electrodiagnostic evaluation of brachial plexus injuries §william mckinley md §associate professor...
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Electrodiagnostic Evaluation of Brachial Plexus Injuries
William McKinley MDAssociate Professor PM&R
Virginia Commonwealth University
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Incidence
10% of all peripheral nervous system injuries
14% of UE neurological injuriesBimodal distribution:
Obstetrical: male = female, R > L Ages 20-30, males (MVA, violence)
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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
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BP Anatomy
Anterior (ventral) rami C5-T1R/T/D/C/B (5-3-6-3-5) “Palindrome” BP extends from vert column to axillaclavicle 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)
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Types of Neural Injury
Stretch / traction - most commonContusion - energy dissipationLaceration - fiber disruptionCompression - ischemia / mechanicalIschemia - decreased nutrients
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Etiologies
Closed Traction injuries Blunt trauma Radiation Tumor Positioning Brachial Neuritis
Open GSW Laceration Surgical trauma Injection needle
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Differential Dx
Proximal mononeuropathies radial, axillary, suprascapular,
musculocutaneous (vs upper / post cord involvement)
Ulnar & median (vs lower trunk / medial cord injury)
Radiculopathy
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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 3 - 90%)
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Obstetrical-related
Risk factors: heavy birth weight long, difficult labor breech presentation short maternal stature
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Thoracic outlet syndrome (TOS)
Somewhat controversialsx represent vascular vs neurogenic
compromise of: C8 / T1 or lower trunk NCS findings can include abnormalities of
median motor, ulnar sensory & motor
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Sports-related injuries
“Burners” or “stingers”Traction of shoulder / head (upper trunk)Sx: paresthesias (rarely weakness)
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Neoplastic
Primary tumors - schwannomas, neurofibromas
Secondary tumors (more common) Pancoast tumor (metastatic disease to the upper
lobe of lung) Lower trunk involvement Horners syndrome
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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
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Peri-operative / Post-anesthetic
Positioning, straps, traction, pressureUsually upper plexus, good prognosis
Sternotomy (lower trunk / C8-T1)
Needle-induced axillary angiography regional anesthesia
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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
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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!
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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
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Motor/Sensory NCS
Distal latency & NCV are not helpfulAmplitude 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
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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”
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Sensory NCS Localization
Nerve Cord Trunk
Musculocut. Lateral Upper
Median (1) Lateral Upper
Median (2-3) Lateral Middle
Radial Posterior Upper
Ulnar Medial Lower
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Motor NCS Localization
Nerve Cord Trunk
Musculocutan lateral upperAxillary posterior upper Suprascapular --- upperRadial posterior middle Median medial low Ulnar medial lower
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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)
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Adjunctive tests
Xrays (C-spine, clavicle, humerus, 1st rib)Myelography - w/i 2-3 weeks, nerve root
avulsion forms diverticulum c/w SA spaceMRI (>CT)
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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
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Axon reflex testing
To evaluate pre vs post ganglionic lesion1% 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)
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Case Study
Hx: MVCClinical 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?
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Sensory Nerve Localization
Nerve Upper Trunk
Middle Trunk
Lower trunk
Lat cord
Post cord
Med. cord
MC ++ ++
Med(1)
++ ++
Med 3 ++ ++
Radial ++ ++
Ulnar ++ ++
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Motor NCS Localization
Nerve Upper trunk
Middle trunk
Lower trunk
Lat cord
Post cord
Median cord
MC ++ ++
Axill ++ ++
SS ++
Radial ++ ++
Median ++ ++
Ulnar ++ ++
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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
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Have a nice Weekend!!!