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Peripheral Neuropathy Flashcards

1
Q

What are the subcategories in the PNS?

A

Somatic: Motor/Sensory

Autonomic: Sympathetic/Parasympathetic

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2
Q

What are the differences between the CNS and PNS?

A

CNS v PNS

CNS contains most somatic cell bodies v. only sensory neurons in dorsal root ganglia and autonomic neurons in ganglia of sympathetic chain

BBB v. Blood nerve barrier (less efficient than BBB)

Oligodendrocytes v. Schwann cells

Mechanical protection by bone (no collagen) v. supported by fibrous collagen

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3
Q

How do the location of the cell bodies of sensory and motor neurons differ?

A

Sensory: cell body in dorsal root ganglion

Motor: cell body in ventral root (in CNS)

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4
Q

What is the difference in where somatic nerves arise from vs autonomic nerves?

A

Somatic nerves arrive from cord (except for cranial nerves in brain) while there is a separate system for autonomic nerves in the PNS

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5
Q

What is the difference in the kind of neuron found in dorsal root ganglia v. autonomic ganglia?

A

Root ganglia: Pseudo-unipolar neuron (cell body in middle of the neuron)

v.

Autonomic ganglia: Mutipolar neuron (cell body at one end of the nerve with the axon going down)

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6
Q

How many pairs of spinal nerves are there and what do they innervate?

A

31

C1-C8: neck and bits of arms
T1-T12: Trunk and bits of arms
L1-L5: legs
S1-S5 + coccygeal: foot, genitals, perineum

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7
Q

What do nerve trunks contain?

A

Sensory, motor and autonomic axon before they branch off to their afferent or efferent endings

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8
Q

Describe nerve hierarchy

A

Axon (in endoneurium)–> fascicle (in perineurium) –> nerve (in epineurium)

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9
Q

What are the endo/peri/epi-neriums made of?

A

Collagen

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10
Q

What is the difference between motor, sensory, and autonomic neurons?

A

Basically the same structure but endings are different

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11
Q

TRUE or FALSE?

Axon diameter does not effect whether or not the neuron is myelinated

A

False

Larger axons are myelinated

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12
Q

Which kind of neuron (myelinated or not) are more critical if damaged?

A

Myelinated (like ones that control fine movement in the hand)

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13
Q

What is the nerve that is most often biopsied?

A

The sural nerve

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14
Q

Why is the sural nerve biopsied?

A

Has no motor function.

Only innervates a small part of the top of the foot

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15
Q

What is the epineurium made of?

A

Fatty tissue

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16
Q

List the unencapsulated sensory endings in skin and their functions

A

Peritrichial: senses hair movement

Merkel: Mechanoreceptor that responds to pressure

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17
Q

List the encapsulated sensory endings in skin and their functions

A

Pacinian corpuscle: vibration, deep touch

End bulb: pressure

Meissner’s corpuscle: light touch, vibration

Ruffini ending: Respond to pressure, skin stretching

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18
Q

Why are not all neurons myelinated?

A

Myelin is vulnerable to damage and disease

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19
Q

What are the 3 main factors which dictate conduction speed?

A

Myelin thickness
Axon diameter
Axonal composition

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20
Q

What does the number of axons in the nerve increase?

A

The amplitude of the axon potential

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21
Q

What are the types of fibers in peripheral nerves?

A

Myelinated: A (alpha, beta, gamma, omega) and B

Unmyelinated: C

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22
Q

What is the difference between group A and B

A

A has a diameter of 1-20 micrometers while B is 1-3

The speed of conduction of A is 5-120 m/s while B is 2-15 m/s

A include afferent fibres for proprioception, virbation, touch , pressure, pain, and temperature, somatic efferent fibres

B include visceral fibres; preganglionic visceral efferents

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23
Q

What is the diameter, speed, and function of C group fibers?

A

Diameter: 0.5-1.5 micrometers
Speed: 0.6-2 m/s
Function: Afferent fibers for pain, temperature; post ganglionic visceral fibres

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24
Q

Which sensory ending group mediates non-specific visceral pain?

A

C

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25
How can peripheral neuropathy occur?
Axons degenerate die Myelin can degenerate Myelin can be attacked Other parts of the nerve can be damaged
26
What are the types of injury?
Wallerian degeneration: Physical damaged to the nerve, many forms including crushing, cutting, stretch Segmental demyelination: Maybe due to damage or disease affecting Schwann cells or directly to myelin Axonal degeneration: Metabolic damage to axon leading to degeneration Loss of neuron: Damage where the neuron dies and therefore there is no regeneration
27
Can peripheral nerves regenerate after damage?
Yes, if the cell body is undamaged the axon can sprout
28
What guides axon sprouts during nerve regeneration?
Schwann cell basal lamina from the original fibre if intact
29
What is the rate of regrowth of a nerve following damage?
1-2 mm/day (slow- can take a year to fix a long nerve in leg)
30
What influences the success of regrowth of nerves?
The underlying cause and severity of the damage
31
How effective is nerve regeneration?
The inflammation can be repaired But the remyelination can be less effective
32
Why is the inflammatory reaction involved in the regeneration of PNS nerves especially interesting?
On the one hand, inflammatory reaction and its mediators in damaged nerve participate significantly in the processes of nerve regeneration . On the other hand, these also develop conditions for neuropathic pain induction .
33
Name the 5 main types of neuropathies and their presentations
Large fiber neuropathy: Affects hands and legs because longer fibres are more vulnerable Small fibre neurophathy: Affects lower legs Proximal motor neuropathy: Affects area above knees Acute mono neuropathies: Can affect multiple places (e.g. trunk), but is localised Pressure palsies: Medial nerve (carpal tunnel), ulnar nerve, lateral popliteal
34
Why are longer nerves more vulnerable?
Nerve itself is more vulnerable to stress due to more metabolic activity (long distance for nerve to have damaged in) Proteins made in cell body in spinal cord or brain and then they have a longer way to go down
35
Define peripheral neuropathy
All general disorders of the peripheral motor, sensory, or autonomic nerves, excluding single nerve lesions (mononeuropathies due to entrapment or trauma - carpal tunnel)
36
What are the kinds or peripheral neuropathy pathologies?
Axonal and demyelinating
37
What are the causes of peripheral neuropathies?
``` Hereditary Metabolic Infections Collage vascular disease Deficiency states Toxins Drugs Malignant disease Misc ```
38
What is the most common type of neuropathy?
Pressure palsies
39
What are the hereditary causes of pheripheral neuropathies and what is the most common one?
Most common: Charcot Marie Tooth - aka Hereditaty motor and sensory neuropathy Hereditary liability to pressure palsies Familial amyloidosis Refsum's disease
40
What are the metabolic causes of peripheral neuropathies?
Diabetes Renal failure Systemic amyloidosis
41
What are the infectious causes of peripheral neuropathies?
Guillain Barre syndrome and leprosy
42
What kind of neuropathy does Gillain Barre cause?
inflammatory demyelinating neuropathy
43
What are the collage vascular disease causes of peripheral neuropathies?
SLE, Systemic vasculitis
44
What are the deficiency state causes of peripheral neuropathies?
Vitamin B1, B6, B12 Thyamine deficiences
45
What are the drugs and toxins which cause peripheral neuropathies?
Alcohol, lead, organic solvents Cytotoxic meds for cancer
46
What are the malignant diseases that cause peripheral neuropathies?
paraneoplastic syndromes Multiple myelomas
47
TRUE or FALSE? CMT disease is only caused by one gene and there is only one kind of CMT
FALSE There are many types of CMT with different patterns of inheritence and different genes (some affect demyelination others axons)
48
What is the most common type of Charcot-Marie-Tooth disease?
Type 1A
49
What are the features of hereditary motor and sensory neuropathy?
Slowly progressive distal muscle weakness and atrophy of hands and feet initially Symmetrical distal sensory deficit Foot deformities Tendon reflexes diminished or absent Course usually slow and often benign but causes disability
50
Why does CMT present symmetrically?
Because it is hereditary
51
What are some foot deformities in CMT?
Pes cavux (high arch) and clawed toes
52
Why are people with CMT described as having champagne bottle legs?
Their legs look like upside down champagne bottles because of loss of muscle mass in lower leg
53
How do people get diagnosed with CMT?
Weakness and atrophy (especially in peroneal muscles) Foot deformities --> gait impairment Clinical signs of peripheral neuropathy or muscle atrophy found incidentally Because of hereditary neuropathy family history
54
TRUE or FALSE? Patients are usually aware of the severity of sensory loss in CMT
FALSE
55
How does the electrophysiology of someone with CMT differ from a normal person?
Nerve conduction is slowed (38m/s) Normal: 50m/s
56
How are peripheral neuropathies diagnosed?
Sural biopsy or DNA test (for CMT)
57
How does a fascicular biopsy of a CMT patient differ from a normal one?
Onion bulb appearance: myelin is not compact and poorly formed so multiple layers are unevenly and widely spaced
58
Why is CMT, a demyelinating disease bad for nerve health?
Lack of myelination in itself might not be as bad but in CMT the demylination leads to axon death --> loss of muscle mass
59
What is the most common mutation in CMT?
PMP22 - affects schwann cell function
60
What are the causes of predominantly motor neuropathies?
Inflammatory/Immune: Acute- Guillain Barre, Chronic - Chronic inflammatory demyelinating polyradiucloneuropathy Acute intermittent porphyria Diphtheritic neuropathy Lead neuropathy Diabetic neuropathy Inheritied motor and sensory neuropathies - CMT
61
How does Guillain Barre usually come about and resolve?
Typically follows a viral inflection Usually is self limiting and recovery can occur but can be fatal if not seen to due to resp muscles
62
How does CIDP compare to Guillian Barre?
Slower and leads to disability
63
What are the main types of predominantly sensory neuropathies?
Global sensory loss Loss of large fibre modalities, ataxic form Loss of small fibre modalities
64
What are causes of global sensory loss?
Carcinomatous sensory neuropathy Diabetes Most of the metabolic/endocrine neuropathies Most of the toxic neuropathies Hereditary sensory neuropathies
65
What are causes of loss of large fibre modalities?
Idiopathic sensory loss ganglionpathies Neuropathy with Sjogren syndrome cisplatin neuropathy (for cancer)
66
What are causes of loss of small fibre modalities?
Hereditary sensory neuropathies Lepromatous neuropathy Diabetic small fibre neuropathy Amyloidosis Fabry disease Tangier disease Painful small fibre neuropathy
67
What are loss of small fibre modalities associated with (symptom-wise)?
Loss of pain and excess pain
68
What are causes of neuropathies presenting with predominantly autonomic dysfunction?
Diabetes Amyloidosis Pandysautonomia Hereditary dysautonomia (Riley-Day syndrome) Rare alcoholic neuropathies
69
How do predominantly autonomic dysfunction neuropathies present?
Postural hypotension - fainting
70
What are the treatments for neuropathy causes?
Treating the cause: Inflammatory neuropathies- intravenous immunoglobulins, steroids, plasmapheresis Vasculitic neuropathy - steroids, immunosupressants B12 for B12 deficiency
71
What are some treatments for the symptoms of neuropathies?
Painful neuropathies - membrane stabilisers (amitriptyline, gabapentin, pregabalin motor problems -Physiotherapy Orthotics
72
Why are B12 deficiencies so bad?
They can affect the spinal cord and brain as well
73
What causes B12 deficiency?
Being a vegetarian or pernicious anaemia
74
How does vasculitis cause neuropathy?
It leads to nerve ischaemia
75
TRUE or FALSE? We don't diagnose the cause of most severe neuropathies
FALSE but it is true that we don't identify the cause of most common neuropathies

Neuro (23 decks)

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