Friday, December 26, 2008

What causes restless legs syndrome?

In most cases, the cause of RLS is unknown (referred to as idiopathic). A family history of the condition is seen in approximately 50 percent of such cases, suggesting a genetic form of the disorder. People with familial RLS tend to be younger when symptoms start and have a slower progression of the condition.

In other cases, RLS appears to be related to the following factors or conditions, although researchers do not yet know if these factors actually cause RLS.

People with low iron levels or anemia may be prone to developing RLS. Once iron levels or anemia is corrected, patients may see a reduction in symptoms.

Chronic diseases such as kidney failure, diabetes, Parkinson's disease, and peripheral neuropathy are associated with RLS. Treating the underlying condition often provides relief from RLS symptoms.

Some pregnant women experience RLS, especially in their last trimester. For most of these women, symptoms usually disappear within 4 weeks after delivery.

Certain medications-such as antinausea drugs (prochlorperazine or metoclopramide), antiseizure drugs (phenytoin or droperidol), antipsychotic drugs (haloperidol or phenothiazine derivatives), and some cold and allergy medications-may aggravate symptoms. Patients can talk with their physicians about the possibility of changing medications.

Researchers also have found that caffeine, alcohol, and tobacco may aggravate or trigger symptoms in patients who are predisposed to develop RLS. Some studies have shown that a reduction or complete elimination of such substances may relieve symptoms, although it remains unclear whether elimination of such substances can prevent RLS symptoms from occurring at all.

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Medical & Scientific Information

RLS and MS
High prevalence of restless legs syndrome in multiple sclerosis. Manconi M; Fabbrini M; Bonanni E, Filippi M, Rocca M, Murri L, Ferini-Strambi L. European Journal of Neurology. 2007;14:534-9.
Background: Multiple sclerosis (MS) is a chronic disease that affects the central nervous system. It can cause a variety of symptoms involving sensation, vision, speech, strength, mobility, and pain. “Secondary RLS” is a term used to describe RLS that has either a known cause or a known association. Some of the neurological diseases associated with RLS are peripheral neuropathy, spino-cerebellar ataxia, and Parkinson’s disease. Patients with MS often complain of RLS symptoms. This has always been viewed more as coincidence than as a real association between these two conditions.
Research: The researchers wanted to see how common RLS was in patients with MS. Over the course of one year, every patient with MS that came to one of the two neurology clinic research sites was evaluated for this study. Patients were not allowed to be in the study if they had any other neurological condition or other medical condition that could cause secondary RLS. They were also excluded if they were on dopaminergic or neuroleptic drugs or clonazepam, and if they: (1) were diagnosed with MS within 6 months; (2) their MS had relapsed within the last 6 months; (3) had any drug or alcohol abuse; (4) had any dementia; (5) or if they were younger than 18 or older than 65 years old. In total, 156 patients (100 females and 56 males) were enrolled in this study. Each patient was examined by two physicians and evaluated for MS and RLS. They each had an MRI as well.
The results of this study showed:
• 91 (58.3%) patients never had RLS symptoms.
• 51 (32.7%) patients had RLS symptoms more than once a week in the last 6 months.
• 12 (7.7%) patients had RLS symptoms less than once a week in the last 6 months.
• 2 (1.3%) patients had prior history of RLS but no active symptoms.
The Bottom Line: In patients with MS, the rate of RLS is three times higher than the average population. The researchers in this study suggest that MS be considered a cause of secondary RLS.
New Questions: The brain lesions of MS can be found in many places, but there was no association between the locations of the brain lesions and whether the patient also had RLS or not—why is this? What is it about MS that makes a person at higher risk for RLS?
* * * * *
RLS and Transplants.
Restless legs syndrome in lung transplant recipients. Minai OA, Golish JA, Yataco JC, Budev MM, Blazey H, Giannini C. J Heart Lung Transplant. 2007;26(1):24-29.
Background: There has been very little research on transplant patients and RLS. In one study, 45% of heart transplant recipients with periodic limb movements were diagnosed with RLS.
Research: The researchers in this study found 42 patients who had received a lung transplant. All the patients were on standard therapy which included immunosuppresion and prophylactic medicines. To be in the study, theses patients could not have a family history of RLS. These patients filled out two questionnaires. The first was to determine if they met criteria for RLS, and the second was to determine the severity of RLS if present.
The results of this study showed that 47.6% (20 of 42) of the patients had RLS. Of those with RLS, 80% had symptom severity that placed them in the moderate to severe category. Of interest, 75% of those diagnosed with RLS were women. All of the patients that were hypothyroid (4 of 42) had RLS. Also, the patients with RLS had a higher concentration of calcium in their blood than the patients without RLS. Finally, the patients with RLS were more likely to test positive for cytomegalovirus (CMV), a virus that is found in transplant patients, due to the immunosuppression medications.
The Bottom Line: Lung transplantation significantly increases a person’s chance of getting RLS. The risk increases if that patient is a woman, if they are hypothyroid, if they have higher calcium levels, or if they test positive for CMV.
New Questions: What is it about transplant recipients that increases their risk of getting RLS— the immunosuppression medications, the prophylactic medications, how the body responds to a new organ, or something else entirely? Does CMV infection cause RLS or could it possibly be exposure to the medication that treats it?