Shenoy - Nerve Entrapments Flashcards
NCS, EMG studies in peripheral entrapment neuropathies
Axon loss timeline:
NMJ first, then motor nerve wallerian degeneration (3-7d) then sensory wallerian degeneration (5-10d), then collateral sprouting 3-6 months, which in turn leads to polyphasics and large MUAPs from 6-12 months onwards.
Axon loss = amplitude loss
Demyelination and remyelination causes _____ segments + _____ diameter of myelin = decreased ______ despite clinical recovery!
Demyelination and remyelination causes Increased internodal segments + Decreased diameter of myelin = decreased CV despite clinical recovery!
Describe the organization of the PNS (epi, peri, endoneurium)
- Epineurium
– Resist mechanical forces
– Vasa nervorum(blood supply) - Perineurium
– Epithelial: around each fascicle
– Fibrous: between fascicles
– Homeostasis
– Blood-nerve barrier - Endoneurium
– Tubular guidance for myelinated axons
Timing changes on EMG:
Recruitment
Membrane instability
When for each?
Timing changes on EMG:
- Recruitment changes may be immediate
- Membrane instability only distal to lesion – proximal muscles 10-14 days
– distal muscles 3-4 wks
– Fibs & amplitudes reduce over time
– Reinnervation changes seen in 3-4 months
* ↑MUAP amplitude and duration
* ↑ polyphasics
Side to side amplitude > ___% is significant
Side to side amplitude > 50% is significant
Conduction block: (AANEM ’99) UL: >__% Amplitude change or __% area LL: >__% Amplitude change or __% area
Conduction block: (AANEM ’99) UL: >30% Amplitude change or 30% area LL: >50% Amplitude change or 40% area
Choosing a strategic needle study means:
Proximal & distal site in peripheral nerve involved + associated myotomes
Axon grows __/day ~ __/month
Axon grows 1mm/day ~ 1”/month
Temperature affects SNAPS more than CMAPS
What other effects does it have?
-Ideal temp for UE and LE
-Change in CV and speed per Celsius
-Change in amp, duration, distal latency
– 32C UE & 30C LL
– 0.2ms /oC or -2.1m/s per /oC for
healthy nerves
– Increased amplitude, distal latency & Duration , decreased CV
– SNAPs more than CMAPs
Describe how too low or too high stimulus intensity during NCS can affect findings: (3)
- low = suboptimal amplitude comparison
- Too high = volume conduction
- increase stimulus duration = falsely increased CV
IDIOPATHIC FACIAL PARALYSIS
Describe the path of CN 7
CN 7 enters the int. auditory meatus then goes to the petrous portion temporal bone –> Tympanic segment
–> stapedius –> chorda tympani
–> to facial muscles
IDIOPATHIC FACIAL PARALYSIS
Entrapment site?
Temporal bone facial canal
IDIOPATHIC FACIAL PARALYSIS
Describe the H&P for someone with this condition?
What is it associated with?
Unilat. Facial weakness (24 -48hrs)
facial numbness &/or pain
unilateral hyperacusis (reduced tolerance to sound)
Tearing and taste changes
inability to close eye
associated w/ HSV infection
IDIOPATHIC FACIAL PARALYSIS
EDx findings for this condition?
- Facial motor Nasalis, frontalis,
orbicularis side to side amplitude
within 10-14 days - CMAP onset latency & blink reflex
unclear predictors - EMG: VMUs in clinically paretic
muscle indicates incomplete lesion
IDIOPATHIC FACIAL PARALYSIS
Tx and Prognosis? (timeline for each)
TX:
* steroids + anti-viral if <72 hrs
* unclear if after 7 days
* eye lubrication
* NCS/EMG within 2 weeks
* Surgical decompression caries many risks
Poor prognosis:
* Severe pain & paresis
* Age>60
* No recovery in 3 wks
SPINAL ACCESSORY NERVE INJURY
Anatomy pathway?
Injury site?
- CN11 –> jugular foramen(bulbar)
- C1-5 efferents to SCM & Trapezius.
Injury site: Usually distal to SCM but proximal to trapezius
SPINAL ACCESSORY NERVE INJURY
Causes? H&P?
- radical neck dissection
- blunt trauma
- CABG
- ACDF
- CEA
SPINAL ACCESSORY NERVE INJURY
Physical Exam findings? Think about your Scapula too!
Physical Exam:
* lateral & inferior scapula at rest
* trapezius weakness w/AROM
shoulder to 90 deg
* lateral and downward rotation of
scapula w/ abduction
* +SCM weakness (cant turn head contralateral)
SPINAL ACCESSORY NERVE INJURY
EDx findings?
What leads to poor outcomes?
What treatment options are there?
EDX (not great predictor):
* serial studies to show change, Trapezius CMAP
* EMG trapezius and SCM for membrane instability and VMUs.
Poor outcome if:
* dominant limb,
* scapular winging
* impaired arm elevation
TX: surgical exploration/grafting.
SUPRASCAPULAR NERVE
What is the anatomy course of the nerve?
Entrapment sites? (2)
Anatomy:
* C5-6 upper trunk under trapezius
* suprascapular notch
* supraspinatus fossa
* AC and GH joints
* spinoglenoid notch –> infraspinatus
Entrapment sites:
* Suprascapular notch (transverse
scapular ligament)
* spinoglenoid notch (lig)
SUPRASCAPULAR NERVE
Common H&P features?
PE Findings? (location of each)
- recalcitrant shoulder pain
- overhead athletes volleyball
- crutch usage
- RTC injuries
- masses/vascular malformations.
- No paresthesias
SUPRASCAPULAR NERVE
PE Findings? (location of each)
Physical Exam:
* weak supra & infraspinatus
(suprascapular notch)
* weak infraspinatus
(spinoglenoid notch)
SUPRASCAPULAR NERVE
EDx findings and Tx?
EDX:
* NCS UE screen including
SNAPs to r/o plexopathy
* EMG screen, add supra &
infraspinatus w. paraspinals to r/o C5-6 vs. plexopathy.
Treatment:
* Imaging to eval for masses
* surgical referral.
AXILLARY NERVE
Nerve course?
Common entrapment sites?
Anatomy:
* C5-6 –> posterior cord –> quadrangular space –> teres minor and deltoid
Entrapment sites:
* Axilla
* Quadrangular space (teres minor/major, medial triceps & humerus) rare.
AXILLARY NERVE
History and Physical Exam findings
HISTORY:
* crutch usage, anterior shoulder
dislocation, trauma
PHYSICAL EXAM
* weak teres minor and deltoid
* decreased sensation axillary patch.
AXILLARY NERVE
EDx, EMG, and Tx?
EDX:
* NCS UE:
– screen including SNAPs to r/o plexopathy
– deltoid CMAP.
- EMG
– screen
– add teres minor and other C5 muscles
– paraspinals to r/o C5-6 vs. plexopathy.
TX: prognosis is based on etiology of injury.
LONG THORACIC NERVE
Anatomy course of nerve
Entrapment sites?
Anatomy:
C5-7 –> thoracic wall –> serratus anterior
Injury sites: long course along thorax, subject to traction
LONG THORACIC NERVE
HPI/Hx?
PE findings?
Hx:
* direct trauma, fall, wrestling, football, mastectomy, thoracic sx.
* * RA can cause Serratus disruption
PE:
* weak serratus anterior,
* resting scapula medial, upward rotation
* forward flexion –> medial winging
LONG THORACIC NERVE
EDx?
Tx and Prognosis?
*NCS UE screen including SNAPs to r/o plexopathy
*Serial CMPs for more predictive outcome
* EMG radiculopathy screen
*add serratus (fingers in ICS), can see EKG artifact.
* paraspinals to r/o C5-6 radiculopathy vs. plexopathy.
Tx: PT strengthening and bracing
Prognosis: Idiopathic is better than trauma, 80% vs 50% recovery
DORSAL SCAPULAR NERVE
Anatomy?
Entrapment sites?
What Hx is usually seen?
Anatomy: C5 –> Dorsal scapular nerve –> rhomboids & levator scapula
Entrapment sites: Scalene medius
Hx:
* weight lifting
* shoulder dislocation
DORSAL SCAPULAR NERVE
PE presentation?
- +weak serratus anterior,resting
scapula lateral, upward rotation - winging is subtle!, overhead elevation decreases winging
DORSAL SCAPULAR NERVE
EDx findings and Tx?
NCS UE screen including SNAPs to r/o plexopathy, EMG screen, add Rhomboids, and other C5 muscles paraspinals to r/o C5-6 vs plexopathy.
Tx requires PT strengthening. Prognosis based on etiology, trauma worse of course
MUSCULOCUTANEOUS NERVE
Anatomy and course? Don’t forget the LAC
Injury sites?
- Anatomy:
– C5-6 –> uppertrunk –> lat.cord
– Coracobrachialis, bicepsbrachii, brachialis –> LAC - Injury sites:
– Brachial plexus injuries
– axilla
– AC fossa
MUSCULOCUTANEOUS NERVE
Possible etiologies of injury?
What other things can look like this that you should rule out?
– anterior dislocation
– weightlifting, arm extension,
– humerus fracture,
– phlebotomy AC fossa
Make sure to rule out:
– R/O C6 radiculopathy, distal biceps injury.
MUSCULOCUTANEOUS NERVE
PE findings?
EDx findings?
Tx?
Weak elbow flexion, with decreased sensation over area of LAC + palpation tenderness over distal biceps tendon.
EDx
– NCS UE screen including
SNAPs to r/o plexopathy, LAC
– EMG screen, add other C5-6
muscles, like RTC muscle, peck
major.
– paraspinals to r/o C5-6 vs
plexopathy.
Tx
Same, PT strengthening and prognosis is based on etiology
MEDIAN NERVE
List the course of the nerve AND the 4 possible entrapment sites:
C6-T1 –> medial & lateral cords –> median nerve
Ligament of Struthers
Pronator Teres (syndrome)
AIN Nerve entrapment
Carpal Tunnel Syndrome
Proximal Median nerve Lesion: ligament of struthers
Anatomy and location?
Incidence?
Hx of patient? What distribution? What muscles are affected?
Anatomy
– 3-6 cm above elbow
– median nerve and brachial
artery tacked down @supracondylar process to the medial epicondyle.
Incidence
0.5-3%, often bilateral
Hx
– Possible Vascular
symptoms
– palmar cutaneous branch
& rest median distribution.
– ALL MEDIAN muscles weak
Proximal Median nerve Lesion: ligament of struthers
3 notable physical exam findings!
cant pronate
wrist flexion w/ ulnar deviation ( no median FCR)
Active Benediction sign ( can’t close fist, no median FDP)
Proximal Median nerve Lesion: ligament of struthers
EDx findings and Tx?
Think about bracing and surgery options..
EDx:
– NCS UE screen
– SNAPs to r/o plexopathy, LAC
– EMG screen, pronator teres +
– FCU negative
Tx:
– OT : strength, brace to avoid
being stuck in extension
– prognosis based on etiology of
injury
– abnormal bony spur - may be
detected in X-ray –> Surgical referral
Proximal Median nerve Lesion: Pronator teres (PT)
Anatomy/course?
Hx features?
PE findings?
Risk factors?
Anatomy: Median nerve runs b/w medial and lateral heads of PT
Hx:
– pain & tenderness medial forearm
– worse w. pronation.
– NUMBNESS in median distribution
including THENAR area
– Easy fatigability
– WEAKNESS of APB, flexor forearm
– No nocturnal exacerbation
PE:
– Pronator strength 5/5, check w/
elbow extended. Can worsen pain.
– Check FDS arch: resist flexion of
flexor superficialis of D3
– Check Lacertus fibrosus (fascial band extending from biceps tendon to forearm fascia) w/ elbow flexed in resisted supination
Risk factors:
Tight FDS arch, Hypertrophic PTeres, Lacterus fibrosus
Proximal Median nerve Lesion: Pronator teres (PT)
EDx and EMG findings? Tx?
EDx:
– NCS: median SNAP Latency WNL
– CMAPs are slow in the forearm segment and MAY show decreased amplitude (axonal)
EMG: PT is normal! But distal muscles can show fibs and PSWs (distal membrane instability)
Tx: Avoid repeated pronation +/- surgical referral
Median nerve : Anterior interossesous nerve (AIN)
Anatomy? Common variants/anastomosis? and H&P related to this injury?
Anatomy: It branches off 5-8 cm distal to lateral epicondyle.
Innervates the motor for pronator quadratus (PQ), FPL, FDP (d2-3).
Also provides sensory to carpal joints but clinically no sensory deficit.
Often involved in Martin gruber anastamosis
H&P:
-Pain & tenderness medial forearm, elbow
-Acute onset D1-2 weakness. No Numbness. Weakness of PQ w/ elbow flexed.
-Okay sign. Decreased Dexterity
Median nerve : Anterior interossesous nerve (AIN)
Risk factors?
EDx findings?
Tx?
Risk factors:
– Gantzer’s muscle - anomalous muscle (accessory head of FPL muscle)
– palmaris profundus, FCR brevis
– trauma
– manifestation of neuralgic amyotrophy
Edx:
– NCS: Screen
– PQ needle pickup unreliable
– EMG: PQ& FPL+
– Screen for radiculopathy & plexopathy.
Tx:
– Nsaids, REST
– cast in SUPINATION
– Surgical referral
Explain the Riche-Cannieu anastamosis:
-What is the anatomy, incidence?
-What EDx clues may indicate it?
-When is it significant to be aware of this?
-How do you confirm this?
Deep ulnar fibers end up innervating the median nerve hand intrinsic muscles (only Motor). Some studies have said that 55-80% of people may have this!
EDx: Median nerve stimulation at the wrist with electrode at APB = low, however stimulation over the ulnar nerve would be normal. The morphology would also look strange
EMG: Spontaneous activity at the ABP despite a normal median CMAP and NCS study (indicates the lesion may be from ulnar nerve).
Significance: People with severe CTS with this variant will have a normal EMG study of the hand, despite having absent SNAPs of the wrist (ulnar innervation saves the hands)
Confirm: comparing motor responses at APB (w/ needle electrode) while stimulating ulnar nerve at the elbow
Explain the borders of the carpal tunnel:
-Outside
-Inside
-Carpal bones floor
-Ulnar and Radial walls
– Outside: palmaris longus, palmar cutaneous nerve (median)
– transverse carpal ligament
– Inside: 4 tendons of FDS, 4 tendons of FDP, FPL, Median nerve
– Carpal bones: Scaphoid, trapezium, hamate, capitate
– Ulnar side: Ulnar Artery & nerve
– Radial side: FCR
Pathophysiology of Carpal Tunnel Syndrome:
-4 common causes
What risk factors exist?
Pathophysiology:
– – – –
-Increased tunnel Pressure
-Microvascular compression
-Nutrient flow impeded
-Ischemia –> demyelination…axonal injury
Risk Factors:
– Increased tunnel Pressure: repetitive activity leading to flexor tenosynovitis
– Age , BMI
– carpal OA
– edema (pregnancy, thyroid)
– masses (ganglion, lipoma)
– Prolonged vibration
– Preexisting (nerve) condition such as DM, radiculopathy, ? Double crush.
– ?Handedness LHD > RHD
– ? Postures w/ low pressures (typing)
– High incidence in poultry workers, construction workers
Common Hx of CTS?
What should your PE include?
– Middle aged females> males
– Paresthesias: D1-3, 4,5
– Worse w/ wrist motion, gripping, hands
elevated, night time waking
– Relief w/ dependent position or
flick (“what do you do when it happens”)
– Subjective hand weakness or dexterity loss
PE:
– Carpal compression (30 sec)
– Phalens , tinels
– Sensory (filaments?)
– motor (LOAF)
– Spurlings
– atrophy
Explain the possible NCS permutations in CTS?
What should you check in your NCS exam?
Explain the combined sensory index? (3)
– NCS does not correlate to clinical symptoms
– may have wnl NCS(small fiber, transient/ischemic
What to check:
Sensory: median (d2or 3) wrist & mid palm, SNAP amplitudes and latencies
Motor: Median distal latency, amplitude, palm for conduction block, Ulnar to eval for neuropathy and martin gruber anastomosis!
CSI:
Compare Median vs. other nerve at same E1, but diff stim sites. Compare velocity differences! If total > 0.9 = CTS!
1) 2nd lumbrical, Med and Ulnar 8 cm away. - Mixed (normal < 0.3)
2) D4 SNAP, Med and Ulnar 14 cm away. - SNAP (normal < 0.4)
3) D1 SNAP, Med and Radial 10 cm away. - SNAP (normal < 0.5)
How should you plan an EMG exam for a CTS patient? Possible findings?
Explain mild-mod-severe grading in CTS?
EMG exam should include:
– Radiculopathy screen R/O C8-T1, peripheral neuropathy, and APB sampling
– Can see membrane instability & occ
myokymia
-EDx can be normal up to 25% of cases = no surgery
Grading:
– Mild: prolonged SNAP distal latency ± amplitude
– Moderate: abnormal median sensory & motor latencies
– Severe : median motor & sensory distal latencies+ absent SNAP or low amplitude CMAP.
Treatment options for CTS:
OT:
Injections:
Surgery:
OT: Dorsal or volar in neutral with slight extension. Strengthen the hand instrinsics and focus on tendon gliding to decrease pressure in tunnel. VERY IMPORTANT to address Ergonomics: modify bothersome postures, computer workstation, changing angle of tool usage
Injections: steroids +/- lido blind or with U/S for weeks/months of relief
Surgery: Same day, 1-2 months rehab. MAY NOT help numbness or current weakness (key is to stop progression).
RADIAL NERVE:
Describe the nerve’s path from root to end
Name 4 common entrapment sites
Path: C5-8 –> posterior cord –> axilla –> spiral groove –> BR & ECRL –> PIN & superficial radial.
4 entrapment sites:
-Saturday night/honeymooners palsy
-PIN syndrome
-Radial tunnel syndrome
-Chieralgia paresthetica
RADIAL NERVE:
Spiral Groove Entrapment
Anatomy:
Typical Hx:
PE findings:
- Anatomy: radial nerve –> axilla –> triceps –> spiral groove –> BR&ECRL
–> elbow supinator & wrist extensor group. - Hx:
-heavy alcohol or sedative binge.
-Honeymooner’s: head resting on medial arm
-Fx of humerus
-Axillary crutches - Physical:
– Sparing of triceps
– Weak Brachioradialis, Wrist and
finger extensors
– Numbness in sup. Radial territory
RADIAL NERVE:
Spiral Groove
NCS and EMG findings and where/what to test?
Tx?
NCS findings:
– NCS: EIP pickup, Stimulation sites
below/above elbow, above spiral
groove.
– Usually demyelinating
– sup. Radial SNAP may be normal
EMG findings:
– deltoid, triceps normal
– BR and distal w. decr recruitment ,
fibs and sharp waves.
– Screen for radiculopathy &
plexopathy.
Tx:
– ROM to prevent contractures, E
stim.
– Dynamic splint ACTIVE FLEXION w/ passive extension
– Surgery if no symptomatic improvement in 4 months
RADIAL NERVE:
PIN Syndrome
Anatomy/path: What muscles are spared?
Hx of PIN syndrome? Common causes?
-Name of injury associated with it?
PE findings?
– Radial nerve –> elbow
– Superficial radial & Post.
Interosseus nerve
– –> supinator muscle under arcade of Frohse
– SPARES SUPINATOR AND ECRL/B (3)!
– Tumor/lipoma, Ganglia,
RA/inflammation
– Fx of ulna w/dislocation of radial
head, MONTEGGIA Fx
– Arcade of Frohse: Fibrous/
tendinous band of supinator
PE:
– Wrist ext and finger ext weakness.
– Radial wrist ext deviation(ECRL/B spared)
– Thumb ext/abduction (radially) weakness
RADIAL NERVE:
PIN syndrome
Explain the NCS and EMG findings of this injury?
Tx?
– NCS: EIP pickup, below/above elbow, above spiral groove.
– Slowing across the supinator
– sup. Radial SNAP NORMAL
– EMG: ALL PIN muscles affected,
– SPARING of supinator and ECRL/B
Tx;
– ROM to prevent contractures, E stim.
– Dynamic splinting
– Surgery referral if no symptomatic
improvement in 4 months
RADIAL NERVE:
Radial Tunnel Syndrome
Explain the course in anatomy:
Explain common Hx complaints:
– Radial nerve –> elbow –> between
the brachialis and brachioradialis
muscles
– posterior interosseous nerve
enters the supinator muscle
Common Hx complaints:
– Recalcitrant tennis elbow
– Lateral elbow pain in the extensor tendon
– Distal to lateral epicondyle
– Nighttime pain common
RADIAL NERVE:
Radial Tunnel Syndrome
Explain Physical Exam findings (most important one?):
Explain EDx findings and Tx:
PE:
– similar to PIN
– Radial wrist ext deviation(ECRL/B spared)
– Tender distal to lateral epicondyle
– incr. pain on supination
EDx: SAME AS PIN!
– NCS: Prolonged latency w/ supination.
– sup. Radial SNAP normal
– EMG: Need to rule out C7 radiculopathy
- TX: Same as PIN
