Neuromuscular diseases consist of what 4 categories?
- Motor neuron disease
- Peripheral neuropathy
- Disorders of NMJ
- Primary disorders of muscle fibers
List the NMJ diseases?
List the types of myopathies?
- Congenital Myopathies
- Muscular Dystrophies
- Myotonic Dystrophies
- Metabolic Myopathy
- Endocrine Myopathy
- Toxic Myopathy
- Inflammatory Myopathy
List the 2 types of Muscular dystrophies?
"Floppy infants" what type of myopathy?
Alcoholics associated with what type of neuromuscular disease?
Which neuromuscular disease is associated with distal muscle involvement?
Muscle weakness + sensory involvement. Which type?
Elevated CK in which type of neuromusclar disease?
Which neuromuscular disease is associated with slowed conduction velocity?
What 2 types of neuromuscular diseases have similar muscle biopsies?
List these features?
Since muscle biopsies are the same, what else will be the same?
Motor neuron disease & peripheral neuropathy
Will have denervation repesented by:
- Atrophic angular target fibers
- Fiber type grouping
- Group atrophy
EMG findings will be the same for these 2 groups
What does fiber type grouping mean? Which neuromuscular disease(s) is/are they associated with?
More muscle fibers innervated by a single motor neuron
Seen with motor neuron diseases and peripheral neuropathy
Myopathies associated with what 2 findings on muscle biopsy?
Disseminated necrosis, inflammation
Which neuromuscular disease is associated with normal muscle biopsy?
Steppage gait (foot drop) seen in what neuromuscular disease?
Which 2 neuromuscular diseases have similar EMG findings? List these features?
Motor neuron diseases, peripheral neuropathy
1) Decreased # of motor units (action potentials)
2) Increased amplitude (due to fiber type grouping)
EMG findings of myopathies (3)?
- Normal # of motor units (action potentials) but shorter in duration
- Decreased amplitude (less # of muscle fibers per motor unit)
Muscle weakness of pelvic girdle associated with what neuromuscular diseases?
Myopathies (specifically muscular dystrophies)
Polyphasic findings on EMG. What neuromuscular disease? What is the reason for these findings?
Polyphasic means muscler fibers of a motor unit are not in sync, not firing all at once.
Deletion of dystrophin? What disease?
X-linked (Duchenne's) muscular dystrophy
Genetic difference between X-linked and Becker's muscular dystrophy? Which one is worse?
Becker's is a mutation in dystrophin
X-linked is a deletion = much worse
Mode of inheritence of Duchenne's?
Only neuromuscular disease that has sensory involvement?
Peripheral neuropathy. Probably asked this question about 3 different times now
Main difference between muscular dystrophies and myotonic dystrophies?
Muscular dystrophy = muscle weakness
Myotonic dystrophy = muscle weakness + difficulty relaxing muscle (myotonia)
Coke colored urine after exercise + muscle cramps. What disease?
What enzyme will be elevated?
What's causes color in the urine?
Myoglobin in urine
McArdle's disease is associated with what deficiency? What is the effect of this defiency?
Muscle phosphorylase defiency
Glycogen cannot break down during exercise to produce ATP, lactate and pyruvate necessary for oxidative phosphorylation
In McArdle's, what enzyme remains "normal" during exercise? Is this a good thing?
Lactate will not increase. Normally, it should. This lack of increase indicates that glycogen is not being used as energy source when it is supposed to (anaerobic).
Muscle biopsy of McArdle's
Muscle necrosis and phosphorylase deficiency
What is the ischemic exercise test? When is it used?
Used in glycogen storage diseases, because of lack of normal rise of serum lactate during exercise in glycogenesis.
Myasthenia gravis is associated with autoantibodies against what?
Postsynaptic AcH receptors on postsynapse of NMJ
What tests (2) would you order to confirm diagnosis of myasthenia gravis?
Ach receptor antibody test, Repetitive stimulation test
Myasthenia gravis classically involves what organ? What occurs in this organ as a result?
Eye, causes ptosis and diplopia
Describe muscle weakness seen in myasthenia gravis? What drug improves these symptoms?
muscle weakness that worsens with use and improves with rest
- symptoms improve with anticholinesterase agents
If patient has a thymectomy and their symptoms improve, what neuromuscular disease are you thinking of?
Myasthenia gravis, can be associated with thymic hyperplasia or thymoma
What disease is associated with autoantibodies against presynpatic Ca2+ channels? What occurs at these channels?
Lambert-Eaton Syndrome, will not allow Ca2+ into the presynapse, thus no Ach is release into the synpase
Describe main difference in muscle weakness features b/t myasthenia gravis and lambert-eaton?
Myasthenia gravis - muscle weakness worsens with use and improves with rest. Eyes usually involved
Lambert eaton - Proximal muscle weakness that improves with use; eyes usually spared
What 2 tests would you like to do to confirm lambert eaton?
Repetitive stimulation test, EMG/NCV (nerve conduction velocities)
If you perform repetitive stimulation test and muscle function improves, is it myasthenia gravis or lambert eaton? Describe mechanism?
Lambert eaton improves with repetitive stimulation bc each stimulatory effect causes more calcium to want to flow into presynapse through channels that are being competitively inhibited. Flow of Ca2+ in, causes AcH to be release into synapse, causes muscle to work.
Repetitive stimulation in myasthenia gravis will actually worsen the symptoms, bc each successive stimulation will cause less and less AcH to be release into synapse, thus the already blocked AcH receptors wont respond to the low levels.
What cancer most commonly causes Lambert-Eaton?
Roughly 40-50% of patients with Lambert - Eaton were caused by small cell lung cancer.
What drug type won't improve Lambert-Eaton?
Acetylcholinesterase inhibitors. Enzyme has nothing to act on. Theres not Ach being released anyways so they cant prevent the breakdown of something that isnt there
Treatment for Lambert Eaton?
3-4 aminopiridine (stimulates AcH release) and immunosuppression