20: Peripheral Neurology - Bennett Flashcards
three forms of neuropathies
segmental demyelination
axonal degeneration
wallerian degeneration
seletive loss of individual myelin internodes with preservation of axon
segmental demyelinationn
remaining schwann cells can proliferate and remyelinate, but reconstituted sheaths are thinner with shorter internodal length
proximally the axon will degenerate back to node of ranvier with possible chromatolysis of cell body
distally the axon and its myelin sheath disintergrate and are digested by the schwann cell
wallerian degeneration
occurs after transection of axon
dysfunction of neuron renders it unable to maintain its axon
axonal dgeneration
begins at peripheral terminal of the axon and proceeds toward cell body with chromatolysis of cell body
if dysfunction can be halted, regeneration and recovery of n. function can occur
persistent impairment of motor function over wks, or months signifies segmental demyelination, axonal interruption, or destruction of motor neurons
motor paralysis
feature of most polyneuropathies is the distribution (muscles of feet and legs affected first and most severely)
state in which the affected muscles ripple and quiver and occasionally cramp
neuromyotonia
use of muscles increases this activity and there is a reduction in efficiency. which the pt experiences as stiffness and heaviness
where does sensory loss tend to affect?
distal segments of limbs, preferably in the legs
pattern 1: loss of touch, vibratory, 2pt discrimination, joint position sense LARGE fibers
pattern 2: loss of paina nd temp with lesser impairment of pressure, vibratory and position sense SMALL fibers
tingling, or burning pain induced by tactile stimuli
dysesthesia
ex: touch foot lightly and the pt says it is painful
stimuli will also radiate and persist after the stimulus is withdrawn
propioceptive deafferentation with retention of a reasonable degree of motor function
basis of ataxia of gait and limb movement
two most frequent manifestations of autonomic disorders
anhydrosis
orthostatic hypertension
occur in small fiber polyneuropahties
other manifestations: un-reactive pupils, lack of tears and saliva, impotence, weak bladder and bowel sphincters
a neuropathic syndrome is determined by:
mode of evolution
clinical presentation
describe acute axonal polyreuropathy
- evolves over several days
- porphyric neuropaty and massive intoxication
- renal and liver failure
- 14-21 d polyneuropahty, progresses for 2-3 wks then a plateau is reached
- recovery requires months
- associated with alcoholism
- pure sensory, no m. involvement
describe subacute axonal polyneuropathy
- evolves in wks
- usually toxic or metabolic
- tend to be chronic in evolution
- management involves removing the offending agent or treating the systemic disorder
- sensory v. motor deficit dependent upon toxic agent
- seen in Parkinson’s pt supplemented with cobalamin / B6
describe chronic axonal polyneuropathy
- progression from 6 mo to 60 yr
- absence of positive symptoms mostly a motor deficit, and absence of systemic disorder
- genetically determined neuropathy
- relapsing-remitting motor and sensory deficit
- charact - similar to CIDP
- autosomal dominant
acute demyelinating polyneuropathy =
synonymous with guillain-barre syndrome
- virus usually precedes the neuropathy, in the majority of cases
- charact
- acute rise of total prtn in CSF in 1st wk
charact =
areflexic motor parlayss iwth mild sensory disturbance, prognosis is good
describe subacute demyelinating polyneuropathy
- acquired neuropathies
- tend to be relapsing and remitting neuropathy
- diptheria toxin
- clinical features similar to GBS but differs in tempo, course and absence of discernable eventa
describe chronic demyelinating polyneuropathy
- wide variety of disorders
- present as mixed axonal-demyelinating finding
- motor and snesory manifestation
- difficult to determine the primary event (axonal degenration ro demyelination)
charcot marie toot =
characterized by demyelinating and remylination motor and sensory defiicts
stork leg appearance
thenar and hypothenar wasting
pes cavus, hammertoes
roussy-levy =
variant of freidrixh’s ataxia and CMT
static tremor with mild distal weakness and sensory loss
pes cavus, claw foot
describe GBS
- acute ascending motor paralysis
- triggered by virus
- weakness is most common symptom, but leg pain, tingling and numbness are initial complaints
- reflexes absent
- respiratory failure willensue
- isntability of heart rate and blood pressure
- CSF prtn is increased without pleocytosis
tx GBS
plasmapharesis
immunoglobulin
tx neuropathies with inflammation
glucocorticoid
immunosuppressants
plasmapharesis
neuropathies with disproteinemia are consistent with…
axonal degeneration
‘
assoc b/q polyneuropahty and multiple myeloma and macrogobulinemia
sensorimotor
does not reverse with suppression of myeloma
describe alcohol neuropathy
- senosorimotor caused by axonal degeneration (pain and paresthesia)
optiic atrophy and myopathy can also be seen
drug induced neuropathy
subacute course
reversible
_____ of diabetics show evidence of peripheral neuropathy
2/3
occurs after long standing hyperglycemia
most commonly recognized form of diabetic neuropathy
distal symmetric,
primarily sensory polyneuropathy
“stoking-glove”
loss of lg sensory and motor fibers –>
diminished light touch and proprioception, the latter resuting in ataxic gait and unsteadiness, as well as loss of muscle function of the feet, and then the ahnds
loss of small fibers –>
diminished pain and temperature perception
spontaneous uncomfortable sensations
neuropathic paresthesias
if occur with contact = dysesthesia
atrophic skin
loss of nails
sweating abnormalities
autonomic neuropathy
structural changes from advanced neuropathy are from
ligamentous laxity and m. weakness
- prominence of metatarsal heads
- crowding of toes
- subluxation of tarsal and metatarsal heads
tx mild pain at night only
amitriptyline
nortriptyline
imipramine
TCAs
acnti-convulsants
gabapentin (neurontin)
lyrica (pregabalin)
good for superficial pain
capsaicin
depletes substance P from the terminals and central connections of cfibers
local anesthetic
mexiletine
muscle relaxants
baclofen and metaxalone
analgesic treatment when associated with muscle cramping
agents that increase circulation to nerve by altering viscosity and blood flow
trental (pentoxyifylline)
alters viscosity and blood flow
pletal (cilostazol)
alters viscosity by inhibiting platelet aggregation
serotonin-norepinephrine re-uptake inhibitor
cymbalta (duloxetine)
how does acupuncture help?
stimulation of these centers, release neurotransmitters
endorphins which promote analgesia circulate in blood and CSF
enkephalins which block the incoming pain signal
describe subacute demyelinating polyneuropathy
- acquired neuropathy
- tend to be relapsing and remitting
- similar to GBS but differs in tempo, coures, and absence of discernable events
- may be induced by diptheria toxin
