UE PNS Disease Flashcards
median neuropathy at wrist - PE findings
positive tinel at wrist, phalen, carpal compression test, +/- thenar atrophy
median neuropathy at wrist - NCS/EMG findings
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
median neuropathy at elbow - Px
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
median neuropathy at elbow - PE findings
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
median neuropathy at elbow - NCS/EMG findings
NCS: abnormal median SNAP and CMAP
EMG: decreased recruitment +/- fibs/sharps
in every medial muscle except PT (if PT syndrome), polyphasicity
median neuropathy at elbow - muscles affected depending on etiology
all median n. innervated muscles will be affected if compression at bicipital aponeurosis or ligament of Struthers
PT will be spared if PT syndrome
median n. innervated muscles
PT, FCR, FDS, PQ, FPL, FDP 2,3, APB, FPB, lumbricals 1,2, opponens pollicis
anterior interosseous innervated muscles
AIN is pure motor branch of median n.
innervates “P” muscles → FPL, FDP 2,3, PQ
anterior interosseous neuropathy - PE findings
cannot make “OK” sign (FPL and FDP 2,3)
cannot make fist
(Froment’s sign is basically reverse…)
Ulnar neuropathy at wrist (Guyon’s canal), types
I motor and sensory
II motor
III sensory
borders: ligament superiorly, flexor retinaculum/hypothenar muscles inferiorly, hook hamate laterally, pisiform medially
localization of ulnar neuropathy at wrist (Guyon’s canal) on NCS
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
ulnar neuropathy at wrist (Guyon’s canal) NCS/EMG findings
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)
ulnar neuropathy at elbow (Arcade of Struthers or cubital tunnel syndrome (2 heads FCU)) NCS/EMG findings
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
radial neuropathy at elbow, DDx spiral groove, NCS/EMG findings
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
radial neuropathy at elbow etiology
often d/t compression between brachialis and brachioradialis
DDx: radial neuropathy at elbow v spiral groove v improper crutch use NCS/EMG findings
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
superficial radial neuropathy - Px, NCS/EMG
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
PIN-opathy etiology
compression at Arcade of Frohse (over supinator muscle) or trauma (Monteggia fx)
Monteggia fx: fx of proximal ⅓ ulna → proximal radius dislocation
PIN-opathy NCS/EMG findings
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
Axillary neuropathy - Px/EDX findings
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
Musculocutaneous neuropathy - px/edx
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
Suprascapular neuropathy - Px/EDX
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
spinoglenoid notch - clinical significance
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
scapular winging ddx
“SALT” serratus anterior (long thoracic n.) → medial winging
trapezius (spinal accessory n.) → lateral winging
long thoracic neuropathy Px/EDX
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
Erb Palsy
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)
upper trunk brachial plexopathy - EDX
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
Klumpke Palsy
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
lower trunk brachial plexopathy - EDX
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
Brachial Plexus pathyway
pass between anterior and middle scalenes and emerges underneath the clavical as cords
Riche Cannieu Anastomaosis
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
Martin Gruber Anastomosis
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
thoracic outlet syndrome
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
thoracic outlet syndrome EDX findings
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)
Parsonage-Turner Syndrome
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
Radiation plexopathy v Pancoast syndrome
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
