Overview

Periodic Limb Movements Disorder (PLMD), also known as periodic limb movements in sleep (PLMS), is a sleep disorder characterized by involuntary movement of the legs, which occurs repetitively during the night. These movements are short and appear in clustered episodes. The movements are often accompanied by brief nocturnal arousals, numbering as many as hundreds per night. PLMD patients often complain of insomnia as well as excessive daytime sleepiness, however, most patients are unaware of their condition and are left untreated.

Prevalence: The prevalence of PLMD increases with age, with 5% in young to mid-aged adults, 29% in adults over 50 years of age, and 44% in elderly subjects. PLMD has also been reported in children and adolescence, although the prevalence is currently unknown.

Comorbidity: PLMD often co-occurs with a related disorder, Restless Legs Syndrome (RLS). RLS is characterized by unpleasant sensations in the legs occurring during the relaxed waking state, often just prior to sleep onset. These symptoms are accompanied by an irresistible urge to move or rub the legs in order to alleviate the unpleasant and sometimes painful leg sensations. Symptoms are worse in the evening and at night, often causing sleep disturbance. The prevalence of RLS is estimated to be 10-15% in adults.  Both PLMD and RLS have been associated with several medical conditions, including myelopathies, peripheral neuropathies, diabetes mellitus, anemia, uremia, and other chronic conditions such as chronic lung disease, rheumatoid arthritis, congestive heart failure and essential hypertension. A high incidence of PLMD has been found in children with Attention-Deficit Hyperactivity Disorder (ADHD).

Diagnosis: Physicians may suspect PLMD in patients who complain of insomnia, daytime sleepiness, and from reports by bed partners of repetitive leg kicks during the night. PLMD may be diagnosed by a full night polysomnographic (PSG) recording in the sleep laboratory, with bilateral EMG of the anterior tibialis muscles for the detection of the leg movements.  Based on traditional scoring criteria, periodic limb movements (PLMs) are counted if the movement is 0.5-5 seconds long and the intervals between movements are between 5-90 seconds long, and at least 4 consecutive movements meet these criteria.  Bilateral movements which appear simultaneously are counted as a single movement. The PLM index (PLMI) represents the number of periodic limb movements per hour of sleep.  A diagnosis of PLMD requires an index of at least 5.

Introduction

The KickStrip^® is a novel Periodic Limb Movement (PLM) detector developed by SLP Ltd., Israel. It is a disposable, noninvasive device designed for the diagnosis of patients suspected by their physician or sleep specialist to have PLMD. The device is a miniature electronic device comprised of a strain gauge flex sensor, a CPU with real time software, a chemical display that presents a score in the morning, and a lithium battery (figure 1). For step-by-step instructions, see patient IFU.  The KickStrip is placed along the bottom front of the leg and extends down to the center of the foot to detect the leg movements. It is activated at bedtime by attaching a green gel sticker to the display area.  It is deactivated in the morning, after the device is detached from the leg and the sensor is cut.  Throughout the night, the software collects the data, identifies each PLM episode, counts the number of PLMs and computes the number of PLMs per hour of recording.  The computed score is then designated to one of four possible outcomes: mild, moderate, severe or no PLMD, according to the code in the “Output Report Table” shown below.  The result may be read by removing the green sticker from the display area, AT LEAST ONE HOUR AFTER REMOVAL OF THE DEVICE FROM THE LEG.  To achieve a valid score, the KickStrip must be used for at least three hours of sleep.  In case of a technical malfunction, the display will show “E” for error.     

Note that the computation is based on RECORDING time, rather than SLEEP time, and from measurements from EACH LEG SEPARATELY.  Thus, the result should not be confused with the polysomnography derived PLMI.  However, clinical studies have shown a good correlation (r=0.78 (p<0.001)) between the KickStrip raw score (before categorizing into 4 possible outcomes) and traditional PLMI.

Indications for Use:

The intended use of the KickStrip® is to monitor periodic limb movements during the night.  The KickStrip may be used by the physician as a screening tool for patients suspected to have PLMD, who may require further evaluation such as polysomnography.  For patients known to have PLMD, the KickStrip may also be used as a titrating tool for drug dosing, and/or as a follow-up tool to monitor treatment outcome.

               The KickStrip display is comprised of seven segments shaped

               like the numeral “8”.  Each segment is silvery gray before use. 

               After use, some of the segments turn black, to form one

               of the following configurations, as described in the following

               table:

  Output Report Table

*Classification is based on the “International Classification of Sleep Disorders (ICSD) Diagnostic and Coding Manual” published by the American Sleep Disorders Association (ASDA) 1990, and modified for KickStrip recording time per leg. 

 Interpretation

                  “2” Moderate   PLMD                                      “E” – Error in study

Contraindications, Warnings and Precautions

• Do not be used on sensitive or broken skin. Advise patient to notify a dermatologist if serious skin reaction develops.

• Consider effects of medications, (dopaminergic/antidopaminergic and opiod medications may have a direct effect on PLMD).

• Consider overall medical status of the patient.

• Instruct the patient to avoid use of Alcohol before the test.

• Do not disassemble. No user serviceable parts inside.