The category of dyssomnia not otherwise specified is for insomnias, hypersomnias, or circadian rhythm disturbances that do not meet criteria for any specific dyssomnia. The most common of these conditions are restless legs syndrome (RLS) and periodic limb movements (PLM).
RLS is an irresistible urge to move the legs accompanied by an uncomfortable (crawling, creeping) sensation in the legs. Walking or stretching of the legs can temporarily alleviate this unpleasant sensation.
Symptoms are typically worse in the evening and night and may considerably delay the onset of sleep. This condition must be differentiated from the generalized body restlessness seen in anxious insomniac patients and from antipsychotic-induced akathisia. RLS is very common among individuals with end-stage renal disease and may also be seen in normal pregnancy and in individuals with iron-deficiency anemia. Serotonergic antidepressants (e.g., SSRIs, clomipramine) may exacerbate RLS/PLM.
The Dyssomnia Not Otherwise Specified category is for insomnias, hypersomnias, or circadian rhythm disturbances that do not meet criteria for any specific Dyssomnia. Examples include
1. Complaints of clinically significant insomnia or hypersomnia that are attributable to environmental factors (e.g., noise, light, frequent interruptions).
2. Excessive sleepiness that is attributable to ongoing sleep deprivation.
3. “Restless legs syndrome”: This syndrome is characterized by a desire to move the legs or arms, associated with uncomfortable sensations typically described as creeping, crawling, tingling, burning, or itching. Frequent movements of the limbs occur in an effort to relieve the uncomfortable sensations. Symptoms are worse when the individual is at rest and in the evening or night, and they are relieved temporarily by movement. The uncomfortable sensations and limb movements can delay sleep onset, awaken the individual from sleep, and lead to daytime sleepiness or fatigue. Sleep studies demonstrate involuntary periodic limb movements during sleep in a majority of individuals with restless legs syndrome. A minority of individuals have evidence of anemia or reduced serum iron stores. Peripheral nerve electrophysiological studies and gross brain morphology are usually normal. Restless legs syndrome can occur in an idiopathic form, or it can be associated with general medical or neurological conditions, including normal pregnancy, renal failure, rheumatoid arthritis, peripheral vascular disease, or peripheral nerve dysfunction. Phenomenologically, the two forms are indistinguishable. The onset of restless legs syndrome is typically in the second or third decade, although up to 20% of individuals with this syndrome may have symptoms before age 10. The prevalence of restless legs syndrome is between 2% and 10% in the general population and as high as 30% in general medical populations. Prevalence increases with age and is equal in males and females. Course is marked by stability or worsening of symptoms with age. There is a positive family history in 50%-90% of individuals. The major differential diagnoses include medication-induced akathisia, peripheral neuropathy, and nocturnal leg cramps. Worsening at night and periodic limb movements are more common in restless legs syndrome than in medication-induced akathisia or peripheral neuropathy. Unlike restless legs syndrome, nocturnal leg cramps do not present with thedesire to move the limbs nor are there frequent limb movements.
4. Periodic limb movements: Periodic limb movements are repeated low-amplitude brief limb jerks, particularly in the lower extremities. These movements begin near sleep onset and decrease during stage 3 or 4 non-rapid eye movement (NREM) and rapid eye movement (REM) sleep. Movements usually occur rhythmically every 20-60 seconds and are associated with repeated, brief arousals. Individuals are often unaware of the actual movements, but may complain of insomnia, frequent awakenings, or daytime sleepiness if the number of movements is very large. Individuals may have considerable variability in the number of periodic limb movements from night to night. Periodic limb movements occur in the majority of individuals with restless legs syndrome, but they may also occur without the other symptoms of restless legs syndrome. Individuals with normal pregnancy or with conditions such as renal failure, congestive heart failure, and Posttraumatic Stress Disorder may also develop periodic limb movements. Although typical age at onset and prevalence in the general population are unknown, periodic limb movements increase with age and may occur in more than one-third of individuals over age 65. Men are more commonly affected than women.
5. Situations in which the clinician has concluded that a Dyssomnia is present but is unable to determine whether it is primary, due to a general medical condition, or substance induced.
Most individuals with RLS also present with PLM during sleep. PLM is characterized by the occurrence of brief, repetitive, and highly stereotyped movements of the limbs (legs and arms) during sleep. These movements are often associated with arousals but not necessarily full awakenings, and the patient is usually unaware of the movements. The subjective complaint associated with PLM is either sleep maintenance insomnia or excessive daytime sleepiness, but some individuals are totally asymptomatic.
Behavioral/psychotherapeutic treatment There is little information on the effects of nonpharmacological interventions on RLS and PLM. Anecdotal reports suggest that strategies such as walking or doing moderate exercise, taking a hot bath, using a heating pad, or having a massage can provide some relief from RLS symptoms. Avoidance measures for RLS and PLM include discontinuation of caffeine and of some cyclic antidepressants, both of which may exacerbate PLM in sleep. Because PLM is often associated with sleep fragmentation, behavioral procedures such as sleep restriction and stimulus control may help to consolidate sleep (Edinger et al. 1996). Also, clinical observations that some patients with RLS and PLM complain of cold feet has led Ancoli-Israel et al. (1986) to use thermal biofeedback in combination with autogenic training to treat PLM. Although impressive reductions in leg movements were reported in this pilot study, additional research with follow-up evaluations is needed to replicate these findings.
Pharmacological treatment Pharmacological treatment is often indicated for RLS and PLM (Chesson et al. 1999; Hening et al. 1999). Medications that increase dopaminergic neurotransmission are the drugs of choice. The combination of carbidopa and levodopa is effective for decreasing RLS symptoms and limb movements (Brodeur et al. 1988). Doses of 25-100 mg of carbidopa plus 100-400 mg of levodopa are often effective in suppressing subjective and objective manifestations but may not last the entire night. Therefore, a second dose in the middle of the night, or use of sustained-release preparations, may be helpful (Collado-Seidel et al. 1999). Some patients also note “augmentation” of symptoms (i.e., the appearance of RLS earlier in the evening or later in the morning), necessitating additional doses of carbidopa-levodopa. More recently, dopamine receptor agonists have been shown to have efficacy for the treatment of RLS and PLM. Specifically, pergolide, 0.05-0.75 mg in a single dose before bedtime, reduced the subjective symptoms of both RLS and PLM during sleep (Earley et al. 1998; Wetter et al. 1999). Pramipexole, 0.125-0.75 mg, another dopamine receptor agonist, has also been reported to be effective in open-label and double-blind studies (Becker et al. 1998; Montplaisir et al. 1999). These drugs appear to produce less augmentation of symptoms than carbidopa-levodopa. Benzodiazepine medications, including clonazepam and temazepam, improve nocturnal sleep continuity in RLS and PLM but have a relatively minor effect on decreasing actual limb movements (Mitler et al. 1986). Tolerance typically does not pose a problem in clinical practice (Montplaisir et al. 1992; Schenck and Mahowald 1996a). No controlled studies have compared benzodiazepines with dopaminergic agents. Other medications used to treat RLS and PLM include oxycodone, propoxyphene, carbamazepine, baclofen, and magnesium (Hornyak et al. 1998; Montplaisir et al. 1992).
Revision date: July 5, 2011
Last revised: by Tatiana Kuznetsova, D.M.D.