Term
| What features characterize "lower motor neuron" dysfunction? |
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Definition
1) Atrophy (from denervation)
2) Fibrillation (spontaneous firing detected with electrode)
3) Fasciculations (spontaneous twitch of group of muscle fibers)
4) Reduced tone (resistance) |
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Term
A patient presents with muscle atrophy, increased tone, hyperreflexia and a present Babinksi sign.
What is going on? |
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Definition
ALS
1) Atrophy is a LMN signs because of degeneration anterior horn neurons
2) Hyper-reflexia, increased tone and Babinski sign are UMN signs because of degeneration of descending corticospinal tracts |
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Term
| What are 2 common causes of Acquired LMN dysfunction? |
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Definition
| Polio and West Nile Virus |
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Term
| How can Axonal degeneration occur in Peripheral Nerves? |
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Definition
Wallerian degeneration
1) Begins distally and proceeds proximally
2) Causes secondary disruption of myelin into balls (Ovoids)
3) Degeneration causes denervation causing weakness, atrophy and reflex loss (if motor neuron)
** If it is a sensory neuron, there can be sensory disturbances and can cause Neuropathic pain ** |
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Term
| When can Axonal Regeneration occur in peripheral nerves? |
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Definition
| Occurs if cell body persists and path can be "re-traced." |
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Term
| How does Segmental Demyelination and Re-myelination occur in peripheral nerves? |
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Definition
1) Demyelination can be caused by injury to myelin sheath or by dysfunction of Schwann cells, affecting neurons anywhere along their length (multifocal).
2) Degree of "conduction block" determines degree of motor/sensory defects, since axon is still innervating muscle. |
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Term
| What type of neuropathies are Diabetes, Alcoholism and Genetic Disorders? |
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Definition
Cause Axonal Polyneuropathy
Remember, Axonal is more common than De-myelinating) |
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Term
| What type of neuropathies are Guillain Barre and MS? |
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Definition
| De-myelinating (less common than Axonal neuropathies) |
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Term
| What is the difference in clinical presentation and Nerve conduction diagnostics between Axonal Neuropathies and Demyelinating Neuropathies? |
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Definition
**MUST confirm with nerve conduction studies**
1) Axonal diseases tend to present first with distal sensory loss, weakness and atrophy, as well as distal reflex loss (remember how Wallerian degeneration progresses)
- Amplitudes are low diffusely (low density of innervation)
2) Demyelinating diseases are "segmental" and tend to present more variably and diffusely.
- Waveforms may be dispersed, often with Conduction slowing (distance/time) |
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Term
| How does Myasthenia gravis develop and how is it treated? |
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Definition
Post-synaptic, autoimmune NMJ disease, where antibodies attack AChR, leading to complement-mediated destruction of receptors.
Extreme muscle weakness, because they can't use the available ACh.
Treat with Immunosuppression and AChE inhibitors |
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Term
| How does Lambert-Eaton Myasthenic Syndrome (LEMS) develop and how is it treated? |
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Definition
Pre-synaptic, autoimmune disease of the NMJ, where antibodies attack voltage-gated Ca channels, disrupting active zones and causing similar symptoms to Myesthenia gravis.
- Would see low motor amplitude at rest , due to low EPP, and marked increased amplitude after exercise due to facilitation of calcium release.
W
- ALSO causes hyporeflexia and dry mouth
2) Treat with AchE inhibitors, immunosuppresion, and 3,4 diaminopyrodine (K-channel blocker that augments calcium release) |
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Term
How can you distinguish between LEMS and Myasthenia gravis clinically?
How would you treat differentially? |
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Definition
LEMS will present with hypreflexia and dry mouth, while Myasthenia Gravis
Treat both with AchE inhibitors and immunosuppresion, but also use a K-channel blocker for LEMS to increase calcium release. |
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Term
| Which diseases are caused by abnormal Dystrophin production? |
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Definition
Remember, Dystrophin links Actin to Sarcolema membrane in muscle.
These are Inherited Muscular Dystrophies
1) Duchenne MD
20) Becker MD |
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Term
| What clinical features should you look for if you suspect a Myopathy? |
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Definition
1) Progressive weakness of proximal limb muscles and neck flexors with mild/no Atrophy (no fasciculations)
**exceptions with facial, ocular and bulbar, respiratory and cardiac symptoms do occur**
2) Normal sensation and reflexes (lost over time)
3) Order Creatinine kinase (CK) to check for inflammatory myopathies, hypothyroid myopathy (endocrine), Dystrophy and metabolic myopathy
4) EMG will measure motor unit potentials to check for muscle necrosis (fibrillations from disconnection but NOT fasciculations)
5) Biopsy for Duchenne/Becker MD. |
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Term
| What information can you get from an EMG? |
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Definition
Motor Unit Potentials (MUPs)
1) Myopathy will show decreased amplitudes because of muscle necrosis, but NO fasciculations.
2) Neurogenic causes will show Fasciculations |
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Term
| What are the 3 types of Acquired and Inherited Myopathies? |
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Definition
ACQUIRED
1) Inflammatory (Polymyositis, Dermatomyositis, Inclusion Body)
2) Endocrine (Thyroid)
3) Toxic (Corticosteroids)
INHERITED
1) MD (Duchenne and Becker)
2) Metabolic (Mitochondrial, Glycogen, Lipid)
3) Congenital (Central Core Myopathy) |
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Term
| A patient presents with weakness, sensory symptoms, muscle atrophy and fasciculations. What is most likely going on? |
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Definition
You see weakness in ALL Motor unit diseases.
1) Sensory symptoms suggests neuropathy and atrophy/fasciculations suggests Motor Neuron issue > Axonal PN |
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Term
A patient presents with fatiguable muscle weakness and ocular symptoms.
What might be going on? |
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Definition
| Fatiguable muscle weakness is characteristic of NMJ issue, which is supported by ocular involvement (this could also be because of myopathy, though) |
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Term
| When do you see Hyporeflexia? |
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Definition
1) Motor neuron issue
2) PN issue (axonal and demyelinating)
3) LEMS (NOT M. gravis) |
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