Peripheral Neuropathies Flashcards
exam 1
Subtypes of neuropathy (3)
- axonal
- demyelinating
- wallerian degeneration
motor cell body is located in the
spinal cord
sensory cell body is located in the
dorsal root ganglion
does the cell body maintains the axon by both manufacturing structural elements and Ntt
yea
includes all neural structures outside the pial membrane of the spinal cord and brainstem.
PNS
extend into the posterior columns and dorsal horns of the spinal cord.
Dorsal roots (sensory afferents)
Peripheral axons of the dorsal root ganglia are the
sensory nerve fibers.
fibers for touch and pressure and spindle afferents.
Larger, heavily myelinated
fibers for sharp and lancinating pain and temperature.
maller, thinly myelinated
fibers for dull, burning, poorly localized pain.
Small unmyelinated
Type I : ____________,CV 80-120m/sec
myelinated
Type II: _________ CV 30-75 m/sec
thinly myelinated
Type III and IV: ___________ CVs 0.5-30 m/sec
unmyelinated with
The efferent roots consist of emerging axons of the
anterior horn cells, lateral horn cells and motor nuclei of the brainstem.
Large myelinated fibers terminate on
muscle.
Small unmyelinated fibers terminate on
sympathetic and parasympathetic ganglia.
transport away from cell body
anterograde
transport towards cell body
retrograde
does axonal transport requires energy? is it dependent of electrical activity?
It does require energy but it is independent of electrical activity
what do drugs like vincristine and viblastine do to axonal transport?
disrupt neurotubule organization resulting in neuropathy
kinesin
anterograde
dynesin
retrograde
what determines the rate of recovery from nerve injury as it is needed to transport structural components?
slow transport
what type of transport carries signal of nerve injury which induces chromatolysis?
retrograde
how do some neurotropic viruses like polio, herpes and rabies enter the nerve body?
enter through peripheral nerve endings and ascend to the nerve body by retrograde transport
Dying forward
wallerian degeneration
dying back
axonal degeneration
degeneration from the point of axonal injury peripherally.
wallerian degeneration
: metabolic derangement results in the most distal parts of the axon to degenerate in a proximal direction.
axonal degeneration
what is the important thing about nerve conduction studies?
can help distinguish between lesions by measuring action potential evoked by sensory nerve or motor
Low amplitude CMAPS and absent SNAPs on NCSs
axonal neuropathy
how does axonal neuropathy usually progress? how is the distribution? what is lost?
- it is usually slow and chronic
- stocking glove distribution
- loss of reflexes distally and muscle wasting
how does axonal neuropathy occurs?
deficiency and genetic
- deficiency in thiamine, pyridoxine, vitamin E
Genetic: HSMN II
Guillan-Barre syndrome
what are some of the clues both in the clinical setting and nerve conduction?
it is a primarily motor syndrome that is rapidly progressive.
clinical setting: areflexia nad ataxia
NCS: conduction block
how do you treat Guillan-Barre syndrome?
immune modulating
what is the most susceptible element of the nerve
myelin
demyelinating polyneuropathy autoimmune
Guillain-Barre syndrome, CIDP, multiple forms associated with certain antibodies.
Demyelinating polyneuropathy Genetic
Charcot-Marie-Tooth Type I, metachromatic leukodystrophy.
individuals nerve are picked off one by one and is seen especially in polyarteritis nodosa
ischemic mononeuritis multiplex
how do you treat ischemic mononeuritis multiplex (vasculitis)
steroids and cyclophosphamide
Disruption of ____________ transport means that organelles cannot be transmitted to the distal axons and cannot renew membrane and neurotransmitters systems.
anterograde
_________ transport sends signal to the cell body to increase metabolic activity and produce growth factors for axonal regeneration.
Retrograde
axonotmesis
After injury axonal sprouting occurs and if the Schwann cell sheathes are not disrupted will regenerate to their original targets as in type 2 nerve injury
neurotmesis
If the Schwann cells are disrupted as in penetration injuries or in cases of intense connective tissue reaction the reinnervation cannot occur
Traumatic Nerve Injury: Seddon’s Classification class 1
Neurapraxia
Traumatic Nerve Injury: Seddon’s Classification class 2
Axonotmesis
Traumatic Nerve Injury: Seddon’s Classification class 3
Neurotmesis
More of a compression with focal demyelination, no denervation, relatively quick recovery
neurapraxia
axonal damage but intact nerve sheath for sprouting to occur through. Slower and sometimes incomplete recovery.
axonotmesis
scarred or disrupted nerve sheath, No recovery.
neurotmesis
