8/30 Neuropathy - Glendinning Flashcards
peripheral neuropathy
lesions affecting peripheral nervous system
- cranial nerves
- spinal nerves
- peripheral nerves
- nerve plexuses
symptoms of neuropathy vary depending on…
potential symptoms
- whether myelin or axons are affected
- which axons are affected
- where the axons are affected
symptoms can include:
- weakness, muscle atrophy
- loss of reflexes
- loss of sensation (numbness)
- abnormal sensation (tingling, burning) - paresthesia
- pain
- autonomic changes (sweating, HR, vascular)
neurotpathic pain
different from nociceptive pain (tissue might be damaged, but nerves/nervous system intact)
- arises from lesions in peripheral and central nervous system
- can include burning, shooting, stinging pain mixed with areas of numbness
- can include changes in pin threshold, quality of pain, and spontaneous pain
DEPRESSION is a common feature of chronic pain
ex. herpes zoster, trigeminal neuralgia
* antidepressants and anti-epileptics are primary drugs used to treat neuropathic pain
radiculopathy
vs
mononeuropathy
vs
plexopathy
vs
polyneuropathy
all FOCAL LESIONS
radiculopathy: sx follow a nerve root pattern (dermatome or myotome)
- often caused by compression of nerve roots from protruding discs
mononeuropathy: sx follow a peripheral nerve
- often caused by injuries
plexopathy: sx follow a nerve plexus
polyneuropathy: generalized process affects peripheral nerves → distal and symmetrical sensorimotor (poss autonomic) distribution
- “glove and stocking” pattern
- common causes: diabetes, alcohol, hypothyroidism, vitB12 def; also pts in intensive care
“Wallerian degeneration”
peripheral neuropathy results from damage/injury to cell bodies, axons, or myelin sheaths → leads to “Wallerian degeneration” aka “dying forward”
- distal axonal degeneration
- “chromatolysis” of cell body
* nucleolus expands and moves to cell wall, Nissel substance disintegrates - recruitment of macrophages
proximal stump can recover at rate of 1-2mm/day
“dying back” of axons
conditions that affect the health of the neuron (ex. metabolic diseases) → “dying back”
- can be accompanied by loss of myelin
longer axons most susceptible and are affected first → distal extremities are affected first
“segmental demyelination”
occurs when myelin sheaths are damaged by trauma or disease
- myelin may be affected secondarily to axonal death
sx of demyelination detected by Nerve Conduction tests, revealing:
- conduction block
- slowed conduction velocity
myelin and conduction can return in days to weeks
trauma affecting myelin : metaphorical “nerve concussion” - rapid effect, slow recovery
non-traumatic peripheral neuropathies
nutritional/metabolid
- diabetes mellitus
- vitamin def
- uremia
non-traumatic peripheral neuropathies
toxic drugs
other toxins
- drugs
- vinblastine, vincristine (affect microtubule formation)
- paclitaxel, cochicine, INH
- toxins
- alcohol, lead, aluminum, arsenic, mercury, acrylamide
non-traumatic peripheral neuropathies
vasculopathic
inflammatory
infection
- vasculitis, amyloidosis
- autoimmune: systemic lupus erythematosus, rheumatoid arthritis, sarcoidosis, Sjogren syndrome, Guillain Barre syndrome
- chronic infl demyelinating polyneuropathy
- herpes zoster
- leprosy
- HIV
- Lyme disease
non-traumatic peripheral neuropathies
inherited
- Charcot-Marie-Tooth neuropathy
diabetic neuropathy
- most common compliation of diabetes
- 30% of diabetic patients
- 75-80% have subclinical neuropathy
- 16% have chronic neuropathic pain
- greatest source of M&M
- 50-75% of all amputations
length-dependent diabetic polyneuropathy
- accounts for 80+% of patients with diabetic neuropathy
sx start in feet → more to more proximal legs and and distal upper limbs
- “glove and stocking” pattern of sensory loss
- paresthesias, dysesthesias, numbness/tingling/burning
- motor weakness of distal limbs
- can lead to trophic changes : calluses and plantar ulcers
pathophys of diabetic neuropathy
axonal degen, dying back, and demyelination occur
- includes effects related to ischemia, oxidative stress, infl processes
sensory neurons more affected than motor, but both may be affected
- sensory often involves just small unmyelinated and myelinated fibers : small fiber polyneuropathy
vitamin B12 deficiency
- most common metabolic neuropathy
- 3-16% prevalence in US; 21% in geriatric pop
- may affect peripheral nerves, optic nerves, spinal cord, brain
- most common feature: loss of vibration sense
- sx affect distal limbs, but begin more commonly in upper limb
