Chapter 028. Sleep Disorders (Part 9)

Restless Legs Syndrome (RLS)Patients with this sensory-motor disorder report an irresistible urge to move the legs, or sometimes the upper extremities, that is often associated with a creepycrawling or aching dysesthesias deep within the affected limbs. For most patients with RLS, the dysesthesias and restlessness are much worse in the evening or night compared to the daytime and frequently interfere with the ability to fall asleep. The symptoms appear with inactivity and are temporarily relieved by movement. In contrast, paresthesias secondary to peripheral neuropathy persist with activity. The severity of this chronic disorder may wax and wane over time...
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Chapter 028. Sleep Disorders (Part 9) Chapter 028. Sleep Disorders (Part 9) Restless Legs Syndrome (RLS) Patients with this sensory-motor disorder report an irresistible urge to movethe legs, or sometimes the upper extremities, that is often associated with a creepy-crawling or aching dysesthesias deep within the affected limbs. For most patientswith RLS, the dysesthesias and restlessness are much worse in the evening ornight compared to the daytime and frequently interfere with the ability to fallasleep. The symptoms appear with inactivity and are temporarily relieved bymovement. In contrast, paresthesias secondary to peripheral neuropathy persistwith activity. The severity of this chronic disorder may wax and wane over timeand can be exacerbated by sleep deprivation, caffeine, alcohol, serotonergicantidepressants, and pregnancy. The prevalence is 1–5% of young to middle-ageadults and 10–20% of those >60 years. There appear to be important differences inRLS prevalence among racial groups, with higher prevalence in those of NorthernEuropean ancestry. Roughly one-third of patients (particularly those with an earlyage of onset) will have multiple affected family members. At least three separatechromosomal loci have been identified in familial RLS, though no gene has beenidentified to date. Iron deficiency and renal failure may cause RLS, which is thenconsidered secondary RLS. The symptoms of RLS are exquisitely sensitive todopaminergic drugs (e.g., pramipexole 0.25–0.5 mg q8PM or ropinirole 0.5–4.0mg q8PM), which are the treatments of choice. Opiods, benzodiazepines, andgabapentin may also be of therapeutic value. Most patients with restless legs alsoexperience periodic limb movements of sleep, although the reverse is not the case. Periodic Limb Movement Disorder (PLMD) Periodic limb movements of sleep (PLMS), previously known as nocturnalmyoclonus, consists of stereotyped, 0.5- to 5.0-s extensions of the great toe anddorsiflexion of the foot, which recur every 20–40 s during NREM sleep, inepisodes lasting from minutes to hours, as documented by bilateral surface EMGrecordings of the anterior tibialis on polysomnography. PLMS is the principalobjective polysomnographic finding in 17% of patients with insomnia and 11% ofthose with excessive daytime somnolence (Fig. 28-3). It is often unclear whether itis an incidental finding or the cause of disturbed sleep. When deemed to be thelatter, PLMS is called PLMD. PLMS occurs in a wide variety of sleep disorders(including narcolepsy, sleep apnea, REM sleep behavior disorder, and variousforms of insomnia) and may be associated with frequent arousals and an increasednumber of sleep-stage transitions. The pathophysiology is not well understood,though individuals with high spinal transections can exhibit periodic legmovements during sleep, suggesting the existence of a spinal generator. Treatmentoptions include dopaminergic medications or benzodiazepines. Figure 28-3 Polysomnographic recordings of (A) obstructive sleep apnea and (B)periodic limb movement of sleep. Note the snoring and reduction in air flow inthe presence of continued respiratory effort, associated with the subsequentoxygen desaturation (upper panel). Periodic limb movements occur with arelatively constant intermovement interval and are associated with changes in theEEG and heart rate acceleration (lower panel). Abbreviations: R.A.T., rightanterior tibialis; L.A.T., left anterior tibialis. (From the Division of SleepMedicine, Brigham and Womens Hospital.) Evaluation of Daytime Sleepiness Daytime impairment due to sleep loss may be difficult to quantify forseveral reasons. First, sleepiness is not necessarily proportional to subjectivelyassessed sleep deprivation. In obstructive sleep apnea, for example, the repeatedbrief interruptions of sleep associated with resumption of respiration at the end ofapneic episodes result in daytime sleepiness, despite the fact that the patient maybe unaware of the sleep fragmentation. Second, subjective descriptions of wakingimpairment vary from patient to patient. Patients may describe themselves assleepy, fatigued, or tired and may have a clear sense of the meaning of thoseterms, while others may use the same terms to describe a completely differentcondition. Third, sleepiness, particularly when profound, may affect judgment in amanner analogous to ethanol, such that subjective awareness of the condition andthe consequent cognitive and motor impairment is reduced. Finally, patients maybe reluctant to admit that sleepiness is a problem, both because they are generallyunaware of what constitutes normal alertness and because sleepiness is generallyviewed pejoratively, ascribed more often to a deficit in motiva ...