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Singh PM&R > Shenoy - Nerve Entrapments > Flashcards

Shenoy - Nerve Entrapments Flashcards

NCS, EMG studies in peripheral entrapment neuropathies

1
Q

Axon loss timeline:

A

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

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2
Q

Demyelination and remyelination causes _____ segments + _____ diameter of myelin = decreased ______ despite clinical recovery!

A

Demyelination and remyelination causes Increased internodal segments + Decreased diameter of myelin = decreased CV despite clinical recovery!

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3
Q

Describe the organization of the PNS (epi, peri, endoneurium)

A
  1. Epineurium
    – Resist mechanical forces
    – Vasa nervorum(blood supply)
  2. Perineurium
    – Epithelial: around each fascicle
    – Fibrous: between fascicles
    – Homeostasis
    – Blood-nerve barrier
  3. Endoneurium
    – Tubular guidance for myelinated axons
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4
Q

Timing changes on EMG:

Recruitment
Membrane instability

When for each?

A

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

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5
Q

Side to side amplitude > ___% is significant

A

Side to side amplitude > 50% is significant

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6
Q

Conduction block: (AANEM ’99) UL: >__% Amplitude change or __% area LL: >__% Amplitude change or __% area

A

Conduction block: (AANEM ’99) UL: >30% Amplitude change or 30% area LL: >50% Amplitude change or 40% area

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7
Q

Choosing a strategic needle study means:

A

Proximal & distal site in peripheral nerve involved + associated myotomes

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8
Q

Axon grows __/day ~ __/month

A

Axon grows 1mm/day ~ 1”/month

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9
Q

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

A

– 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

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10
Q

Describe how too low or too high stimulus intensity during NCS can affect findings: (3)

A
  • low = suboptimal amplitude comparison
  • Too high = volume conduction
  • increase stimulus duration = falsely increased CV
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11
Q

IDIOPATHIC FACIAL PARALYSIS

Describe the path of CN 7

A

CN 7 enters the int. auditory meatus then goes to the petrous portion temporal bone –> Tympanic segment
–> stapedius –> chorda tympani
–> to facial muscles

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12
Q

IDIOPATHIC FACIAL PARALYSIS

Entrapment site?

A

Temporal bone facial canal

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13
Q

IDIOPATHIC FACIAL PARALYSIS

Describe the H&P for someone with this condition?

What is it associated with?

A

 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

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14
Q

IDIOPATHIC FACIAL PARALYSIS

EDx findings for this condition?

A
  • 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
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15
Q

IDIOPATHIC FACIAL PARALYSIS

Tx and Prognosis? (timeline for each)

A

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

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16
Q

SPINAL ACCESSORY NERVE INJURY

Anatomy pathway?

Injury site?

A
  • CN11 –> jugular foramen(bulbar)
  • C1-5 efferents to SCM & Trapezius.

Injury site: Usually distal to SCM but proximal to trapezius

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17
Q

SPINAL ACCESSORY NERVE INJURY

Causes? H&P?

A
  • radical neck dissection
  • blunt trauma
  • CABG
  • ACDF
  • CEA
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18
Q

SPINAL ACCESSORY NERVE INJURY

Physical Exam findings? Think about your Scapula too!

A

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)

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19
Q

SPINAL ACCESSORY NERVE INJURY

EDx findings?
What leads to poor outcomes?
What treatment options are there?

A

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.

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20
Q

SUPRASCAPULAR NERVE

What is the anatomy course of the nerve?

Entrapment sites? (2)

A

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)

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21
Q

SUPRASCAPULAR NERVE

Common H&P features?

PE Findings? (location of each)

A
  • recalcitrant shoulder pain
  • overhead athletes volleyball
  • crutch usage
  • RTC injuries
  • masses/vascular malformations.
  • No paresthesias
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22
Q

SUPRASCAPULAR NERVE

PE Findings? (location of each)

A

Physical Exam:
* weak supra & infraspinatus
(suprascapular notch)
* weak infraspinatus
(spinoglenoid notch)

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23
Q

SUPRASCAPULAR NERVE

EDx findings and Tx?

A

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.

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24
Q

AXILLARY NERVE

Nerve course?
Common entrapment sites?

A

Anatomy:
* C5-6 –> posterior cord –> quadrangular space –> teres minor and deltoid

Entrapment sites:
* Axilla
* Quadrangular space (teres minor/major, medial triceps & humerus) rare.

25
Q

AXILLARY NERVE

History and Physical Exam findings

A

HISTORY:
* crutch usage, anterior shoulder
dislocation, trauma

PHYSICAL EXAM
* weak teres minor and deltoid
* decreased sensation axillary patch.

26
Q

AXILLARY NERVE

EDx, EMG, and Tx?

A

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.

27
Q

LONG THORACIC NERVE

Anatomy course of nerve
Entrapment sites?

A

Anatomy:
C5-7 –> thoracic wall –> serratus anterior

Injury sites: long course along thorax, subject to traction

28
Q

LONG THORACIC NERVE

HPI/Hx?
PE findings?

A

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

29
Q

LONG THORACIC NERVE

EDx?
Tx and Prognosis?

A

*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

30
Q

DORSAL SCAPULAR NERVE

Anatomy?
Entrapment sites?
What Hx is usually seen?

A

Anatomy: C5 –> Dorsal scapular nerve –> rhomboids & levator scapula

Entrapment sites: Scalene medius

Hx:
* weight lifting
* shoulder dislocation

31
Q

DORSAL SCAPULAR NERVE

PE presentation?

A
  • +weak serratus anterior,resting
    scapula lateral, upward rotation
  • winging is subtle!, overhead elevation decreases winging
32
Q

DORSAL SCAPULAR NERVE

EDx findings and Tx?

A

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

33
Q

MUSCULOCUTANEOUS NERVE

Anatomy and course? Don’t forget the LAC

Injury sites?

A
  • Anatomy:
    – C5-6 –> uppertrunk –> lat.cord
    – Coracobrachialis, bicepsbrachii, brachialis –> LAC
  • Injury sites:
    – Brachial plexus injuries
    – axilla
    – AC fossa
34
Q

MUSCULOCUTANEOUS NERVE

Possible etiologies of injury?

What other things can look like this that you should rule out?

A

– anterior dislocation
– weightlifting, arm extension,
– humerus fracture,
– phlebotomy AC fossa

Make sure to rule out:
– R/O C6 radiculopathy, distal biceps injury.

35
Q

MUSCULOCUTANEOUS NERVE

PE findings?
EDx findings?
Tx?

A

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

36
Q

MEDIAN NERVE

List the course of the nerve AND the 4 possible entrapment sites:

A

C6-T1 –> medial & lateral cords –> median nerve

Ligament of Struthers
Pronator Teres (syndrome)
AIN Nerve entrapment
Carpal Tunnel Syndrome

37
Q

Proximal Median nerve Lesion: ligament of struthers

Anatomy and location?
Incidence?
Hx of patient? What distribution? What muscles are affected?

A

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

38
Q

Proximal Median nerve Lesion: ligament of struthers

3 notable physical exam findings!

A

cant pronate

wrist flexion w/ ulnar deviation ( no median FCR)

Active Benediction sign ( can’t close fist, no median FDP)

39
Q

Proximal Median nerve Lesion: ligament of struthers

EDx findings and Tx?
Think about bracing and surgery options..

A

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

40
Q

Proximal Median nerve Lesion: Pronator teres (PT)

Anatomy/course?
Hx features?
PE findings?
Risk factors?

A

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

41
Q

Proximal Median nerve Lesion: Pronator teres (PT)

EDx and EMG findings? Tx?

A

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

42
Q

Median nerve : Anterior interossesous nerve (AIN)

Anatomy? Common variants/anastomosis? and H&P related to this injury?

A

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

43
Q

Median nerve : Anterior interossesous nerve (AIN)

Risk factors?
EDx findings?
Tx?

A

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

44
Q

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?

A

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

45
Q

Explain the borders of the carpal tunnel:
-Outside
-Inside
-Carpal bones floor
-Ulnar and Radial walls

A

– 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

46
Q

Pathophysiology of Carpal Tunnel Syndrome:
-4 common causes

What risk factors exist?

A

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

47
Q

Common Hx of CTS?

What should your PE include?

A

– 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

48
Q

Explain the possible NCS permutations in CTS?

What should you check in your NCS exam?

Explain the combined sensory index? (3)

A

– 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)

49
Q

How should you plan an EMG exam for a CTS patient? Possible findings?

Explain mild-mod-severe grading in CTS?

A

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.

50
Q

Treatment options for CTS:
OT:
Injections:
Surgery:

A

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).

51
Q

RADIAL NERVE:

Describe the nerve’s path from root to end

Name 4 common entrapment sites

A

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

52
Q

RADIAL NERVE:
Spiral Groove Entrapment

Anatomy:
Typical Hx:
PE findings:

A
  • 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
53
Q

RADIAL NERVE:
Spiral Groove

NCS and EMG findings and where/what to test?
Tx?

A

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

54
Q

RADIAL NERVE:
PIN Syndrome

Anatomy/path: What muscles are spared?

Hx of PIN syndrome? Common causes?
-Name of injury associated with it?

PE findings?

A

– 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

55
Q

RADIAL NERVE:
PIN syndrome

Explain the NCS and EMG findings of this injury?

Tx?

A

– 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

56
Q

RADIAL NERVE:
Radial Tunnel Syndrome

Explain the course in anatomy:
Explain common Hx complaints:

A

– 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

57
Q

RADIAL NERVE:
Radial Tunnel Syndrome

Explain Physical Exam findings (most important one?):
Explain EDx findings and Tx:

A

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
58
Q
A

Singh PM&R (3 decks)

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