PNS

Question 1

Myelination of peripheral nerve axons and repair

Answer 1

Schwann Cell

Question 2

A high concentration of sodium channels and permits ‘saltatory conduction’.

Answer 2

Node of Ranvier

Question 3

Conduct rapidly
◦ Motor
◦ Touch, vibration, and
proprioception

Answer 3

Heavily myelinated fibers –

Question 4

Conduct slowly
◦ Pain and temperature ◦ Autonomic response

Answer 4

Less myelinated or unmyelinated fibers

Question 5

Peripheral neuropathies can impair sensory, motor, or autonomic function, either singly or in combination. Can be further classified into those that primarily affect the:

Answer 5

◦ Cell body (e.g., neuronopathy or ganglionopathy)
◦ Myelin (myelinopathy) ◦ Axon (axonopathy).

Question 6

Mildest grade of nerve injury, Axonal
continuity is maintained
Cause: Compression, ischemia due to vascular compromise and metabolic derangement or demyelinating diseases
◦ Reversible and full recovery can occur

Answer 6

Neuropraxia

Question 7

The axon is damaged but preserving surrounding connective tissue
◦ Wallerian degeneration (Axon and myelin degenerate distal to site of injury)
◦ Recovery can occur due to preservation of Schwann cells and their basal lamina
◦ Proximal stump either stays in place or retracts slightly
◦ Central chromatolysis (swelling of the neuronal body, disruption of Nissl granules in the center and displacement of the nucleus to the periphery)

Answer 7

Axonotmesis

Question 8

Complete nerve transection
◦ Chances of recovery very poor
Traumatic neuroma (Pseudotumor)
◦ Benign painful nodular thickening
◦ A failure of the outgrowing axons to find their distal target can produce traumatic
neuroma.

Answer 8

Neurotmesis

Question 9

Common cause of mononeuropathy

Answer 9

-Brachial plexopathy from neoplasms of the apex of the lung
-Obturator palsy from pelvic malignant neoplasms
-Cranial nerve palsies from intracranial tumors