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
subacute combined degeneration
primary or secondary effect of B12 definiciency in which lateral and dorsal columns of spinal cord affected
- can lead to sx of ataxia and spasticity occuring together with sx of peripheral neuropathy
causes of B12 deficiency
B12 ingested through animal protein → deficiency often seen in vegans/vegetarians or people with gluten sensitivity/malabsorption
may also see pernicious anemia also bc B12 needed to produce red blood
pathophys of B12 deficiency neuropathy
without B12, myelin production is abnormal → decreased nerve conduction velocity
need to differentiate from MS, but once you do, treat with B12 therapy
Guillan Barré
aka
acute inflammatory demyelinating polyneuropathy (AIDP)
most common cause of acute paralysis seen in clinical practice
- incidence 1/100k
- all countries, all ages, all seasons
most rapidly progressing and potentially fatal form of neuropathy
major features of Guillain Barré
primarily motor symptoms
- ascending symmetric paralysis → acute cases? can affect breathing and require resp support
may begin with parasthesias in toes/fingers, aching in thighs/back
2 sx used to make diagnosis
- decreased nerve conduction velocity (with conduction blocks)
- increased protein in CSF with normal cell count (albuminocytologic dissociation)
cause of GBS
60% of time, GB begins 1-3 weeks after infection or vaccination
ex. Campylobacter jejuni or Herpesvirus infection (NOT a definitive link!)
infection causes an autoimmune/infl attack on peripheral myelin
GBS inflammatory process
widespread infl process affecting myelin sheaths
- lymphocytes attach to vessel wall → migrate through wall and enlarge
- lymphocytes attack myelin (segmental demyelination); axons may also be affected
- severe cases → nerve cell body may die
see presence of polymorphonuclear leukocytes
dx of GB
usually follows inf or vaccination
2 more important diagnostic tests are:
- CSF analysis → increased protein
- nerve conduction test → decreased cond velocity
Charcot-Marie-Tooth Disease
“hereditary motor and sensory neuropathy”
- group of several hereditary diseases that directly affect either myelin (CMT1) or axons (CMT2)
