Myopathy: A
Closer Look
Dr shabeel pn
Myopathy
Definition
neuromuscular disorders in which the
primary symptom is muscle weakness due
to dysfunction of muscle fiber.*
* Definition by the National Institute of Neurological Disorders and Stroke
Let’ Start With Basics!
Muscle Anatomy: gross and
microscopic
MUSCLE FIBER
Function of Muscle
Motor Unit
A motor unit is made up of a motor neuron and
all the muscle cells it stimulates. Motor units
vary in size. Small motor units are used for
precise, small movements; large motor units
are are used for gross movements.
The number of cells within
a motor unit determines
the degree of movement
when the motor unit is
stimulated. Muscle tone is
maintained by
asynchronous stimulation
of random motor units.
Normal Muscle
Characteristics of the Three Muscle Fiber Types
Fiber Type
Slow Twitch
Type I
Fast Twitch A
Type IIA
Fast Twitch B
Type IIB
Contraction time
Slow
Fast
Very fast
Size of motor
neuron
Small
Large
Very large
Resistance to
fatigue
High
Intermediate
Low
Activity used for
Aerobic
Long term
anaerobic
Short term
anaerobic
Force
production
Low
High
Very high
Mitochondrial
density
High
High
Low
Capillary density
High
Intermediate
Low
Oxidative
capacity
High
High
Low
Glycolytic
capacity
Low
High
High
Abnormal Muscle
Myopathy: symptoms
Muscle Weakness
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Proximal Muscles>distal muscles
Fatigue
Difficulty rising from a chair, floor,
tub
Difficulty with stairs
Difficulty with overhead tasks
Respiratory muscles
Bulbar weakness- speech,
swallowing, oculomotor, facial
Myopathy: symptoms
Pain
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Mostly with inflammatory and
metabolic
High serum CK level
Aching, dull, cramping
Patients will say: “sore”, “ache”,
“spasm”
No numbness or paresthesias
Physical Exam:
Full exam is important!
Observation – look for muscle
atrophy, deformities
Strength testing – manual
muscle test
ROM testing
Functional testing
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Stand up from a chair
Walk
Step up on a low stool
Don’t forget REFLEXES and
SENSATION
Myopathic Disorders
Inflammatory Myopathies
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Polymyositis
Dermatomyositis
Inclusion body myositis
Viral
Muscular dystrophies
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X-linked
Limb-girdle(ar/d)
Congenital
Fasioscapulohumeral (ad)
Scapuloperoneal (ad)
Distal (Welander) (ad/r)
Myotonic Syndromes
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Myotonic dystrophy (ad)
Inherited
Schwarz-Jampel
Drug-induced
Congenital myopathies
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Central core disease
Nemaline myopathy
Myotubular
Fiber-type disproportion
Metabolic myopathies
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Glycogenoses
Mitochondrial
Periodic paralysis
Endocrine myopathies
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Thyroid
Parathyroid
Adrenal/steroid
Pituitary
Drug-induced/toxic
Myopathy: types
Muscular dystrophies
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Inherited
Abnormal muscle proteins
Progressive course and early onset
Congenital
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Slowly progressive or non-progressive
Distinct finding on muscle biopsy
Metabolic
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Defect in intracellular energy production
Inflammatory
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Acquired
Caused by immune or infectious process
Almost always are associated with elevated
Creatinine Kinase level in serum.
Atrophic
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Drug-induced (Colchicine, AZT, ETOH, Statins
(1/10,000 per year)
Endocrine (steroid)
CK is most often normal
Myotonic
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Congenital or adult
Cardiopulmonary compromise
Epidemiology
Worldwide incidence of all inheritable
myopathies is about 14%
Overall incidence of muscular dystrophy is about
63 per 1 million.
Worldwide incidence of inflammatory
myopathies is about 5–10 per 100,000 people.
More common in women
Corticosteroid myopathy is the most common
endocrine myopathy and endocrine disorders
are more common in women
Overall incidence of metabolic myopathies is
unknown.
Diagnosis
Case:
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59 year-old male with history of smoking, who was diagnosed with severe
COPD/emphysema 2.5 years ago. Since then, he had several hospitalizations
due to worsening SOB and productive cough. He was treated with high doses of
IV corticosteroids followed by very slow oral steroid tapers. After the last
hospitalzation 4 months ago, he has been maintained on a Prednisone 5 mg
daily.
Normally, the patient is independent with transfers, ambulation and ADL’s. His
walking tolerance is about 1-2 blocks, limited by SOB.
2 weeks ago, patient presented to his PMD c/o progressive functional decline in
walking tolerance, and especial difficulty with transfers and stairs.
Exam revealed a thin male, with O2 saturation of 93% on RA. No apparent
respiratory distress was noted. No cushinoid features were seen. Pertinent
positives included visibly apparent atrophy in the proximal muscles groups of
both UE and LE. Strength testing was within normal limits. Patient had difficulty
standing up from a sitting position. He was unable to perform squats.
Labs – WBC 11.8, Glu 120, otherwise normal. CK - normal
NCS/EMG - normal
DIAGNOSIS
Steroid induced myopathy.
STEROID INDUCED MYOPATHY
Insidious disease process
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weakness of proximal muscles of the upper and lower limbs
and neck flexors.
First described by Cushing in 1932
An excess of either endogenous or exogenous corticosteroids is
believed to cause the condition.
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Chronic or acute (less common)
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Catabolic effect on muscle – gluconeogenesis from aminoacids
STEROID INDUCED MYOPATHY
Fluorinated steroids are implicated
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Dexamethasone
Triamcinolone
Also seen with non-fluorinated ones
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Prednisone
Inhaled steroids
Pathophysiology
decreased protein synthesis
increased protein degradation
alterations in carbohydrate metabolism
mitochondrial alterations
electrolyte disturbances
decreased sarcolemmal excitability
Epidimiology
For a given dose of steroid, women appear to be twice
as likely as men to develop muscle weakness
Worldwide incidence or prevalance is unknown
Diagnostic studies
Labs
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Routine Labs
Special labs
Creatinine Kinase – normal
Urine Creatinine – increased
No myoglobinuria or rhabdomyalysis
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Muscle biopsy
type IIB fibers are mostly affected
No inflammation, necrosis or regeneration
DIAGNOSTIC STUDIES
Electrodiagnostic studies
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Normal nerve conduction studies (NCS)
Electromyography can be normal
(EMG tests type I fibers, while SM mostly affects
IIB)
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DON’T FORGET:
A chronically or critically ill patient, can have other
co-morbid conditions, that may impact NCS or
EMG
TREATMENT
Steroid treatment modification
Pain control
Prevention of contractures
Avoid exercise to the point of exhaustion
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Aerobic exercise
ROM
Moderate resistance exercise
Assistive devices
Other: ventilation, percutaneous enteric feed
MYOPATHY RELATED TO
CRITICAL ILLNESS
Common in patients even after a brief period in the
intensive care unit. Estimated to be about 25%.
Gained recognition in the last decade
Often misdiagnosed or missed
Can occur in conjunction with polyneuropathy
Associated with prolonged ventilation and difficult
weaning
Differential Diagnosis
Motor neuron disease
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ALS
Late onset spinal muscular atrophy
Post-polio syndrome
Neuromuscular junction disorders
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Myasthenia Gravis
Lambert-Eaton myasthenic syndrome
Motor neuropathy
Myelopathy/ spinal stenosis
Parkinson’s
QUESTIONS?
What is PPS?
Initiated January 1, 2002
Inpatient Rehab Facility Prospective Payment System
(IRF-PPS) is the reimbursement program for Medicare Part-A
patients based on their specific impairment + level of
functioning upon admission
21 general Rehab Impairment Categories (RIC), 85 specific
Impairment Group Codes (IGC), Admission FIM scores and
sometimes Age, determine the Case Mix Group (CMG)
The CMG determines the one-time fixed reimbursement
amount per patient per stay at an IRF and generates an
Average Length of Stay (ALOS) based on national norms
~ 70% Rusk population are MCR Part-A recipients
What is the 60% Rule?
To qualify as an IRF, a provider must
deliver intensive rehabilitation services to
a population of inpatients, currently 60%
of whom, fall into one or more of 13
specific impairment categories, (the
“CMS 13”), from the total 21 Rehab
Impairment Categories (RICs)
PPS vs. CMS 60% Rule
PPS:
21 IGCs
Specific ICD-9-CM
codes for comorbs that
provide additional
reimbursement
3 Tiers (B,C,D) – High
to low levels of
additional
reimbursement
60% Rule:
13 Qualifying IGCs
Specific ICD-9-CM
codes for etiologies and
comorbs that qualify
cases in the ruling
No impact on
reimbursement
Compliance maintains
facility’s status as an
IRF
Active Comorbidities
“Conditions resulting in functional deficits that will be
addressed or monitored during the inpatient rehab
stay”:
Medical conditions requiring consults, testing
and/or medications
Conditions affecting ADLs
Conditions or complications that affect rehab
treatment course or plan of care
How Can Health Care
Providers Contribute?
Familiarize yourselves with commonly seen comorbid
conditions, including, but not limited to, qualifiers in
the 60% rule and PPS reimbursable comorbidities
Identify patients who have deficits indicative of
myopathy and discuss deficits with the rehab
physicians
Clearly document the current deficits, assign
accurate motor and cognitive FIM scores to represent
the patient’s true functional levels of assistance and
burden of care while in rehab
Clearly document any residual deficits from previous
illnesses/events that are still being addressed in
therapy sessions, including “resolving” conditions
Specificity in Documentation –
Importance of Communication
between Therapists and MDs
Rehab-designated Medical Records Coders can only
assign ICD-9-CM Codes for conditions included in
physician documentation
If therapies or nursing alone provide documentation conditions will not be coded
Accurate coding contributes to both qualifying cases
in the 60% Rule and additional reimbursement for
PPS
60% rule Qualifying ICD-9-CM Codes and
Verbiage for Myopathy
359.0 - Congenital Hereditary Muscular Dystrophy
359.1 - Hereditary Progressive Muscular Dystrophy
359.2 - Myotonic Disorders
359.3 - Familial Periodic Paralysis
359.4 - Toxic Myopathy
359.5 - Myopathy in Endocrine Diseases Classified Elsewhere
359.6 - Symptomatic Inflammatory Myopathy in Diseases Classified Elsewhere
359.81 - Critical Illness Myopathy
359.89 - Other Myopathies
710.3 - Dermatomyositis
710.4 - Polymyositis
Contact your PPS Coordinators
anytime with Questions 
Meryl Eisdorfer, R.N.,B.S.N.
x 33754, In-house pager: 1910
meryl.eisdorfer@nyumc.org
Randi Farkas, M.A.,CCC-SLP
x 33744, In-house pager: 2522,
Cell: 917-589-9386
randi.farkas@nyumc.org