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Neuro > Peripheral Neuropathy > Flashcards

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
Q

How can peripheral neuropathy occur?

A

Axons degenerate die
Myelin can degenerate
Myelin can be attacked
Other parts of the nerve can be damaged

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26
Q

What are the types of injury?

A

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

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27
Q

Can peripheral nerves regenerate after damage?

A

Yes, if the cell body is undamaged the axon can sprout

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28
Q

What guides axon sprouts during nerve regeneration?

A

Schwann cell basal lamina from the original fibre if intact

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29
Q

What is the rate of regrowth of a nerve following damage?

A

1-2 mm/day (slow- can take a year to fix a long nerve in leg)

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30
Q

What influences the success of regrowth of nerves?

A

The underlying cause and severity of the damage

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31
Q

How effective is nerve regeneration?

A

The inflammation can be repaired

But the remyelination can be less effective

32
Q

Why is the inflammatory reaction involved in the regeneration of PNS nerves especially interesting?

A

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 forneuropathic pain induction .

33
Q

Name the 5 main types of neuropathies and their presentations

A

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
Q

Why are longer nerves more vulnerable?

A

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
Q

Define peripheral neuropathy

A

All general disorders of the peripheral motor, sensory, or autonomic nerves, excluding single nerve lesions (mononeuropathies due to entrapment or trauma - carpal tunnel)

36
Q

What are the kinds or peripheral neuropathy pathologies?

A

Axonal and demyelinating

37
Q

What are the causes of peripheral neuropathies?

A 
Hereditary
Metabolic
Infections
Collage vascular disease
Deficiency states
Toxins
Drugs
Malignant disease
Misc
38
Q

What is the most common type of neuropathy?

A

Pressure palsies

39
Q

What are the hereditary causes of pheripheral neuropathies and what is the most common one?

A

Most common: Charcot Marie Tooth - aka Hereditaty motor and sensory neuropathy

Hereditary liability to pressure palsies

Familial amyloidosis

Refsum’s disease

40
Q

What are the metabolic causes of peripheral neuropathies?

A

Diabetes

Renal failure

Systemic amyloidosis

41
Q

What are the infectious causes of peripheral neuropathies?

A

Guillain Barre syndrome and leprosy

42
Q

What kind of neuropathy does Gillain Barre cause?

A

inflammatory demyelinating neuropathy

43
Q

What are the collage vascular disease causes of peripheral neuropathies?

A

SLE, Systemic vasculitis

44
Q

What are the deficiency state causes of peripheral neuropathies?

A

Vitamin B1, B6, B12

Thyamine deficiences

45
Q

What are the drugs and toxins which cause peripheral neuropathies?

A

Alcohol, lead, organic solvents

Cytotoxic meds for cancer

46
Q

What are the malignant diseases that cause peripheral neuropathies?

A

paraneoplastic syndromes

Multiple myelomas

47
Q

TRUE or FALSE? CMT disease is only caused by one gene and there is only one kind of CMT

A

FALSE

There are many types of CMT with different patterns of inheritence and different genes (some affect demyelination others axons)

48
Q

What is the most common type of Charcot-Marie-Tooth disease?

A

Type 1A

49
Q

What are the features of hereditary motor and sensory neuropathy?

A

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
Q

Why does CMT present symmetrically?

A

Because it is hereditary

51
Q

What are some foot deformities in CMT?

A

Pes cavux (high arch) and clawed toes

52
Q

Why are people with CMT described as having champagne bottle legs?

A

Their legs look like upside down champagne bottles because of loss of muscle mass in lower leg

53
Q

How do people get diagnosed with CMT?

A

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
Q

TRUE or FALSE?

Patients are usually aware of the severity of sensory loss in CMT

A

FALSE

55
Q

How does the electrophysiology of someone with CMT differ from a normal person?

A

Nerve conduction is slowed (38m/s)

Normal: 50m/s

56
Q

How are peripheral neuropathies diagnosed?

A

Sural biopsy or DNA test (for CMT)

57
Q

How does a fascicular biopsy of a CMT patient differ from a normal one?

A

Onion bulb appearance: myelin is not compact and poorly formed so multiple layers are unevenly and widely spaced

58
Q

Why is CMT, a demyelinating disease bad for nerve health?

A

Lack of myelination in itself might not be as bad but in CMT the demylination leads to axon death –> loss of muscle mass

59
Q

What is the most common mutation in CMT?

A

PMP22 - affects schwann cell function

60
Q

What are the causes of predominantly motor neuropathies?

A

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
Q

How does Guillain Barre usually come about and resolve?

A

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
Q

How does CIDP compare to Guillian Barre?

A

Slower and leads to disability

63
Q

What are the main types of predominantly sensory neuropathies?

A

Global sensory loss

Loss of large fibre modalities, ataxic form

Loss of small fibre modalities

64
Q

What are causes of global sensory loss?

A

Carcinomatous sensory neuropathy

Diabetes

Most of the metabolic/endocrine neuropathies

Most of the toxic neuropathies

Hereditary sensory neuropathies

65
Q

What are causes of loss of large fibre modalities?

A

Idiopathic sensory loss

ganglionpathies

Neuropathy with Sjogren syndrome

cisplatin neuropathy (for cancer)

66
Q

What are causes of loss of small fibre modalities?

A

Hereditary sensory neuropathies

Lepromatous neuropathy

Diabetic small fibre neuropathy

Amyloidosis

Fabry disease

Tangier disease

Painful small fibre neuropathy

67
Q

What are loss of small fibre modalities associated with (symptom-wise)?

A

Loss of pain and excess pain

68
Q

What are causes of neuropathies presenting with predominantly autonomic dysfunction?

A

Diabetes

Amyloidosis

Pandysautonomia

Hereditary dysautonomia (Riley-Day syndrome)

Rare alcoholic neuropathies

69
Q

How do predominantly autonomic dysfunction neuropathies present?

A

Postural hypotension - fainting

70
Q

What are the treatments for neuropathy causes?

A

Treating the cause:
Inflammatory neuropathies- intravenous immunoglobulins, steroids, plasmapheresis

Vasculitic neuropathy - steroids, immunosupressants

B12 for B12 deficiency

71
Q

What are some treatments for the symptoms of neuropathies?

A

Painful neuropathies - membrane stabilisers (amitriptyline, gabapentin, pregabalin

motor problems -Physiotherapy

Orthotics

72
Q

Why are B12 deficiencies so bad?

A

They can affect the spinal cord and brain as well

73
Q

What causes B12 deficiency?

A

Being a vegetarian or pernicious anaemia

74
Q

How does vasculitis cause neuropathy?

A

It leads to nerve ischaemia

75
Q

TRUE or FALSE?

We don’t diagnose the cause of most severe neuropathies

A

FALSE

but it is true that we don’t identify the cause of most common neuropathies

Neuro (23 decks)

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