As people usually ignore the cause of their daytime impairments, PLMS during sleep are mostly found through laboratory examination rather than clinical complaints.Video-Polysomnography may be recommended to distinguish PLMS from other leg movements during sleep time which may be similar to PLMS when it comes to duration and pattern. Measures from PSG allocated to the diagnostic of PLMD are essentially based on electromyography (EMG) measuring muscle activity. EMG electrodes are usually placed on anterior tibialis muscle.Recent studies showed actigraphy may be combined to PSG as a screening tool for PLMD diagnosis. Actigraphs are watch-shaped devices - usually worn by adult population on the wrist - used to record sleep and wake periods for at least a week. Recent actigraphy devices allow more precise recordings which helps evaluating if actual movements meet diagnostic criteria for PLMD. Recent studies showed actigraph records reflect quite accurately PLMI criterion.Crucial for the diagnosis are the inter-movement intervals and the frequency of PLMS - each movement must happen within a 4 to 90 second interval from the previous movement. The periodic limb movement index (PLMI), which corresponds to the number of periodic limb movements per hour, must be more than 15 movements per hour in adults and 5 movements or more per hour in children.
The diagnosis of PLMD requires a visible cause-effect relationship between PLMS and an observed sleep disturbance or daytime impairment (both disturbance and impairment have to be clinically significant).Other relevant causes of Insomnia and Hypersomnia have to be ruled out before diagnosing PLMD (most importantly anxiety, obstructive sleep apnea, and narcolepsy). Furthermore, symptoms can not be better explained by any other conditions.For the differential diagnosis it is important to differentiate PLMD from other leg movements during sleep, which are high-frequency:
alternating leg movement activity (ALMA) are very similar events and could be mistaken for PLMS
hypnagogic foot tremor (HFT) events are also very similar to PLMS and could be misdiagnosed
excessive fragmentary myoclonus (EFM) events are shorter than PLMS

Classification
PLMD is classified in the third edition of the International Classification of Sleep Disorders (ICSD-3) which presents current sleep disorders nosology. ICSD-3 is divided in 7 sections and PLMD is classified in the Sleep-Related Movement Disorders section. There are some updates from ICSD-2. The diagnosis is more strict. A simple complaint is no longer enough: a significant clinical impairment is needed. Sleep impairments need to be clearly caused by PLMS and the symptoms also need to be explained solely by the PLMS. Treatment
PLMD can be effectively treated with dopaminergic agents (pramipexole, ropinirole, cabergoline, and rotigotine) and it has been found that patients with a low ferritin level respond well to oral iron supplements.