Spinal nerve roots, plexus

Question 1

Positioning of fibers in the cauda equina?

Answer 1

head is medial, sides add on as going down to legs most lateral

Question 2

Disc herniations cause involvement of what nerve root? Which direction do they usually herniate?

Answer 2

The lower one, usually herniate laterally

Question 3

Where do most nerve roots exit compared to the vertebrae?

What is the exception?

Answer 3

Thoracic, lumbar, sacral roots exit below the numbered vertebrae.
Cervical nerve roots exit above, except C8, which exits between C7-T1

Question 4

Spot common for spread of mets / infx in the spinal cord?

Answer 4

Batson’s plexus: mesh of epidural veins

Question 5

ligament causing hypertrophy and compression in spinal cord

Answer 5

Ligamentum flavum

Question 6

Two nerve systems (3 nerves) responsible for sensation of face/head (dermatomes)

Answer 6

Trigeminal and C2 (greater and lesser occipital nerves)

Question 7

Dermatome shoulder

Answer 7

C5

Question 8

Dermatome lateral arm and first two digits

Answer 8

C6

Question 9

Dermatome middle digit

Answer 9

C7

Question 10

Dermatome fourth/fifth digits

Answer 10

C8

Question 11

Dermatome anteromedial shin?

Answer 11

L4

Question 12

Dermatome anterolateral shin and dorsum of foot / big toe?

Answer 12

L5

Question 13

Dermatome small toe, lateral foot, sole, calf

Answer 13

S1

Question 14

Most common cervical disc herniation problem and its symptoms?

Answer 14

C7 roots from C6-7 herniation, causes weakness of tricep, loss of tricep reflex, loss of sensation in third finger.

Question 15

Symptoms of C4-5 disc problem?

Answer 15

C5 nerve root damage causing weakness of delt, infraspinatus, bicep, decr bicep/pectoralis reflex, and loss of sensation of shoulder, upper lateral arm

Question 16

Symptoms of C6 nerve root problem?

Answer 16

Weakness of bicep, wrist extension, loss of bicep/BR dtr, loss of sensation of lateral forearm and sensation of 1st/2nd fingers

Question 17

Sx of C8 radiculopathy?

Answer 17

Weakness of intrinsic hand muscles, loss of sensation of 4/5th digits and medial forearm

Question 18

Sx of T1 radiculopathy

Answer 18

just medial arm numbness without motor. Can also cause horner’s.

Question 19

Sx of L4 radiculopathy?

Answer 19

Weak iliopsoas and quad, loss of knee dtr, loss of sens of knee, medial lower leg

Question 20

How to distinguish femoral neuropathy from L4 radiculopathy?

Answer 20

Weak thigh adduction in radiculopathy

Question 21

Sx of weak foot dorsiflexion, big toe extension, foot inversion/eversion, and loss of sensation of foot dorsum, big toe

Answer 21

L5 radiculopathy (L4-L5 herniation)

Question 22

Peroneal neuropathy vs L5 radiculopathy

Answer 22

weak foot inversion with radiculopathy

Question 23

What is neurapraxia?

Answer 23

Temporary impairment after mild mechanical disruption, lasting hours-wks

Question 24

Rate of axonal regeneration if structural elements are intact after Wallerian degeneration of distal nerves

Answer 24

1mm/day

Question 25

Abs in Myasthenia? (two)

Answer 25

Anti-AchR-Ab: against POST-synaptic nicotinic ACh receptors (85% in generalized, 50% in ocular) Anti-MuSK Ab: muscle specific tyrosine kinase Abs if neg AChR Ab

Question 26

In MG, what do you see with RNS at 3/sec?

Answer 26

Decrement in CMAP amplitude >10%

Question 27

Percent of MG with thymoma?

Answer 27

12%

Question 28

Acronym for Brachial Plexus?

Answer 28

RTDCB: Roots, trunks, divisions, cords, branches: RT Drinks Cold Beer

Question 29

Thumb movements act out: in plane abduction? in plane adduction? Opposition?

Answer 29

Radial, ulnar, median: | R spread, U unite, M oppose (meet)

Question 30

Supply for thumb abduction perpendicular to plane of palm? Why important?

Answer 30

Median nerve branch abductor pollicus brevis after passage through carpal tunnel, so should be WEAK in CT!

Question 31

Name the nerve branches of the posterior cord

Answer 31

STAR: Subscapularis, Thoracodorsal, Axillary, Radial

Question 32

Muscles innervated by the musculocutaneous nerve?

Answer 32

BBC: biceps, brachialis, coracobrachialis

Question 33

What is Erb Duchenne palsy? What is involved, what is the position?

Answer 33

Upper brachial plexus TRUNK injury of C5 and C6, causing Bellman's / Waiter's tip position with arm held at side, internally rotated, and wrist flexed with spared hand and fingers. Weak shoulder, elbow, wrist extensor.

Question 34

What is a lower trunk injury called, what does it involve, and what is the positioning.

Answer 34

Klumpke's palsy - C8-T1, causes hand and finger weakness, ulnar side sensory loss of hand/forearm, atrophy of hypothenar muscles

Question 35

Causes of lower brachial plexus trunk injury: 3

Answer 35

1. upward traction (grabbing tree branch during fall) 2. thoracic outlet 3. pancoast

Question 36

nerve damaged in upper humeral fracture and what does it cause?

Answer 36

Axillary: deltoid weakness, shoulder numbness

Question 37

What is Parsonage-Turner syndrome?

Answer 37

brachial plexitis (inflammatory) causing burning shoulder and lateral neck pain with weakness lasting 6-12 wks

Question 38

What is spared of the median nerve supply in Carpal tunnel?

Answer 38

wrist flexion, 2/3 digit flexion, and sensation over thenar eminance b/c branches are before the carpal tunnel. BUT thumb abduction out of plane should be weak

Question 39

Nerve branch for hip flexion, knee extension with sensory loss medial LE and knee cap? How does this occur?

Answer 39

femoral nerve, can occur from neuropathy in pelvic area issues or from meralgia paresthetica in obesity, pregnancy with entrapment in inguinal ligament

Question 40

Nerve branch for thigh adduction, and small inner thigh patch sensation?

Answer 40

obturator

Question 41

Nerve for knee flexion, sensation of lateral foot / leg, bottom of foot

Answer 41

Sciatic

Question 42

Nerve for plantarflexion, foot inversion, toe flexion, sensory sole of foot

Answer 42

tibial

Question 43

nerve for foot eversion, sensory lateral leg and top of foot

Answer 43

superficial peroneal

Question 44

nerve for foot dorsiflexion and toe extension, and inner big toe sensation?

Answer 44

deep peroneal (palsy causes foot drop)

Question 45

What is recruitment on EMG? What is the pattern with myopathic vs neuropathic conditions?

Answer 45

Recruitment is continuous firing pattern when muscle is voluntarily contracted. In myopathy it is continuous / increased b/c more motor units are activated to get force, but amplitude is decreased. In neuropathy it is reduced/interrupted b/c some motor units aren't activated by the voluntary contraction.

Question 46

Motor unit potentials are small in duration and amplitude in neuropathic or myopathic conditions?

Answer 46

myopathic

Question 47

third digit sensory disturbance | What radiculopathy?

Answer 47

C7 radiculopathy

Question 48

C5 vs C6 radiculopathy?

Answer 48

Both have shoulder abduction and external rotation and elbow flexion weakness. C5 sensory is shoulder and upper lateral arm. C6 has more motor issues with forearm pronation and wrist extension and radial flexion weakness, and sensory for C6 is lateral forearm and 1st two digits

Question 49

radiculopathy in finger abduction, thumb opposition and abduction weakness and sensory digit 4/5 and medial forearm/arm

Answer 49

C8/T1

Question 50

scapular winging

Answer 50

long thoracic nerve causing serratus anterior winging

Question 51

Saturday night palsy?

Answer 51

radial nerve palsy with arm stuck flexed at elbow and wrist, pronated, and fingers flexed, and radial sensory loss in posterior arm/hand.

Question 52

arcade of Frohse?

Answer 52

like radial nerve saturday night palsy but with elbow spared due to posterior interosseus nerve entrapment

Question 53

Benediction sign

Answer 53

ulner nerve palsy with claw hand, hyperextension of 4/5th digit which are flexed and can't extend