Neuropathy Flashcards by Catherine Parkhurst

What is peripheral neuropathy?

Lesions affecting the peripheral nervous system: spinal nerves, nerve plexuses, peripheral nerves, cranial nerves

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What do the symptoms of neuropathy depend on?

1 Axons are myelinated or not
2 Which axons
3 Where axons are affected

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What are potential symptoms of neuropathy?

1 Weakness and muscle atrophy
2 Loss of reflexes
3 Loss of sensation/numbness
4 Abnormal sensation (tingling, burning)
5 Pain
6 Autonomic changes

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How might a small fiber nerve present with neuropathy?

Pain, temp and autonomic loss

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How might a neuropathic lesion present with myelin damaged?

Large fiber vibration and position sense loss + motor loss

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How might a sensory ganglia lesion present?

Only sensory symptoms

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How does neuropathic pain differ from nociceptive pain?

Nociceptive: tissue may be damaged, nerves intact

Nerves are damaged!

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How does neuropathic pain arise?

Lesions in the PNS and CNS

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What are common features of neuropathic pain?

Burning, shooting, stinging pain
Areas of numbness
Changes in pain threshold, quality of pain, spontaneous pain

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What is a common feature of chronic pain?

Depression

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How do we often treat neuropathic pain?

Antidepressants and anti-epileptic drugs

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What is it called when symptoms follow a nerve root pattern?

Radiculopathy

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What is a mononeuropathy or plexopathy?

Lesions affect specific nerves or plexuses

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What is a mononeuropathy multiplex?

Stems from a specific disease like diabetes or vasculitis

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What is a polyneuropathy?

Generalized process affecting peripheral nerves

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What is a distal and symmetrical distribution neuropathy, and what causes it?

Glove and stocking pattern

Diabetes, alcohol, hypothyroidism, B12 deficiency (intensive care pts)

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What is the prevalence of polyneuropathy?

31% with >=1 bilateral sensory deficit

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What are the 3 things to injure to cause peripheral neuropathy?

Damage to: cell bodies, axons or myelin sheaths

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What does axonal damage produce?

Wallerian degeneration = dying forward

distal axonal degeneration
chromatolysis of cell body: nucleolus expands and moves to cell wall, Nissl substance disintegrates)
recruitment of macrophages

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How quickly can a proximal nerve stump recover?

1-2mm per day

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What causes a “dying back” of axons?

Conditions that affect the health of the neuron (e.g. metabolic dz)
Loss of myelin often accompanies!

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Which axons are affected first in “dying back”?

Longer axons: distal extremities are affected first!

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What causes “segmental demyelination”?

Myelin sheaths are damaged by trauma or disease

- Affected secondarily due to axonal death

how are symptoms of demyelination detected?

Nerve conduction tests: conduction block or slowed CV

How quickly can myelin and conduction return?

Days to weeks

When do we see atrophy with neuropathy?

Only when the axon is interrupted: | Wallerian degeneration or axonal degeneration

What are examples of non-traumatic peripheral neuropathies?

Nutritional/metabolic: DM, B12 deficiency Toxic drugs: chemotherapies Other toxins: alcohol, lead, arsenic, mercury Vasculopathic: vasculitis, amyloidosis Inflammatory: Guillain Barre Infection Inherited: Charcot-Marie-Tooth neuropathy

What is the greatest source of morbidity and mortality in diabetes patients?

Diabetic neuropathy

What is the most common complication of diabetics?

Diabetic neuropathy: 30% of them have it, 75-80% have subclinical neuropathy

What is length-dependent diabetic polyneuropathy?

Begin at feet, move to more proximal legs and distal upper limbs = "glove and stocking" sensory loss

What are the symptoms of length-dependent diabetic polyneuropathy?

paresthesias, dysesthesias, numbness, tingling, burning | motor weakness

What conditions lead to the glove and stocking diabetic polyneuropathy?

Most nutritional, metabolic and toxic diseases

What are long term sequelae of length-dependent diabetic polyneuropathy?

trophic changes like calluses and plantar ulcers

What is the pathophysiology of diabetic neuropathy?

Axonal degeneration, dying back, demyelination Ischemia, oxidative stress and inflammation Sensory neurons > motor

What is sensory-only diabetic neuropathy called and what is involved?

small fiber polyneuropathy: only small unmyelinated and myelinated fibers

How do peripheral nerve fascicles appear in diabetic neuropathy?

- Decreased number of myelinated and unmyelinated axons | - Thickening in the walls of blood vessels

What's the most prevalent metabolic neuropathy?

B12 deficiency

What does B12 deficiency affect?

peripheral nerves, optic nerves, spinal cord and brain

Where do the symptoms of B12 deficiency neuropathy present?

Distal limbs, more often in upper limb Loss of vibration sense May affect lateral + dorsal columns of SC

What is subacute combined degeneration? How does it present?

In B12 deficiency, neuropathy affecting lateral/dorsal columns of SC --> ataxia and spasticity can occur together w/ peripheral neuropathy symptoms

What causes B12 deficiency?

Lack of animal protein

Who often has B12 deficiency?

vegetarians or gluten sensitive individuals

What else can B12 deficiency cause?

pernicious anemia | myelin production is abnormal

What is the most common cause of acute paralysis seen in clinical practice?

Guillain Barre or acute inflammatory demyelinating polyneuropathy

What is the most rapidly progressing and potentially fatal form or neuropathy?

Guillain Barre

What are the major features of Guillain Barre?

Motor primarily Ascending symmetric paralysis that may affect breathing Paresthesias in toes and fingers, aching thighs/back Decrease nerve conduction velocity --> increase protein in CSF with normal cell count

What is used to make a diagnosis of Guillain Barre?

Decreased nerve conduction velocity | Increased protein in CSF with normal cell count

What is the cause of Guillain Barre?

1-3 weeks after infection or vaccination, causing an autoimmune or inflammatory attack on peripheral myelin

How are myelin sheaths attacked?

Lymphocytes attach to vessel, migrate through and enlarge Lymphocytes attack myelin and/or axons Presence of polymorphonuclear leukocytes Nerve cell body may die in severe cases

What is Charcot-Marie-Tooth Disease?

Hereditary motor and sensory neuropathy

What are the two types of Charcot-Marie-Tooth Disease?

CMT1: myelin affected CMT2: axons affected

How does CMT1 present?

Primarily distal muscle affected, particularly the peroneal nerve Small fiber types carrying pain/temp NOT affected

How do we identify CMT?

Slowly progressive nature | Reduced conduction velocity in all nerves

What is the pathology of CMT1?

Fewer numbers of myelinated axons in peripheral nerves

How do we diagnose neuropathy?

``` Neuro exam Small vs. large fibers Pattern of symptoms Neuropathic pain? History Temporal evolution Nerve conduction velocity test ```

What are two other big conditions that can produce neuropathy?

Renal failure | hypothyroidism