RESTLESS LEGS SYNDROME

Restless legs syndrome (RLS) is a sensorimotor disorder characterized by a complaint of a strong, nearly irresistible, urge to move the legs. This urge to move is often but not always accompanied by other uncomfortable paresthesias felt deep inside the legs or as a feeling that is simply difficult or impossible to describe. When paresthesias are present, the sensation may vary from uncomfortable to painful. The urge to move and any accompanying sensations are engendered or made worse by rest (lying or sitting) and are at least partially and temporarily relieved by walking or moving the legs. The relief is usually immediate. The urge to move the legs worsens in the evening or night with relative relief in the morning. The symptoms disturb quiet resting and often profoundly disturb the patient’s ability to go to sleep or to return to sleep after an awakening. Patients may complain of involuntary jerking or twitching movements of the legs while sitting or lying awake. These may take the form of periodic limb movements during wakefulness (PLMW).

PERIODIC LIMB MOVEMENT DISORDER

Periodic limb movement disorder (PLMD) is characterized by periodic episodes of repetitive, highly stereotyped, limb movements that occur during sleep (PLMS) and by clinical sleep disturbance that cannot be accounted for by another primary sleep disorder.

PLMS occur most frequently in the lower extremities. They typically involve extension of the big toe, often in combination with partial flexion of the ankle, the knee, and sometimes the hip. Similar movements can occur in the upper limbs. Individual movements may be associated with an autonomic arousal, a cortical arousal, or an awakening. Typically, the patient is unaware of the limb movements or the frequent sleep disruption. An arousal may precede, coincide with, or follow the limb movement, suggesting that a central generator may give rise to both the periodic movements and the related sleep disturbance. Marked night-to-night variability in the number of movements has been documented. In some cases, the periodic limb movements may also occur while awake and are designated PLMW.

A clinical history of sleep onset or sleep maintenance problems, or both, is most consistently reported in association with PLMD. Occasionally, the patient is aware of limb movements in association with sleep disruption but typically not to the extent found on polysomnography. Many individuals with PLMD report having unrefreshing sleep, and some have a subjective complaint of excessive daytime sleepiness. Clinical symptoms, bed-partner observations, or parental reports for children may help in the clinical indication of PLMD. However, these factors have not been found to have sufficient specificity or sensitivity to supplant polysomnography in the diagnostic criteria. It is necessary to integrate a detailed clinical history and the polysomnographic findings to assess the role of this phenomenon as a sleep disorder.

A sensitive technique, such as pressure transducer airflow monitoring or esophageal manometry, should be used to monitor breathing during polysomnography to reasonably exclude sleep related breathing disorders (SRBDs) as the direct cause of the PLMS. When independent PLMS are present in patients with SRBDs, a separate diagnosis of PLMD may be considered if the PLMS persist despite adequate continuous positive airway pressure and a clinical sleep disturbance remains that is not otherwise explained. In general, polysomnography for the diagnosis of PLMD should be performed after the biologic effect of a medication or substance, such as an antidepressant, known to induce or aggravate PLMS has ended. When PLMS and a specific insomnia syndrome are present, then a clinical decision regarding the role of PLMS in the generation or exacerbation of insomnia symptoms must be made.

Normative data on the frequency of PLMS at various ages may be misleading in that most studies have not used sensitive monitoring techniques to exclude limb movements at the termination of SRBD events, and most have not reported medications that might induce, worsen, or suppress PLMS. An additional confound is the known night-to-night variability of PLMS. The commonly used cutoff of five movements per hour of sleep has been supported by recent work for the pediatric age group but is problematic for the elderly, in whom studies have found higher rates of PLMS in apparently asymptomatic individuals.

SLEEP RELATED LEG CRAMPS

Sleep related leg cramps are painful sensations caused by sudden and intense involuntary contractions of muscles or muscle groups, usually in the calf or small muscles of the foot, occurring during the sleep period. They may arise from either wakefulness or sleep.

Sleep related leg cramps usually start abruptly but may in some cases be preceded by a less painful warning sensation. The muscle contractions last for a few seconds up to several minutes and then remit spontaneously; the frequency of sleep related leg cramps varies considerably from less than yearly to multiple episodes every night. The cramp can be relieved by strongly stretching the affected muscle and sometimes also by local massage, application of heat, or movement of the affected limb. Some people can have leg cramps primarily during the daytime without having significant leg cramps that disturb sleep.

SLEEP RELATED BRUXISM

Sleep related bruxism is an oral activity characterized by grinding or clenching of the teeth during sleep, usually associated with sleep arousals.

In sleep, jaw contraction frequently occurs. This contraction can take two forms: isolated sustained jaw clenching, termed tonic contractions, or a series of repetitive (phasic) muscle contractions termed rhythmic masticatory muscle activity (RMMA). When these contractions are particularly strong during sleep, they frequently produce tooth-grinding sounds and are referred to as sleep related bruxism. This condition can lead to abnormal wear of the teeth, tooth pain, jaw muscle pain, or temporal headache. Severe sleep related bruxism may also result in sleep disruption. This may involve not only the patient, but also the bed partner, since the sounds made by friction of the teeth are usually perceived as being unpleasant and can be quite loud and disturbing to those nearby. The disorder is typically brought to dental or medical attention because of the tooth damage or disturbing sounds. Less commonly, it may present as a cause of disturbed sleep.

Temporomandibular joint pain, accompanied by limited jaw movement, is not a rare consequence. Bruxism can occur during waking, but this is a different disorder and not known to be associated with sleep related bruxism. Sleep related bruxism without clear cause is termed primary, whereas secondary sleep related bruxism may be associated with the use of psychoactive medications, recreational drugs or a variety of medical disorders. Treatment-induced secondary sleep related bruxism is termed iatrogenic.

SLEEP RELATED RHYTHMIC MOVEMENT DISORDER

Sleep related rhythmic movement disorder (RMD) is characterized by repetitive, stereotyped, and rhythmic motor behaviors (not tremors) that occur predominantly during drowsiness or sleep and involve large muscle groups. The occurrence of significant clinical consequences differentiates RMD from developmentally normal sleep related movements.

Typically seen in infants and children, RMD comprises several subtypes. Body rocking may involve the entire body, with the child on hands and knees, or it may be limited to the torso, with the child sitting. Head banging often occurs with the child prone, repeatedly lifting the head or entire upper torso, and forcibly banging the head back down into the pillow or mattress. Alternately, the child may sit with the back of the head against the headboard or wall, repeatedly banging the occiput. Combining head banging and body rocking, the child may rock on hands and knees, banging the vertex or frontal region of the head into the headboard or wall. Head rolling consists of side-to-side head movements, usually with the child in the supine position. Less common rhythmic movement forms include body rolling, leg banging, or leg rolling. Rhythmic humming or inarticulate sounds often accompany the body, head, or limb movements and may be quite loud.

Episodes often occur near sleep onset, although they may also occur at any time during the night and even during quiet wakeful activities, such as listening to music or traveling in vehicles. The movement frequency can vary, but the rate is usually between 0.5 per second and two per second. Duration of the individual movement clusters also varies but generally is less than 15 minutes. Cessation of movements may occur following environmental disturbance or being spoken to. Children who have sufficient language development to be asked about event recall in the morning are typically amnestic for the episodes.

Sleep related rhythmic movements are common in normal infants and children. Without evidence for significant consequences, the movements alone should not be considered a disorder. This edition of the ICSD introduces new criteria for classification of these sleep related rhythmic movements, which include a requirement that sleep related rhythmic movements should be considered a disorder only if the behaviors markedly interfere with normal sleep, cause significant impairment in daytime function, or result in self-inflicted bodily injury that requires medical treatment (or would result in injury if preventive measures were not used).

SLEEP RELATED MOVEMENT DISORDER, UNSPECIFIED

This diagnosis is assigned when patients have sleep related movement disorders that belong to this general category but (a) cannot be classified elsewhere; or (b) are suspected of being associated with an underlying psychiatric condition that causes the movement disorder. Thus, in many cases, “sleep related movement disorder, unspecified” is a temporary diagnosis given when the patient needs a sleep diagnosis before the underlying psychiatric condition can be diagnosed (e.g., movements believed secondary to posttraumatic stress disorder flashbacks prior to firm establishment of the psychiatric diagnosis). Once the psychiatric diagnosis is established, that will become the sole diagnosis (unless the sleep complaint is unusually severe, the complaint needs the specialized skills of a sleep specialist, or the relationship between the movements and the supposed underlying condition is questionable). In some patients, an underlying psychiatric condition, while suspected, cannot ever be established, and in those patients, “sleep related movement disorder, unspecified” will remain a permanent diagnosis.

SLEEP RELATED MOVEMENT DISORDER DUE TO DRUG OR SUBSTANCE

Sleep related movement disorders in which the movement is due to a drug or substance (toxin or other bioactive substance) are included here. The actual code number that is given depends on the substance that is involved and whether this is due to dependence or abuse of a substance or is associated with poisoning, adverse effects of or under-dosing of a drug, medication, or biological substance. Once the specific substance and its use (abuse, dependence, side effect, etc.) is coded, “sleep related movement disorder due to drug or substance” may be used as a secondary diagnosis to further clarify the path by which the substance affects sleep. An example of a sleep related movement disorder due to a substance is tardive dyskinesia or tardive akathisia where sleep related movements are due to dopamine receptor-blocking antipsychotic agents. As with “sleep related movement disorders due to medical condition,” the category “sleep related movement disorder due to drug or substance” is a temporary diagnosis. Once the movement disorder is properly characterized as either tardive dyskinesia or akathisia, for example, the temporary diagnosis of “sleep related movement disorder due to a substance” is no longer applied.

SLEEP RELATED MOVEMENT DISORDER DUE TO MEDICAL CONDITION

This diagnosis is intended for sleep related movement disorders for which there is a clinical suspicion that an underlying medical or neurologic condition may cause the sleep disorder. An example would be sleep disruption from Parkinson’s disease. Thus, in many cases, “sleep related movement disorder due to medical condition” is a temporary diagnosis, given when a sleep diagnosis is required before the underlying medical condition can be fully diagnosed. Once the presence of a medical or neurological condition is clearly established, that condition becomes the sole diagnosis (unless the sleep complaint is unusually severe, the complaint needs the specialized skills of a sleep specialist, or the relationship between sleep disruption and the supposed underlying condition is questionable). In some patients, an underlying medical condition, while suspected, cannot ever be established, and in those patients ”sleep related movement disorder due to medical condition” will remain a permanent diagnosis.

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Source: American Academy of Sleep Medicine, International Classification of Sleep Disorders, 2nd ed.: Diagnostic and Coding Manual, Westchester, Illinois: American Academy of Sleep Medicine, 2005.