Basic Science Conference Nerves & Arteries Orthopaedic Research of Virginia Matthew Byington DO November 27, 2012

Basic Science Basic Science ConferenceConference

Nerves & ArteriesNerves & Arteries

Orthopaedic Research of VirginiaMatthew Byington DONovember 27, 2012

Outline Outline

Peripheral nerves: histology & physiology

Peripheral nerve injury & regeneration

NCV / EMG basics Peripheral compression neuropathies Vascular disorders

Peripheral Nerve Peripheral Nerve HistologyHistology

Neuron:1. Cell Body2. Dendrite3. Axon4. Presynaptic

terminal

Peripheral Nerve Peripheral Nerve HistologyHistology

Schwann Cells (PNS) Surround cell body &

axons Provide support and

nutrition, maintain homeostasis, form myelin, and assist in signal transduction

Make myelin

PhysiologyPhysiology

Electrical and chemical signals

Resting Potential -normal= -50 to -80mV, maintained by

Na+/K+ pump Action Potential -

depolarization beyond threshold transmits signal rapidly

Peripheral Nerve Peripheral Nerve Cross Sectional AnatomyCross Sectional Anatomy

Epineurium Encompasses nerve

and runs between fascicles

VascularPerineurium Layer that covers

individual fascicles Tensile strengthEndoneurium Inner most collagenous

matrix that surrounds axons within fascicles

Nourish & protect axons

Traumatic Nerve InjuryTraumatic Nerve InjuryClassificationClassification

1943: Seddon Neuropraxia Axonotmesis Neurotmesis

1951: Sunderland Type I- V


1st Degree (Neuropraxia) Interruption of conduction at site of injury Axon preserved No wallerian degeneration Motor fibers more susceptible to injury than sensory fibers


1st Degree (Neuropraxia) Large myelinated fibers more

susceptible than fine or nonmyelinated fibers

Electrophysiologic Studies– NCV slowing or complete conduction block– Fibrillation potentials– Positive sharp waves


1st Degree (Neuropraxia) Complete functional recovery after 1st

degree injuries because axonal continuity preserved and changes responsible for the conduction loss are fully reversible

Full restoration of function may take as long as 3 to 4 months after the injury


2nd Degree (Axonotmesis) Axon and myelin sheath disruption …

leads to conduction block with Wallerian degeneration

Endoneurium, perineurium and epineurium intact

Axon regenerates along intact endoneurial tube


2nd Degree (Axonotmesis) Complete loss of motor and sensory

functions Complete functional recovery

expected Time to recovery depends on severity

and level of injury, as axons must regenerate distally

Usually months to recovery


3rd Degree (Axonotmesis) Axons and endoneurial tube disrupted Perineurium and epineurium intact Complete loss of function Onset of recovery delayed longer due to

more severe retrograde injury to cell bodies, fibrosis

With longer delays in recovery, target organs may undergo changes that prevent full recovery


4th Degree (Axonotmesis) Only epineurium left intact Nerve in continuity, but extensive

intraneural scarring and disruption of fascicular structure

Wallerian degeneration Complete loss of sensory and motor

function Minimal useful recovery Usually requires excision of damaged

segment and repair or reconstruction


5th Degree (Neurotmesis) Complete loss of continuity of nerve Varying amounts of scar form between

severed ends, with neuroma formation at proximal stump

Wallerian degeneration of distal stump Spontaneous recovery negligible Requires surgical repair

Causes of Nerve InjuryCauses of Nerve Injury

Compression Stretch Ischemic Traumatic

Causes of Nerve InjuryCauses of Nerve InjuryAcute Compression Immediate onset Mechanical

deformation of nerve fibers responsible for pathologic changes

Chronic Compression Delayed/ gradual

onset Ischemia significant

factor in genesis of injury

Clinical exampleClinical example

Doctor, why is my thigh numb??

Meralgia Parasthetica???


Extent and Severity of Compression Injuries:

Magnitude and rate of applied force

Duration Manner which

applied (localized or over a long segment)

Studies have shown that excessive tourniquet times and pressures can lead to prolonged EMG changes

Recommended: UE no more than

50-100mmHg above systolic

LE no more than 2x systolic

Limit duration <2hrs


Stretch1. Acute

– Abrupt application of force of considerable magnitude

– “Stinger” = acute neuropraxia

2. Chronic– Slow stretching of nerve over

period of time– Usually tolerate significantly

more

Variable degree of injuryCauses: Fracture displacement,

joint dislocation, trauma, etc.

Physiology of Nerve Physiology of Nerve DegenerationDegeneration

Wallerian Degeneration

Breakdown of axon distal to site injury

Begins within hours post injury

Myelin and axons deteriorates

Schwann cells proliferate

Macrophages phagocytize myelin and axonal debris

Physiology of Nerve Physiology of Nerve RegenerationRegeneration

Rate of regeneration varies depending on the type & location

In humans, an average outgrowth of 1-2 mm/day is generally quoted

Proximal budding occurs after 1 month delay

Functional Recovery Functional Recovery after Nerve Injuryafter Nerve Injury

Clinical outcomes variable and related to:

1. AGE – single most important factor2. Level of injury - distance regenerating

axons must go to reach target organs, distal > prox

3. Length of injury zone4. Type of injury – sharp transection > crush5. Timing of nerve repair6. Status of end organ at time of re-

innervation7. Technical expertise of surgeon

Nerve RepairNerve Repair

Primary Repair Preferable: 0-3 weeks Immediate repair technically

easier though emergent repair not necessary– Time limit of repair up to 18 months

Nerve RepairNerve RepairEpineurial Repair Standard Orientation critical 9-0 monofilament

Grouped Fascicular Repair Not clinically better than

epineurial Indications

1. Median nerve in distal forearm 2. Ulnar nerve in distal forearm 3. Sciatic nerve in thigh

Nerve RepairNerve Repair

Tension Encourages gapping

and scar formation Reduces blood flow:

8% elongation = 46% decrease in perfusion

Grafting better than repair in tension (autografts)

Rehabilitation of Rehabilitation of Nerve InjuriesNerve Injuries

During re-innervation continued motor and sensory rehab critical

Sensory re-education improves results

Assists brain in reinterpreting misdirected axon impulses

EMG / NCV StudiesEMG / NCV Studies

EMG / NCVEMG / NCV

EMG– Determines health of muscle and,

indirectly, the nerve supply– Fibrillations

Spontaneous activity at rest; indicates denervation

– Insertional activity Activity during needle insertion; high is bad

– Motor unit potentials Few, wide, and low amplitude = BAD

EMG / NCVEMG / NCV

NCV– Provides additional info on nerve function– Nerve conduction measured (saltatory

conduction)– >50 meters/second normal in extremities

EMG/NCVWhen get to assess nerve damage?

* as early as 3 weeks; monthly as needed

Nerve Compression Nerve Compression SyndromesSyndromes

Radial Tunnel Radial Tunnel SyndromeSyndromeSymptoms Proximal / lateral arm pain No motor or sensory

dysfunction .. PAIN only No PIN dysfunction Normal EMG/NCS Provocative test: resisted

long finger extension Tenderness over radial

neck or supinator Recurrent or unresponsive

lateral epicondylitis– Coexists in 5%

Radial Tunnel Radial Tunnel SyndromeSyndrome

Causes of Compression:

Recurrent radial vessels (leash of Henry)

ECRB leading edge Arcade of Frohse Distal Supinator

Treatment: Longer periods of

conservative care 6-12mths (NSAIDS, splinting, work modifications)

Operative release often disappointing

Careful patient selection

Posterior Interosseous Posterior Interosseous Nerve SyndromeNerve Syndrome

Pain at lateral elbow Weakness and radial

deviation with wrist extension (ECRL innervated above PIN)

Motor neuropathy EMG/NCS diagnostic Sites of compression

same as radial tunnel

Posterior Interosseous Posterior Interosseous Nerve SyndromeNerve Syndrome

Treatment Initial conservative

(MRI r/o mass) Decompression: if no

recovery by 3 months or progression

If condition persists >18 months irreversible muscle fibrosis occurs

Pronator SyndromePronator Syndrome

Compression neuropthy of proximal median n.

Sites of Compression: Supracondylar process

(1% of population) Ligament of Struthers Bicipital aponeurosis Deep head of PT ** Accessory head of FPL Origin of FDS


Confused with CTS No Tinels sign at wrist No night symptoms Sensory disturbance

over region of palmar cutaneous branch and anterior proximal forearm

Provacative tests:A. Flexion past 120 deg. - Supracondylar

process or ligament of

StruthersB. Resisted supination with elbow flexion - Bicipital aponeurosisC. Resisted pronation with elbow extended - Pronator headsD. Resisted MF PIP flexion - FDSEMG usually normal, though

may be positive in PQ & FPL


Treatment: Nonoperative

usually successful Decompression

considered if fails to respond after 3-6 months

Requires global decompression (proximal to distal) of all potential areas

Anterior Interosseous Anterior Interosseous Nerve SyndromeNerve Syndrome

Sites of Compression: Pronator teres FDS Arcade Lacertus Fibrosus Enlarged bicipital bursa Accessory FPL (Gantzer’s m.)Diagnosis Motor loss without sensory

involvement Loss of FPL & FDP - Index

produce characteristic finding

EMG/NCS diagnostic R/O Brachial Neuritis if B/L

– Parsonage-Turner Syndrome

Anterior Interosseous Anterior Interosseous Nerve SyndromeNerve Syndrome

Treatment: Observe for 3-6

months Surgical

decompression for failures

Quadrilateral Space Quadrilateral Space SyndromeSyndrome

Compression of Axillary N. and posterior humeral circumflex a

Traumatic and atraumatic causes

Vague shoulder discomfort and pain with fatigue when arm held above shoulder level

Reproduction of sx with FABER position

Paresthesias and Deltoid weakness

Arteriogram (FABER) EMG/NCV may be

positive

Quadrilateral Space Quadrilateral Space SyndromeSyndrome

Treatment: Conservative for

6 months Surgical

decompression if:1. Fails conservative2. Positive

arteriogram

Suprascapular Nerve Suprascapular Nerve EntrapmentEntrapment

Overhead repetitive sports

Suprascapular notch Spinoglenoid notch Trauma, traction,

space occupying lesions, etc.

Predominantly motor nerve


Symptoms: Vague dull, achy

pain posterior and lateral shoulder or asymptomatic

Weakness in ER and Abduction with overhead activity

Atrophy of infraspinatus +/- supraspinatus


Diagnosis: EMG/NCS helpful MRI: space

occupying lesion (ganglion)

Treatment: Conservative 4-6

months (unless space occupying lesion present)

Decompression if failure of nonoperative treatment or progression

Stinger SyndromeStinger Syndrome

Brachial Plexus stretch/ neuropraxia

Unilateral shoulder and/or arm pain with burning dysesthesias and often muscle weakness involving the biceps, deltoid, and spinatus muscles

Symptoms transient with full recovery typical

More severe neuro injury can occur

Majority go unreported


3 Mechanisms:1. Brachial plexus

stretch (traction injuries)

2. A direct blow to the plexus

3. Nerve root compression in the neural foramen (extension-compression)


Treatment Symptomatic usually May return to play if

PE normal Remove from game

if any radiating arm pain and neurologic deficit or loss of cervical range of motion

Thoracic outlet Thoracic outlet syndromesyndrome Relatively common Compression of lower trunk/medial cord of

brachial plexus and vascular structures Sites of compression

– Ant/medial scalene muscles– Cervical or first rib– Clavicle malunion or Pec minor– Subclavian artery disease

Presents with pain and parasthesias (usually ulnar) with overhead activity– Complaints usually neurological

Thoracic outlet Thoracic outlet syndromesyndrome Symptoms

– Presents with pain and parasthesias (usually ulnar) with overhead activity

– Complaints usually neurological Physical Exam

– Wright Test Abduction / ER with neck rotated away leads to

loss of pulse and reproduction of symptoms– Adson Test

Extension of arm with neck extended towards side

– Roos Hands open/close repeatedly while held overhed

Thoracic outlet Thoracic outlet syndromesyndrome Difficult to diagnose

– NCV/EMG invariably normal– Diagnosis dependent on history and

various non-specific provocative tests Rx:

– Usually conservative; PT, stretching, postural training, mobilization, and strengthening of shoulder girdle

– Surgical: only in recalcitrant cases Surgeon experience key

Effort ThrombosisEffort Thrombosis

Rare Has been described in baseball,

swimming, wrestling, and backpacking Sx: tiredness, heaviness, possible

swelling with activities (may last for few days)

Work-up consisits of venography or CT/MR venograms– May show thrombois of subclavian at level

of first ribTreatment: Vascular procedures

(thrombolysis) and/or first rib resection

Popliteal ArteryPopliteal ArteryEntrapment SyndromeEntrapment Syndrome Less common diagnosis on differential of leg

pain in athletes/runners– Sx: pain, fatigue, cramping, paresthesias, swelling,

coldness Causes

– Variation in artery course– Hypertrophy or fibrous bands of medial gastroc

Symptoms– Calf cramping following light exercise which improves

with vigorous exercise– Tingling sensation in toes after vigorous exercise

Physical Exam– Diminished pulses with knee hyperextension and ankle

plantarflexion

Popliteal ArteryPopliteal ArteryEntrapment SyndromeEntrapment Syndrome Ranges from intermittent claudication to

possible life threatening limb ischemia Intermittent occlusion from plantar flexion

motion– May note change in pulse with PF

Arteriogram/MRA Rx: (depends on vessel)

– No vessel injury: release (usually medial head gastroc)– Vessel injury: vascular surgical managment

Questions ??Questions ??

Documents

Basic Science Conference Nerves & Arteries Orthopaedic Research of Virginia Matthew Byington DO November 27, 2012