Skeletal Muscle and Peripheral Nerve Pathology II Flashcards
botulism
clostridium botulinum neurotoxin
-blocks release of ACh from presynaptic neurons
canned food
botulism
double vision, blurry vision, slurred speech, difficulty swallowing, dry mouth, muscle weakness (shoulders to body)
botulism
type I muscle fibers
aerobic
high lipid
oxidative
one slow fat red ox
type 1 muscle fiber slow - aerobic exercise high lipid red colored - high myoglobin oxidative
ATPase at differnt pH levels
shows type 1 or type 2 fibers - in checkerboard pattern
perifascicular atrophy
dermatomyositis
corticosteroid use
type 2 fiber atrophy and sparing of type 1 fibers
reinnervation
switch in fiber type
increase in motor unit size - more myofibers innervated by individual axon
type grouping
of muscle fibers
-with ongoing denervation and reinnervation
loss of checkerboard
skeletal m disorder
either myopathy or neurogenic issue
neurogenic injury
fiber type grouping and grouped atrophy**
creatine kinase
released with segmental myofiber degeneration
exercise
myofiber hypertrophy
cytoplasmic inclusions
seen in several primary forms of myopathy
three primary inflammatory myopathies
polymyositis
dermatomyositis
inclusion body myositis
lymphocytes in atrophic muscle fibers
inflammatory myopathy
dermatomyositis
systemic autoimmune disease
proximal muscle weakness and skin changes
swollen hands and lesions on knuckles
dermatomyositis autoAbs
anti-M2 - gottron papule and heliotrope rash (around eyes)
anti-Jo1 - lung disease, nonerosive arthritis, mechanic hand rash
anti-P155/P140 - paraneoplastic anc juvenile
gottron papules and heliotrope rash
dermatomyositis hand lesions
-with anti-Mi2
interstitial lung disease, nonerosive arthritis, mechanic hand rash
dermatomyositis
-with anti-Jo1 - worse prognosis
paraneoplastic and juvenile dermatomyositis
anti-P155/P140
perifascicular atrophy
dermatomyositis
proximal muscle weakness, myalgias, elevation in serum creatine kinase, heliotrope rash, gottron papules, dysphagia
dermatomyositis
heliotrope rash
around eyes
-with dermatomyositis
association with dermatomyositis
interstitial lung disease
rapidly progressive and can lead to death
also - cardiac involvement
polymyositis
like dermatomyositis - but no skin lesions
has myalgia and weakness
inflammation in muscles
endomysial mononuclear inflammatory cells in muscles
polymyositis
age of dermatomyositis and polymyositis
30-40yo
age of inclusion body myositis
> 60yo
quadriceps progressive muscle weakness in patient 65yo
inclusion body myositis
nuclei in middle of muscle cell
inclusion body myositis
tx of polymyositis and dermatomyositis
corticosteroids
tx of inclusion body myositis
respond poor to steroids/immunosuppressants
common complication of statins
myopathy
within 6 weeks - check CK levels
if weakness - RTO for eval
toxic myopathies
statins
chloroquine, hydroxychloroquine
thyrotoxic
alcohol
acute toxic rhabdomyolysis, myoglobinuria, renal failure
with binge drinking alcohol
ethanol myopathy
type II fibers
inherited skeletal m disease
RyR - malignant hyperthermia
AD NEM and AR NEM - childhood weakness - floppy infant
XL, Xq28, AD, and AR - severe congenital hypotonia - floppy infan and poor prognosis with X-linked form
malignant hyperthermia
mutation in RyR
muscular dystrophies
most X-linked
mutations in dystrophin**
duchenne and becker muscular dystrophy
differ in amount of loss of dystrophin function
both LOF mutations of dystrophin - on X chromosome
over time - disease progression - fatty replacement
dystrophin
mutated in muscular dystrophy
dystrophin stain
absent in duchenne
reduced in becker
walking delayed and can’t keep up with peers
duchenne dystrophy
see marked elevation of creatine kinase during first decade of life - then falls as muscle mass loss
pseudohypertrophy
enlargement of lower leg muscles with weakness
-fat replacement
crawl around, hands to stand up, hands on hip to stand
muscular dystrophy - duchennes or becker
myotonic dystrophy
auto dominant
-skeletal m weakness, cataracts, endocrinopathy, cardiomyopathy
myotonia
sustained involuntary contraction of muscles
mutation in myotonic dystrophy
expansion of CTG triple repeats in 3’ non-coding region of DMPK gene
association with myotonic dystrophy
hirsutism
symptoms with exercise or fasting
lipid or glycogen metabolism diseases
bad with exercise
mitochondrial myopathies
mcardles disease
can’t break down sugars
ragged red fiber and phonograph record
myopathies due to inborn errors of metabolism
DDx for infantile hypotonia
primary disease of skeletal muscle
abnormality of brain
neuronopathy - spinal muscular atrophy
spinal muscular atrophy
rare hypertrophy of muscle fibers with surrounding atrophic fibers
periodic paralysis
ion channel myopathies
can be hyperK, hypoK, or normoK
RYR1 mutation
malignant hyperthermia
-anesthetic trigger hypermetabolic state
tetany and excessive heat production
rimmed vacuoles
inclusion body myositis
MPNST
malignant peripheral nerve sheath tumor
peripheral nerve sheath tumor
schwannoma
neurofibroma
malignant peripheral nerve sheath tumor
loss of merlin
schwannoma
schwannoma
benign
cell differentiation and often arise from peripheral nerves
schwannoma histo
dense eosinophilic antoni A areas and loose pale antoni B areas
also hyalinized blood vessels
veracay bodies
antoni A area where tumor cell nuclei align with areas of anuclear zone
in schwannoma
tinnitus and hearing loss
schwannoma at CPA - cerebellopontine angle
CN VIII
aka acoustic neuroma
neurofibroma
benign nerve sheath tumor
heterogenous composition
neoplastic schwann cells admixed with perineural like cells, fibroblasts, mast cells, CD34 spindle cells
NF1
associated with neurofibromas
multiple** superficial cutaneous neurofibromas
diffuse neurofibroma - large plaquelike elevation of skin
plexiform - deep - nerve roots or large nerves
MPNST
high grade tumors
divergent differentiation - focal areas that exhibit other lines of differentiation
triton tumor
triton tumor
MPNST
malignant peripheral nerve sheath tumor
cafe au lait spots
with neurofibromatosis type I
b/l CN VIII schwannoma and multiple meningiomas
neurofibromatosis type II
NF2
associated with schwannomas