Restless Legs Syndrome and Related Periodic Leg Movements of Sleep: Tips and Tools for Proper Screening and Diagnosis



Restless Legs Syndrome and Related Periodic Leg Movements of Sleep: Tips and Tools for Proper Screening and Diagnosis


Rachel E. Salas

Russell J. Rasquinha

Charlene E. Gamaldo



Restless legs syndrome (RLS) is a sensorimotor condition that can be experienced by both adults and children. Th ough broadly described as an “urge to move the legs,” RLS is a clinical condition based on fulfillment of four essential criteria (Table 6.1). In severe cases, significant sleep disruption can occur and sufferers may be at increased risk for developing several comorbid medical and psychiatric conditions. Periodic limb movements of sleep (PLMS) are a series of stereotypical limb movements and are common objective findings associated with RLS. However, PLMS can also be found in association with other sleep disorders and medical conditions. PLMS can cause significant sleep disruption alone or in combination with clinical symptoms associated with RLS. Th ough individuals with RLS often (81.0% of cases) discuss their symptoms with their primary care physician, their condition is rarely (6.2% of cases) recognized as RLS by their providers (1). Th us, RLS remains an underdiagnosed and undertreated condition. However, one of the biggest diagnostic challenges of RLS is that a variety of conditions, such as cramps, positional discomfort, and local leg pathology, can superficially satisfy all four diagnostic criteria for RLS and thereby “mimic” RLS. Definitive diagnosis of RLS, therefore, requires exclusion of these specific conditions, which may be more common in the population than true RLS. Th is chapter seeks to provide an overview and useful tools proven to be effective in screening and diagnosing individuals with RLS. Topics to be covered include definition and diagnostic criteria, diagnostic evaluation, differential diagnosis, classification, epidemiology and demographics, and overall health impact of RLS and PLMS.


RESTLESS LEGS SYNDROME (DEFINITION AND DIAGNOSTIC CRITERIA)

Restless legs syndrome (RLS) is a disorder that is defined by four essential diagnostic criteria. To fulfill all four essential criteria, the patient must endorse experiencing uncomfortable sensations (usually in the legs) associated with an urge to move that peaks in severity at night and improves almost immediately with movement. The essential criteria for diagnosis of RLS as defined by the International RLS Study Group (IRLSSG) (2) and the National Institutes of Health (NIH) are listed in Table 6.1.


RLS in Children

The RLS diagnosis is clinical and thus relies on the patient to report an accurate history. Th is poses a problem for children, who may be less equipped at articulating their symptoms, and likely results in RLS often being underdiagnosed in the pediatric population. Children with RLS can also present with a unique set of symptoms as compared to their adult counterparts (Table 6.2). For this reason, specific criteria for diagnosing RLS in the pediatric population have been established.









TABLE 6.1 Essential Criteria for Diagnosis of Restless Legs Syndrome







  1. Urge to move the legs



  2. Urge to move begins or worsens when sitting or lying down



  3. Urge to move is partially or totally relieved by movement



  4. Urge to move is worse in the evening or night than during the day or only occurs in the evening or night









TABLE 6.2 Restless Legs Syndrome Criteria in Children





































Definite RLS


1.

Meets essential criteria for RLS


2.

Child reports (in their own words) descriptors consistent with leg discomfort (i.e., oowies, tickle, spiders, boo-boos, want to run, energy in legs)

OR

2.

Supportive criteria are met (minimum 2 of 3)




  1. Sleep disturbance for age



  2. A biologic parent or sibling has definite RLS



  3. The child has a polysomnographically documented periodic limb movement index of 5 or more per hour of sleep.


Probable RLS


1.

A biologic parent or sibling has definite RLS


2.

Meets essential criteria for RLS

OR

2.

Behavioral manifestations of lower extremity discomfort when sitting or lying (such as rubbing the legs), accompanied by motor movements of the affected limbs (characteristic of essential criteria 2-4)


Possible RLS


1.

The child has periodic limb movement disorder.


2.

The child has a biologic parent or sibling with definite RLS, but the child does not meet definite or probable childhood RLS definitions.


RLS, restless leg syndrome.


Adapted from Simakajornboon N, Kheirandish-Gozal L, Gozal D. Diagnosis and management of restless legs syndrome in children. Sleep Med Rev 2009 04/01;13(2):149-156.



PERIODIC LIMB MOVEMENTS IN SLEEP

Periodic limb movements in sleep are a series of stereotypical limb movements that are observed on a polysomnogram (PSG).



  • The diagnostic criteria for PLMS are used to calculate the PLMS index, which represents the number of periodic limb movements per hour.


  • The PLMS index indicates the clinical severity of PLMS. According to the guidelines set by the American Academy of Sleep Medicine (AASM) (4), a PLMS index of greater than 15 in adults and greater than 5 in children is considered clinically significant.


  • Any PLMS index below 15 in adults is not clinically significant, because they can be frequently encountered in the general population and do not usually result in sleep complaints or excessive daytime sleepiness (EDS) (5). Table 6.3 shows the criteria used to assess PLMS on a PSG. Figure 6.1 visually demonstrates the scoring criteria for a periodic limb movement series.









TABLE 6.3 Criteria Used to Indicate a Periodic Leg Movements as per the AASM Scoring Manual









  1. Leg movements (LMs) must be repetitive and must occur in a sequence of 4 or more.



  2. Each LM starts when the electromyography (EMG) of the anterior tibialis has crossed 8 mV above resting and ends when the EMG dips below 2 uV above baseline.



  3. Each LM must be between 0.5 and 10 sec in duration.



  4. Each LM occurring within 0.5 sec before or after a respiratory event such as an apnea and/or hypopnea is considered to be associated with the respiratory event and is not counted.a



  5. An arousal and a LM should be considered associated with each other when there is less than 0.5 sec between the end of one event and the onset of the other event, regardless of which is first.



  6. A periodic leg movement series is defined by at least 4 consecutive LM events (see Fig. 6.1 ), where the minimum period length is 5 sec between LMs and the maximum period length is 90 sec.



  7. LMs on different legs separated by less than 5 sec between LM onsets are counted as a single leg movement.


a LMs associated with respiratory events typically improve following therapy for the associated respiratory disorder (such as positive airway pressure for sleep apnea).



DIAGNOSTIC EVALUATION: TIPS AND TOOLS BEYOND THE FOUR ESSENTIAL CRITERIA

RLS is a condition established solely on the presence of four essential criteria. However, establishing the diagnosis strictly based on these criteria yields a specificity of 84% with an estimated positive predictive value of 40% (6). For instance, although symptoms primarily occur in the legs, approximately 50% of patients also report restlessness in the arms (7); and individuals with severe symptoms even report sensations in the trunk and/or face. RLS has even been reported to affect the phantom limb of amputees (8). The diagnostician must also consider the verbal and comprehensive capabilities of the adult patient during the RLS assessment. For instance, older adults with early to moderate dementia may be unable to understand and reliably answer questions related to a RLS diagnostic evaluation. Th erefore, older persons with mild to moderate dementia and sleep disturbance may require adjunctive objective diagnostic tools to help identify RLS (9). Th us, attempting to accurately diagnose RLS based on the four criteria can often exclude those who have the condition yet include those, upon further assessment, who do not. Th is section, therefore, presents additional tools, as summarized in Table 6.5, shown to increase the specificity of RLS diagnosis. Validated questionnaires such as the Johns Hopkins Telephone Diagnostic Interview (JH-TDI), which incorporates many of the strategies listed in Table 6.5, have shown increased positive predictive value over the four criteria (10).


Rule 1: Ask Additional Questions Regarding RLS Characteristics

During the clinical assessment, adjunctive questions allowing for further description of the patient’s symptoms can be invaluable. The clinician should remain aware of the fact that progression of RLS, RLS augmentation, or a possible RLS variant can complicate the presentation in some patients (11). One study of a series of RLS cases has also characterized a potential RLS variant called quiescegenic nocturnal dyskinesia (QND), which shares considerable overlap with RLS and should be considered when evaluating for RLS. Individuals with QND present with all of the diagnostic criteria of RLS except for the presence of excessive involuntary leg

movements when resting in the evening or before sleep onset without any related uncomfortable sensations or urge to move the legs (12).






FIGURE 6.1 How to score a periodic limb movement series.








TABLE 6.4 Additional Characteristics Unique to Restless Leg Syndrome in Relation to the Four Diagnostic Criteria







  1. An urge to move the legs




    • always in the legs but may also involve upper extremities, trunk, and/or face



    • may be described as a “creepy crawly feeling” or “internal itch”



    • may be described as “painful” in 50% of patients



  2. The urge to move begins or worsens when sitting or lying down




    • examples: sitting in a car, at the movies, in a conference, on a plane flight, or sitting at a desk



    • no specific body position causes symptoms (i.e., crossing the legs)



  3. The urge to move is partially or totally relieved by movement




    • usually immediately or soon after movement begins



    • symptoms should not recur while actually moving



    • symptoms may recur soon after movement has stopped



    • counter stimulus (i.e., rubbing legs, hot/cold baths) serve as alternative to movement



  4. The urge to move is worse in the evening or night than during the day or only occurs in the evening or night




    • sensory symptoms associated with the “urge to move” have a circadian pattern with worsening or onset in the evening or at night



    • symptom occurrence and severity peak late evening or middle of night



    • protective, relief period in the morning



Rule 2: Evaluate for Supportive Medical History

Evaluating for a supportive medical history, which includes a family history of RLS, response to medication, and history of conditions known to be associated with RLS (see Table 6.10), will assist in making the diagnosis and aid in classifying RLS as primary or secondary (see Classification section).


Rule 3: Rule Out RLS Mimics

It is important to consider the several conditions that mimic RLS symptoms, particularly with relation to the “feeling in the legs,” in the diff erential diagnosis (6) (Table 6.6) as the management may differ from that of RLS. Several disorders can present with symptoms similar to RLS; however, a careful history (see Tables 6.4 and 6.5) will reveal
that the diagnostic criteria are not met and therefore the RLS diagnosis cannot be made. Th is will then prompt further evaluation for other etiologies on the differential.








TABLE 6.5 Tools/Supportive Features for Accurate Restless Leg Syndrome Diagnosis beyond the Essential Criteria





Adjunctive questions on clinical features


Johns Hopkins Telephone Diagnostic Interview


Medical history (i.e., iron deficiency anemia)


Positive family history of RLS


Improvement with dopaminergic therapy (such as carbidopa/levodopa)


Evaluating and ruling out mimics (see Table 6.6 )


Presence of PLMS


Identifying potential RLS aggravators









TABLE 6.6 Differential Diagnosis for Restless Leg Syndrome (including Restless Leg Syndrome Mimics)





Leg cramps


Peripheral neuropathy


Radiculopathy


Arthritis


Chronic back pain


Positional discomfort


Pronounced or frequent unconscious foot or leg movements (habitual foot tapping, leg shaking)


Local leg injury/arthritis


Positional ischemia (numbness)


Sleep transition phenomena (e.g., hypnic jerks)


General nervous movements


Varicose veins


Painful legs and moving toes


Claudication


Vesper’s curse (transient nocturnal cord stenosis)


Periodic limb movement disorder



Rule 4: Assess for Potential Symptom Aggravators

Finally, when assessing RLS severity and when considering potential treatment options, it is important to assess patients for possible RLS aggravators. These are listed in Table 6.7.


Rule 5: Pursue Relevant Objective Markers

In certain situations, a clinician may also choose to pursue a work-up aimed at uncovering more objective markers related to RLS. For example iron deficiency is prevalent in 25% of RLS cases, with some cases of RLS completely resolving upon successful repletion of iron stores (13). For that reason most RLS experts recommend that a fasting iron profile be performed on all potential sufferers (Table 6.8) (11). In addition, based on the patient’s history and physical findings, the clinician may consider evaluating for other potential etiologies known to be associated with RLS
(Table 6.8). For instance, 48% of patients with low-density lipoprotein have RLS (14) and approximately 21% of RLS sufferers have concurrent diabetes (15).








TABLE 6.7 Potential Aggravators





Nicotine


Antidepressants (especially selective serotonin reuptake inhibitors)


Central-acting antihistamines


Alcohol


Dopaminergic antiemetics


Antipsychotics


Sleep deprivation


Over-the-counter cold medications









TABLE 6.8 Serum Evaluation for Restless Legs Syndrome





























All Patients: Evaluate for Iron Deficiency (level suggests iron deficiency)a

Optional (Based on Clinical Presentation): Evaluate for Potential Underlying Etiologies


Serum iron (<60 μg/dL)

Thyroid studies


Ferritin (<45 mcg/L)

Autoimmune studies (i.e., ANA, ESR)


Percent iron saturation (<16%)

Vitamin studies (i.e., folate, vitamin B12)


TIBC >400%

Neuropathy screen

Vascular studies

Renal studies

LDL


a Iron panel should be ideally performed on a fasting serum sample.



“TO DO OR NOT TO DO A POLYSOMNOGRAM”

If the diagnosis of RLS is complicated by coexisting diseases such as a chronic pain syndrome or kidney disease, a polysomnogram may help validate the presence of PLMS and hence RLS. Even in a patient with RLS symptoms, one must exclude other sleep disorders like sleep apnea if the patient demonstrates the appropriate risk factors and symptoms such as snoring and excessive daytime sleepiness. If there are concerns about the cause of actual sleep disruption in the face of what appears to be minimal RLS symptoms, then a PSG may help to define the sleep disruption as related to PLMS (therefore RLS) or not to PLMS (therefore not RLS). If, following adequate treatment of RLS sensory symptoms, the patient still has sleep disruption, a PSG should be considered. In the condition of periodic limb movement disorder (PLMD), the only way to make the diagnosis is with a PSG. PLMD is a diagnosis of exclusion and should be made if the patient only reports excessive daytime sleepiness and does not meet the diagnostic criteria for RLS.1


EVALUATING FOR PRESENCE OF PLMS IN RLS

RLS sufferers may often experience involuntary leg movements in association with their sensory symptoms and demonstrate increased periodic limb movements in wakefulness (PLMW) on PSG or suggested immobilization tests (SIT) (16), and 80% of patients with RLS will demonstrate a PLMS index greater than 15. For that reason, demonstration of increased leg activity by virtue of a PSG or with research tools such as leg activity meters (17) or SIT (18) can provide additional supportive evidence if needed.



  • The SIT has been developed in the research setting to serve as a measure of RLS severity and to assist in the diagnosis. The sensitivity and specificity of RLS utilizing the SIT is 81%, and 81%, respectively, with a PLMW index of greater than 40 on the SIT (18). When combined with a traditional PSG, the specificity and sensitivity of the test reaches 82% and 100%, respectively, making this test an effective tool for diagnosis (16).









    TABLE 6.9 Conditions Associated with Periodic Leg Movements of Sleep







    Narcolepsy


    REM sleep behavior disorder


    Neurodegenerative disorders


    Tourette’s syndrome


    Peripheral neuropathy


    Rheumatological disorders


    End-stage renal disease


    Pregnancy


    Posttraumatic stress disorder


    Sleep apnea


    Antidepressants (exceptions: bupropion, trazodone)


    Moderate dementiaa


    a In a study performed on older adults with early to moderate dementia and nighttime sleep disturbance, the most common risk factors for RLS symptoms were a PLMS index >15, based on PSG, and use of selective serotonin reuptake inhibitors (SSRIs) (9) .



  • The significance of excessive leg movements—whether demonstrated by PSG, leg activity meters, or SIT—must always be considered within in the clinical context of the patient’s presentation. As shown in Table 6.9, PLMS are very nonspecific findings and can be found as a normal variant of age as well as in association with a variety of medical, neurologic, and primary sleep disorders (19

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Jun 20, 2016 | Posted by in RESPIRATORY | Comments Off on Restless Legs Syndrome and Related Periodic Leg Movements of Sleep: Tips and Tools for Proper Screening and Diagnosis

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