Peripheral Nerves and Muscles pt. I Flashcards
What are the causes of peripheral nerve injury (5)
Nutritional, toxic, vascular, inflammatory, genetic
Charcot-Marie-Tooth nuropathies are in what etiologic category?
Inherited
What is Guillain-Barre Syndrome (BGS)?
Common, acute motor neuron demyelination
What kind of paralysis is associated with GBS?
ascending paralysis: “rubbery legs”, decreased DTR’s (deep tendon reflexes)
T/F
GBS is not lethal
False,
Possibly lethal from respiratory failure
What kind of condition is GBS?
Autoimmune: macrophages near nerve roots.
What causes GBS?
60% Idiopathic, viral: C.jejuni, EBV, CMV, HIV
Who is at most risk for GBS?
Males, ages 15-35 or 50-57 (biphasic distribution i.e. two specific age ranges implicated)
T/F
90% of GBS cases self resolve
True
What is the tx for GBS?
Ventilation, Plasmapheresis, I.V. antibodies
What is Chronic Inflammatory Demyelating Polyneuropathy (CIDP)?
Chronic version of GBS. Symmetricl, segmental demyelination/remyelination.
What cells are affected by CIDP?
Motor and sensory neurons, “onion-skin” Schwann cells.
What are some symptoms of CIDP?
Pain, paresthesia, ataxia, decrease DTRs
What kind of disorders is CIDP associated with?
Autoimmune disorders: lupus, HIV
What is the treatment for CIDP?
Plasmapheresis, immunosuppression,
What is the prognosis for CIDP patients?
Possible recovery, MC some residual
What is the #1 cause of perpheral neuropathy?
Diabetic peripheral neuropathy. 50% of Diabetes millitus cases.
What is diabetic peripheral neuropathy?
Axonal & demyelinating (mixed), symmetric
What happens with hyperglycemia relate to DPN?
Hyperglycemia = vascular injury -> nerve injury. Damaged vasa nervorum
What are some sensory abnormalities with DPN?
Decreased sensation: vibratory, soft touch, pain
What are some other signs of DPN?
Ulcers, gangrene, decreased (sluggish) DTRs
What is the tx for DPN?
Blood glucose, daily inspection. analgesics, anticonvulsants (because act on CNS to reduce pain).
How do environmental toxins cause misc. peripheral neuropathies?
Alter axonal transport of cytoskeletal damage (ADRs, lead, methyl-mercury). Longest neurons.
What does systemic vasculitis have to do with PN?
1/3 of vasculitis patients have peripheral neuropathy, polyarteritis nodosa (produces polyneuritis multiplex). Altered sentation (pain) and motor function.
What is a genetic misc PN?
Charcot Marie Tooth disease. PMP22 gene mutations. Axonal or demyelinating, motor and sensory
Who is most susceptible to Charcot Marie?
Young adults, slowly progressive (1:2,500)
What is a very notable condition associated with Charcot-Marie-Tooth disease?
Extreme pes cavus (foot)
What are neuromuscular jnx disorders?
Pres-synaptic Ca++ influx -> ACh -> post-synaptic ACh receptor -> myofiber depolarization (some sort of muscle contration, activity)
What is myasthenia gravis?
Autoimmune condition: acetylcholine receptor antibodies. Degradation of post synaptic ACh receptors
Rare: 3:100,000
What kind of lesions are noted with MG?
Thymic lesions: hyperplasia (60%), thymoma (20%) Autoreative T cells and B cells
What is the hallmark of MG?
Extraocular weakness: diplopia, ptosis
What age/gender is affected by MG
All Ages
Females (MC): Age: 20-30
Males: ages 50-70 years
T/F
MG symptoms get better as the day progresses and show relief with e-stimulation
False
MG symptoms get WORSE as the day progresses. E stim makes it worse.
What test is used for MG?
Tensilon test (edrophonium) Inhibits ACh receptor antibodies.
What is the tx for MG
Immunosuppression, cholisterase inhibitors, plasmapheresis, thymectomy.
What is the overall survival for MG
95% 5-year survival
What is Lamber-Eaton syndrome (LES)?
Autoantibodies inhibit pre-synaptic Ca++ channels. Decrease ACh release -> weakness (limb girdles)
T/F
Repetitive e-stimulation improves LES? LES is rare
True
What age group/gender is found having LES?
Females (2x), - 60 yrs old
What is paraneoplastic syndrome? What is the prognosis?
Small cell lung CA. Often seen paired with LES. Poor prognosis
What is the tx for LES?
Plasmapheresis, immunosuppression. Decrease autoantibodies
What are some characteristics of congenital myasthenic syndromes
Mutations alter neuromuscular juntion proteins. All forms: presynaptic, synaptic, postsynaptic.
What conditions may congential myasthenic syndromes mimic?
LES or MG. Few respond to achetylcholinesterase inhibitors.
What are some infections that can lead to neuromusclular jxn disorders?
Soil bacteria -> neurotoxins.
What is tetanus?
Clostridium tetani: increased ACh release (flooding channels with ACh). Spasticity. 10% lethal.
What is Botulism?
Clostridium botulinum: Decreased ACh release. Descending paralysis (flaccidity): eyes -> throat -> respiration.
What are skeletal muscle tissue disorders?
Peripheral axons innervate multiple myocytes. Checkerboard (link pink, dark pink muscle fiber types)
What determines myofiber type?
Peripheral axons, not training.
What are Type I fibers?
Slow twtich, dark, aerobic, fat met.
What are Type II fibers?
Fast twitch, white, anaerobic, glycogen met.
What is myopathy?
Disease of muscular origin, weakness. May be primary or secondary to neuropathy.
What are some similarities of neuropathy and myopathy?
Both have muscle atrophy, fibrotic & fatty replacement
What are neuropathic changes?
Altered innervation. Grouped atrophy. Altered muscle fiber patterns. Motor units: fewer and larger.
What are some features of disuse atrophy?
Atrophy of primarily type II fibers. Localized (fx), generalized (quadriplegia)
What are some features of glucocorticoid atrophy?
Atrophy of primarily type II fibers. Endogenous (Cushing disease), exogenous (MC) - taking some sort of medication.
What are congenital myopathies?
Group of inherited diseases (umbrella term for specific disorders), perinatal/childhood onset. Static (doesn’t get better or worse) hyptonia, Tx is palliative
What is Muscular dystrophy?
Progressive, inherited, rarely congenital.
What are the MC cause of MD?
Dystrophinopathies. Dystrophin gene mutation: X chromosome. Myocyte degeneration outpaces repair
What are the 2 types of MD?
Duchenne MD (DMD) Becker MD (BMD) Less severe, shows up in adolescence. more variable.
What is Duchenne MD?
Dystrophin protein is absent = more severe. Weakness by age 5, wheelchair by teens. Fatal by young adulthood.
What is Becker MD?
Abnormal dystrophin = severity is variable. Adolescent onset. May have a NEARLY normal life span.
What are some essential/shared characteristics of dystrophinopathies?
Vary by severity. Clumsiness, weakness, fatigue (can’t keep up). Pelvic girdle weakness (possible shoulder girdle weakness, advanced stages). Pseudohypertrophy (look cut and develped but aren’t) of calf muscles (fibro-fatty infiltrate).
What lab findings indicate dystrophinopathies?
Increase creatine kinase (muscle breakdown)
What causes death with dystrophinopathies?
Cardiorespiratory insufficiency: cardiomyopathy, arrythmia, pneumonia.
What is Gower sign? What condition does it indicate?
Children using hands to push on legs in order to stand up (bc of weak pelvic girdle muscles). Duchenne muscular dystrophy.
What is polymyositis:
Aquired Inflammatory myopathy. Autoimmune, T cells attack the endomysium; prox. muscle weakness (shoulder/pelvic girdle muscles), myalgia, dysphagia (difficulty swallowing), males age 45-60.
What is dermatomyositis?
Inflammatory myopathy: Autoimmune, attack on muscle and skin, pruritus (itching), skin lesions, myalgia, prox. muscle weakness, MC inflamm. myopathy in CHILDREN, paraneoplastic syndrome in adults.
What is inclusion body myositis?
Inflammatory myopathy: tau proteins in the cytoplasm, progressive weakness and wasting, dysphagia - may be degenerative. MC inflammatory. Myopathy in elderly (>60 years).
What is thyrotoxic myopathy?
Overproduction of thyroxine (thyrotoxicosis), goiter or Graves disease, acute or chronic, prox. muscle weakness and necrosis.
What is ethanol myopathy, and what are some of it’s causes?
Binge drinking, rhabdomyolysis progresses to acute renal failure (myoglobinuria - dark urine), acute myalgia, myocyte swelling/necrosis.
What is drug myopathy?
ADR (adverse drug reaction), various meds, myopathic signs/symptoms, MC without inflammation.
What kind of drugs are most implicated in drug myopathies?
Statins (decreased cholesterol, myalgia, cramps).
What are some general characteristics of peripheral nerve sheath tumros?
Tumors arise in PNS. MC in adults, benign or malignant. Schwann cell differentiation is common. Soft tissue mass: impingement -> pain, LOF
What is a Schawannoma?
Benign, peripheral nerve sheath tumor, 90% sporadic.
What cranial nerve is MC implicated in scwannomas?
MC involves CN VIII (vestibular schwannoma)
What is a schwannomatosis?
Familial, multiple CNS and cutaneous schwannomas.
T/F
Schwannomatosis involves vestibular scwannomas
False,
No vestibular scwannomas (avoids CN VIII)
What is a neurofibroma?
Benign nerve sheath tumor. Cutaneous, subQ (diffuse), plexiform (in nerve plexuses).
What is a neurofibromatosis type II?
BILATERAL vestibular schwannomas, autsomal dominant, Merlin gene. Vision/hearing problems
T/F
NF2s are known for cutaneous lesions
False
No cutanenous lesions
What is Neurofibromatosis Type 1
Pronounced neurofibromas, vascular stenosis. Decreased cognition, seizures.
NF1 is AKA?
vonRecklinghausen disease
What mutation is found with NF1
Autosomal dominant, mutation on chromosome 17
Besides multiple cutaneous lesions, what other kind of skin lesions/marks can arise with NF1?
Cafe au lait spots, axillary freckling, Lisch nodules (pigmented nodules of the iris)
What is NF1 at risk for?
Risk of malignant peripheral nerve sheath tumors (transformed neurofibromas, MC plexiform).
What is a key way to keep NF1 and NF2 straight?
NF1 was named first, because they involve leasions that are seen clearly on the body. NF2 is seen on MRI therefore found second.
What are some characteristics of malignant peripheral nerve sheath tumors?
Large mass, anaplastic, infiltrative.
What is the % of patients have malignant peripheral nerve sheath tumors that come from NF1?
50%
What is a traumatic neuroma?
Post neuronal injury (surgery). Reactive (non neoplastic) lesion. Painful mass: Scwann cells, axons, & CT.
