What is the method for grading the severity of Periodic Limb Movements in Sleep (PLMS)?

From the Guidelines

To grade the severity of periodic limb movements of sleep (PLMS), calculate the Periodic Limb Movement Index (PLMI) by dividing the total number of limb movements by total sleep time in hours, with a PLMI of 5-24 considered mild, 25-49 moderate, and 50 or more severe, as suggested by recent clinical practice guidelines 1. When assessing PLMS, it's crucial to consider not just the frequency but also whether the movements cause arousals and if they correlate with symptoms like daytime sleepiness or insomnia. The severity grading helps determine whether treatment is necessary, with more aggressive interventions typically reserved for moderate to severe cases that cause sleep disruption or daytime symptoms. Key points to consider in grading PLMS severity include:

• The frequency of limb movements per hour of sleep
• The presence of arousals associated with these movements
• The correlation of PLMS with symptoms such as daytime sleepiness or insomnia
• The use of polysomnography to record these movements, which typically appear as repetitive leg jerks lasting 0.5-5 seconds and occurring in sequences of 4 or more movements separated by intervals of 5-90 seconds. Medications like dopamine agonists (pramipexole, ropinirole), gabapentin, or clonazepam may be considered for symptomatic cases based on severity, as per the American Academy of Sleep Medicine clinical practice guidelines 1.

From the Research

Grading Severity of Periodic Limb Movements of Sleep

To grade the severity of periodic limb movements of sleep (PLMS), several factors and methods can be considered:

• The periodic limb movement index (PLMI) is a key measure, which represents the number of periodic limb movements per hour of sleep 2.
• Polysomnography (PSG) is a crucial diagnostic tool for assessing PLMS, as it provides objective measurements of sleep and movement patterns 2, 3.
• The International Classification of Sleep Disorders (ICSD-2) separates sleep-related movement disorders into categories, including simple, repetitive movement disorders like PLMS 3.
• The American Academy of Sleep Medicine has developed practice parameters for the dopaminergic treatment of restless legs syndrome and periodic limb movement disorder, which include recommendations for grading severity and treating PLMS 4.

Assessment and Grading

The severity of PLMS can be assessed based on:

• The frequency and intensity of periodic limb movements during sleep, as measured by PLMI 2.
• The presence of symptoms such as restless legs syndrome, nocturnal leg jerks, and sleep disturbances 5, 2.
• The impact of PLMS on sleep quality, daytime functioning, and overall health 2, 6.
• The response to treatment, including dopaminergic agents like levodopa, pergolide, pramipexole, and ropinirole 5, 6, 4.

Limitations and Future Directions

While there are established methods for assessing and grading PLMS, there are limitations to the current evidence:

• The predictive value of demographics, symptoms, and clinical history is modest, highlighting the need for objective measures like PSG 2.
• The clinical importance of elevated PLMI values continues to evolve, and further research is needed to fully understand the implications of PLMS 2.
• The development of standardized scoring rules and clinical guidelines for PLMS is ongoing, with efforts to improve the reliability and validity of assessments 3, 4.