Pathophysiology of Restless Legs Syndrome and Periodic Limb Movements in Sleep Arthur S. Walters, M.D. Professor of Neurology Associate Director Sleep Medicine Vanderbilt University School of Medicine Nashville, Tennessee Disclosures for last year Consultant to UCB Pharma on adult and pediatric RLS. The International Restless Legs Syndrome Study Group (IRLSSG) Consists of over 130 physicians and scientists from 17 countries dedicated to research on Restless Legs/Periodic Limb Movements in Sleep. Developed a consensus definition of RLS published originally in 1995 and updated for better clarity and republished in 2003. Same definition also was accepted by International Classification of Sleep Disorders Version 2. Obligate Clinical Features RLS An urge to move the legs usually accompanied or caused by uncomfortable and unpleasant sensations in the legs. The urge to move or unpleasant sensations begin or worsen during periods of rest or inactivity such as lying or sitting. The urge to move or unpleasant sensations are partially or totally relieved by movement such as walking or stretching, at least as long as the activity continues. The urge to move or unpleasant sensations are worse in the evening or night than during the day or only occur in the evening or night. Supportive Clinical Features of RLS Positive Family History of RLS. Improvement with dopaminergic therapy. Periodic Limb Movements In Sleep (PLMS). At least 4 movements in a row – at least 8 mcv high, 0.5-10 seconds in duration and 5-90 seconds apart. Periodic Limb Movements in Wakefulness (PLMs). --PLMS Associated Features of RLS Sleep Disturbance. Neurological Examination – Normal in idiopathic or familial cases. Evidence of Peripheral Neuropathy or Radiculopathy in “secondary cases”. Serum ferritin < 50 mcg/L. Clinical course— Most patients middle to older age, but may be seen in children. Usually progressive but static course may be seen. Remissions of a month or more may be seen in 15% of cases. Therapy of RLS First line– Dopaminergic Agents L-Dopa, ropinirole, pramipexole Second line – Opioids Anticonvulsants – gabapentin, pregabilin Benzodiazepines – clonazepam, diazepam Iron Therapy Pathogenetic Mechanisms and Hypotheses Summary of talk Therapy has led to pathogenetic hypotheses- Iron, Dopaminergic agonists,Opioids We will also review Genetics Immunologic Hypothesis Summary of talk Circadian Control of RLS/PLMS Brief Summary of Neurophysiology of RLS/PLMS Relationship of RLS/PLMS to Cardiovascular Disease Iron pathogenesis and RLS Some RLS patients present with iron deficiency. Their serum and CSF ferritin levels are low (Earley et al, 2000). With MRI, Allen et al. (2001) revealed that RLS patient’s iron level is low at the Substantia Nigra (SN) area and the MRI iron values of this area correlate with RLS severity. Conner, et al. (2003) found SN dopaminergic cells intracellular Fe level is low in both primary and secondary RLS patients with post-mortem autopsy. Dopaminergic system pathogenesis in RLS A-11 dopaminergic diencephalo spinal lesions lead to a restless rat. DA agonist treatment with pramipexole improves restlessness (Ondo et al Mov Disord 2000). In human RLS in basal ganlia circuit there is down regulation of D2 receptors and up regulation of Tyrosine Hydroxylase, the rate limiting step for dopamine synthesis (Connor et al Brain 2009) Dopaminergic system pathogenesis in RLS L-DOPA treatment of RLS pushes symptoms to an earlier time of day (Augmentation). When augmentation occurs the Dim Light Melatonin onset (DLMO) occurs earlier (Garcia-Borreguero et al. 2004) This supports a role for the circadian pacemaker in the production of RLS symptoms and supports a role for dopaminergic deficit in the triggering of the onset and timing of the onset of RLS symptoms. Dopaminergic system pathogenesis in RLS L-DOPA Suppresses Prolactin Increases Growth Hormone However, in RLS patients this response occurs more at night when RLS symptoms are expected to be maximum (Garcia-Borreguero et al 2004). This suggests that a circadian dip in dopamine levels at night triggers the symptoms of RLS. RLS Genetics Family H. RLS Genetics Linkage studies have yielded 5 chromosomes but no genes Allelic Association studies have yielded 4 variants of common genes that account for over 50% of all RLS ( Simultaneous publication by group of David Rye, NEJM and group of Juliane Winkelmann Nat Genet 2007) Genetics of RLS/PLMS The gene found in common by both Juliane Winkelmann and David Rye on chromosome 6 is the BTBD9 gene which stands for Broad complex- tramtrackbric-a-brac - domain 9. May have something to do with iron metabolism since there was a drop is serum ferritin of 13% for each copy of the variant of the gene. Genetics of RLS/PLMS The Meis 1 gene (one of the 6 genes associated with RLS) may also have something to do with general iron metabolism ( Silver et al SLEEP 2010) Genetics of RLS/PLMS Another two genes that convey genetic risk for RLS were recently discovered– Protein tyrosine phosphatase receptor type delta gene (PTPRD) and the Nitric Oxide Synthase gene (NOS). ADHD is more common in RLS/PLMS and vice versa. These genes also convey genetic risk for ADHD The Immunologic Hypothesis About 15% of RLS patients undergo remissions of a month or more that are independent of therapy. This is reminiscent of Multiple Sclerosis, an immunologically mediated Neurological Disease also characterized by exacerbations and remissions. The immunologic hypothesis RLS is more common in Rheumatoid Arthritis (up to 1/3) but not osteoarthritis (4%) (Auger et al 2005; Salih et al 1994). RLS is more common in Multiple Sclerosis (up to 1/3). (Auger et al 2005; Manconi et al 2007). Multiple Sclerosis and Rheumatoid Arthritis but not osteoarthritis are thought to have an immunologic diathesis. RLS and the immunologic hypothesis Hornyak M et al. Neurology 2008; 70: 1620-2. Double blind crossover study. 10 RLS patients either hydrocortisone 40 mg iv or saline placebo. Statistically significant Improvement in sensory leg discomfort (p = 0.032). The immunologic hypothesis Gamignani et al Mov Disord 2006 RLS in 29 of 97 consecutive patients with polyneuropathy More often sensory neuropathy of small fiber type (15 of 29 vs. 16 of 68;P 0.009). In the RLS group, dysimmune neuropathies, significantly more frequent (11 of 29 vs. 10 of 68; P = 0.016). Weinstock and Walters Background: Irritable Bowel Syndrome (IBS) is frequently associated with Small Intestinal Bacterial Overgrowth (SIBO). Small Intestinal Bacterial Overgrowth can be detected by a positive Lactulose Breath Test (LBT). Weinstock and Walters RLS Group - 33 General Population Controls -25 2nd control group were GI disease was excluded - 30 27% RLS patients had Irritable Bowel Syndrome (IBS) as opposed to 4% in the general population controls (p=.0326) Weinstock and Walters A positive LBT was found in 67% of RLS patients as opposed to 28% of General Population controls (p =.0074) and10 % of Completely Healthy controls This indicates that a full 57% of positive LBTs and therefore Small Intestinal Bacterial Overgrowth can be attributed to RLS Prevalence of SIBO in RLS RLS > controls with 2003 and 2009 criteria * *P<0.001 vs. controls both criteria (30/39 patients screened randomized for treatment) for The immunologic Hypothesis SIBO ---cytokines and/or translocation of lipopolysaccharides ---- increased Hepcidin--- abnormal central processing of iron. Alternatively SIBO may induce a direct auto-immune attack on the brain and/or peripheral nervous system in RLS. RLS and the immunologic hypothesis We did a survey of the 40 conditions frequently associated with RLS.(Secondary forms of RLS) 30 of the 40 associated with inflammation or immune dysfunction. Other Than Multiple Sclerosis and Rheumatoid Arthritis other examples include Narcolepsy and Celiac Disease. Secondary RLS: 43 disorders/risk factors 21 can have peripheral iron deficiency 34 can have systemic Bacterial Overgrowth inflammation or immune disorders 1 17 can have small intestinal bacterial overgrowth (SIBO) 2,3 Iron deficiency Inflammatory and/or immune 1. Weinstock et al. Inflamm Bowel Dis. 2009 (in Press).. 2. Weinstock et al. Dig Dis Sci. 2008;53:1252-1256. 3. Weinstock et al. Dig Dis Sci. 2009 (in Press). Dopaminergic and opiate system pathogenesis in RLS The effect of the dopaminergic agents and the opioids is probably specific to the dopaminergic and opiate receptors since blockade of the effects of these drugs in RLS treated patients brings back the symptoms of RLS. Opioids may act through the Dopaminergic System The effect of the opioids is probably mediated through the dopaminergic system since opiate receptor blockers only reverse the therapeutic effects of the opioids in RLS treated patients, but dopaminergic receptor blockers reverse the therapeutic effect of either the opioids or dopaminergic agents in RLS treated patients. (Akpinar, et al.1987; Montplaisir, et al. 1990) Naloxone Pimozide V V V V Opioids >>>> Dopamine>>>> RLS Opiate Receptor Pet Scanning and RLS Abnormalities in Post-synaptic Receptor Binding in Medial Pain Pathways (von Spiczak et. al. 2005). Degree of binding correlated negatively with severity of RLS This further implicates the endogenous opiate system in the pathogenesis of RLS and suggests that RLS symptoms trigger the release of endogenous opiates in the medial pain system. Opioid Hypothesis for RLS Walters AS, Ondo WG, Zhu W, Le W. Journal of the Neurological Sciences 279: 62-65; 2009. . Post-mortem study of 5 RLS patients and 6 controls. In thalamus Beta endorphin reduced by 37.5% (p= .006, effect size 2.16). In thalamus Met enkephalin reduced by 26.4% (p =.028, effect size 1.58). Possible in vitro model of RLS (Sun et al. APSS 2003—Winner of honorable mention Young Investigator Award) Iron deficiency causes cell death in the substantia nigra in rats The dying cells in the substantia nigra are primarily dopaminergic although glial cells are affected as well. Opioids protect against the dopaminergic cell death under conditions of iron deprivation. 200 180 Percent of cells survival 160 140 Control 0.1 uM Def 1 uM Def 10 uM Def 100 uM Def 120 100 80 60 40 20 0 0 2 4 7 10 Days 12 14 21 % of cells survival 250 200 Control 150 5 uM DADLE 100 50 uM DADLE 50 200 uM DADLE 0 0 2 4 6 7 10 14 % of cells survival Days Control 250 200 5 uM DADLE + 50 uM Def 150 100 50 uM DADLE + 50 uM Def 50 0 0 2 4 6 7 10 14 200 uM DADLE + 50 uM Def % of cells survival Days 250 200 150 Control 100 50 uM Def 50 0 0 2 4 6 Days 7 10 14 Summary of animal model of RLS Low Fe V V V DA Cell Death High opioids and Low Fe V V V Less DA Cell Death Mu-Opioid Receptor Knockout Mice Genotyping +/- +/- +/+ +/- 230 bp PGK Mutant Allele Primer 1 Primer 2 230 bp Primer 2 WT Allele Building up a colony at UAB Genotypes identified by PCR. Mating heterozygous mu-Opioid receptor knockout mice to obtain homozygous mutant mice. Results to date of Mu opiate receptor deficient mouse # 1 Animals are more hyperactive during the sleep period as is characteristic of RLS (in mice this is during the day). Mice are more sensitive to pain as has been previously described in human RLS by Stiasny Kolster et al 2004 Results to date of Mu opiate receptor deficient mouse #2 Serum iron is low compared to control mice. Next Step is to sacrifice brains to see if there is brain iron deficiency, downregulation of D2 receptors and upregulation of Tyrosine Hydroxylase as in human RLS. New Project CSF study of RLS patients and controls to look for alterations in Beta endorphin Met enkephalin Leu enkephalin Early issue on definition of RLS Are RLS patients worse at night only because they are lying down or are the symptoms under circadian control? Our Early Circadian Studies Patients were still worse at night even though they were lain down semicontinuously both day and night. This effect was largely independent of sleep or sleep deprivation. Our Early Circadian Studies This suggests that criteria 3 and 4 for RLS are largely independent of one another and should be kept separate and not combined: Worsening at rest, e.g. sitting or lying Worsening at night New Project Bright Light at night to push the symptoms of RLS/PLMS to a later time of night. This will more definitively prove that RLS/PLMS is controlled by a circadian rhythm May be used as a therapy in situations where daytime symptoms are prominent. Neuroanatomy What structures are involved in RLS/PLMS? RLS patients have more gray matter in the pulnivar of the thalamus – by high resolution T1weighted MRI (Etgen et. al. 2005). By functional MRI during the sensory symptoms of RLS the thalamus and cerebellum are activated and during the PLMs the brain stem is activated near the red nucleus (group of Claudia Trenkwalder). Peripheral and Central Mechanisms in RLS There was decreased temperature perception in RLS patients with and without peripheral neuropathy. This suggests that there is a peripheral processing abnormality in patients with RLS due to peripheral neuropathy and a central sensory processing abnormality in patients with idiopathic RLS that may lead to the sensory symptoms of RLS (Schattschneider et al J Neurol 2004). Peripheral and Central mechanisms in RLS (cont) Static hyperalgesia as tested by pricking pain was abnormal in idiopathic RLS. This is normally thought to be suggestive of abnormalities in the peripheral nervous system. The peripheral processing abnormality may take place by some unknown mechanism since these patients did not have peripheral neuropathy. No peripheral neuropathy in these patients and the static hyperalgesia was normalized by long-term dopaminergic treatment implicating a central processing abnormality in RLS (Stiasny-Kolster et. al. 2004). Neurophysiology Blink reflex H reflex Elicitation of the flexor response by stimulation of the foot and comparison to PLMS. Brainstem auditory evoked responses Somatosensory evoked responses Central magnetic stimulation Paired transcranial magnetic stimulation Examination of the cortical silent period. Neurophysiology Brain stem generator inhibits lumbosacral generator for PLMS under normal circumstances. Lumbosacral generator becomes disinhibited under conditions of complete spinal cord transection or when sensory input from RLS overcomes the inhibition from the brain stem. PLMS ARE THEN PRODUCED. Integrated Motor and Sensory Model Brain Stem ( - ) V V --------------------------spinal cord transection V V Neuropathy/Radiculopathy V V V V LS spinal generator for PLMS <<<<<< RLS (+) SLEEP, Vol. 32, No. 5, 2009; 589-597 Relationship of RLS to Medical Conditions Four large epidemiologic studies from groups of Jan Ulfberg, John Winkelman and Barb Phillips all show Hypertension 1.5 x more likely in RLS-- Heart Disease 2.5 x more likely in RLS-- RLS and Stroke Elwood et al., J Epidemiol Community Health 2006;60:69-73. 1986 men aged 55-69 years After 10 years, 107 with RLS experienced an ischemic stroke Compared to controls relative odds of an ischemic stroke was 1.67 (1.07-2.60) P = 0.024 PLMS and daytime hypertension In patients with daytime hypertension, there is a direct correlation between the number of PLMS and the severity of the hypertension (Espinar-Sierra 1997). Recently reproduced in a much larger cohort by group of David Rye. Autonomic Nervous System and PLMS Group of Jacques Montplaisir – Pennestri et al. (Neurology 2007) Our group -- Siddiqui et al (Clin Neurophysiol). Fake PLMs little rise in BP. Real PLMs associated with rises in BP that are much greater (on up to avg 19 mm Hg for RRLMS) suggesting that autonomic nervous system may play a role in pathogenesis of PLMS. RRLMS>PLMS with arousals> PLMS without arousals> PLMW> Fake PLMs. Blood pressure changes associated with PLMS EEG Beat to beat BP Anterior tibialis EMG Nasal canula Abdominal strain gauge Pennestri et al., Neurology (2007) Autonomic arousals occur in tandem with PLMS (in RLS) Pennestri et al., Neurology (2007) Autonomic Nervous System and RLS/PLMS continued 80% of patients with RLS have PLMS. Previous literature shows that hypertension and heart disease are associated with RLS. Perhaps rise in BP associated with PLMS are the cause of heart disease and perhaps stroke associated with RLS. Hypothetical spinal cord positive feedback mechanism mediating dopamine responsive Restless Legs Syndrome Clemens, Rye and Hochman, Neurology 67: 125-130 (2006) 1) DA inhibits preganglionic sympathetics, thus, in its absence, basal sympathetic tone may increase. 2) Increased adrenaline via innervation of skeletal muscle, in turn, might irritate muscle spindles. 3) The resulting enhanced input from pain-encoding high threshold muscle afferents in lamina I are insufficiently suppressed in the absence of DA or D2-like receptors. Hypertension and RLS/PLMS Interestingly vasodilators were among the first treatments used by Ekbom in the 1940’s and 1950’s for RLS Phenoxybenzamine an alpha adrenergic receptor blocker was used to treat PLMS and normalized the peripheral pulse responses (Ware et al Sleep 1988) Hypertension and RLS/PLMS Controlled studies are needed to: Verify the response of RLS to antihypertensives. Verify the response of PLMS to antihypertensives. Stroke and RLS RLS patients with no prior history of stroke Tendency toward an increased number of silent strokes compared to controls. However, study was small and much need for statistical correction due to other stroke risk factors Stroke and RLS/PLMS Is RLS/PLMS mediated by its increased association with hypertension or heart disease ? Or is RLS/PLMS an independent risk factor for stroke? New Project Repeat study looking for silent stroke by MRI in RLS patients However, recruit patients with no other stroke risk factors. Will also correlate PLMS with number/size of silent strokes. Summary of pathophysiologic mechanisms for RLS/PLMS Low dopamine, iron and opioids may contribute to the pathogenesis of RLS/PLMS The discovery of susceptibility genes for RLS will give us new hypotheses for the pathogenesis of RLS. Immunologic mechanisms represent a possible new frontier for RLS research. Summary of pathophysiologic mechanisms for RLS/PLMS RLS/PLMS are under circadian control Suprasegmental Disinhibition may contribute to the pathogenesis of PLMS Increased sympathetic tone in the absence of dopaminergic innervation may explain the increased prevalence of hypertension, heart disease and perhaps stroke in RLS/PLMS – probably more relevant to adult RLS.