Neuromuscular Diseases Flashcards
Movement tested: shoulder shrug (elevation)
Main muscles?
Nerve root?
Peripheral nerve?
Movement tested: shrug (elevation)
Main muscles: trapezius
Nerve root: C2-5
Peripheral nerve: spinal accessory
Movement tested: shoulder abduction
Main muscles?
Nerve root?
Peripheral nerve?
Movement tested: shoulder abduction
Main muscles: deltoid/ supraspinatus
Nerve root: C5 & C6
Peripheral nerve: axillary/ suprascapular
What is the behavior of motor units in effort?
With increasing effort, tension increases by:
- (1) increasing the firing rates of individual units and by,
- (2) recruiting more units into the effort.
These are recruited such that, with full effort, the electrical activity of individual motor units can no longer be recognized.
What are fasciculations?
Irritation of motor neurons or motor axons can result in spontaneous discharge of individual motor axons and contraction of the motor unit. These can be seen on the skin surface as random, involuntary twitches
What do persistent fasciculations indicate?
Persistent fasciculations, especially in a muscle that is showing weakness or atrophy, indicates damage to the anterior horn cell or its axons.
What is a fibrillation?
- The spontaneous contraction of individual muscle fibers is termed a fibrillation but it is not visible from the skin surface.
- Muscle fibers that have been denervated for days to weeks become hyperirritable (to the point where they are spontaneously active).
How do you detect fibrillations?
Needle electromyography can detect fibrillations, which are fairly reliable signs of damage to motor nerve fibers, but which may also be seen in muscles diseases (especially those that damage the distal motor axons).
What is the result of conditions that damage some motor units?
Such conditions usually result in:
- overall weakness of the muscle but high firing rates of individual motor units that are still intact.
- This is because of the decreased number of motor units which must be activated at maximal frequencies in order to generate any muscle force
What is the impact of damage to upper motor neurons?
Voluntary motor activity is also driven by descending motor tracts of the central nervous system that are collectively referred to as “upper motor neurons.” Damage to these “upper motor neurons” makes it impossible to achieve high firing rates of the motor units during voluntary contraction. This is similar to the finding of low frequency of firing of the individual motor units that would be seen with inadequate effort.”
What is motor neuron disease?
General term for conditions that result in degeneration of the anterior horn cells (lower motor neurons) and the upper motor neurons of the cerebral cortex that give rise to descending tracts that control movement.
What are the lower motor neuron signs seen in motor neuron disease?
- Atrophy
- Fasciculations
- Decreaesed reflexes
What are the upper motor neuron signs seen in motor neuron disease?
- Spasticity
- Increased reflexes
- Upgoing toes
What is ALS?
Most patients have clinical signs of both upper and lower motor neuron disease and are diagnosed with amyotrophic lateral sclerosis - ALS
What are the two inherited degenerative motor neuron diseases?
1) Werdnig-Hoffmann disease in infants
2) Kugelberg-Welander disease in children and young adults)
* characterized by anterior horn cell degeneration only, and there are even more rare inherited forms of amyotrophic lateral sclerosis.
What is primary lateral sclerosis?
- The variant of motor neuron disease that selectively involves the upper motor neurons is called primary lateral sclerosis.
- In the great majority of cases there is eventually some evidence of lower motor neuron involvement.
- For this reason most neurologists no longer feel this to be distinct from ALS despite the fact that the clinical course tends to be longer than in the usual variety of ALS.
- Some patients survive ten years or longer.
- Often shows signs of evolution to a more typical ALS pattern.
