1. Electrodiagnostic Evaluation of Brachial Plexus Injuries
William McKinley MD
Associate Professor PM&R
Virginia Commonwealth University

2. Incidence 10% of all peripheral nervous system injuries
14% of UE neurological injuries
Bimodal distribution:
Obstetrical: male = female, R > L
Ages 20-30, males (MVA, violence)

3. BP lesion localization
Know clinical ANATOMY!!!
Root/trunk/division/cord/branch (RTDCB)
Motor/sensory innervation
Comprehensive Edx eval
NCS & needle EMG
Consider less common motor/sensory NCS

5. BP Anatomy Anterior (ventral) rami C5-T1
R/T/D/C/B ( ) “Palindrome”
BP extends from vert column to axilla
clavicle separates R/T from C/B
Supraclavicular (roots & trunks)
Infraclavicular (cords & branches)
Cords named in relation to Axillary artery
Lateral (C5,6,7) Posterior (C5-T1) Medial (C8-T1)

7. Types of Neural Injury Stretch / traction - most common
Contusion - energy dissipation
Laceration - fiber disruption
Compression - ischemia / mechanical
Ischemia - decreased nutrients

9. Etiologies Closed Open Traction injuries Blunt trauma Radiation Tumor
Positioning
Brachial Neuritis
Open
GSW
Laceration
Surgical trauma
Injection needle

10. Differential Dx Proximal mononeuropathies Radiculopathy
radial, axillary, suprascapular, musculocutaneous (vs upper / post cord involvement)
Ulnar & median (vs lower trunk / medial cord injury)
Radiculopathy

11. Neuralgia Amyotrophy
“Brachial plexopathy”, “Parsonage-Turner syndrome”
Sx - Acute pain, proximal (upper trunk) /shoulder innervation involvement
SS, long thoracic, axillary often affected
Good prognosis
Recovery (year 1- 35%, year %)

12. Obstetrical-related Risk factors: heavy birth weight
long, difficult labor
breech presentation
short maternal stature

13. Thoracic outlet syndrome (TOS)
Somewhat controversial
sx represent vascular vs neurogenic compromise of:
C8 / T1 or lower trunk
NCS findings can include abnormalities of median motor, ulnar sensory & motor

14. Sports-related injuries
“Burners” or “stingers”
Traction of shoulder / head (upper trunk)
Sx: paresthesias (rarely weakness)

15. Neoplastic Primary tumors - schwannomas, neurofibromas
Secondary tumors (more common)
Pancoast tumor (metastatic disease to the upper lobe of lung)
Lower trunk involvement
Horners syndrome

16. Radiation-induced Related to total dosage & time-dependent
> 6000 Rads
between 6-24 months
favors upper trunk involvement
“myokymia” on needle EMG
Ddx: recurrent tumor

17. Peri-operative / Post-anesthetic
Positioning, straps, traction, pressure
Usually upper plexus, good prognosis
Sternotomy (lower trunk / C8-T1)
Needle-induced
axillary angiography
regional anesthesia

18. Classifications of BP injuries
Open vs Closed (etiology)
Supraclavicular (R/T) vs infraclavicular (C/B)
Supraclavicular is more common
Preganglionic vs postganglionic
Upper (Erbs) vs middle vs lower (Klumpke) trunks
Complete vs incomplete

21. Preganglionic Injury Nerve root avulsion
dorsal & ventral rootlets
invested by pia mater / dural funnel
etiology: traction (occasionally missile, knife)
Significant traction causes dural rupture / root vulnerability
ventral > dorsal root (esp C8-T1) at higher risk
POOR Prognosis!

23. Edx eval of BP Injury Nerve Conduction Studies (NCS)
common (median, ulnar)
(evaluates lower trunk & medial cord)
less common (radial, MC, Axillary, SS)
proximal NCS (C5-6, Erbs point)
(technically possible, difficult, uncomfortable)
Needle EMG (recruitment, abnl spont pot’s)
Late-responses (H-reflex, F wave)- may be abnormal but ? less useful

24. Motor/Sensory NCS Distal latency & NCV are not helpful
Amplitude is “key” parameter
remains NL(on distal stim) if no axonal loss (cond block, demyelination) or with preganglionic BPI (SNAP NL)
look for decreased side-side > 50%
motor day 4-7 (NMJ fragmentation)
sensory day 8-10

25. Localizing NCS involement
Terminal branches of Brachial Plexus
Median, Ulnar, Radial, Axillary, MC
sensory & motor
travel to and from the CNS thru the various roots, trunks, divisions & cords in a fairly consistent “pattern”

26. Sensory NCS Localization

27. Motor NCS Localization

28. Needle EMG Abnormal spontaneous potentials
positive sharp waves, fibrillations
7-10 days (paraspinal), 2-4 weeks (distal m’s)
Important: follow “pattern” of BP innervation
Paraspinal M’s WNL! (distal to Post rami)
Decreased recruitment (voluntary MUAP)

29. Adjunctive tests Xrays (C-spine, clavicle, humerus, 1st rib)
Myelography - w/i 2-3 weeks, nerve root avulsion forms diverticulum c/w SA space
MRI (>CT)

30. Somatosensory Evoked Potential (SSEP)
Supraclav. Fossa / Erbs pt. (N9) / cervical spine (N13) / contra somatosensory cortex (N19)
sensory fibers / post column / thalamus
Considerations (less than ideal agreement)
Postganglionic-N9 Abnl (> 30% side-side diff.)
Preganglionic- Nl N9 w/ Abnl N13

33. Axon reflex testing To evaluate pre vs post ganglionic lesion
1% SQ histamine normally leads to a vasodilation, wheal & flare due to reflex between DRG & cutaneous receptors
“Triple response” in light of clinical picture c/w BPI = lesion proximal to DRG (ie: preganglionic root avulsion & poor prognosis)
Loss of flare = postganglionic (better prognosis)

34. Case Study
Hx: MVC
Clinical exam: Prox UE wk (Sh Fl/Abd, EF), numbness lateral arm/forearm/hand
What NCS & needle exam abnormalities will assist in localizing the site of injury?

36. Sensory Nerve Localization

38. Motor NCS Localization

40. Brachial Plexus Injuries (Summary)
Know your ANATOMY!!!
Needle EMG:
localizing pattern of involement
paraspinal m’s WNL (unless preganglionic)
NCS:
localizing pattern of involvement
amplitudes often most affected

41. Have a nice Weekend!!!