Peripheral Nerve Pathology

Question 1

what is a motor unit and what is it composed of

Answer 1

functional unit of neuromusclar system

- lower motor neurons, axon, muscle fibers

Question 2

nerve fiber? composed of

Answer 2

structural component of peripheral nerve

- axon, schwann cell, and myelins sheath

Question 3

what do axons contain

Answer 3

organelles

Question 4

what does not occur in the axons? where does it occur

Answer 4

no protein synthesis

- delivered from perikaryon

Question 5

internodes

Answer 5

mylinated segments

one schwann cell per internode

Question 6

what are internodes separated by

Answer 6

nodes of ranvier

Question 7

endoneruium

Answer 7

surrounds individual nerve fibers

Question 8

perineurium

Answer 8

encloses each fascicle

Question 9

epineurium

Answer 9

encloses entire nerve

Question 10

what happens in remyelination in segmental demylination

Answer 10

new internodes are shorter

new myelin sheath is thinner

Question 11

what does segmental demyelination look like under the microscope

Answer 11

onion ring

Question 12

how does axonal degeneration occur

Answer 12

injury due to a focal lesion results in wallerian degeneration distal to lesion

Question 13

what happens to muscle fibers in affected motor unit that has axonal degeneration

Answer 13

denervation atrophy

Question 14

what happens in nerve regeneration

Answer 14

-proximal stumps of degenerated axons sprout and elongate, develop new growth cones
- growth cones guided by Schwann cells
-

Question 15

what is the histological evidence of nerve regeneration

Answer 15

regenerating cluster: multiple closely aggregated thinly myelinated small-caliber axons

Question 16

name an immune-mediated Neuropathy disease

Answer 16

Guillian-Barre Neuropathies

Question 17

how is Guillian-Barre characterized clinically. how threatening is this disease

Answer 17

weakness beginning with distal muscles rapidly progressing to proximal muscles

• life threatneing
• loss of deep tendon reflex
• nerve velocity slowed

Question 18

2/3 of Guillian-barre cases are preceded by what

Answer 18

acute influenza

or pt has recovered before onset of neuropathy

Question 19

what is the morphology of Guillian-Barre

Answer 19

inflammation of peripheral nerve
segmental demyelination
remyelination

Question 20

what are CSF values for Guillian-Barre

Answer 20

elevated protein CSF

Question 21

name an infectious polyneuropathies

Answer 21

leprosy

Question 22

mycobacterium leprae invade what cells in the nervous system

Answer 22

schwann cells

varicella-Zoster ( shingles)

Question 23

how does polyneuropathy occur in lepromatous leprosy

Answer 23

symmetric poluneuropathy
involves pain fibers
loss of sensation leading to injuries and large traumatic ulcers on extremities

Question 24

what are the two types of leropsy

Answer 24

lepromatous

tuberculoid

Question 25

what is a difference in clinical presentation in lepromatous and tuberculoid leprosy

Answer 25

more localized nerve involvement in tuberculoid leprosy

Question 26

what is the MOA for tuberculoid leprosy

Answer 26

• cell-mediated immune response by nodular granulomaotus inflammation in dermis
• schweann cells, loose myelin b/c they were in the vicinity

Question 27

what is the morphology for varicella-Zoster

Answer 27

neuronal destruction and loss

• mononuclear inflammatory infiltrates
• regional necrosis with hemorrhage
• axonal destruction after death of sensory nerves

Question 28

what does the histology of Varicella-zoster look like

Answer 28

intranucluar inclusions seen in satellite cells around ganglion cells in dorsal root ganglion

Question 29

what is the morphology for peripheral neuropathy in adult-onset diabetes mielitis

Answer 29

axonal neuropathy
segmental demyelination
endoneruial arteries with thickening and hyalinization

Question 30

what is the clinical course of peripheral neuropathy in adult-onset DM

Answer 30

symmetric neuropathy most common
sensation in distal extremities
motor abnormalities less evident
ulcers that heal poorly

Question 31

Name traumatic neuropathies of peripheral nerve

Answer 31

transection

compressed neuropathy

Question 32

how does transection try to fix itself

Answer 32

regeneration is difficult because discontinuity between proximal and distal portions of nerve sheath
- axons grow and make a mass of tanlged axons called traumatic neuroma

Question 33

describe traumatic neuroma

Answer 33

small bundles of axons appear randomly oriented but are surrounded by organized layers of Schwann cells

Question 34

what syndrome is associated with compression neuropathy

Answer 34

carpal tunnel syndrome

Question 35

explain carpal tunnel syndrome

Answer 35

compression of median nerve by transverse carpal ligament

Question 36

Name a hereditary neuropathy

Answer 36

hereditary motor and sensory neuropathies HMSN

Question 37

HMS present as spectrum of disorders all caused by mutations in genes involved in

Answer 37

formation and maintenance of myelin

Question 38

what are the 2 types of HMSN diseases

Answer 38

I: Charcot-Marie-tooth-Disease
I: CMT disease

Question 39

clinical presentation for I: Charcot-Marie-tooth-Disease

Answer 39

may be asymptomatic

• distal muscle weakness
• atrophy of calf muscle
• orthopedic problems of foot

Question 40

what chromosomes are involved in HMSN I CMT disease

Answer 40

17p11.2
1
16

Question 41

what is the morphology for CMT disease

Answer 41

demyelinating neuropathy
“onion bubs”
hypertrophic neuropathy: palpable

Question 42

what is the clinical course for CMT diseae

Answer 42

slowly progressive
normal lifespan
disability of sensorimotor deficits