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45 Cards in this Set

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List 3 neuromuscular junction disorders
1. Myasthenia gravis
2. Lambert-Eaton myasthenic syndrome
3. Congenital myasthenia
Is Myasthenia gravis caused by a presynaptic or postsynaptic neuromuscular junction disorder?
Postsynaptic
Is Lambert-Eaton myasthenic syndrome caused by a presynaptic or post-synaptic neuromuscular junction disorder?
Presynaptic
Describe the muscle weaknesses associated with Myasthenia Gravis.
1. Ocular (binocular diplopia, ptosis)
2. Bulbar (chewing, swallowing, speaking)
3. Limbs (proximal > distal)
Which disease is an autoimmune neuromuscular disease leading to fluctuating muscle weakness and fatiguability?
Myasthenia gravis
In Myasthenia gravis, what do antibodies attacks, and what is the result?
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)
Ocular Myasthenia gravis is only associated with which symptoms?
1. Ptsosis
2. Diplopia
How is Myasthenia Gravis diagnosed?
1. Painless fatiguable weakness
2. Ice pack test
3. Edrophonium (Tensilon) test
4. Ab against AChR or MuSK
5. Electrophysiologic studies (NCS)
When performing electrophysiologic studies to diagnosis MG, what are you looking for?
Repetitive nerve stimulation --> DECREMENTAL response

Single fiber EMG --> increased jitter
List 2 tumors that are associated with myasthenia gravis
1. Thymoma
2. Thymic hyperplasia

(Rarely other tumors: Small cell lung carcinoma)
List some autoimmune diseases that are associated with myasthenia gravis
1. Aplastic anemia
2. Thyrotoxicosis
3. SLE
4. RA
5. Sjogren syndrome
6. Mixed connective tissue disease
7. Multiple sclerosis
What is the appropriate symptomatic treatment for myasthenia gravis? What treatments are used for long term therapy?
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)
How long does neonatal myasthenia gravis normally last?
< 12 weeks
(usually 3 weeks long)
What causes neonatal myesthenia gravis?
Passive transfer of maternal AChR antibodies
(transient disease)
Are most congenital myasthenic disorders autosomal recessive or dominant? Which disease is an exception?
Mostly autosomal RECESSIVE
(except Slow channel syndrome, which is AD)
Which NMJ disease is frequently paraneoplastic?
Lambert-Eaton Myasthenic syndrome
What do antibodies attack in Lambert-Eaton myasthenic syndrome?
Pre-synaptic VGCC (voltage-gated calcium channels)
List 2 diseases associated with Lambert-Eaton Myesthenic syndrome
1. Cancers (small cell lung carcinoma)
2. Lymphoma
What is the difference in response to fast repetitive nerve stimulation seen in MG and LEMS?
MG --> decremental response

LEMS --> incremental response
Compare the effects of MG and LEMS on postsynaptic folds of the neuromuscular junction
MG --> simplification of postsynaptic folds (autoimmune attack)

LEMS --> Upregulation of postsynaptic folds
Does botulism cause problems at the presynaptic or postsynaptic side of the neuromscular junction?
Pre-synaptic
What is the result of Botulism on the neuromuscular junction?
Impaired ACh vesicle docking, fusion, and release from the presynaptic side
List some signs/symptoms associated with Botulism.
1. Constipation
2. Generalized and extraocular muscle weakness
3. Difficulty swallowing
4. Difficulty breathing
5. May require mechanical ventilation
Raw honey fed to babies less than six months can cause what kind of NMJ disorder?
Botulism
"floppy infant" syndrome
Which enzymes may be elevated in myopathies?
1. Creatine phosphokinase (CK or CPK)
2. Aldolase
3. Lactase
4. ALT, AST
What are some general signs of myopathies.
1. Muscle cramps or exercise-induced pain
2. Myoglobulinuria
List some inherited forms of myopathy
1. Muscular dystrophies
2. Metabolic myopathies
3. Congenital myopathies
4. Mitochondrial myopathies
List some acquired forms of myopathy
1. Inflammatory myopathies (Polymyositis, dermatomyositis, inclusion body myositis)
2. Infectious myopathies
3. Toxic myopatheis
What kind of EMG and NCS tests results are indicative of myopathy?
EMG --> myopathic motor unit potentials, early recruitment

NCS --> normal
List some various causes of elevated CK.
1. Myopathy
2. Muscle trauma
3. Exercise
4. Increased muscle mass
List 4 characteristics of muscular dystrophies
1. Hereditary
2. Progressive
3. Degenerative
4. Variable onset and intensity
Compare the effects of muscle use in patients with MG and LEMS.
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
Lambert-Eaton Myasthenic syndrome causes autonomic dysfunction, resulting in what kind of symptoms?
1. Dry mouth
2. Impotence
3. Constipation
4. Urinary incontinence
List 7 muscular dystrophies
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)
What is the inheritance pattern of Duchenne muscular dystrophy, and which protein is mutated?
X-linked
Dystrophyn
What is the inheritance pattern of Becker muscular dystrophy, and which protein is mutated?
X-linked
Dystrophyn
(milder form that DMD)
What is the inheritance pattern of limb-girdle muscular dystrophy?
AD, AR, or X-linked
List 6 drugs that can cause toxic myopathies
1. Lipid lowering agents (statins, fibrates)
2. Antiretrovirals (Zidovudine)
3. Amiodarone
4. Procainamide
5. Choroquine
6. D-penicillamine
Exercise-induced cramps, pain, weakness, and stiffness along with myoglobinuria are signs of what kind of disease?
Metabolic myopathy
What are "ragged red fibers," and what may they be indicative of?
Abnormal mitochondria clustered next to the muscle membrane

May be seen in:
1. Mitochondrial myopathies
2. Non-specifically in elderly patients
Episodic attacks of sudden, transient weakness is associated with what kind of disease?
Muscle channellopathy
List some things that can induce periodic paralysis seen with muscle channellopathies.
1. Rigorous exercise
2. Large carbohydrate meals
3. Emotional stress
4. Changes in serum K+ levels
What are the two types of periodic paralyses associated with muscle channellopathies?
1. Hypokalemic periodic paralysis
2. Hyperkalemic periodic paralysis
Which attacks last longer-- those associated with hypokalemic or hyperkalemic periodic paralysis?
Hypokalemic periodic paralysis lasts longer (hours to days)
(hyperkalemic periodic paralysis lasts minutes to hours)
Which channels are defective in hypokalemic and hyperkalemic periodic paralysis?
Hypokalemic --> Ca2+ channels
Hyperkalemic --> Na2+ channels