Disorders of impaired neutral conduction and transmission Flashcards
1
Q
Myelination
A
- a sheath of proteins and fats surrounding an axon
- provides insulation, prevents current flow across the axonal membrane
- increases speed of action potentials and distance a current can spread
- thicker myelin leads to faster condution and greater chances for action potential propagation
2
Q
Demyelination
what does it do to the function of a neuron
A
- lower membrane resistance
- allows leakage of electrical current across membrane
- decreases speed or blocks propagation of action potentials
3
Q
Disorders of impaired conduction in the NS
A
- CNS: multiple sclerosis
- PNS: peripheral neuropathy; Guillain-barre
4
Q
Describe what happens with MS
A
- CNS demyelination
- immune system produces antibodies that attack oligodendrocytes
- patches of demyelination called Plaques in CNS white matter
- damage to myelin sheaths in brain and SC which slows/blocks transmission of signals
- also lose grey matter volume
5
Q
Where can the plaques in MS occur
A
- subcortical
- brainstem
- spinal cord
- CNS white matter
6
Q
Incidence of MS
A
- Onset 20-40 years
- women are 3x more affected than men
7
Q
List some risk factors for MS
A
- whites of European ancestry,
- living further from equator (prior to puberty),
- smoking,
- low levels of Vitamin D,
- obesity during adolescence.
- OS&S: 2% risk for child, 5% for sibling or fraternal twin, 25% identical twin.
- Viruses: Epstein-Barr, measles, canine distemper, herpes virus-6, chlamydia pneumonia.
8
Q
MS
Symptoms
A
- fatigue
- weakness
- impaired cognition
- visual probelms
- decreased sensation
- slurred speech
- pain
- bowel/bladder changes
- cognitive/affective disorders
- exacerbations/remssions
9
Q
MS
Diagnosis
A
- difficult as signs may resolve when edema decreases
- Lumbar puncture and evoked potentials (EP) also used.
improved with use of imaging (plaques).
looking for oligodendorcytes that are broken up
10
Q
MS
PT role
A
- exercise at lower intentsity
- Avoid overexertion and high temperatures.
- Small ↑’s (½ºF) in body temp may alter activity of membrane proteins in axons, further disabling AP conduction.
- Sweating, dizziness, muscle weakness, slowed reaction times, reduced energy, difficulties with attention/ concentration.
- Uthoff’s sign: better in 30 minutes.
- “Pseudo exacerbation”: last < 24 hours.
- exacerbations last >24 hours \, separated y ≥30 days
11
Q
MS
Types
A
- Relapsing remitting
- secondary progressive
- primary progressive
- progressive relapsing
12
Q
Relapsing/remitting MS
A
- During relapses, new signs/sxs + old signs/symptoms recur or worsen.
- Relapses f/b remission (full or partial recovery from deficits acquired during relapse.
- without treamtent most transition to secondary progressive MS
13
Q
Secondary progressive MS
A
- continuous neurological decline
- fewer or no relapses
14
Q
Primary progressive MS
A
- steady functional decline from time of onset
- predominantly SC s&s
15
Q
progressive relapsing MS
A
- steady functional decline with superimposed relapses + partial remission s
- Fxn never fully recover during remission
- PRMS is now considered to be a form of PPMS
16
Q
Peripheral Polyneuropathy
A
- any pathologic change in peripheral nerves
- destruction of myelin surrounding largest most myelinated sensory and motor fibers
- results in disrupted proprioception and weakness due to desctruction of myelin in sensory and motor neurons
17
Q
Causes of periperhal polyneuropathy
A
- autoimmune disease
- metabolic abnormalities
- toxic chemcials
- hereditary disorders
18
Q
What damage is done with a diabetic polyneuropathy, what symptoms might be felt and how can one limit the pogression
A
- both axons and myelin are damaged
- decreased sensation along with pain, paresthesias and dysesthesias
- glycemic control (A1C<7) can limit progression in type 1 but not type 2
19
Q
PT role with diabetic polyneuropathy
A
- balance and strength training to reduce fall risk
- gait and balance improve with exercise
- orthoses may be used to stabilize weight-bearing joint
- prevent sprains and strains
- prevent dropping of forefoot during gait
- prevent deformities from paresis, paralysis and lack of sensation
20
Q
Guillain-Barre Sydrome
A
- acute inflammation demyelinated polyneuropathy
- AIDP is most common form
21
Q
What happens with
Guillian Barre Syndrome
A
- immune system attacks schwann cells
- affects sensory and motor function
- if severe, peripheral autonomic function
- often occurs 1-2 weeks after a mild infection (resp. or GI)
22
Q
DX of Guillian Barre
A
- EMG
- lumbar puncutre
- MRI
23
Q
Guillain-Barre
Signs and symptoms
A
- Primary sign is ascending skeletal Muscle paralysis
- difficulty with chewing, swallowing, speaking, facial expressions if motor CN’s affected
- weakness>sensory loss; may have deep aching pain or hypersensitivity to touch
- 3-10% die of cardiac or respiratory failure
- in some cases demyelination is extreme and axons within myelin sheath degenerate resulting in residual complications
24
Q
Guillain-barre Syndrome
Treatment: medical
A
- plasmapheresis: removes antibodies
- intravenous immunogoblin therapy: neutralizes antibodies
- 25% of patients require ventilatory
25
# Guillian-Barre
Treatment: PT/OT
- Acute phase: stretching and ROM
- Recovery phase: gentle exercise and functional mobility
- monitor for DVT, PE, autonomic symptoms
- use BORG scale and monitor during submax aerobic training for dysautonmia
26
# Guillain-barre
Treatment: SP/RT
- SP: chewing, swallowing, speaking, breath support for speech
- RT: breathing, secretions
27
# Guillain-barre
poor prognostic signs
| just be aware of
- over 60
- reach peak of symptoms withing 7 days
- being on a vent
28
Synpatic Transmission
1. action potential reaches axon terminal
2. the change in electrical potential causes opening of voltage-dependent Ca2+ channels and influx of Ca2+
3. increase leves of Ca2+ then promote movement of synpatic vesicles to the membrane
4. Synaptic vesicles bind with membrane, then release NT into synaptic cleft
5. NT diffuses across the synpatic cleft and activates a membrane receptor
29
Neuromuscular junction transmission
1. AP reaches presynaptic terminal of neuron, membrane of presynaptic terminal depolarizes.
2. Voltage-gated calcium ion (Ca+2) channels open; Ca+2 influxes into the nerve terminal.
3. Synaptic vesicles move toward a release site in membrane, fuse with membrane, then…
4. Rupture to release a NT (Ach) into synaptic cleft.
5. When ACh binds to receptors associated with membrane channels on mm cell; Na+ channels open briefly.
6. Influx of Na+ initiates a series of events that produce contraction of mm cell.
30
disorders of Impaired tranmission in the NMJ
- disease of NMJ interfere with the lock (receptor) or the key (AcH)
- Myasthenia Gravis
- Lambert-Eaton Syndrome
31
Myasthenia Gravis
| what is it and incidence
- Autoimmune disease
- antibodies attack and destroy nicotinic receptors on muscle cells
- onset in women: 20-30 years of age
- onset in men 60-70
- women more often than men
32
How does myasthenia gravis affect the NMJ
- normal amounts of AcH are released into the cleft
- BUT
- few receptors are availble for bindign, resulting in increaseing weakness with repetitive muscle contractions
33
Which muscles tend to be most affected in myasthenia gravis
- affects muscles that contract a lot
- eye, fascial, respirtory muscles, proximal stabilizing muscles
34
# Myasthenia Gravis
Signs and symptoms
- Muscles that contract frequently = dropping of eyelids, misalignment of eyes
- facial expression
- swallowing
- proximal limb movements
- respiration
35
# Myasthenia gravis
Diagnostic testing
- Tensilon is used.
- Tensilon inhibits the enzyme that breaks down ACh, thus leaving more ACh in the synaptic cleft to bind repeatedly with muscle cell receptors.
- This rapidly improves muscle strength by increasing muscle response to nerve impulses.
- The muscle strength increase occurs within a minute of administration of the drug and lasts only a few minutes
36
# Disorders of impaired transmission
Lambert-Eaton Syndrome
- antibodies destroy voltage-gated Ca2+ channels in the presynpatic terminal
- less ACh released
- decreased excitation of muscle cells cause muscle weakness
- Botox works same way-- inhibits release of Ach @ NMJ so mm’s can’t contract
