Sleep Disorders: Restless Leg Syndrome and Periodic Limb Movement Disorder
Guest: Dr. Michael Frye - Pulmonary, Critical Care, Allergy & Sleep Medicine, MUSC
Host: Dr. Linda Austin – Psychiatry, MUSC
Dr. Linda Austin: I’m Dr. Linda Austin. I’m interviewing Dr. Michael Frye, who is Associate Professor of Medicine and Medical Director of the MUSC Sleep Center. Dr. Frye, let’s talk about restless leg syndrome and, something related, periodic limb movement. What, exactly, are restless legs?
Dr. Michael Frye: Patients who have restless legs have symptoms that are gnawing. This discomfort, it’s almost an indescribable low-grade type of pain in their legs at night which causes them to want to move their legs. And they find that if they do move their legs, it temporarily relieves that discomfort; gnawing pain. This happens mostly in the evenings. And, for unclear reasons, it goes away in the wee hours of the night, just before dawn. So, for patients, their symptoms are much worse in the evening and throughout the first part of the night.
Periodic limb movement disorder is associated with restless leg syndrome in about 70 percent of cases. Patients who have this gnawing discomfort in their legs, once they get to sleep, they often have a repetitive jerking of their legs at about 30-second intervals. Now, there are some patients who don’t have the gnawing discomfort before they go to sleep who end up having some jerking of their legs throughout the night. So, you can have periodic limb movement disorder by itself, for other causes. But, it’s most often associated with restless leg syndrome.
Dr. Linda Austin: So, these are highly overlapping, but not always overlapping?
Dr. Michael Frye: Exactly.
Dr. Linda Austin: Who tends to get either or both of problems? Is this something that comes on in old age, or do kids get it sometimes? Who is vulnerable?
Dr. Michael Frye: Most patients that we see have one of three conditions. They’ll have an anemia, that’s often an iron-deficiency anemia. But it may also be a B12, or folate-deficiency anemia. They’ll have another electrolyte disturbance, most notably, renal insufficiency, which we can detect by doing a simple blood test. And, another common population is patients during pregnancy.
Dr. Linda Austin: I guess all three of those are treatable conditions; even pregnancy?
Dr. Michael Frye: Yes, they are.
Dr. Linda Austin: Pregnancy being the most easily treated; with the passage of time.
Dr. Michael Frye: Right. So, we screen for these common underlying conditions. And if we find a contributing cause that might be causing the restless leg syndrome, and the periodic limb movement, we, often, are able to resolve the problem. Some patients don’t have any of those three underlying conditions, and we have what we call idiopathic restless leg syndrome. That condition is still treatable with medications.
Dr. Linda Austin: Idiopathic, meaning it makes us, doctors, feel like idiots because we don’t know what the heck is going on.
Dr. Michael Frye: That’s it. There’s no identifiable underlying cause that we can determine. The cause is unknown. But, fortunately, it is still treatable.
Dr. Linda Austin: And, does that tend to be chronic, or lifelong, even?
Dr. Michael Frye: It does. And, most of these patients, if we do our initial screening and don’t find any of the reversible causes for restless leg syndrome, the condition tends to persist throughout their life. Some patients worsen with it, or have a waxing and waning course. But it’s less often that they will totally resolve their condition.
Dr. Linda Austin: Dr. Frye, thanks so much for talking with us today.
Dr. Michael Frye: Thanks for having me.
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