Restless legs syndrome: Diagnostic time-savers, Tx tips

Other clues to an RLS diagnosis

In addition to the essential criteria, the NIH and the IRLSSG developed a number of supportive and associated clinical features ( TABLE 1 ) that provide further help in differentiating RLS from conditions with similar symptoms.

Supportive clinical features

Although not every patient with RLS will have all (or possibly any) of the findings that are identified as supportive, their presence will lend support to an RLS diagnosis. These include:

• family history (1st-degree relative with RLS)
• improvement with dopaminergic therapy
• periodic leg movements during sleep (PLMS) in patients <50 years of age
• periodic leg movements while awake in patients of any age.¹⁷

In interpreting the second feature—dopaminergic therapy—it is important to note that while patient response often wanes over time, an initial response (often obtained by patient history, if the patient has ever been treated with a dopaminergic agent) has a sensitivity of 80% and a specificity of 100% for diagnosis of RLS.¹⁶ Keep in mind, too, that periodic leg movements—typically defined as jerking, repetitive motions—are present in many other disorders, and also tend to increase in elderly patients who do not have RLS.

Associated clinical features

Similarly, a diagnosis of RLS is not dependent on the presence of these findings. They’re noteworthy, however, because they’re experienced by many patients with RLS.¹⁶

A natural progression of RLS that follows an identifiable pattern is the first associated feature. The course of RLS varies, however, depending in part on the age of onset. Patients who develop RLS in young adulthood tend to have a slower progression, with long periods of remission, while RLS tends to progress more rapidly in those who develop the condition as older adults.¹⁵

Sleep disturbances. Leg movements typically result in frequent awakenings and increased sleep latency. Because of these disruptions, RLS patients often experience daytime somnolence and an inability to pay attention; they also have trouble performing daytime duties.

No abnormal findings. There are no physical exam or lab abnormalities associated with primary (idiopathic) RLS. The presence of abnormal findings should raise questions about the diagnosis, and cause clinicians to explore the possibility of a secondary cause.

CASE STUDY: Would you suspect RLS?

Grace (not her real name), a 54-year-old woman who underwent gastric bypass surgery several years ago, has come in today seeking help for chronic insomnia. She reports that she experiences uncomfortable sensations deep in her legs when she lies down at night. She says that she is able to get some relief from these sensations when she gets up and walks. She also notes that when she tries to lie still, she feels a need to move her legs.

Grace says that when she does fall asleep, she moves her legs so frequently that her husband has begun sleeping in a separate bed—symptoms that immediately arouse suspicion of RLS. If she were your patient, how would you support (or refute) the diagnosis, and how would you treat it?

Rule out conditions that mimic RLS

When evaluating patients like Grace with suspected RLS, it is crucial to be aware of conditions with similar symptoms—some of which may coexist. The differential diagnosis and spectrum of movement disorders that should be considered in patients with RLS symptoms are listed in TABLE 2. While some of the presenting symptoms overlap, keeping the essential criteria of RLS in mind may help in identifying distinguishing characteristics.

Neuropathic pain syndrome may occur at rest or during intense activity, for example, and peripheral vascular disease is provoked by activity, while RLS is brought on by rest.

Symptoms of neuroleptic-induced akathisia may occur day or night; in contrast, RLS typically follows a circadian rhythm.

Similarly, the urge to move the legs that patients with RLS experience is powerful, but the movement itself is voluntary. This feature distinguishes RLS from sleep starts (hypnagogic jerks), for example, which are involuntary movements.

TABLE 2
RLS: Distinguishing features and differential diagnosis^6,26,33