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Neuromuscular Disorders
Wilma J Koopman RN(EC) MScN CCN(C) Nurse Practitioner
LHSC University Hospital London Ontario
March 19 2013 CNA Neuroscience Nursing Review Course
Objectives:
1. Review anatomy and function of neuromuscular disorders
2. Describe common NM diseases: ◦ Guillain Barre syndrome
◦ Muscular Dystrophies
◦ Myasthenia Gravis
3. Discuss treatments and nursing management of common NM diseases
ANATOMY AND FUNCTION
Peripheral Nervous system :
Anterior Horn cells (ALS) , Peripheral nerve (GBS) , Neuromuscular Junction (MG), muscle ( DMD)
Pathophysiology maybe anatomical, metabolic, inflammatory, immunological and idiopathic
Anatomy and Function
Lower motor neurons
Peripheral nerves
Neuromuscular Junction
Muscle
Lower Motor Neurons (LMN) Cell body in the anterior gray column of the spinal cord (eg
polio , ALS)
Nerve fibre extends to the muscle
Includes cranial nerves and spinal nerves of the PNS
Peripheral Nerves (PN) PN carry input to CNS via sensory ganglia (afferent fibers)
with output to muscles and autonomic ganglia via motor (efferent) fibers.
Are mixed nerves-motor, sensory, or autonomic
CELL BODY
AXON
Myelin sheath
Schwann cell
Node of Ranvier
Synaptic terminals
Dendrites Nucleus Synapses
Nerve Physiology
Action potential generated in cell body moves along the nerve as the membrane depolarizes
Opening Na channels
Depolarization and impulse propagation of impulse are saltatory (ie moves from one node to another
node in myelinated axons)
Autonomic Nervous System
contains motor neurons that regulated activities of visceral organs
Effect smooth and cardiac (involuntary) muscles and glands
ANS – sympathetic, parasympathetic
Sympathetic: fight or flight ◦ Heart rate and BP increases, bowel and bladder function reduced
Parasympathetic – homeostasis
decreases heart rate , increases gastrointestinal and bladder activity
MUSCLE
Skeletal and cardiac muscle is striated
Smooth muscle (ie GI tract, urinary system) unstriated
Muscle is surrounded by connective tissue and a rich blood supply
Contains important proteins, and the energy system for muscle contraction
Eg Muscular dystrophies or mitochondrial diseases
Neuromuscular Junction (connection between motor axon and muscle fibers )
Guillain Barre Syndrome (GBS)
Acute immune mediated polyneuropathies are
classified under the eponym GBS
Heterogenous condition, many variants
Most often presents as an acute monophasic
paralyzing illness provoked by a preceding
infection
Case
63 yr old male
URI 8 days and diarrhea 2 days pre admission
Paresthesia hands and feet and abnormal taste
one day pre admisssion
Followed by imbalance and leg weakness
(proximal > distal) presenting to ER
Case
PMH
Hypertension
Intentional 30 lb wt loss
ER exam
Cardiac, resp, GI systems normal
Cranial Nerves normal
Mild proximal >distal weakness
UE Proximal 4/5 distal 5/5)
LE Proximal 4-/5 distal 4+/5
DTRs absent except right triceps
Sens dec vib jps toes, dec pp fingers
Case
Course in Hospital
24 hrs after admission ICU ..intubation,
tracheostomy, G-J tube
Paralyzed (including craniobulbar ) except for
plantar flexion
Treated with IVIG
4 months in ICU
Case
Neurology floor
Sept to Nov ..multiple complications…infections (UTI, RESP), Right subclavian DVT, Right thigh hematoma. Pain
Power improved
Facial 4;Shoulder abductors 2;biceps, triceps, 1, wrist extensors 0, Finger flexors 2, intrinsics, finger extensors, 0
Hip flexion 2, Hamstrings 4, quadriceps 0, ADF 2-2+;APF 5
Decreased PP to wrist and ankles, Vib mildly impaired
DTR returned
Transferred to Rehab
GJ tube and trach in place
AIDP-Guillain Barre Syndrome
(GBS) Most common cause of acute flaccid paralysis in western Countries
Incidence 1-2/100, 000
All age groups-both sexes
Monophasic paralytic illness
Variable progression and severity
1/3 require mechanical ventilation:median 27 days
Progression 2-4 weeks, recovery in 6-24 months
Favorable prognosis, residual deficits in 20%, mortality rate 5-8%
GBS- Pathophysiology Auto-immune
Develop auto-antibody and cell-mediated immune response against myelin/gangliosides -local inflammatory reaction-segmental demyelination+/-axonal degeneration
Immune responses towards infecting organisms cross-react with neural tissues
In ~10% of cases immune response is directed against ganglioside epitopes in axonal membrane(molecular mimicry)
animal model disease; EAN –experimental allergic neuritis
Pathogenesis of GBS
Demyelination (90%) > axonal (10%)
Immune-mediated - molecular mimicry – 2/3 have preceding infection
• Campylobacter, mycoplasma, herpes viruses (CMV, VSV, Mono etc)
– Campylobacter and gangliosides
Humoral (cytokines and antibodies) and cellular attack on myelin antigens
Hartung, Willison, Kieseier
Curr. Opin. Neurol 2002
Diagnostic Features of GBS
Progression over days to a few weeks
Relative symmetry
Mild sensory signs or symptoms
Cranial nerve involvement
Onset of recovery 2-4 weeks after halt of progression
Autonomic dysfunction
Initial absence of fever
Elevated CSF protein after I week of symptoms
Abnormal results of electrodiagnostic studies with slowed conduction or prolonged F waves
GBS: Clinical Features
Progressive, fairly symmetric muscle weakness
Depressed or absent deep tendon reflexes
Pts present days to a week after onset of sx
Variable course - mild walking difficulty to
complete paralysis of all limbs, face, respiratory
and facial muscles
Clinical Features (cont‘d)
Onset: Usual – proximal legs: 10% arms and
facial muscles
Ventilation 30%
Facial, oropharyngeal weakness 50%
Oculomotor 15%
Paresthesias:hands and feet with weakness in
> 80%, but abnormalities on exam mild
Clinical Features (cont‘d)
Prominent severe pain in lower back
Dysautonomia 70%
-tachycardia (Most common), bradycardia, other
arrythmias
-urinary retention, ileus
-hypertension / hypotension; orthostatic
hypotension
-loss of sweating
Unusual features
Papilledema
Facial myokymia
Hearing loss
Meningeal signs
Vocal cord paralysis
Mental changes ( hallucinations, delusions, REM
sleep abn)
Clinical Course
Progresses for two weeks,
By 4 weeks, 90% have reached nadir
Disease progression > 8 weeks consistent with a
diagnosis of Chronic Inflammatory
Demyelinating Polyneuropathy (CIDP)
Diagnostic Tests
Lumbar Puncture (CSF)
Electrophysiology (EPS)
Antibodies (Ab)
MRI Spine ( only with clinical suspicion)
Other:
Viral studies
EPS
Laboratory Features
Lumbar Puncture
CSF protein elevated-normal WBC (albuminocytologic dissociation) present in 80-90% by one week post symptom onset
Electrophysiology ( EMG and NCS)
Demyelination, conduction block
Axonal features (later or in axonal variants)
• Antibodies
eg GQ1b 85-90% Miller Fisher Variant
GBS-Post-Infectious Illness
Triggering bacterial or viral illness –2/3 of pts-either gastroenteritis or URTI
Latency to neuropathic symptoms 1-4 weeks
Most frequent antecedent pathogens:
-Campylobacter jejuni-30%(40-60% in Japan & China)
-Cytomegalovirus-20%
-Epstein Barr virus 5-10%
Classification of GBS
AIDP – acute inflammatory demyelinating
polyneuropathy
MFS - Miller Fisher Syndrome
AMAN- acute motor axonal neuropathy
AMSAN -acute motor/sensory axonal
neuropathy
Common GBS Variants
AIDP (GBS) most common in NA (85-90 % of
cases)
MFS –opthalmoplegia ataxia, and areflexia (5%)
AMAN, AMSAN – axonal forms (5-10 %) more
frequent in China, Japan and Mexico
Variant:AIDP (GBS)
Progressive symmetric muscle weakness absent / reduced reflexes
Myelin of peripheral nerve is site of immune attack
Inflammatory demyelination starts at level of nerve roots leading to conduction block
Multifocal patchy widespread peripheral nerve demyelination
Reversal of conduction block and remyelination can occur rapidly over weeks to months
Secondary axonal degeneration delays and may result in incomplete recovery
Variant: Miller Fisher Syndrome
Opthalmoplegia, ataxia, areflexia
I/3 may have extremity weakness
Anti GQ1B Ab present in 85-89 %
Ab linked to oculomotor nerves
EPS absent sensory responses without sensory
conduction slowing
If weak may also have motor nerve abnormalities
Variant: AMAN
Most preceded by campylobacter jejuni infection
Freq in Japan, China in young people
Summer predilection
DTR preserved
Sensory nerves not affected
EPS-selective motor and axonal involvement
Variant: AMSAN
More severe form of AMAN with sensory involvement
Marked axonal degeneration, incomplete recovery
EPS -axonal both sensory and motor nerves
AMAN and AMSAN strongly associated with Ab to the gangliosides GM1, GD1a, GD1b, GalNac all present in peripheral nerve axons
These Ab can be induced by campylobacter jejuni infection
Pathophysiology is that of antibody and complement mediated axonal nerve damage
Diagnostic Criteria
National Institute of Neurological Disorders and Stroke
(NINDS) (Annals of Neurology 1978)
Required Features:
Progressive weakness of one limb, ranging from minimal to
total paralyis of all four limbs, trunk, bulbar, and facial
muscles and external opthalmoplegia
Areflexia (hyporeflexia at knees and biceps acceptable)
Diagnostic Criteria (NINDS)
Supportive Features:
Progressive symptoms over days to 4 weeks
Relative symmetry
Mild sensory signs or symptoms
Cranial nerve involvement, especially bilateral facial involvement
Recovery starting 2-4 weeks after progression halts
Autonomic dysfunction
No fever at onset
Elevated CSF protein with cell count <10 mm3
Electrodiagnostic abnormalities consistent with GBS
Diagnosis Doubtful if:
Sensory level (decrement or loss of sensations
per neurologic examination
Marked persistent asymmetry of weakness
Severe and persistent bowel and bladder
dysfunction
> 50 WBC in CSF
Differential Diagnosis
Other acute polyneuropathies:
-acute arsenic poisoning, n-hexane (in glue-sniffing neuropathy
-vasculitis
-Lyme Disease
-Tick paralysis ( (mostly in children)
-Porphyria
-Sarcoidosis
-Leptomeningeal disease
-Paraneoplastic disease
-Critical illness
Differential Diagnosis
Spinal Cord Disorders (SCD):
Acute myelopathies due to spinal cord
compression, and acute transverse myelitis can
be confused as DTRS depressed in acute stage
of spinal cord disease
Acute bowel and bladder dysfunction and a
sensory level point to SCD .
MRI---focal spinal cord lesion
Differential Diagnosis
Neuromuscular Junction Disorders
Botulism, Lambert Eaton myasthenic syndrome
May present with acute weakness, sensory S&S
absent
Differential Diagnosis for Miller
Fisher Syndrome
Brainstem Stroke (acute vs gradual onset)
Wernicke‘s Encepahlopathy (mental status,
nystagmus)
Brainstem encephalitis (mental status)
Myasthenia gravis (EPS)
Prognostic Factors
Associated with poorer prognosis:
Older age
Rapid onset (<7 days ) to presentation
Need for ventilation
Average distal motor response amplitude reduction to <
20% of normal
Preceding diarrheal illness
Long term outcome
At 6 months 65% able to walk independently
80% recover completely or have minor deficits
5-10% have a prolonged course with several months of ventilator dependency and very delayed and incomplete recovery
3% remain wheelchair bound
5% die (if ventilator dependent 20% die)
Causes of Death:
Acute respiratory distress syndrome, sepsis, PE, unexplained cardiac arrest
Acute Treatment & Management
of the GBS patient
Acute Treatment
Plasma exchange or Intravenous
Immunoglobulin can be used
Both are equally effective
IVIG is easier to administer and therefore used
more commonly
Costs of both Rx are similar (approx. $10,000
per course)
IVIG
IVIG is a blood product and requires consent
Side effects may include headache & flu-like symptoms (approx 50%), aseptic meningitis.
Serious but rare side effects include anaphylaxis, DVT/PE, or stroke
The total dose is usually 2g/Kg and is divided into 2 – 5 days (depending on patients ability to tolerate the volume)
IVIG
Requires frequent monitoring (VS @ pre, 15
minutes then q 1h)
Start slowly then increase if tolerated
If severe reaction – Stop and call MD
If mild reaction – try slowing the rate down
May take 3-10 days to work
Plasmapheresis
PLEX or Plasma Exchange
Essentially, each PLEX exchange removes 60% of the antibodies in the system
– 1st Rx 60%
– 2nd Rx 84%
– 3RD Rx 93%
– 4th Rx 97%
– 5th Rx 99%
Acute Management - Autonomic
Cardiac/Hemodynamic
Serious and potentially fatal, and occur in approximately 20% of patients
Severe bradycardia or heart block possibly causing asystole and may require pacemaker
Dysrythmias (Afib, VFib) may require intervention
Swings in BP
Acute Management - Autonomic
Nursing Care
Monitor VS – be concerned with changes or fluctuation eg. HR 60 and then 85, or SBP 150 then 100
– Abrupt swings in BP may herald a sudden arrhythmia
More significant changes in VS may require intervention (eg. brady – atropine)
Severe bulbar dysfunction and quadraplegia – more likely to have cardiovascular instability
Acute Management - Autonomic
Nursing Care
Monitor ECG
In beginning stages of the disease, monitor these with position changes and mobilizing (eg. standing up). IF there are changes, maintain bedrest
Acute Management – Autonomic
Bowel and Bladder
Constipation is common
50% develop paralytic ileus (some had Ogilvie‘s
Syndrome develop)
Urinary retention may develop
Acute Management – Autonomic
Nursing Care
Assess bowels daily
Aggressive bowel regime to maintain BMs q1-2
days (especially if on narcotics)
Urinary catheterization intermittently if urinary
retention present. May need indwelling catheter
for hemodynamic monitoring in acute phase
Acute Management - Respiratory
30% GBS patients require ICU for respiratory
support
Respiratory compromise may be caused by 2
mechanisms
– Neuromuscular weakness of diaphragm
– Bulbar dysfunction causing difficulty with secretion
management
Acute Management - Respiratory
Nursing Care
Monitor for respiratory decline (tachypnea,
sweating, orthopnea, paradoxical breathing,
accessory muscle use)
O2 satn and gases will only change in later
stages
FVC – look for trend downwards (not just
absolute value to be > 1 litre), look for difference
sitting to supine
Acute Management - Respiratory
Nursing Care
If intubated, PFTs done at 2 weeks are best
predictor for need for ongoing ventilator support
Tracheostomy should not be performed prior to
this unless on an individual basis.
Acute Management - Pain
Often one of the first symptoms – back pain
May also develop neuropathic pain over time
(burning, numbness/tingling)
NSAIDS, tylenol, and narcotics are helpful
If Neuropathic pain – gabapentin, amitriptyline
may also be useful
Acute Management – Prevention of
Complications
Prevent secondary nerve injury - protect elbows
(ulnar nerve) and behind knees (peroneal nerve)
with foam pads
Prevent DVT & PE – ensure LMWH or heparin
ordered for non-ambulatory patients
Prevent skin breakdown – ensure adequate
nutrition (if not taking p.o. need for NG), and
position changes/pressure relief bed
Acute Management - Psychosocial
Patient & family need education, support, &
reassurance. Pt. may need to go to ICU
(remember 30%)
If pt. is deteriorating, reassure them that this
disease most commonly improves!
Pts not needing ICU – excellent recovery
Pts needing ICU – a review of 20 yrs GBS pts
admitted to ICU at LHSC demonstrated that 63%
returned to walking independantly
Acute Management –
‗Pearls‘ to Remember
The earlier in the course of the disease, the
more likely pt. will deteriorate (eg. Pt admitted 3
days after symptom onset vs. 9 days)
The quicker the weakness worsens (eg. shift to
shift) = the more likely the patient will develop
respiratory compromise and require ICU
Acute Management –
‗Pearls‘ to Remember
If quick changes, keep on bedrest (more likely to
have autonomic problems)
If patient further into course of disease with little
change in weakness, consider slow mobilization
BUT monitor position changes (VS, ECG, and
symptoms)
Muscular Dystrophy (MD)
Inherited group of progressive muscle disorders
Result from defects in a number of genes
required for normal muscle function
Some of the genes have been identified
Muscle weakness is the primary symptom
Muscular Dystrophy
OVERVIEW
Clinical Features
Diagnosis
Management and Treatment
Clinical Vignettes
Pediatric MD
Most common childhood form of MD is
Duchenne (DMD)
Others include:
Becker (BMD)
DMD and BMD are caused by a mutation in the
dystrophin gene …..dystropinopathies
Muscle fiber degeneration is the primary pathologic
process
Adult MD
Most common is Myotonic Muscular Dystrophy
(DM1)
Facioscapulohumeral MD
Limb Girdle MD (types 1A, 1B, 1C etc)
Genetics and MD
X-linked:
Duchenne and Becker MD
Autosomal recessive:
Limb Girdle MD 2A, 2B, 2C, etc
Autosomal dominant:
Myotonic Dystrophy 1
Facioscapulohumeral MD
Limb Girdle 1A 1B 1C etc
X-Linked Recessive Inheritance
X-linked recessive disease usually occurs in males who have inherited a recessive X-linked mutation from their mother.
Rarely, the disease may be seen in females who have inherited mutations in the same gene X-linked from both parents.
More typically, the mother is a carrier and is unaffected,
Female carriers of X-linked disorders may have mild clinical manifestations related to the disorder —
Clinical Characteristics
DMD is associated with the most severe clinical
symptoms
Occurs in 1/3500 live male births (prevalence 3
per 100,000)
BMD has a similar presentation to DMD but a
relatively milder course
Rarer---1/30,000 male births
Genetics and Pathogenesis
DMD is caused by a defective gene located on the X chromosome that is responsible for the production of dystrophin
Dystrophin is located on the cytoplasmic face of the plasma membrane of muscle fibers, functioning as a component of a large, tightly associated glycoprotein complex
Dystrophin gene
Dystrophin
Dystrophin normally stabilizes the complex
therefore shielding it from degradation
In the absence of dystrophin the glycoprotein
complex is digested by proteases.
Loss of these membrane proteins may initiate
the degeneration of muscle fibers resulting in
muscle weakness
Dystrophinopathies
Duchenne MD: caused by an absence of
dystrophin
Becker MD: caused by a deficiency of dystrophin
DMD
Caused by mutations in dystrophin gene in the X
chromosome at Xp21
This large gene expresses dystrophin
It is present in the heart, striate and smooth
muscle and brain
Treatment
Management has improved, treatment elusive
Over 30 different drugs have been tried
Only steroids (prednisone, prednisilone,
deflazacort) appear to slow progression
Looking at molecular therapy…DNA gene
transfer, …..stem cell therapy
Clinical Overview of DMD
First descriptions in mid 1800‘s
―clinical picture of slowly progressive muscle wasting disease marked by symptoms that develop before age 5‖
Early on affects proximal hip and shoulder girdle muscles, anterior neck and abdominal muscles
If only receiving supportive care...limited to a wheelchair in late childhood, early teens and usually die of complications of respiratory insufficiency and/or cardiomyopathy in their late teens or early twenties
Historical descriptions
Meryon 1852 (Duchenne, 1861)
Meryon..4 brothers….described one
In infancy the child was a dead weight
Throughout early childhood..never jumped
At age 8 trouble climbing stairs
Age 11 couldn‘t stand
Age 14 extremeties very weak
Age 16 died
Further Historical Highlights
Erb (1891) studied 29 DMD pts
Described the clinical and muscle pathologic
features that typify DMD
1930-1970 resports of increased CK in DMD
and female carriers
Late 1980‘s gene discovery
Mutations in dystrophin gene …diagnostic
testing
Diagnosis
History physical exam
CK (10X n early on)
DNA testing
Rarely EMG , muscle biopsy
Other Clinical manifestations
Respiratory Insufficiency
If not receiving corticosteroids: between ages 11-20 yrs
FVC declines to <60-70% of N. (2L)
This correlates with decreased cough,..pneumonia
Decreased night time ventilation then respiratory failure
When FVC < 1.0 L and PCO2 45 mm Hg, 3-5 yr
survival
Cardiomyopathy
ECG abnormalities early on ( increased R/S amplitude in lead VI and deep Q waves in V5 V6)
Late stage of DMD atrial arrythmias
Echocardiogram reveals primary alteration in left ventricular function
Resting tachycardia common throughout each stage of DMD
Gastrointestinal Dysfunction
Involves both voluntary and smooth muscles (due to deficiency in dystrophin)
Bulbar weakness( upper voluntary skeletal muscle portion of pharyngeal-esophagael tractand lower involuntary smooth muscle portion)
Freq clearing of throat, and coughing esp at mealtime
Delayed gastric emptying
Acute gastric dilatation (diaphragmatic pressure)
Chronic intestinal dysfunction..constipation, distention hypomotilty, impaction
Management
Maintain ambulation
Optimize cognition
Anticipate complications
eg. wt gain, joint contractures, respiratory
insufficiency, scoliosis, GI hypomotility,
cardiomyopathy
Pediatric DMD Health care team
Pt, family
Primary care Dr, neurologist, orthopaedic
surgeon, cardiologist, pulmonologist, social
worker, PT, OT, school teachers
Issues over the decades
Diagnosis……..biopsy to DNA
Respiratory Failure……BIPAP
Adults living with pediatric diseases
Families of NM Adults……caregivers to distant
support
Research:science to psychology
Adult DMD
Health care team
Neurologist, APN
Respirologist, Palliative Care Consultant
Nutritionist, OT, PT, Physiatry, social work, PSW
Case 1
Transferred to adult NM clinic Oct 2004 (age 24)
Works part time, lives alone with support care of 14-16 hrs per day
PMH
DX age 6
Difficulty arising from the floor age 8
Using wheelchair age 12
BiPAP at night age 18
No Family hx of DMD (has 2 healthy brothers)
Case 1: Surveillance
P 110 beats/min
ECG : (2005) NSR, deep Q wave lead 111, AVF
Echo: normal
FVC: (2005) 0.6L FEV1 0.41L PCO2 47 PO2 78
MBS: 2006, 2007-mild oropharyngeal dysphagia
Annual flu shot, Pneumovax
Antibiotic Rx on order (Levofloxacin)
Ocular exam : early cataracts, normal intraocular pressures
Allied Health team
Physio: lower limb splints, breath stacking in
exsuflator
OT: seating, upper limb splints
Social Work
Nutrition
Speech Language Pathologist
What is MG?
Rare Autoimmune Disorder of the Neuromuscular
Junction (NMJ)
Affects Voluntary Muscles
– Fluctuating muscular weakness
– Worsening weakness with repetitive action
NMJ in MG
Three main mechanisms of dysfunction
Acetylcholine Receptors (AChRs) by muscle
autoantibodies:
– Blockade of AChRs by antibodies at the receptor
binding sites
Source: Meriggioli and Sanders,
2009
AChR Antibodies Anti-AChR (Binding, Blocking, Modulating)
Present in 65 - 80% MG cases
Source: Macko slides
NMJ in MG
Three main mechanisms of dysfunction AChRs by
muscle autoantibodies:
– Blockade of AChRs by antibodies at the receptor
binding sites
– Degradation of AChRs
Source: Meriggioli and Sanders, 2009
Neuromuscular Junction
Destruction by AChR antibodies
and complement
Source: Macko slides
NMJ in MG Three main mechanisms of dysfunction AChRs by
muscle autoantibodies:
– Blockade of AChRs by antibodies at the receptor
binding sites
– Degradation of AChRs
– Damage to the muscle endplate distortion of
postsynaptic membrane folds
Source: Meriggioli and Sanders, 2009
Ach Receptors are Internalized and NMJ
simplified by antibody and complement
Source: Macko slides
Auto Antibodies Found
Antibodies to AChR protein:
– 85 % of patients with generalized myasthenia
– 60% of those with ocular myasthenia
Anti-MuSK Ab
– 40% of seronegative cases
Thymus Gland
Role in autoimmune process
Thymoma or Hyperplasia in MG
– 10 - 15% of MG patients
– Greater than 80% found at early onset of disease
– Equal in Men and Women
– Occur at any age
Source: Meriggioli and Sanders, 2009
CT of Thymus Gland
Normal vs. abnormal presentation (Thymona) in Myasthenia Gravis.
Source:
Epidemiology
Rare Disease
– 20 per 100,000 in the US population
– Age <40 yrs: Women more than men
– Age >50 yrs: Men more than women
– Equal in both sexes for puberty and >40 yrs.
Source: Meriggioli and Sanders, 2009
Clinical Feature of MG Muscle fatigue causing weakness
– Activity exacerbates symptoms
– Fluctuates throughout the day
– Improves with rest or early morning
Involvement of specific muscle groups
Source: Meriggioli and Sanders, 2009
Myasthenia Gravis Classification
Ocular MG (15%)
–Ptosis
–Diplopia
Generalized MG
Clinical Presentation
Ocular Muscles
Initial symptom – ocular in 85% patients:
– ptosis (32%)
– diplopia (14%)
– ptosis and diplopia (36%)
– blurred vision (3%)
Source: Grob et al., 2008
Facial & Bulbar Muscles Facial Weakness
– Eyelid closure
– Drooling
Bulbar /Oropharyngeal Weakness
– Dysarthria (nasal speech)
– Dysphagia
– Dysphonia
– Jaw weakness (chewing problems)
Source: Meriggioli and Sanders, 2009
Neck & Limb Weakness
Neck Muscle Weakness
– Neck flexion
– Neck extension (head droop)
Limb Muscle Weakness
– Proximal symmetrical
– Arms > Legs
Source: Meriggioli and Sanders, 2009
Respiratory Muscles Respiratory weakness of:
Intercostal muscles
Diaphragm
Source: Meriggioli and Sanders, 2009
Emergency issues in MG
Detection of an impending crisis
Management of an impending crisis
Nursing/medical history
Medication list
Prodromal events
Patients presenting with
undiagnosed MG
Differential Diagnosis of presenting symptoms
Ocular
Bulbar
Differential diagnosis:
Ocular symptoms: Brain tumor
Bulbar: brain stem stroke, ALS
Respiratory: MI, PE
Assessment
Pts with established MG
Provocative factors:
Infection **
Idiopathic
Medications
Stress induced
Drugs reported to cause an exacerbation:
Antibiotics: macrolides, floroquinolones,
aminoglycosides
Antidysrythmic agents: beta-blockers, calcium channel
blockers, quinidine
Miscellaneous: corticosteroids
TESTS
To differentiate between cholinergic or
myasthenic crises
Edrophonium: Tensilon challenge test:
Other tests
Ice pack
Electromyography-probably not available on a
emergent basis
Other tests
Pulmonary Function studies
FVC, FEV1 supine , standing
Pulse oximetry
ABG‘s
Emergent Signs and symptoms
Worsening dysphagia and dysarthria despite
taking medication
Severe choking
Emergent Signs and Symptoms
Weak breathing-breathing worsening 30 minutes
after taking pyridostigmine
Fast shallow breathing when beginning to feel tired
Weak voice
Head drop
Signs and Symptoms of Crisis
Restlessness, apprehension
Generalized muscle weakness
Dyspnea
Increased bronchial secretions, sweating
Dysarthria dysphagia
Complications of Emergent Issues
Respiratory failure
Hypoxemia and respiratory acidosis may render the
patient somnolent, and unresponsive
Pneumonia may be a cause of death
Chronic respiratory failure
Cholinergic vs Myasthenic Crises
MG Crisis
Prodrome of infection
S&S of worsening MG
12-16% of generalized MG patients experience
crisis
Cholinergic Crisis
Over medication with anticholinesterase drugs
Symptoms
Abdominal cramping/diarrhea (MUSCARINIC
Effects-slow)
Profound generalized weakness, excessive
pulmonary secretions and impaired respiratory
function (NICOTINIC Effects-rapid)
Crises
Both are medical emergencies
May require tracheal intubation and assisted
ventilation
Parameters: Negative Inspiratory Force (NIF) <-
20cm H20
FVC <15cc/kg body weight
Humidified Air and Oxygen (if PO2<70)
Cholinergic Crisis Management
Stop ChE
Intubate
Ventilate
Treat underlying cause:
Infection, electrolyte disturbance (hypokalemia,
hypocalcemia, hypermagnesium )
Resume ChE at lower dose and escalate slowly
MG Crisis Management
Intravenous immunoglobulin ( IVIg)
Blood product –safe
Modulates the immune system – how?
Benefits seen in 70%of patients within 2 weeks
Common side effects –mild
MG Crisis Management
Plasma Exchange (Plex)
Removes the antibodies which cause weakness
Benefits in 70% of patients within 2 weeks
Few serious effects
More difficult to arrange on short notice
IVIg and Plex equal in terms of efficacy
Plasmapheresis more rapid effect than
IVIG ( removes circulating antibodies
including those implicated in MG…3
days versus 2 weeks with IVIG)
IN HOSPITAL CARE
Admit to a monitored unit
Admit with pneumonia-?aspiration
Treat with Plasmaphersis, or IV Ig
Ongoing care with a neurologist
Clinical Vignettes
Interactive Review
Case 1
72 year old healthy male
Admitted to medical service
2 month history of dysphagia, difficulty handling
secretions, dysarthria, SOB
CPAP for OSA
Developed increasing SOB, unable to lay flat to
sleep
Anxious, drooling, unable to swallow
Rx: IvIg, Mestinon, Pred
Azathioprine, CPAP/BiPAP
LOS 20 days
Readmitted for 3 days
Dysphagia, dysarthria, unable to handle secretions
Rx with IVIG, treated with AZA, Pred, Mestinon
Case 2
69 year female in Northern Ontario
Dx locally with MG treated with Mestinon
Three days before admission 2 visits to local emerg
Mestinon increased to 120 mg every 2-3 hours
Transferred to UC unable to handle secretions, dysarthric,
proximal fatiguable weakness, facial weakness, constant
double vision, ptosis
Intubated within 24 hours
Mestinon stopped
Solumedrol IV 500mg BID
Complications: upper GI bleed, MI, diverticulitis-abscesses
IVIG contraindicated – renal dysfnction
Plasmapheresis-cardiac risk
Mestinon slowly reintroduced
Prednisone 50 mg every other day
Case 3
24 y.o.Female presents to the ER w/ one week worsening symptoms of
diplopia, dysphagia, dysarthria, facial weakness and fatigue which she
reports is worse during the afternoon. She states that she just got over a cold
over 2 wks ago. You noticed during the interview that she is restless, her
voice is becoming more nasal and dysarthric and she has a weak cough and
SOB.
Exam: BP 130/88 P-99 RR-32 T-99F
PMH: MG diagnosed x 1.5 years limited to ocular symptoms and have been
symptom free x 3 months
Current Meds: prednisone 20 mg daily, vitamins
Impaired Communication Symptoms: Dysarthria, Dysphonia,
facial weakness
Conserve energy
Limit interview question to Yes/No answer
Find alternate way of communication—ie writing
Patient education
Potential for Aspiration r/t Bulbar
Weakness Symptoms: dysphagia, dysarthria,
weak cough,dysphonia
Keep HOB up
Assess breath sounds
Provide suction
Keep pt informed
Encourage small sips of liquid
Ineffective Respiratory Function
Symptoms: weak cough, Dyspnea
Assess and respiratory status—RR and effort
Assess gag and cough
Suction oral secretion
Check serial FVC
O2 support
Standby for ventilatory support
Provide pt education and emotional support
Altered Visual Function
Symptom: diplopia
Provide alternating eye patch
Provide pt education on energy conservation
???
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