Noninflammatory Muscle Disorders (Bertorini) Flashcards
type to neuropathy that causes sensory or autonomic problems.
peripheral
Gower’s sign
Myopathy
the patient needs to use his hands to raise from the floor and then ”climb over his legs” in figures to achieve the standing position
In what type of neuropathy will pts have sensory deficits
peripheral neuropathy
- have proximal muscle atrophy and weakness
2. have distal muscle atrophy and weakenss
myopathy
Peripheral neuopathy
winging of the scapula
myopathy
*occurs because the weak muscles cannot fix the scapula to the rib cage.
Some neuropathies affect individual nerves and these are called_________
mononeuropathies
In what type of neuropathy is muscle fatigue a hallmark
disease of neuromuscular transmission
involves fasciculations
motor neuron disease
sometimes in peripheral neuropathy/polyneuropathy
development of droopy eyelids or ptosis (arrows) after sustained upward gaze
disease of neuromuscular transmission
i.e. myasthenia gravis
Decreased or absent muscle stretch reflexes
peripheral neuropathy/polyneuropathy
motor neuron dz (most, but not all)
*in late stage myopathy, these are gone/decreased
proximal muscle weakness
disease of neuromuscular transmission
myopathy
weakness fluctuates
disease of neuromuscular transmission
sensory loss
peripheral neuropathy/polyneuropathy
distal muscle weakness
peripheral neuropathy/polyneuropathy
increased muscle stretch reflex
ALS (motor neuron dz)
*** this is an exception, most motor neuron dz has decreased muscle stretch reflexe
often involves extraocular muscles
disease of neuromuscular transmission
When the motor neuron depolarizes, it causes the muscle fibers of that motor unit to also depolarize and their individual action potentials summate (A+B+C+D) forming the potentials that are called …
motor unit action potentials (MUAPs)
describe normal muscle fiber type distribution
motor neurons innervate either type I or type II muscle fibers (only fibers of one type are innervated by each motor neuron) they are intermixed with fibers from other motor neurons in an almost “checkerboard” pattern
atrophic fibers stain dark with many stain, but in particular _____ stain
nonspecific esterase
Trauma –> periph neuropathy/motot neuron dz –> atrophy/weakness and stains with NON-SPECIFIC ESTERASE
atrophic and angular fibers
periph neuropathy
motor neuron dz
Sprouting of axons from the other intact neurons take over and reinnervate previously denervated fibers, thus more fibers of single neurons remain, forming groups of both fiber types seen histologically. This is called …
fiber type grouping
fiber type grouping results in what changes on an EMG
- larger AP
(bc more fibers are innervated by a single neuron - decreased # of AP
(bc there are fewer motor neurons)
Recall, fiber type grouping occurs after neuronal or axon damage –> sprouting of axons to reinnervate
lost checkerbaord pattern is the result of
sprouting (fiber type grouping)
Larger Motor Unit Action Potentials on EMG
motor neuron dz
periph neuron dz
elevated CK or CPK
myopathy
*necrotic muscle fibers leak some of the sarcoplasmic components
asynchronous depolarization of individual fibers of the motor unit causes ______ AP on EMG
What neuromuscular dz type causes it?
polyphasic
myopathy
when the muscle contraction is very weak, there is a (normal or decreased) number of motor unit action potentials
normal
fewer fibers innervated by a motor neuron registers on EMG as ….
more fibers innvervated by a motor neuron registers on EMG as…
smaller AP
Larger AP
How is the motor unit potential altered in myopathes
small in size and short in duration
MUP = summation of AP for each fiber in a motor unit
pale muscle fibers in picture micrograph
= necrotic fiber = myopathy
slow conduction velocitys or low AP amplitude
peripheral neuropathy
smaller AP and normal # AP
Why?
myopathy
smaller AP bc muscle fibers dysfunction
normal # AP bc neurons/axons in tact
very slow prolonged latency and small compound muscle action potential in a…
demyelinating neuopathy
normal conduction studies/velocity
everything but peripheral neuropathy
increased number of motor unit action potentials as compared to the strength of contraction
myopathy
The time that it takes for the action potential to travel from the stimulus to response sight is the …
distal latency
How is a nerve conduction velocity measured?
determine distal latency and proximal latency for an stretch of a nerve and divide
distance between 2 paints/latency diff btween the 2 points = conduction velocity
larger AP and decreased number AP
motor neuron dz
peripheral neuopathy
normal number and amplitude of AP
neuromuscular transmission defect
result of repetitive nerve stimulation test in neuromuscular transmission defect
progressive decrease in amplitude
Proximal weakness (often symmetrical) Normal sensation Normal reflexes Elevated muscle enzyme in serum Small (brief) motor unit potentials on EMG, with normal or “increased” recruitment on maximal effort Polyphasic Normal number APs, just weakened Abnormal muscle biopsy (i.e., inflammation, glycogen storage)
myopathy
floppy infants at birth
congenital myopathy
e.g.
central core disease, myotubular myopathy, “nemaline” or “rod” myopathy and congenital muscular dystrophy
hereditary and progressive myopathies
muscular dystrophies
myotonic dystrophies
Some are caused by abnormalities or deficiencies of the muscle membrane or nuclear proteins; e.g., Duchenne’s, Becker’s, limb girdle, fascioscapulohumeral
and oculopharyngeal dystrophies
characterized by the presence of progressive myotonia (= difficuty relaxing contracted muscle) and weakness
myotonic dystrophies
characterized by the presence of progressive weakness and atrophy
muscular dystrophies
Some are caused by abnormalities or deficiencies of the muscle membrane or nuclear proteins; e.g., Duchenne’s, Becker’s, limb girdle, fascioscapulohumeral
and oculopharyngeal dystrophies
progressive weakness in the shoulder and hip muscles
various Limb-girdle muscular dystrophies
mutation causes lack of dystrophin
Duchenne’s Muscular Dystrophy
FRAMESHIFT MUTATION
Duchenne’s Muscular Dystrophy mode of inheritence
X linked
presentation of Duchenne’s Muscular Dystrophy
MALE progressive muscle weakness elevated serum CK abnormal heart psedohypertrophy low IQ
muscle changes in Duchenne’s Muscular Dystrophy
atrophy and necrosis
segmental fiber over contraction
connective tissue prolieration
pathophys of Duchenne’s Muscular Dystrophy
Frameshift mutation –> lack of dystrophin in SR membrane leads to excessive intracell Ca –> activation of neutral proteases (by Ca) –> digestion of structural proteins (troponin, Z-band, etc) –> muscle atrophy
restores the reading frame producing a message that although smaller, makes sense = functional protein = novel treatment for Duchenne’s MD
exon skipping
milder form of duchenne’s muscular dystophy
becker’s muscular dystrophy (not a complete absence of dysrophi, just reduced levels)
mode of inheritance of myotonic dystrophy
AD
genetic defect assc with myotonic dystrophy
inc CGT repeated on chrom 19 (encodes a kinase)
genetic defect in proximal myotonic dystrophy
chrom 3
Mental retardation in newborns of myotonic mothers is called
congenital myotonic dystrophy
due to anticipation
more severe phenotypes in younger generations
anticipation
=myotonic dystrophy
aquired myopathies are due to
autoimmune disease or infections
=Inflammatory myopathy
what autoimmune diseases have been known to cause inflammatory myopathy
polymyositis, dermatomyositis, inclusion body myositis, sarcoidosis
trichinosis
infectious agent known to cause inflammatory myopathy
Cataracts Balding Diabetes Central sleep apnea Megaesophagus; megacolon Heart conduction defects Percussion and grip myotonia Facial, neck, and distal weakness
myotonic dystrophy
elevated serum CK abnormal heart psedohypertrophy low IQ winging of the scapulae lordosis large calf muscles
Duchenne’s Muscular Dystrophy
exercise intolerance with muscle pain and weakness
myoglobinuria
rhabdo
metabolic myopathy
pathophys of metabolic myopathy
disorders of glycogen or lipid metabolim (or ETC) deprives muscle cells of energy needed for contraction and relaxation –> cannot maintain their membrane integrity
deficiency in muscle phosphorylase causes…
Mc Ardie’s Dz
–> glycogen cannot bread down (it accumulates) therefore, ATP cannot be made during exercise
cause proximal muscle weakness and their muscle biopsies show non-specific findings and only selective type II muscle fiber atrophy
endocrine myopathies
present with severe proximal weakness resembling amyotrophic lateral sclerosis
hyperparathroidism
obese pt present with muscle spasms, very high serum creatine kinase levels, and hyperlipidemia
Hypothyroidism
glycogen accumulation
Mc Ardie’s Dz
muscle fiber atrophy,vacuolization ,myofibrillary degeneration ,-mitochondrial dysfunction , or fiber necrosis.
toxic myopathy
causes of toxic myopathies
cholesterol lowering drugs Herbicides anesthetics narcotics GCS ethanol
CHANGE your shit if you get toxic myopathy
compound action potential becomes larger during fast stimulation rates
presynaptic disorders of neuromuscular transmission
fluctuating muscle weakness that worsens with muscle activity and at the end of the day patients typically are weaker than in the morning. Patients frequently have droopy eyelids (ptosis) which increases with sustained upward gaze. They may also have double vision and proximal limb weakness and may develop difficulty swallowing and breathing.
myasthenia gravis
etiology of myasthenia gravis
abs that bind and destroy Ach receptorts
a short acting anticholinesterase drug that produce a rapid improvement of the myasthenic weakness
Edrophonium or Tensilon
Tx for myasthenia gravis
Anticholinesterase immunosuppressants to dec Abs Plasma Exchange thymectomy corticosteriods
CAP IT
decreased salivation decreased reflexes Transient improvement in muscle power following exercise proximal limb weakness fatigue difficulty rising from sitting position dec ability to walk or climb stairs
eaton lambert syndrome
etiology of Eaton Lambert syndrome
Abs against pre-synaptic voltage gated Ca channels –> impairs release of Ach
= affects both NICOTINIC and MUSCARINIC activity
Therapy for eaton lambert syndrome
AchE inhibitors
immunosuppressives
phasmaphoresis
corticosteropds
muscle fiber vacuolization
toxic myopathy
fluctuating muscle weakness that worsens with muscle activity
myasthenia gravis
Transient improvement in muscle power following exercise
eaton lambert syndrome
muscle pain during exercise
Mc Ardie’s Dz
+/- lung tumor
eaton lambert syndrome
Weakness, MUSCLE PAIN, MUSCLE BREAKDOWN (RHABDO), MYOGLOBINURIA with exercise
metabolic myopathies
Mc Ardies is an example
muscle spasms not weakness
hypothyroidism
dry mouth
eaton lambert syndrome
difficulty relxing
myotonic dystrophy
