Peripheral Nerve Pathology - Alston Flashcards
What are the characteristics of autonomic nerve fibers as well as pain and temperature sensation? What are their conduction speeds?
Thin, unmyelinated fibers, slow
What are the fiber characteristics of light touch and motor nerves? What is the conduction speed?
Large diameter, myelinated fibers, fast
Wallerian degeneration is the term to describe what type of neuropathic pattern?
Axonal neuropathy
What are the stages of neuronal regeneration after an axon is transected? (Characteristics of Wallerian degeneration)
- Day 1: Sheath disintigrates into spherical structures called myelin ovoids and macrophages are recruited to clean up.
- Outgrowth of new branches (Schwann cells guide the growth.)
- Pruning of sprouting axons
Traumatic neuromas (psuedotumor) can result when what part of the healing process fails as a result of Wallerian degeneration?
Failure of the outgrowing axons to find their target - whorled proliferation of axons and Schwann cells results in painful nodule
Reduction of signal strength would be a characteristic of what neuropathic change?
Axonal neuropathy (axonal loss)
Are axons sparing in demyelinating diseases?
Yes, typically myelin is the primary target.
How might Schwann cells and their myelin sheaths appear in a demyelinating disease?
Thinner and shorter
Slower nerve conduction would be a characteristic of what neuropathic change?
Demyelination
What part of the neuron is most commonly affected in neuronopathies? (Examples?)
Damage is at the level of the neuron cell body (viruses -herpes and certain toxins- platinum)
Mononeuropathies affect one or more nerves? What is the cause?
Single nerves are affected - often due to trauma, entrapment, infection
Polyneuropathies affect one or more nerves? Progression? Symmetric/asymmetric?
Usually multiple nerves symmetrically. Often start in feet and ascend w/ progression (stocking glove - hands start to be affected when deficit reaches knees)
Mononeuritis multiplex affects one or many nerves? Pattern? Often due to?
Damage is to several nerves, but in haphazard pattern - often due to vasculitis
Polyradiculoneuropathies are unique in that damage presents where? Symmetric/Asymmetric? Location?
Affect nerve roots as well as peripheral nerves - Symmetric in proximal and distal body
Pt has weakness in distal limbs that has advanced over the past few days since he, “got vaccinated.” Decreased sensation and +1 Reflexes in the lower extremities w/ slow nerve conduction velocity in the lower legs. CSF proteins are high. Papilledema present. What is the likely diagnosis? What kind of neuropathic process is occurring? Where? How is this process mediated? Outcome?
Guillain-Barré - Inflammatory (Peripheral) neuropathy resulting in prominant demyelination near the nerve root, but can be widespread peripherally. T- cell (immune) mediated. Can result in respiratory depression - most recover.