. Approximately 80-90% of patients with Restless Legs Syndrome (RLS) will also have PLMD.
PLMD is characterised by repetitive limb movements during sleep. These movements usually involve the legs; however the arms may also be involved in severe cases. Abnormal limb movements result in daytime tiredness by causing periods of wakefulness during the night (called arousals) and disrupting the brain’s sleep-patterns. The abnormal movements also prevent the brain from transitioning into stages of deep sleep, causing the sufferer to wake feeling tired and unrefreshed. PLMD is also often disruptive for the sufferer’s bed partner.
Episodes of movement occur most commonly in the period soon after sleep-onset, but may not persist throughout the entire night. Both legs are usually affected, however the abnormal movements may occur in only one limb.
PLMD can occur in conjunction with other sleep-disorders, such as narcolepsy, snoring, obstructive sleep apnoea, or REM-behaviour disorders.