Neuro of the PNS

Question 1

Axonal Neuropathies are due to _______ and ______ insults

Answer 1

toxic, metabolic

Question 2

During Axonal Neuropathies, the axons often degenerate in a __________, resulting in a __________ pattern

Answer 2

length-dependent fashion, “dying-back”

Question 3

Which types of axons in Axonal Neuropathies are most susceptible?

Answer 3

Longest axons

Question 4

What is the Axonal Neuropathy Electrophysiologic hallmark ?

Answer 4

reduction in signal amplitude owing to the dropout of axons from affected peripheral nerves with relative preservation of conduction velocity.

Question 5

In Demyelinating Neuropathies, what are the primary targets of the damage?

Answer 5

Schwann cells with their myelin sheaths

Question 6

T/F are axons relatively preserved during Demyelinating Neuropathies?

Answer 6

True

Question 7

During Demyelinating Neuropathies, individual myelin sheaths degenerate in a __________ resulting in _______ damage of myelin segments

Answer 7

seemingly random pattern, discontinuous

Question 8

During Demyelinating Neuropathies, in response, ________ proliferate and initiate repair through the formation of new myelin sheaths, but now _____ and _______ than the original ones

Answer 8

Schwann cells
shorter
thinner

Question 9

What is the electrophysiologic Demyelinating Neuropathy hallmark?

Answer 9

is slowed nerve conduction velocity, reflective of the loss of myelin.

Question 10

What do Neuronopathies result from and what do they lead to?

Answer 10

destruction of neurons, leading to secondary degeneration of axonal processes.

Question 11

What are examples of neuronopathy insults ?

Answer 11

Infections like herpes zoster and toxins like platinum compounds

Question 12

In neuronopathies, because the damage is at the level of the neuronal cell body, the peripheral nerve dysfunction is equally likely to affect the ________ and ________ parts of the body

Answer 12

proximal, distal

Question 13

In peripheral axonopathies, it ONLY affects the __________ extremities

Answer 13

distal

Question 14

What are Mononeuropathies?

Answer 14

single nerve and result in deficits in a restricted distribution dictated by nerve anatomy ex: Trauma, entrapment, and infections

Question 15

Polyneuropathies affect ________ nerves and is usually __________

Answer 15

multiple nerves, usually symmetric

Question 16

What are Polyneuropathies?

Answer 16

axons are affected in a length-dependent fashion leading to deficits that start in the feet and ascend with disease progression. The hands start when deficits at knee, resulting in a characteristic “stocking and glove” distribution of sensory deficits.

Question 17

What are Mononeuritis multiplex?

Answer 17

individual nerves in a haphazard fashion. right wrist drop from involvement of the right radial nerve and a left foot drop from peroneal nerve damage. Vasculitis is a common cause.

Question 18

What are Polyradiculoneuropathies

Answer 18

nerve roots as well as peripheral nerves, leading to diffuse symmetric symptoms in proximal and distal parts of the body.

Question 19

Guillain-Barré Syndrome is an acute inflammatory__________

Answer 19

Demyelinating Polyneuropathy

Question 20

In Guillain-Barré Syndrome, where does the weakness begin?

Answer 20

in the distal limbs that rapidly advances to affect proximal muscle function (“ascending paralysis”)- respiratory compromise

Question 21

What are the histologic features of Guillain-Barré Syndrome

Answer 21

inflammation and demyelination of spinal nerve roots and peripheral nerves (radiculoneuropathy)

Question 22

What are 2/3 of causes of Guillain-Barré Syndrome preceeded?

Answer 22

by an acute, influenza-like illness convalescing by the time the neuropathy becomes symptomatic

Question 23

What are the inciting agents of Guillain-Barré Syndrome ?

Answer 23

Campylobacter jejuni,CMV, EBV, andMycoplasma pneumoniaeas well as prior vaccination

Question 24

What are Guillain-Barré Syndrome’s main clinical feature?

Answer 24

Ascending paralysis and areflexia

Question 25

Why are nerve conduction velocities slowed in Guillain-Barré Syndrome?

Answer 25

because of multifocal destruction of myelin segments in many axons within a nerve.

Question 26

What is the most common chronic acquired inflammatory peripheral neuropathy?

Answer 26

Chronic Inflammatory Demyelinating Poly(radiculo)neuropathy-CIDP

Question 27

Chronic Inflammatory Demyelinating Poly(radiculo)neuropathy-CIDP has _________ mixed with _________ polyneuropathy that persists for 2 months or more

Answer 27

symmetric, sensorimotor

Question 28

What are examples of systemic autoimmune disease associated neuropathy

Answer 28

rheumatoid arthritis, Sjögren syndrome, or systemic lupus erythematosus

Question 29

What are examples of infections neuropathies ?

Answer 29

1. Leprosy : Schwann cells invaded byMycobacterium leprae
2. Lyme Disease: uni/bilateral facial palsies
3. HIV infection: distal sensory neuropathy that is often painful.
4. Varicella-Zoster Virus: most common viral infection of PNS.

latent infection persists within neurons of sensory ganglia
virus is reactivated-> transported along the sensory nerves to the skin -> infects keratinocytes-> painful, vesicular skin eruption in a distribution that follows sensory dermatomes (shingles).

Question 30

What is the most common cause of peripheral neuropathy?

Answer 30

diabetes

Question 31

How does Distal symmetric diabetic polyneuropathy typically present?

Answer 31

with sensory symptoms like numbness, loss of pain sensation, difficulty with balance, and paresthesias or dysesthesias

Question 32

Which disease is the most common inherited peripheral neuropathy?

Answer 32

Charcot- Marie Tooth-

Question 33

What is the neuromuscular junction ?

Answer 33

the interface of motor nerve axons and skeletal muscle that serves to control muscle contraction

Question 34

What symptoms would you see in a patient with a disease in the neuromuscular junction

Answer 34

painless weakness, fatigue

Question 35

How does the nueromuscular junction stimulate muscle contraction?

Answer 35

Upon depolarization, presynaptic nerve terminals release acetylcholine (ACh) into the synaptic cleft–> postsynaptic sarcolemma contains localized clustering of ACh receptors > initiate signal leading to muscle contraction.

Question 36

Myasthenia Gravis (NMJ) is an autoimmune disease with autoantibodies directed against

Answer 36

postsynaptic Ach receptors

Question 37

Who does Myasthenia Gravisaffect more?

Answer 37

young females, older males

Question 38

How does Myasthenia Gravis typically present?

Answer 38

with fluctuating weakness that worsens with exertion and often over the course of the day.Diplopia and ptosis (extraocular muscles) are common

generalized weakness severity can require mechanical ventilation

Question 39

What are toxins that affect the NMJ?

Answer 39

1. Botulism
   condition caused by exposure to a neurotoxin (botulinum toxin, popularly known as Botox) produced by the anaerobic gram-positive organismClostridium botulinum
   Botox acts by blocking the release of ACh from presynaptic neurons
2. Curare is the common name for plant-derived muscle relaxants that block ACh receptors, resulting in flaccid paralysis. Poison on arrow tips by indigenous people in the Amazon rain forest

Question 40

Majority of benign and malignant neoplasms of peripheral nerve sheaths are composed of cells that show evidence of __________ differentiation.

Answer 40

Schwann cell

Question 41

What are the 3 common types of peripheral nerve sheath tumors?

Answer 41

1. schwannoma
2. neurofibroma
3. malignant peripheral nerve sheath tumor (MPNST).

Question 42

What are peripheral nerve sheath tumors associated with?

Answer 42

familial tumor syndromes, including neurofibromatosis type 1 (NF1), neurofibromatosis type 2 (NF2), and schwannomatosis.

Question 43

What are Shwannomas?

Answer 43

benign tumors that exhibit Schwann cell differentiation
local compression of the involved nerve or adjacent structures (e.g., brainstem or spinal cord)

Question 44

Shwannomas typically arise from ________

Answer 44

peripheral nerves I

Question 45

What are acoustic neuroma?

Answer 45

schwannomas occurring at the cerebellopontine angle, attached to the vestibular branch of 8th CN. Tinnitus and hearing loss.

Question 46

What are Neurofibromas?

Answer 46

benign nerve sheath tumors more heterogeneous than schwannomas admixed with perineurial-like cells, fibroblasts, mast cells, and CD34+ spindle cells