Peripheral Nerve - ENC Flashcards
Definition of neurapraxia
- Axonal continuity maintained with intact connective tissue elements.
- Myelin may be disrupted.
- Associated with local conduction block.
Definition of axonotmesis
- Axonal and myelin disruption.
2. Wallerian degeneration followed by regeneration within distal segment along intact endoneurial conduits.
Definition of neurotmesis
- Complete nerve transection.
At what rate do axons regenerate?
- 1-2mm/day or approximately 1 inch/month.
What are the 5 terminal nerves of the brachial plexus?
- Musculocutaneous.
- Axillary.
- Radial.
- Median.
- Ulnar.
What two nerves branch directly from cervical roots of the brachial plexus?
- Dorsal scapular nerve (C4-5) to rhomboids and levator scapulae.
- Long thoracic nerve (C5-7) to serratus anterior.
What roots form the superior trunk of the brachial plexus?
- C5 and C6.
What terminal nerves branch directly from the superior trunk of the brachial plexus?
- Suprascapular nerve and nerve to subclavius.
What root forms the middle trunk of the brachial plexus?
- C7 root.
What roots form the inferior trunk of the brachial plexus?
- C8 and T1
What forms the lateral cord and what are its branches?
- Anterior divisions of the superior and middle trunks form the lateral cord.
Branches:
- Lateral pectoral n. (C5-7).
- Musculocutaneous n. (C5-7).
- Lateral contribution to the median n.
What forms the medial cord and what are its branches?
- Anterior division of the inferior trunk forms the medial cord.
Branches:
- Medial pectoral n. (C8-T1).
- Medial brachial and antebrachial cutaneous n.
- Ulnar nerve (C7-T1).
- Medial contribution to the median n.
What forms the posterior cord and what are its branches?
- All three posterior divisions form the posterior cord.
Branches:
- Upper and lower subscapular n. (C5-6).
- Thoracodorsal n. (C6-8).
- Axillary n. (C5-6).
- Radial n. (C5-T1).
What is the “benediction sign”?
- Absent flexion of radial three digits due to the loss of thenar muscles, FPL, and lateral half of lumbricals.
What is anterior interosseus syndrome?
- Pure motor syndrome involving weakness of FPL, FDP 1 and 2, and pronator quadratus.
What is the classic finding of anterior interosseus syndrome?
- Patient cannot make an “O” due to inability to flex thumb at IP join and index and DIP joint.
What is posterior interosseus syndrome?
- Pure motor syndrome involving finger extensor paralysis (finger drop), with weakness of wrist extension only in ulnar direction.
What spinal nerve roots form the lumbar plexus?
- Usually T12-L4.
What spinal nerve roots form the sacral plexus?
- Usually L5-S4.
What are the major nerves given off by the lumbar plexus?
- Iliohypogastric and ilioinguinal (L1).
- Genitofemoral (L1-2).
- Femoral (L2-4).
- Lateral femoral cutaneous (L2-3).
- Obturator (L2-4).
Which muscles are innervated by the femoral nerve?
- Iliacus.
- Psoas.
- Quadriceps femoris.
- Sartorius.
What are the major nerves given off by the sacral plexus?
- Sciatic (L4-S3).
2. Pudendal (S2-4).
What is supracondylar process syndrome?
- Entrapment of the median nerve at the distal humerus under the ligament of Struthers.
- Pronator teres weakness distinguishes this from more distal entrapments.
What is the difference between the ligament of Struthers and the arcade of Struthers?
- The ligament of Struthers extends from the supracondylar process of the distal humerus to the medial epicondyle and forms a potential site of compression of the median nerve and brachial artery.
- The arcade of Struthers is a fascial arcade of the intermuscular septum that the ulnar n. traverses on its course from the anterior to the posterior compartment of the arm.
What is the arcade of Frohse?
- Fibrous proximal border of the supinator muscle that acts as a tight band under which the posterior interosseus n. passes to enter the supinator muscle between its superficial and deep heads.
- Most common site of compression in posterior interosseus n. syndrome.
