Chapter 21 Flashcards
Axonal neuropathy
• Direct injury to axon
Wallerian degeneration (destroy axon and myelin degrades)
↓ amplitude
Demyelinating neuropathy
• Damage to SCHWANN cells or myelin SPARES AXON
random internode demyelination
slowed nerve conduction velocity
Mononeuropathy
asymmetric
• Entrapment: carpal tunnel syndrome = thenar atrophy
• Trauma: shoulder dislocation = axillary nerve palsy
Polyneuropathy
symmetric axonal loss
• ‘stocking and glove’ paresthesia/anesthesia
• Diabetics, alcoholism
Polyneuritis multiplex
randomly affects portions of individual nerves
• Autoimmune: RA wrist drop, polyarteritis nodosa
Guillain—Barre Syndrome
- acute motor neuron demyelination –>ASCENDING paralysis; respiratory failure possible
- Autoimmune: idiopathic –>viral
- Males
- Ages 15-35 or 50-57
- Ventilation
Chronic Inflammatory Demyelinating Polyneuropathy
CIDP
• Relapsing chronic GBS onion-skin Schwann cells • associated with immune disorders: lupus, HIV • Males (2x) • 40-60 (older) • MC some residual LOF
Diabetic Peripheral neuropathy
• #1 cause of peripheral neuropathy, 50% of DM
↓ sensation: distal, symmetric
what/how do environmental toxins injure peripheral nerves
- Alter axonal transport or cytoskeletal damage
- ADRs, lead, methyl-mercury
- Longest neurons
what genetic condition injures peripheral nerves
- PMP22 gene mutation
- Charcot-Marie-Tooth disease
- Axonal or demyelinating, motor & sensory
- Pes cavus
Myasthenia gravis
NMJ disorder degrade post-synaptic Ach receptors • Extraocular weakness worse w e-stim • Females (MC): 20-30 years
Lambert-Eaton Syndrome
NMJ disorder • Auto-antibodies inhibit PRE-SYNAPTIC Ca++ channels • Repetitive e-stimulation improves • Females MC • 60 years
Congenital myasthenic syndromes
- Mutations alter NMJ proteins pre/post/synaptic
* Mimic MG or LES few respond to AChase inhibitors
what infections effect NMJs?
- Clostridium tetani: ↑ACh release
* Clostridium botulinum: ↓ACh release; DESCENDING paralysis
what causes ascending paralysis?
descending paralysis?
ascending- GBS
descending- botulism
what determines myofiber type?
peripheral axons
types of skeletal muscle disorders
o Neuropathic changes: altered innervation, grouped atrophy
o Disuse atrophy: primarily type II fibers, localized or generalized
o Glucocorticoid atrophy: primarily type II fibers, endogenous (cushings) or exogenous (MC)
dystrophinopathies & features
inherited skeletal muscle disorders
MC cause of MD, dystrophin gene mutation: X chromosome
Can’t “keep up”
Pelvic girdle weakness (later shoulder)
Pseudohypertrophy of calf muscles
↑ creatine kinase
Death: cardiorespiratory insufficiency
Duchenne MD
inherited skeletal muscle disorder o Dystrophin is ABSENT o More severe & more common than becker o Gower sign • males • Childhood onset Fatal by early adulthood
Becker MD
inherited skeletal muscle disorder o ABNORMAL dystrophin o Variable severity—less severe than duchenne • Males • Onset in adolescence Possible normal lifespan
list of inflammatory myopathies
polymyositis, dermatomyositis, inclusion body myositis
polymyositis
inflammatory myopathy
autoimmune
T-cell attack
males
dermatomyositis
autoimmune
muscle & skin inflammation
MC inflammation myopathy in kids
Paraneoplastic syndrome in adults
inclusion body myositis
Tau proteins in cytoplasm
MC inflammatory myopathy in elderly >60
list of toxic myopathies
thyrotoxic myopathy
ethanol myopathy
drug myopathy
thyrotoxic myopathy
overproduction of thyroxine
goiter/graves disease
ethanol myopathy
binge drinking
rhabdomyolysis –>acute renal failure
drug myopathy
no inflammation
statins MC
what age group are peripheral nerve sheath tumors MC in?
adults
schwannoma
benign
MC sporadic
CN VIII
schwannomatosis: familial, NO vestibular schwannomas
neurofibromatosis type 2
benign
brain –> bilateral vestibular schwannomas
merlin gene
no cutaneous lesions
neurofibromas
benign
cutaneous, subcutaneous & plexiform
neurofibramtosis type 1
benign
cutaneous neurofibromas
axillary freckling, Lisch nodules, Cafe au lait (california)
inc risk of malignant peripheral nerve sheath tumors
malignant peripheral nerve sheath tumors
MC transformed plexiform neurofibroma
50% of all cases arise in NF1 pts –> 3-10% of all NF1 pts
Traumatic neuroma
reactive lesion –> non-neoplastic
post-neuronal injury (surgery)
painful mass
