UE PNS Disease

Question 1

median neuropathy at wrist - PE findings

Answer 1

positive tinel at wrist, phalen, carpal compression test, +/- thenar atrophy

Question 2

median neuropathy at wrist - NCS/EMG findings

Answer 2

NCS:
abnormal median SNAP to thumb, digit 2, digit 3
abnormal medial CMAP to APB (w increasingly mod-sev disease)

EMG:
normal v decreased recruitment (i.e., axonal loss)
+/- fibs/sharps (active deinnervation)
polphasicity (reinnervation, i.e., Hx n. damage)

milder disease only w abnormal SNAPs; increasing severity w motor involvement, consider surgical flexor retinaculum release

Question 3

median neuropathy at elbow - Px

Answer 3

similar to CTS, typically by tight PT, tight bicipital aponeurosis, or tight ligament of Struthers

any of these can squeeze the median n. and cause a compressive neuropathy

Question 4

median neuropathy at elbow - PE findings

Answer 4

possibly

weak wrist flexion (FCR), PIP flexion (FDS), thumb flexion (FPL), DIP flexion of digits 2, 3 (FDP 2, 3), pronation (PQ)

in PT syndrome, usually PT is spared because its innervation occurs more proximally

Question 5

median neuropathy at elbow - NCS/EMG findings

Answer 5

NCS: abnormal median SNAP and CMAP

EMG: decreased recruitment +/- fibs/sharps
in every medial muscle except PT (if PT syndrome), polyphasicity

Question 6

median neuropathy at elbow - muscles affected depending on etiology

Answer 6

all median n. innervated muscles will be affected if compression at bicipital aponeurosis or ligament of Struthers

PT will be spared if PT syndrome

Question 7

median n. innervated muscles

Answer 7

PT, FCR, FDS, PQ, FPL, FDP 2,3, APB, FPB, lumbricals 1,2, opponens pollicis

Question 8

anterior interosseous innervated muscles

Answer 8

AIN is pure motor branch of median n.

innervates “P” muscles → FPL, FDP 2,3, PQ

Question 9

anterior interosseous neuropathy - PE findings

Answer 9

cannot make “OK” sign (FPL and FDP 2,3)

cannot make fist

(Froment’s sign is basically reverse…)

Question 10

Ulnar neuropathy at wrist (Guyon’s canal), types

Answer 10

I motor and sensory

II motor

III sensory

borders: ligament superiorly, flexor retinaculum/hypothenar muscles inferiorly, hook hamate laterally, pisiform medially

Question 11

localization of ulnar neuropathy at wrist (Guyon’s canal) on NCS

Answer 11

dorsal ulnar cutaneous n. (DUC) SNAP because DUC branches off to innervate web space between digits 4,5 proximal to guyon’s canal

if normal → Guyon’s canal

if abnormal → lesion proximal to Guyon’s canal
should also see abnormal SNAPs to digits 4,5; abnormal CMAP to ADM, FDI

Question 12

ulnar neuropathy at wrist (Guyon’s canal) NCS/EMG findings

Answer 12

NCS: abnormal SNAPs to digits 4,5; abnormal CMAP to ADM, FDI

EMG: abnormal activity (decreased recruitment, +/- fibs/sharps) to ulnar hand muscles (ADM, FDI, interossei, lumbricals 3,4), polyphasicity

EMG: normal activity in proximal ulnar muscles (FCU, FDP 4,5)

Question 13

ulnar neuropathy at elbow (Arcade of Struthers or cubital tunnel syndrome (2 heads FCU)) NCS/EMG findings

Answer 13

NCS: abnormal ulnar SNAPs to digits 4,5; abnormal CMAP to ADM, FDI
abnormal DUC (branches off before Guyon's canal), normal MAC SNAP (branches off before cubital tunnel)

if MAC SNAP abnormal → lower trunk injury or somewhere more proximal to elbow

EMG: abnormal activity (decreased recruitment = axonal loss, fibs/sharps = active deinnervation, polyphasicity = reinnervation) - to ulnar hand muscles (ADM, FDI)
abnormal activity in proximal ulnar muscles (FDP 4,5)(+/- FCU); polyphasicity

Question 14

radial neuropathy at elbow, DDx spiral groove, NCS/EMG findings

Answer 14

Px same, DDx based on Hx humeral shaft fracture or prolonged compression (spiral groove, Honeymooner’s palsy, Saturday Night Palsy)

Px: weakness of wrist extensors and finger extensors with numbness and tingling in posterior forearm and thumb/snuff box
(ECRL/ECRB, [PIN: EIP, ED, ECU])
elbow flexion may be weak w brachioradialis involvement

triceps and anconeus preserved bc innervation proximal to elbow/spiral grove

NCS: abnormal SNAP to thumb and snuff box
abnormal CMAP to EIP

EMG: abnormal activity in all muscles except triceps and anconeus

Question 15

radial neuropathy at elbow etiology

Answer 15

often d/t compression between brachialis and brachioradialis

Question 16

DDx: radial neuropathy at elbow v spiral groove v improper crutch use NCS/EMG findings

Answer 16

radial neuropathy at elbow (brachialis/BR compression) same as at spiral groove, except latter w Hx humeral shaft fx

improper crutch use → affects posterior cord → therefore triceps and anconeus will be abnormal as well on EMG

sensation will also be affected in entire arm (rather than just forearm) w improper crutch use

can also find axillary n. findings d/t posterior cord involvement

Question 17

superficial radial neuropathy - Px, NCS/EMG

Answer 17

pure sensory → posterior forearm and dorsal hand

usually hx tight handcuffs or IV

NCS: only abnormal SNAP to thumb and snuff box
normal CMAP

EMG: normal

Question 18

PIN-opathy etiology

Answer 18

compression at Arcade of Frohse (over supinator muscle) or trauma (Monteggia fx)

Monteggia fx: fx of proximal ⅓ ulna → proximal radius dislocation

Question 19

PIN-opathy NCS/EMG findings

Answer 19

PIN is pure motor n.

NCS: normal SNAPs to radial, ulnar, median n.
abnormal CMAP to EIP

EMG: abnormal activity in all PIN muscles (ED, EIP, EPL; ECU) +/- supinator
ECRL, ECRB, BR, triceps, anconeus all spared

Question 20

Axillary neuropathy - Px/EDX findings

Answer 20

improper crutch use, trauma, stretching compression

→ weak shoulder abduction (deltoid) and external rotation (teres minor) with impaired sensation over deltoid

NCS: SNAP unavailable (nothing good to test)
abnormal CMAP to deltoid

EMG: abnormal activity in deltoid, teres minor

Question 21

Musculocutaneous neuropathy - px/edx

Answer 21

injury to musculocutaneous n. usually d/t trauma/compression → terminal portion is LAC (lateral cutaneous n.) supplies lateral forearm

Px: weakness of elbow flexion (brachialis); perhaps supination (biceps); numbness of lateral forearm

NCS: abnormal SNAP to forearm, abnormal CMAP to biceps

EMG: abnormal activity in biceps, brachialis

Tx: rehab, remove surgery

Question 22

Suprascapular neuropathy - Px/EDX

Answer 22

C5, C6 → upper trunk → suprascapular n. → supraspinatus → n. passes through spinoglenoid notch → infraspinatus

injury d/t trauma, cysts, stretching, upper trunk lesions (Parsonage-Turner Syndrome - neuralgic amyotrophy) → weakness w shoulder abduction (SS) and/or external rotation (IS)

NCS: SNAP unavailable
CMAP abnormal to supraspinatus

EMG: abnormal activity w SS and/or IS

Tx: rehab/surgery

Question 23

spinoglenoid notch - clinical significance

Answer 23

suprascapular n. courses through, if entrapped will have abnormal IS EDX findings

if lesion more proximal (e.g., upper trunk, cysts), abnormal SS and IS findings

Question 24

scapular winging ddx

Answer 24

“SALT” serratus anterior (long thoracic n.) → medial winging

trapezius (spinal accessory n.) → lateral winging

Question 25

long thoracic neuropathy Px/EDX

Answer 25

medially winged scapula "SALT" = serratus anterior, long thoracic n. NCS: SNAP unavailable CMAP abnormal to serratus anterior EMG: abnormal activity in serratus anterior Tx: rehab

Question 26

Erb Palsy

Answer 26

upper trunk (C5, C6) brachial plexopathy d/t excessive traction forces S/SX: Weakness of all upper trunk muscles: deltoid, teres minor (axillary n.); SS, IS (suprascapular n.); biceps, brachialis (musculocutaneous n.); ECRL, ECRB (radial n.) Waiter's tip → arm adducted, internally rotated, pronated, wrist flexed Sensory loss over lateral arm and dorsolateral forearm (radial n., musculocutaneous n. → LAC)

Question 27

upper trunk brachial plexopathy - EDX

Answer 27

NCS: abnormal median sensory (C5, C6), abnormal LAC (musculocutaneous n.) EMG: abnormal activity and decreased recruitment in upper trunk muscles *remember median motor is C8-T1*

Question 28

Klumpke Palsy

Answer 28

lower trunk (C8, T1) brachial plexopathy → affects median motor and ulnar inn'v muscles → FDS, FDP, FCU, lumbricals, intrinsic hand muscles + sensory loss of medial arm, medial forearm, and hand PE: claw hand, wartenberg sign, froment sign, OK sign

Question 29

lower trunk brachial plexopathy - EDX

Answer 29

NCS: abnormal ulnar SNAP, **normal median SNAP** (clues that this is lower trunk injury) EMG: abnormal activity and decreased recruitment in lower trunk muscles lower trunk muscles: lumbricals, intrinsic hand, FDS, FDP, FCU

Question 30

Brachial Plexus pathyway

Answer 30

pass between anterior and middle scalenes and emerges underneath the **c**lavical as **c**ords

Question 31

Riche Cannieu Anastomaosis

Answer 31

ulnar n. essentially controls motor fibers of hand median motor fibers in hand cross over to join the ulnar n. median n. will show no CMAP ulnar n. stim over APB will show CMAP

Question 32

Martin Gruber Anastomosis

Answer 32

will appear as though there is conduction block at the elbow w ulnar n. in some, median fibers cross over in forearm to join ulnar n. → median n. innervates ADM, FDI, and APB etc. stimulate median n. at elbow recording over ADM → normal CMAP

Question 33

thoracic outlet syndrome

Answer 33

rare, vascular / neurogenic vascular: compression of subclavian/axillary vessels → UE pulse loss, color changes, cold limb, swollen limb, aching pain neurogenic: lower trunk brachial plexopathy (C8, T1) → lower trunk compressed by clavicle and first cervical rib, anterior and middle scalenes, pec major → pain, sensory distubrance in medial arm and medial forearm, 4th and 5th digits, all worse w overhead activity e.g., swimming

Question 34

thoracic outlet syndrome EDX findings

Answer 34

PE: Roos and Adson tests NCS: abnormal ulnar SNAP/CMAP, abnormal median CMAP (C6 fibers are sensory), MAC EMG: abnormal spontaneous activity and possible decreased recruitment of median and ulnar muscles in the hand (lower trunk muscles)

Question 35

Parsonage-Turner Syndrome

Answer 35

AKA neuralgic amyoptrophy, brachial neuritis, idiopathic brachial plexopathy usually u/l and follows viral illness or surgery Px: shoulder pain ~2wks → weakness suprascapular n./long thoracic n./AIN are commonly involved EDX depends on fibers involved likely active denervation, decreased recruitment in affected muscles on EMG *serial EMGs have value for prognosis* may be self limited 1-2 years

Question 36

Radiation plexopathy v Pancoast syndrome

Answer 36

XRT plexopathy: typically upper trunk w Hx radiation Myokimia on EMG *NO PAIN → painless myokimia* Pancoast: upward invasion of lung CA → compresses lower trunk fibers *PAINFUL*, without myokimia on EMG may have i/l Horner syndrome