Peripheral Neuropathies

Question 1

Define peripheral neuropathy

Answer 1

damage/disease involving nerves of the PNS which may affect sensation, movement, gland, organ function

Question 2

What are large myelinated axons responsible for

Answer 2

motor and sensory info
- light touch, movement, vibration, proprioception

Question 3

What are small myelinated axons responsible for

Answer 3

autonomic fibers and sensory axons
- light touch, pain, temp

Question 4

What are small unmyelinated axons responsible for

Answer 4

autonomic
- sensory and enhancement of pain and temp

Question 5

Describe the inputs of the cervical, brachial, lumbar, sacral, and coccygeal plexuses

Answer 5

Question 6

What are some of the most common causes of peripheral neuropathy

Answer 6

• DM
• Alcoholism
• carpal tunnel syndrome
• post herpetic neuralgia
• spinal radiculopathy

Question 7

What is the most common pattern of peripheral neuropathy

Answer 7

generalized sensorimotor polyneuropathy with axonal degeneration - diabetes

Question 8

What are the 3 types of peripheral neuropathies

Answer 8

• mononeuropathies: 1 nerve)
• polyneuropathies: multiple symmetric nerves
• mononeuritis multiplex: multiple non-symmetric nerves

Question 9

What are the 4 causes of peripheral neuropathies

Answer 9

• traumatic
• systemic
• infectious/autoimmune
• hereditary

Question 10

Describe some systemic causes of PN

Answer 10

• vitamin deficiencies
• medications
• toxins/poisons
• systemic diseases
• cancer

Question 11

What are some of the major autoimmune causes of PN

Answer 11

• DM
• RA
• Guillan Barre
• Sjogren’s
• Celiac
• SLE
• necrotizing vasculitis

Question 12

What is one of the major hereditary causes of PN

Answer 12

Charcot Marie Tooth Disease
- flaw in gene responsible for making neurons/myelin sheath
- extreme weakness, wasting of muscles in lower legs
- pes cavus foot deformity

Question 13

Describe the pathophys of Wallerian Degeneration

Answer 13

• axon degenerates distal to focal
• often caused by carpal tunnel or direct trauma
• can regenerate

Question 14

Describe segmental demyelination

Answer 14

segments of myelin coating break down but axon is spared (Charcot Marie, GBS, SLE, RA, Sjogren’s)

Question 15

Describe Axonal Degeneration

Answer 15

• most common neuronal response to injury (DM, toxins, meds, nutritional deficiencies)

Question 16

Which type of demyelination or degeneration is associated with better recovery outcomes

Answer 16

segmental demyelination because only the myelin needs to be restored rather than the axon as well

Question 17

What is the typical symptomatic presentation of PN

Answer 17

• onset with numbness
• burning/tingling
• weakness

Question 18

Describe some of the physical exam findings for PN

Answer 18

• cranial nerve exam
• fundoscopic exam may show optic pallor
• strength testing may show mild weakness
• motor exam may show fasciculations or atrophy, changes in muscle tone
• reduced tendon reflex
• foot drop
• proximal weakness

Question 19

What labs should be explored in PN

Answer 19

• fasting serum glucose
• Hgb A1C
• BUN
• Cr
• CBC
• ESR
• UA
• B12, folate
• TSH
• serology (viral, autoimmune)

Question 20

What is often the most useful initial lab study for PN

Answer 20

electromyography: detects electrical potential generated by muscle

nerve conduction study: measures speed of transmission along a nerve from pt A to pt B

Question 21

What is the pathophys of EtOH neuropathy

Answer 21

• direct poisoning of nerve by alcohol and effects of poor nutrition associated with alcoholism
• generalized sensorimotor polyneuropathy with features of axonal degeneration

Question 22

Describe the pathophys of diabetic neuropathy

Answer 22

• distal to proximal sensorimotor symmetric polyneuropathy
• stocking and glove distribution: lower extremities then upper extremities
• sharp, burning, tingling, temp, numbness
• charcot arthropathy

Question 23

Describe charcot arthropathy

Answer 23

complication of diabetic neuropathy
- bones become weakened and fractured
- little pain as result of neuropathy
- ulceration and infection can result

Question 24

Describe the pathophys of entrapment neuropathy

Answer 24

• mild/intermittent pressure damaging myelin sheath
• will slow nerve conduction
• conditions can increase risk (pregnancy, hyperthyroidism, DM)
• can improve if pressure relieved

Question 25

Describe the pathophys of Bell's Palsy

Answer 25

- lesion/inflammation in Facial nerve (CN VII) - unilateral - syx at ear then evolving over a few hours/days - numbness, hyperacusis **- skin changes could indicate ramsey hunt syndrome**

Question 26

How is Bell's Palsy managed

Answer 26

usually spontaneous recovery within 12 weeks - oral prednisone for a week - acyclovir

Question 27

How would you differentiate Bell's palsy from a CVA

Answer 27

- stroke = drooping only in lower face, can still raise forehead - palsy = drooping of whole side of face including forehead

Question 28

General treatment of PN

Answer 28

- treat the cause if acquired - ASMs, SNRIs, TCAs, lidoderm patch, topical capsaicin, **gabapentin** - rehab with PT/OT/TENS - acupuncture, injections, nerve blocks

Question 29

What type of inheritance is involved in charcot marie tooth

Answer 29

autosomal dominant (common in diabetic neuropathy)