Polysomnography demonstrates significant abnormalities in RLS, commonly increased latency to sleep, and higher arousal index. Polysomnography with a preceding immobili- zation test may provide an indicator of the motor sign of RLS, periodic limb movements, under standard conditions of sleep and during quiet resting, both of which can provoke RLS symptoms.
Functionai Consequences of Restless Legs Syndrome
Forms of RLS severe enough to significantly impair functioning or associated with mental dis- orders, including depression and anxiety, occur in approximately 2%—3% of the population.
Although the impact of milder symptoms is less well characterized, individuals with
RLS complain of disruption in at least one activity of daily living, with up to 50% reporting a negative impact on mood, and 476% reporting a lack of energy. The most common conse- quences of RLS are sleep disturbance, including reduced sleep time, sleep fragmentation, and overall distuibance; depression, generalized anxiety disorder, panic disorder, and post- traumatic stress disorder; and quality-of-life impairments. RLS can result in daytime sleep- iness or fatigue and is frequently accompanied by significant distress or impairment in affective, social, occupational, educational, academic, behavioral, or cognitive functioning.
The most important conditions in the differential diagnosis of RLS are leg cramps, posi- tional discomfort, arthralgias/arthritis, myalgias, positional ischemia (numbness), leg edema, peripheral neuropathy, radiculopathy, and habitual foot tapping. ”I(notting” of the muscle (cramps), relief with a single postural shift, limitation to joints, soreness to pal- pation (myalgias), and other abnormalities on physical examination are not characteristic of RLS. Unlike RLS, nocturnal leg cramps do not typically present with the desire to move the limbs nor are there frequent limb movements. Less common conditions to be differen- tiated from RLS include neuroleptic-induced akathisia, myelopathy, symptomatic venous insufficiency, peripheral artery disease, eczema, other orthopedic problems, and anxiety- induced restlessness. Worsening at night and periodic limb movements are more common in RLS than in medication-induced akathisia or peripheral neuropathy.
While is it important that RLS symptoms not be solely accounted for by another medical or behavioral condition, it should also be appreciated that any of these similar conditions can occur in an individual with RLS. This necessitates a separate focus on each possible condi- tion in the diagnostic process and when assessing impact. For cases in which the diagnosis of
RLS is not certain, evaluation for the supportive features of RLS, particularly PLMS or a fam- ily history of RLS, may be helpful. Clinical features, such as response to a dopaminergic agent and positive family history for RLS, can help with the differential diagnosis.
Depressive disorders, anxiety disorders, and attentional disorders are commonly comor- bid with RLS and are discussed in the section ”Functional Consequences of Restless Legs
Syndrome." The main medical disorder comorbid with RLS is cardiovascular disease.
There may be an association with numerous other medical disorders, including hyperten- sion, narcolepsy, migraine, Parkinson’s disease, multiple sclerosis, peripheral neuropathy, obstructive sleep apnea, diabetes mellitus, fibromyalgia, osteoporosis, obesity, thyroid disease, and cancer. Iron deficiency, pregnancy, and chronic renal failure are also comor- bid with RLS.
Reiationship to Internationai Ciassification of
The International Classification of Sleep Disorders, 2nd Edition (ICSD-2), presents similar diag- symptoms.
A. A prominent and severe disturbance in sleep.
B. There is evidence from the history, physical examination, or laboratory findings of both (1) and (2): 1. The symptoms in Criterion A developed during or soon after substance intoxication or after withdrawal from or exposure to a medication.