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45 Cards in this Set
- Front
- Back
List 3 neuromuscular junction disorders
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1. Myasthenia gravis
2. Lambert-Eaton myasthenic syndrome 3. Congenital myasthenia |
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Is Myasthenia gravis caused by a presynaptic or postsynaptic neuromuscular junction disorder?
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Postsynaptic
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Is Lambert-Eaton myasthenic syndrome caused by a presynaptic or post-synaptic neuromuscular junction disorder?
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Presynaptic
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Describe the muscle weaknesses associated with Myasthenia Gravis.
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1. Ocular (binocular diplopia, ptosis)
2. Bulbar (chewing, swallowing, speaking) 3. Limbs (proximal > distal) |
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Which disease is an autoimmune neuromuscular disease leading to fluctuating muscle weakness and fatiguability?
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Myasthenia gravis
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In Myasthenia gravis, what do antibodies attacks, and what is the result?
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1. ACh-receptors at the NMJ are attacked.
*Results in simplification of postsynaptic folds, inhibiting the stimulatory effect of ACh 2. MuSK Ab (muscle specific kinase) |
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Ocular Myasthenia gravis is only associated with which symptoms?
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1. Ptsosis
2. Diplopia |
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How is Myasthenia Gravis diagnosed?
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1. Painless fatiguable weakness
2. Ice pack test 3. Edrophonium (Tensilon) test 4. Ab against AChR or MuSK 5. Electrophysiologic studies (NCS) |
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When performing electrophysiologic studies to diagnosis MG, what are you looking for?
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Repetitive nerve stimulation --> DECREMENTAL response
Single fiber EMG --> increased jitter |
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List 2 tumors that are associated with myasthenia gravis
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1. Thymoma
2. Thymic hyperplasia (Rarely other tumors: Small cell lung carcinoma) |
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List some autoimmune diseases that are associated with myasthenia gravis
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1. Aplastic anemia
2. Thyrotoxicosis 3. SLE 4. RA 5. Sjogren syndrome 6. Mixed connective tissue disease 7. Multiple sclerosis |
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What is the appropriate symptomatic treatment for myasthenia gravis? What treatments are used for long term therapy?
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Symptomatic treatment:
AChE inhibitors (increase availability of ACh at the NMJ) Immunomodulatory therapy: 1. IVIg 2. Plasma exchange 3. Corticosteroids 4. Immunosuppresants (azathioprine, mycophenolate mofetil) |
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How long does neonatal myasthenia gravis normally last?
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< 12 weeks
(usually 3 weeks long) |
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What causes neonatal myesthenia gravis?
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Passive transfer of maternal AChR antibodies
(transient disease) |
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Are most congenital myasthenic disorders autosomal recessive or dominant? Which disease is an exception?
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Mostly autosomal RECESSIVE
(except Slow channel syndrome, which is AD) |
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Which NMJ disease is frequently paraneoplastic?
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Lambert-Eaton Myasthenic syndrome
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What do antibodies attack in Lambert-Eaton myasthenic syndrome?
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Pre-synaptic VGCC (voltage-gated calcium channels)
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List 2 diseases associated with Lambert-Eaton Myesthenic syndrome
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1. Cancers (small cell lung carcinoma)
2. Lymphoma |
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What is the difference in response to fast repetitive nerve stimulation seen in MG and LEMS?
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MG --> decremental response
LEMS --> incremental response |
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Compare the effects of MG and LEMS on postsynaptic folds of the neuromuscular junction
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MG --> simplification of postsynaptic folds (autoimmune attack)
LEMS --> Upregulation of postsynaptic folds |
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Does botulism cause problems at the presynaptic or postsynaptic side of the neuromscular junction?
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Pre-synaptic
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What is the result of Botulism on the neuromuscular junction?
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Impaired ACh vesicle docking, fusion, and release from the presynaptic side
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List some signs/symptoms associated with Botulism.
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1. Constipation
2. Generalized and extraocular muscle weakness 3. Difficulty swallowing 4. Difficulty breathing 5. May require mechanical ventilation |
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Raw honey fed to babies less than six months can cause what kind of NMJ disorder?
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Botulism
"floppy infant" syndrome |
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Which enzymes may be elevated in myopathies?
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1. Creatine phosphokinase (CK or CPK)
2. Aldolase 3. Lactase 4. ALT, AST |
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What are some general signs of myopathies.
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1. Muscle cramps or exercise-induced pain
2. Myoglobulinuria |
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List some inherited forms of myopathy
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1. Muscular dystrophies
2. Metabolic myopathies 3. Congenital myopathies 4. Mitochondrial myopathies |
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List some acquired forms of myopathy
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1. Inflammatory myopathies (Polymyositis, dermatomyositis, inclusion body myositis)
2. Infectious myopathies 3. Toxic myopatheis |
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What kind of EMG and NCS tests results are indicative of myopathy?
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EMG --> myopathic motor unit potentials, early recruitment
NCS --> normal |
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List some various causes of elevated CK.
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1. Myopathy
2. Muscle trauma 3. Exercise 4. Increased muscle mass |
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List 4 characteristics of muscular dystrophies
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1. Hereditary
2. Progressive 3. Degenerative 4. Variable onset and intensity |
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Compare the effects of muscle use in patients with MG and LEMS.
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MG--> muscle use results in fatigue (gets worse with exercise and by the end of the day)
LEMS --> muscles are apparently fatiguable, but somehow muscle strength improves with muscle use |
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Lambert-Eaton Myasthenic syndrome causes autonomic dysfunction, resulting in what kind of symptoms?
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1. Dry mouth
2. Impotence 3. Constipation 4. Urinary incontinence |
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List 7 muscular dystrophies
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1. Duchenne (DMD)
2. Becker (BMD) 3. Limb-girdle (LGMD) 4. Emery-Dreifuss (EDMD) 5. Facioscapulohumeral (FSHMD) 6. Oculopharyngeal (OPMD) 7. Myotonic dystrophy (DM1, DM2) |
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What is the inheritance pattern of Duchenne muscular dystrophy, and which protein is mutated?
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X-linked
Dystrophyn |
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What is the inheritance pattern of Becker muscular dystrophy, and which protein is mutated?
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X-linked
Dystrophyn (milder form that DMD) |
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What is the inheritance pattern of limb-girdle muscular dystrophy?
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AD, AR, or X-linked
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List 6 drugs that can cause toxic myopathies
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1. Lipid lowering agents (statins, fibrates)
2. Antiretrovirals (Zidovudine) 3. Amiodarone 4. Procainamide 5. Choroquine 6. D-penicillamine |
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Exercise-induced cramps, pain, weakness, and stiffness along with myoglobinuria are signs of what kind of disease?
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Metabolic myopathy
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What are "ragged red fibers," and what may they be indicative of?
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Abnormal mitochondria clustered next to the muscle membrane
May be seen in: 1. Mitochondrial myopathies 2. Non-specifically in elderly patients |
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Episodic attacks of sudden, transient weakness is associated with what kind of disease?
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Muscle channellopathy
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List some things that can induce periodic paralysis seen with muscle channellopathies.
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1. Rigorous exercise
2. Large carbohydrate meals 3. Emotional stress 4. Changes in serum K+ levels |
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What are the two types of periodic paralyses associated with muscle channellopathies?
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1. Hypokalemic periodic paralysis
2. Hyperkalemic periodic paralysis |
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Which attacks last longer-- those associated with hypokalemic or hyperkalemic periodic paralysis?
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Hypokalemic periodic paralysis lasts longer (hours to days)
(hyperkalemic periodic paralysis lasts minutes to hours) |
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Which channels are defective in hypokalemic and hyperkalemic periodic paralysis?
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Hypokalemic --> Ca2+ channels
Hyperkalemic --> Na2+ channels |