5.6 disorders of PNS

Question 1

components of peripheral nerve

Answer 1

1. epineurium
2. perineurium
3. endoneurium
4. schwann cell
5. axon

Question 2

epineurium

Answer 2

dense CT
binds all nerve fasicles together

Question 3

perineurium

Answer 3

CT sheath surrounding each fasicle

Question 4

endoneurium 2

Answer 4

delicate CT from surrounding each axon.

has components which promote axonal growth

Question 5

schwann cell 2

Answer 5

myelinates axons and supports unmyelinated axons

central to axon development and maintenance

Question 6

peripheral nerve disorders anatomical category 4

Answer 6

mononeuropathy
polyneuropathy
mononeuritis multiplex
polyradiculoneuropathy

Question 7

polyradiculoneuropathy

Answer 7

affects multiple spinal nerve and spinal roots

Question 8

peripheral nerve disorders based off neuronal target of disease 3

Answer 8

neuronopathy
axonopathy
neuromuscular junction

Question 9

two divisions of axonopathy

Answer 9

demyelinating

axonal

Question 10

what are the two injury sites of an axon

Answer 10

proximal = still attached to cell body

distal = no longer connected to cell body but connected to effecter cell

Question 11

changes that occur to the proximal axon 3

Answer 11

nucleus goes to the side

cell body swells

chromatolysis - breakdown of nissl bodies and rER

Question 12

changes that occur to the distal axon 5

Answer 12

NMJ stripping denervation

Wallerian degeneration

myelin breakdown

macrophages clearing debris

effector cell atrophy

Question 13

what is wallerian degeneration

Answer 13

when there is degeneration from distal to proximal end of the distal axon

Question 14

stage of peripheral nerve regeneration 4

Answer 14

proximal axon sprouts

guideded into the endoneurium tube with schwann cells

tube guides axonal growth

complete recovery

Question 15

what affects peripheral nerve regeneration 3

Answer 15

how close to the cell body the injury is - closer lesser chance of survival

restoring contact w effector cell

type of injury

Question 16

three main types of traumatic peripheral nerve injuries

Answer 16

neuropraxia
axonotmesis
neurotmesis

Question 17

neuropraxia

Answer 17

transient block in nerve conduction, axon, myelin and endoneurium intact

rapid recovery

ex. cold, ischemia

Question 18

axonmtesis

Answer 18

axon and myelin locally damaged but endoneurium intact

ex. nerve stretch injury

Question 19

neurotmesis

Answer 19

axon, myelin and endoneurium damaged

ex. sharps injury

Question 20

common causes of neuropathy >5

Answer 20

Alcoholism + autoimmune
B12 deficinecy and other vitamin deficiencies
Cancer
Diabetes

Others include:

toxin exposure
genetic
inflammation
trauma

Question 21

MND aetiology

Answer 21

idiopathic 90% of cases
familial 10%

Question 22

key 2 hypotheses plus others

Answer 22

genetic
excitotoxicity
oxidative stress
inflammaging
mitochondrial abnormalities

Question 23

genetic hypothesis for MND 3

Answer 23

due to mutations in genes including SOD gene which is an exnyme responsible for removing free radicals.

against: only 10% of cases familial

some ppl have mutations without disease

Question 24

excitotoxicity hypothesis of MND

Answer 24

loss of glutamate transporters resulting in glutamate build up which binds to receptors and causing overexcitation of the cell

against: only few have decreased glutamate transporters

drugs preventing glutamate binding not extending lfie significantly

Question 25

amytrophy

Answer 25

muscle wasting

Question 26

lateral sclerosis

Answer 26

loss of neurons in lateral corticospinal tract

Question 27

clinical features of MND affecting LMN

Answer 27

wasting lack of tone fasiculations hyporeflexia atrophy

Question 28

clinical features of MND affecting UMN

Answer 28

weakness tone no fasiculations hyperreflexia no atrophy

Question 29

initiation of mnd and disease progression 4

Answer 29

starts as weakness in arms and legs and gradually spreads as disease spreads axonal architecture and function fails, denervationof target neuron or celll death will begin when weakness spreads to respiratory failiure death two years after diagnosis

Question 30

investigations in MND

Answer 30

physical exam Nerve conduction studies: EMG MRI brain and spine

Question 31

key features you see in physical exam on MND 2

Answer 31

tongue atrophy and fasiculations "split hand" muscle wasting on one side of hand

Question 32

MND management

Answer 32

multidisciplinary team to help PFTs to establish lung function palliative care riluzole - NDMA antagonist whcih prevents glutamate from binding, extends life to 90 days

Question 33

guillian barré syndrome

Answer 33

acute onset of muscle weakness whcih spreads upwards from distal limbs commonly follows a respiratory/gastro infection

Question 34

pathology of guillian barré syndrome 2

Answer 34

auto immune response due to molecular mimicry. The illness mimics the antigens of peripheral nerve proteins resulting in attack against them. results in demyelination of spinal nerve roots and peripheral nerves

Question 35

guillian barré clinical features 3

Answer 35

acute onsent weakness starting distally back pain autonomic dysfunction

Question 36

GB syndrome investigations 6

Answer 36

physical exam spirometry lumbar puncture nerve conduction studie MRI w gallidium antibody test

Question 37

in GB key findings from physical exam

Answer 37

signs of weakness autonomic dysfunction such as varying heart rate

Question 38

why lumbar puncture in guillian barré syndrome

Answer 38

can show signs of inflammation

Question 39

mysathenia gravis patho 3

Answer 39

auto-immune destruction of receptors on post synaptic neurons. primarily destruction of acetylcholine receptors, preventing acetylcholine from binding to illicit a response also causes chronic inflammation resulting in further destruction.

Question 40

MG clinical features 6

Answer 40

opthalmaplegia ptosis dipoplia repeated movement causes increased weakness dysphagia dysarthria shortness of breath

Question 41

MG investigations general

Answer 41

physical exam spirometry chest CT

Question 42

MG diagnostic investigations

Answer 42

1. EMG 2. repetitive nerve stimulation 3. tension edrophonium test 4. ice pack test 5. antibodies

Question 43

tension endrophonium test

Answer 43

uses a cholinesterase inhibitor which keeps the acetylcholine in the synapse allowing it to bind indicates its MG

Question 44

ice pack test

Answer 44

if corrects ptosis after two minutes indicates that MG

Question 45

why do CT chest

Answer 45

looking for thymoma which is associated with MG

Question 46

MG key findings in physical exam 5

Answer 46

ptosis facial paresis fatigability in repeated movements proximal weakness