Peripheral Neuropathies Flashcards
Define peripheral neuropathy
damage/disease involving nerves of the PNS which may affect sensation, movement, gland, organ function
What are large myelinated axons responsible for
motor and sensory info
- light touch, movement, vibration, proprioception
What are small myelinated axons responsible for
autonomic fibers and sensory axons
- light touch, pain, temp
What are small unmyelinated axons responsible for
autonomic
- sensory and enhancement of pain and temp
Describe the inputs of the cervical, brachial, lumbar, sacral, and coccygeal plexuses
What are some of the most common causes of peripheral neuropathy
- DM
- Alcoholism
- carpal tunnel syndrome
- post herpetic neuralgia
- spinal radiculopathy
What is the most common pattern of peripheral neuropathy
generalized sensorimotor polyneuropathy with axonal degeneration - diabetes
What are the 3 types of peripheral neuropathies
- mononeuropathies: 1 nerve)
- polyneuropathies: multiple symmetric nerves
- mononeuritis multiplex: multiple non-symmetric nerves
What are the 4 causes of peripheral neuropathies
- traumatic
- systemic
- infectious/autoimmune
- hereditary
Describe some systemic causes of PN
- vitamin deficiencies
- medications
- toxins/poisons
- systemic diseases
- cancer
What are some of the major autoimmune causes of PN
- DM
- RA
- Guillan Barre
- Sjogren’s
- Celiac
- SLE
- necrotizing vasculitis
What is one of the major hereditary causes of PN
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
Describe the pathophys of Wallerian Degeneration
- axon degenerates distal to focal
- often caused by carpal tunnel or direct trauma
- can regenerate
Describe segmental demyelination
segments of myelin coating break down but axon is spared (Charcot Marie, GBS, SLE, RA, Sjogren’s)
Describe Axonal Degeneration
- most common neuronal response to injury (DM, toxins, meds, nutritional deficiencies)
Which type of demyelination or degeneration is associated with better recovery outcomes
segmental demyelination because only the myelin needs to be restored rather than the axon as well
What is the typical symptomatic presentation of PN
- onset with numbness
- burning/tingling
- weakness
Describe some of the physical exam findings for PN
- 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
What labs should be explored in PN
- fasting serum glucose
- Hgb A1C
- BUN
- Cr
- CBC
- ESR
- UA
- B12, folate
- TSH
- serology (viral, autoimmune)
What is often the most useful initial lab study for PN
electromyography: detects electrical potential generated by muscle
nerve conduction study: measures speed of transmission along a nerve from pt A to pt B
What is the pathophys of EtOH neuropathy
- direct poisoning of nerve by alcohol and effects of poor nutrition associated with alcoholism
- generalized sensorimotor polyneuropathy with features of axonal degeneration
Describe the pathophys of diabetic neuropathy
- distal to proximal sensorimotor symmetric polyneuropathy
- stocking and glove distribution: lower extremities then upper extremities
- sharp, burning, tingling, temp, numbness
- charcot arthropathy
Describe charcot arthropathy
complication of diabetic neuropathy
- bones become weakened and fractured
- little pain as result of neuropathy
- ulceration and infection can result
Describe the pathophys of entrapment neuropathy
- mild/intermittent pressure damaging myelin sheath
- will slow nerve conduction
- conditions can increase risk (pregnancy, hyperthyroidism, DM)
- can improve if pressure relieved
Describe the pathophys of Bell’s Palsy
- 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
How is Bell’s Palsy managed
usually spontaneous recovery within 12 weeks
- oral prednisone for a week
- acyclovir
How would you differentiate Bell’s palsy from a CVA
- stroke = drooping only in lower face, can still raise forehead
- palsy = drooping of whole side of face including forehead
General treatment of PN
- treat the cause if acquired
- ASMs, SNRIs, TCAs, lidoderm patch, topical capsaicin, gabapentin
- rehab with PT/OT/TENS
- acupuncture, injections, nerve blocks
What type of inheritance is involved in charcot marie tooth
autosomal dominant (common in diabetic neuropathy)
