Download Pathogenesis - North East Sleep Society

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.