Comorbidity in restless legs syndrome among a sample of Swedish adults

[Restless legs syndrome, periodic limb movements, and psychopharmacology]

Restless legs syndrome (RLS) and the often associated periodic limb movement disorder in sleep (PLMD) frequently occur in the general population as a primary disorder. In addition to organic disease, secondary forms are caused by psychotropic medication. Several antidepressants, antipsychotics, lithium, and opioid withdrawal have been shown to induce or exacerbate RLS and PLMD, while several antiepileptics used as mood stabilizers and some benzodiazepines demonstrate therapeutic potential for treating RLS/PLMD. Systematic or controlled studies for evaluating these side effects still do not exist. Among the antidepressants at higher risk of inducing this disorder are selective serotonin reuptake inhibitors, venlafaxine, and some tetracyclic antidepressants. Under medication with some tricyclic substances, periodic limb movements were observed more often. For some antidepressants with differing transmitter profiles such as bupropion RLS/PLMD ameliorating effects or at least neutral effects (Trazodon, Nortriptylin) have been described in small studies. In case of continued of or newly occurring insomnia a thorough history should be taken to identify a possible RLS/PLMD as an intolerable side effect of treatment. A change in medications should be considered if clinically feasible. In case of RLS/PLMD occurring in psychotic patients switching the antipsychotic and additionally using a second line medication such as antiepileptics or a benzodiazepine should be considered.

[Restless-legs syndrome]

Restless-legs syndrome (RLS) is a sensorimotor disorder, characterized by an irresistible urge to move the legs usually accompanied or caused by uncomfortable and unpleasant sensations. It begins or worsens during periods of rest or inactivity, is partially or totally relieved by movements and is exacerbated or occurs at night and in the evening. RLS sufferers represent 2 to 3% of the general population in Western countries. Supportive criteria include a family history, the presence of periodic-leg movements (PLM) when awake or asleep and a positive response to dopaminergic treatment. The RLS phenotypes include an early onset form, usually idiopathic with a familial history and a late onset form, usually secondary to peripheral neuropathy. Recently, an atypical RLS phenotype without PLM and l-DOPA resistant has been characterized. RLS can occur in childhood and should be distinguished from attention deficit/hyperactivity disorder, growing pains and sleep complaints in childhood. RLS should be included in the diagnosis of all patients consulting for sleep complaints or discomfort in the lower limbs. It should be differentiated from akathisia, that is, an urge to move the whole body without uncomfortable sensations. Polysomnographic studies and the suggested immobilization test can detect PLM. Furthermore, an l-DOPA challenge has recently been validated to support the diagnosis of RLS. RLS may cause severe-sleep disturbances, poor quality of life, depressive and anxious symptoms and may be a risk factor for cardiovascular disease. In most cases, RLS is idiopathic. It may also be secondary to iron deficiency, end-stage renal disease, pregnancy, peripheral neuropathy and drugs, such as antipsychotics and antidepressants. The small-fiber neuropathy can mimic RLS or even trigger it. RLS is associated with many neurological and sleep disorders including Parkinson's disease, but does not predispose to these diseases. The pathophysiology of RLS includes an altered brain-iron metabolism, a dopaminergic dysfunction, a probable role of pain control systems and a genetic susceptibility with nine loci and three polymorphisms in genes serving developmental functions. RLS treatment begins with the elimination of triggering factors and iron supplementation when deficient. Mild or intermittent RLS is usually treated with low doses of l-DOPA or codeine; the first-line treatment for moderate to severe RLS is dopaminergic agonists (pramipexole, ropinirole, rotigotine). In severe, refractory or neuropathy-associated RLS, antiepileptic (gabapentin, pregabalin) or opioid (oxycodone, tramadol) drugs can be used.