Disorders of Peripheral Nervous System Flashcards
What is the most common cause of acute evolving motor & sensory deficits?
Guillain-Barré syndrome (GBS)
What age groups are affected by GBS?
- Young adults
- 50-80 y/o
T/F: females are more likely to get GBS
False- slightly more males develop GBS
What is the etiology of GBS and what often precedes GBS?
- Immune-mediated disorder
- Acute infection often precedes
What are some common triggers for GBS?
- Viral (Haemophilus influenza, Epstein-Barr, Cytomegalovirus)
- Bacterial (Campylobacter jejuni)
- Surgery
- Vaccines
What is the pathogenesis of GBS in regards to demyelination of PNS?
- Antibodies bind to myelin of Schwann cells
- Macrophages respond to inflammatory signals & strip myelin from nerves
In regards to pathogenesis of GBS how does remyelination occur?
Schwann cells divide & remyelinate nerve axons
Why may there be axonal damage in an individual with GBS?
Inflammation
What axons are affected by GBS?
- Motor
- Motor and sensory
What is the clinical presentation of Acute Inflammatory demyelinating polyneuropathy (AIDP)?
A variant of GBS
progressive paralysis & areflexia due to demyelination
What is the clinical presentation of acute motor axonal neuropathy (AMAN)?
A variant of GBS
Axon involved, more severe, more respiratory involvement, more significant residual impairments
What is the clinical presentation of acute motor & sensory axonal neuropathy (AMSAN)?
A variant of GBS
Same as AMAN but with sensory involvement
What is the clinical presentation of Acute sensory ascending neuropathy (ASAN)?
A variant of GBS
Sensory > Motor
What is the clinical presentation of Miller Fisher syndrome?
A variant of GBS
Opthalmoplegia, ataxia, areflexia with sparing of strength
What is the clinical presentation of chronic inflammatory demyelinating polyneuropathy?
A variant of GBS
Slower onset, relapses & remissions or slow progression
What are the clinical manifestations of GBS?
- Variation b/w subtypes
- Ascending symmetrical weakness & distal sensory impairments
- Flaccid paralysis
- Absence of DTRs
- Time from onset to peak impairment < 4 weeks
- 30% require mechanical ventilation
What are the GBS stages and what occurs in each?
- Progressive impairment (distal to proximal)
- Static phase (2-4 wks)
- Recovery (proximal to distal, may take months or years)
What symptoms are required for diagnosis of GBS?
- Progressive weakness in > 1 extremity
- Loss of DTRs
What symptoms are supportive of a diagnosis of GBS?
- Weakness developing rapidly ceasing to progress by week 4
- Symmetric weakness
- Mild sensory signs & symptoms
- Facial weakness
- Recovery starts 2-4 wks after progression ceases
- Tachycardia, cardiac arrhythmias, & labile BP possbile
- Absence of fever
In order to diagnose GBS what features must the CSF have?
- CSF protein levels increase after 1 week (continue to increase with serial exams)
- CSF contains < 10 mononuclear leukocytes/mm3
In order to diagnosis GBS what must the electrodiagnostic test show?
Nerve conduction velocity slowed
What are some interventions for GBS?
- Control of autoimmune responses
- Mechanical ventilation
- Prevention of effects of immobility
What is the prognosis of GBS in regards to:
- Mortality rate?
- Recurrent form?
- 1 year?
- Mortality rate: 5%
- Recurrent form: 10%
- 1 year: 67% complete recovery, 20% significant disability)
What are the indications of a poor prognosis of GBS?
- Older
- Increase time before recovery begins
- Need for artificial respiration
- Reduced evoked potential (sign of axonal damage)
What is polio?
Virus invades cell bodies of lower motor neurons in ventral horn of spinal cord resulting in asymmetric flaccid paresis or paralysis
What is post- polio syndrome?
New neuromuscular symptoms occurring decades (average 25 years) after recovery from the acute paralytic episode
How many survivors are there of acute poliomyelitis in US? And how many will develop post-polio?
- 1.63 million survivors
- 1/4 to 1/2 will develop post-polio
What is the etiology of post-polio syndrome?
- Denervated muscles were reinnervated by collateral sprouting from surviving nerves
- Axons innervating more muscle fibers than originally intended
- Nervous system can no longer support giant motor units
- Prune back axonal sprouts
What are the clinical manifestations of post-polio syndrome?
- Declining muscle strength in previously affected & unaffected muscles
- Myalgia
- Joint pain
- Muscle atrophy
- excessive fatigue
How is post-polio diagnosed?
- Clinical
- EMG
- Muscle biopsy
What are the intervention strategies for post-polio syndrome?
- Treat symptoms
- Modify lifestyle
- Surgery (for deformities)
- Avoid working to fatigue
What is the prognosis of post-polio syndrome?
- Slowly progressive
- Stable period (3-10 years)
- Decreased function & quality of life
What is Myasthenia Gravis?
- Motor end plate disorder
- Most common neuromuscular transmission disorder
What is Myasthenia Gravis characterized by?
Fluctuating weakness & fatiguability of skeletal muscles
What is the age of onset of Myasthenia Gravis?
- Males: 50 to 60 years
- Females: 20 to 30 years
Is Myasthenia Gravis more common in females or males?
Females > males (3:2)
What is the etiology of Myasthenia Gravis?
Autoimmune disorder affecting neuromuscular junction & motor end plate
What is the pathogenesis of Myasthenia Gravis?
- Anti-Ach receptor antibodies (block receptor site & cause endocytosis of receptor)
- Acetylcholine receptors decreased & flattened which decreases efficiency of neuromuscular transmission
- so failure of nerve impulses to cross neuromuscular junction to stimulate muscle contraction
- Thymus may trigger the autoimmune response
What are the clinical manifestations of Myasthenia Gravis?
- Skeletal muscle fatigue & weakness (Activity causes fatigue & rest restores activity)
- Weak neck & facial muscles
Patients with Myasthenia Gravis have weak neck & fascial muscles. How does this manifest?
- Diplopia
- Ptosis
- Weak neck muscles
- Nasal speech
- Dysphagia
- Nasal regurgitation
- Aspiration of food
What are the three diagnostic methods of Myasthenia Gravis?
- Immunologic - Detect anti-Ach receptor antibodies
- Pharmacologic - acetylcholinesterase inhibitor (blocks Ach reuptake) Improves strength & endurance
- Electrophysiological - repeated stimulation shows a rapid decrease in motor action potential amplitude
What are some interventions for Myasthenia Gravis?
- AChE inhibitor meds
- Surgery (removal of thymus)
- Corticosteroids
- Plasmapheresis
What is the prognosis of Myasthenia Gravis?
- Slowly progressive disorder (periods of exacerbation & remission)
- Myasthenia crisis
What is Myasthenia crisis?
- medial emergency
- Respiratory muscle weakness
