Neuropsychiatric Dimensions of Movement Disorders in Sleep

Several authors have highlighted a link between PLMS and psychiatric disorders. A recent community survey of 18,980 persons documented a 3.9% prevalence of PLMS and high associations with stress, having a mental disorder, and certain lifestyle and health factors, such as high caffeine(Drug information on caffeine) intake and diabetes.¹² Patients with PLMS have been reported to have high rates of a history of depression.⁶ Increased rates of PLMS are reported in patients with attention-deficit/hyperactivity disorder (ADHD)¹³ or posttraumatic stress disorder, and in those who have frequent nightmares.¹⁴

In patients who present with symptoms of sleep disturbance, such as excessive daytime sleepiness, insomnia, or frequent awakening, the clinician is faced with deciding whether to treat patients with a high PLMS index. A trial of treatment can be undertaken in these patients once other sleep disorders have been excluded and possible exacerbating factors such as caffeine, hypnotics, and stress have been curtailed. Dopamine(Drug information on dopamine)rgic drugs, dopamine agonists, opiates, benzodiazepines, and anticonvulsants are all used, with dopaminergic drugs or dopamine agonists regarded as first-line treatment.¹⁵

RLS is a common disorder, the most comprehensive account of which was provided by Ekbom.¹⁶ The main symptom is an unpleasant and uncomfortable sensation frequently localized in the legs, with the shins being more affected than the calves (hence, the designation “anxietas tibiarum”). The symptoms are typically bilateral and may sometimes affect the thighs or feet and less often the buttocks and lower back. The descriptors typically used are “creeping,” “pulling,” “stretching,” “restless sensations,” “aching,” and occasionally, “painful.” The affected person may attempt to obtain relief by rubbing the skin, massaging the legs, stretching and kicking, swinging the legs, or standing and walking.

The symptoms of RLS appear only when the limbs are at rest, and are almost invariably worse in the evening or at night. Typical situations for the worst symptoms are lying in bed or sitting for prolonged periods. In severe cases, long trips or even a visit to the theater can become impossible. The untreated patient has the worst symptoms between 11 PM and 4 AM, and the least symptoms between 6 AM and 12 noon. Sleep deprivation results from difficulty in initiating sleep and maintaining sleep after arousals.

Eighty percent of RLS sufferers have a PLMS index greater than ^5,17 and the presence of PLMS is supportive of the diagnosis of RLS. Sleep studies of RLS patients also show increased sleep latency and reduced total sleep time, sleep efficiency, and slow-wave sleep. Sleep efficiency is often below 50%. Neurologic findings are normal.

The prevalence of RLS ranges from 2.5% to 15% of the general population, increasing with age.¹⁸ Some studies have reported a higher prevalence in women, but this is not a consistent finding. Family history of RLS is positive in 34% to 92% of cases.^19,20

The differential diagnosis of RLS includes peripheral neuropathy, peripheral claudication, leg cramps, akathisia, and in children, ADHD.²¹ Sachdev²² describes several features for differentiating between akathisia and RLS. In particular, akathisia sufferers report an inner feeling of restlessness with a compulsion to move in response to this feeling, with only partial amelioration of the subjective restlessness. Patients with RLS, on the other hand, report sensory symptoms in the legs, which may be deep and which typically occur when the legs have been in a recumbent position.

Akathisia does not have the characteristic worsening at nighttime seen in RLS, and akathisic patients feel worst when they are standing or sitting in one spot. PLMS and dyskinesia while awake are uncommon in patients with akathisia, who often have a tremor of extrapyramidal rigidity owing to neuroleptic medication. RLS can be idiopathic or secondary to a number of conditions, including pregnancy, iron deficiency, and renal failure; in these cases, RLS usually remits with resolution of the underlying condition.