Dyssomnia Not Otherwise Specified

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.