Hand 1 Flashcards
Order from inner to outer
Myelin
Perineurium
Endoneurium
Fascicles
Epineurium
Axon
Axon
Myelin
Endoneurium around individual axons
Fascicle = group of axons
Perineurium around fascicle
Epineurium around group of fascicles
What cells make myelin
Schwann cells
What is the intrinsic vs extrinsic BS to nerves
Intrinsic: plexus within loose connective tissue / epineurium
Extrinsic : vasa nervosum
How do APs move between areas of myelin? What are these areas called?
Nodes of Ranvier
Saltatory conduction here
How care for the following nerve injuries:
Laceration
Open wound w/ nerve rupture
Closed injuries
Laceration = fix ASAP to avoid fibrosis/retraction
Open wound w/ nerve rupture = allow demarcation (2-3wks) so you can resect all dead tissue for a healthy wound bed at time of repair
Closed injuries = watch 3-6mo recovery
Define following terms and recovery time
Neurapraxia
Axonotmesis
Neurotmesis
Neurapraxia - axonal level nerve block
Conduction block, architecture preserved
<3mo
Axonotmesis - discontinuity of axons
Surrounding nerve tube acts as a guide to allow nerve to grow in the right direction
1mm/day
Neurotmesis - complete disruption of entire nerve
Requires surgical intervention
What are the EMG findings for the following
Neurapraxia
Axonotmesis
Neurotmesis
Neurapraxia
- Normal insertional activity
- No spont activity
Axonotmesis and neurotmesis hard to differentiate on EMG
- Increased insertional activity
- Fib/positive sharp waves spont activity
What are the best options for nerve repair in the given circumstances:
No tension
<2-3cm gap in sensory nerve
<5cm defect
>5cm defect
No tension - direct repair!
= epineurium repair (not fascicle repair bc more scarring)
- Max 10% stretch
<2-3cm gap in sensory nerve - conduit
GRAFT
<5cm defect - allograft but only for sensory n
>5cm defect or any motor involvement - autograft
What are your options for a digital nerve defect?
SENSORY only!!!
Primary repair
<3cm = conduit
>3cm = allograft of autograft
Autograft of choice is MABC > LABC
What is the double Oberlin transfer? What is it done for?
Gain elbow flexion (feeding goal)
Ulnar n from FCU
Median n from FDS/FCR
To motor br biceps/brachialis
What does EMG vs NCS measure?
EMG: electrical activity of muscle w/ voluntary contraction
NCS: nerve conduction velocity, latency, amplitude
NCS
- What happens w/ axonal loss
- What happens w/ demyelination
Axonal loss: drop amplitude
- Still conducting, just not as strong
Demyelination: drop velocity -> increase latency
What is most common cause of CTS
Edema / vascular sclerosis
Reduced epineurial blood flow
Splinting keeps pressure at neutral to keep blood flow constant
In theory a CSI should work for CTS bc not inflammatory
What are the 2 ways to test sensory nerves? Examples of each
Threshold test = measures 1 nerve fiber innervating a receptor. Best for eval nerve after repair
- Static vs moving 2 pt discrimination
Innervation density test = multiple overlapping receptive fields. Best for gradual nerve changes (compressive neuropathy)
- Semmes Weinstein monofilament
- Vibration tests
What are the best provocative tests for CTS
Direct compression > Phalen > Tinel
Semmes Weinstein (density test) > 2 pt discrim (threshold)
Findings on EMG for CTS
Distal motor latencies > 4.5 msec
Sensory latencies > 3.5 msec
Benefit of endoscopic > open CTR
Endoscopic = open long term
Quicker return to work (less incisional/pillar pain early)
Cons: $$, higher risk complication
4 sites of median nerve compression (not CTS)
Ligament of struthers = supracondylar process humerus (get an XR)
Lacertus fibrosis (aka biceps aponeurosis)
Deep head pronator (medial epicondyle/deep volar forearm) - why pronator syndrome often associated with medial epicondylitis
FDS arcade
How do you determine a proximal compressive median neuropathy vs CTS
Proximal compression you’ll have the sensory br median nerve involved (palm numbness)
AIN syndrome
- Sx
- Muscles innervated
- Causes
- Trt
Sx: forearm pain, inability to make O sign index/thumb
Different than other median compressive neuropathy bc motor involvement
- FPL
- FDP index/long
- PQ
Causes:
- Compression by FDS/FCR/PT/FPL
- Parsonage Turner (viral)
- Ddx = tendon rupture (think RA)
Trt: obs obs obs obs
Name the sites of ulnar nerve compression at cubital tunnel
Tunnel itself = osborne’s ligament
Arcade struthers = fascia as nerve passes from ant to post in the arm
Medial triceps
Medial IM septum
FCU
Deep flexor/pronator
Anconeus
What is Wartenberg sign
Lose adductor interosseous of 5th digit
Unopposed EDM (radial n.)
abducted small finger
Ulnar n palsy
What is Froment sign
Weak thumb adduction - compensatory FPL flexion during pinch
Ulnar n palsy
What are the 3 zones of ulnar n compression a Guyons canal + cause
1 = proximal to nerve bifurcation = sens + motor
- Ganglion
2 = motor only
- Hook hamate frx
3 = sensory only
- Ulnar art thrombosis
**Dorsal sensory br comes off proximal to the wrist so would not be involved in a Guyon issue
What is the anatomy of Guyon tunnel
Roof = volar carpal lig
Floor = transverse carpal lig
Radial = hamate
Ulnar = pisiform
What are sites of radial n compression (FLEAS)
Fascial band radial head
Leash of Henry
ECRB
Arcade Froshe (proximal supinator)
Supinator distal
Presentation of PIN syndrome, which patients, trt
Motor deficit
- Extending MP joints, thumb IP
- Wrist extension w/ radial dev (ECU out, ECRL intact)
Think RA w/ boggy capsule off radio-capitellar jt
Trt non op as long as not a space occupying lesion
Sx radial tunnel syndrome
Most likely compression site
Trt
No motor/sens deficit - EMG/NCS normal
Pain syndrome
Arcade of Froshe most common
Think lateral epicondylitis
Nonop
Presentation of radial sens n compression
Cause
Trt
Forearm pain
+Tinel between BR/ECRL tendon
Direct trauma - tight handcuffs/watch
Diagnostic inj - remove offending agent
What is the Adson test for?
Thoracic outlet syndrome
Decrease radial a pulse w/ inhalation bc subclavian compression
Which nerves create the upper middle lower trunks
C5/6 - upper
C7 - middle
C8/T1 - lower
How do the trunks divide to make divisons
top 2 ant divisions combine = lateral cord
Lower ant div continues own own = medial cord
All 3 posterior divisions combine into 1 = posterior cord
What are the 2 branches off C5?
Dorsal scapular
Phrenic
What nerve roots contribute to long thoracic n?
C5/6/7
Where does suprascap nerve come from?
Upper trunk (C5/6)
Name branches off the
Lateral cord (1)
Posterior cord (3)
Medial cord (3)
Lateral cord (1)
- Lateral pec
Posterior cord (3)
- Upper, middle, lower subscap
Medial cord (3)
- Medial pec
- Medial brachal
- MABC
What are the 5 terminal branches and the cranial nerve contributions
MCN - C5/6/7
Ax - C5/6
Rad - C5-T1 (all)
Med - C5-T1 (all)
Ulnar - C7-T1 (low plexus)
What nerve roots indicate Horners syndrome
C8-T1 avulsion
What is the Smith 3-5-7 rule for donor tendon transfer selection
Estimates excursion:
Wrist flexors/extensors 3cm
MCP extensors 5cm
FDP 7cm
What differentiates a radial nerve injury from PIN?
Radial nerve will involve BR and ECRL
What are 3 transfers for radial nerve out
FCR -> EDC
PL -> EPL
PT -> ECRB
What are 2 transfers for median nerve out to regain opposition
PL -> thumb prox phalanx
Think elderly severe CTS
ADM -> thumb prox phalanx
Think congenital absence
Trt subungal hematoma w/ intact nail plate
Nail plate perforation for pain relief
How much nail bed must be intact to prevent a hook nail
At least 50% of distal phalanx must be there as a bony support to the nail bed
Treat finger tip pulp loss up to 1cm
2ary intention
FT skin graft 2nd choice
Treat finger tip volar oblique injury with exposed bone
Adult: cross finger
Kid/younger: moberg (thumb) flap
- Do this in the young bc more likely to overcome any IP contracture
Treat finger tip dorsal oblique or transverse injury w/ exposed bone
V-Y advancement
Treat volar thumb fingertip injury with exposed bone
<2cm = moberg volar thumb advancement
>2cm = FDMA (from dorsal 1st digit)
Treat dorsal thumb fingertip injury with exposed bone
FDMA
What is a complication of shortening and closing fingertip injuries
Lumbrical plus finger
Order the following from which recovers first to last after nerve injury
Motor
Sympathetic
Proprioception
Pain
Temp
Return (lose in the opposite order)
1 sympa
2 pain
3 temp
4 proprioception
5 motor
