peripheral nerve injuries

Peripheral Nerve Injuries

Chye Yew Ng MBChB(Hons) FRCS(Tr&Orth) British Diploma in Hand Surgery

European Board of Hand Surgery Diploma

Consultant Hand & Orthopaedic SurgeonFellowship Director, Upper Limb Fellowship

Wrightington Hospital

www.wrightington.com

Overview

Basic science

Classification of nerve injuries

Principles of nerve surgery

What (I think) you may be asked


Please draw the cross section of a nerve

Axon

Fascicle

Nerve

Endoneurium

Epineurium

Perineurium

EpiPEn = Epi – Peri – Endo

A&E

Extrinsic & Intrinsic vascular supplyLongitudinal – Segmental -

Interconnected


Degeneration & Regeneration

Lee & Wolfe. Peripheral nerve injury & repair. JAAOS 2000


Central Neuronal Death & Neuroprotection

Neuronal death after peripheral nerve injury

Acetyl-L-carnitineArrests sensory neuronal deathSpeeds up regeneration

N-acetyl-cysteineProvides sensory and motor neuronal protection

Hart et al. Neurological Research 2008


Nerve Injury & Recovery

Motor

Proprioception

Touch

Temperature

Pain

Sympathetic

Recovery

Inju

ry



Mechanoreceptors Characteristics

Meissner’s corpuscles•Rapidly adapting•Sensitive to light touch

Merkel’s discs

•Slowly adapting•Pressure, texture •Low frequency vibration•Static 2PD

Pacinian corpuscles

•Rapidly adapting•High frequency vibration•Rapid indentations of skin•Ovoid, 1mm in length

Ruffini terminals•Slowly adapting•Skin stretch

Sub

cuta

neous

Cuta

neous


Slowly Adapting Rapidly Adapting

Low frequenc

y vibration

Merkel Meissner

High frequenc

y vibration

Ruffini Pacinian


Mechanisms of Injuries

Crush / compression

Stretch / traction

Laceration /

transection

Metabolic disturbance

Ischaemia

Radiation

Electrical injury

Thermal injury


Classification of Nerve Injuries

Seddon

BMJ1942

Neurapraxia(Transient Block)

Axonotmesis(Lesion in

Continuity)

Neurotmesis(Division of a

nerve)

Brain1943

• Localised degeneration of the myelin sheaths

• Complete interruption of axons

• Preservation of supporting structures (Schwann tubes, endoneurium, perineurium)

• All essential parts destroyed

• Interruption can occur without apparent loss of continuity



Neurapraxia Axonotmesis Neurotmesis

Motor - - -Sensory +/- - -Autonom

ic +/- - -NCS

Conduction block at the site

Distal conduction preserved

Loss of conduction both at and distal to the lesion

Loss of conduction both at and distal to the lesion

EMG No fibrillation Fibrillation ++ Fibrillation ++

Recovery

Days to weeks provided the cause is removed

Months provided the cause is removed

No recovery unless repaired



Sunderland

1951I II III IV V

Focalconduction

block

NO Wallerian

degeneration

AxonalDisruption

Axon+

Endoneurium

Disruption

Axon +

Endoneurium+

Perineurium

Disruption

Axon +

Endoneurium+

Perineurium+

EpineuriumDisruption

Cross-innervation


Sunderland’s Classification

Grabb & Smith’s Plastic Surgery 6th edition. Chapter 9


Physiological Conduction Block

Type AIntraneural circulatory arrestMetabolic block with no nerve fibre pathologyImmediately reversible

Type BIntraneural oedemaIncreased endoneurial fluid pressureReversible within days or weeks



Lundborg

1988

Physiological

conduction block

Myelindamage

Axonal damage

Axon +

Endodamage

Axon +

Endo +

Peridamage

Axon +

Endoneurium+

Perineurium+

Epineurium

damage

Type A

Type B

Sunder

land1951

I II III IV V

Seddon

1942


Axonotmesis

(Lesion in Continuity

)

Neurotmesis(Division of a nerve)



Lundborg

1988

Physiological

conduction block

Myelindamage

Axonal disruptio

n

Axon +

Endo

Axon +

Endo +

Peri

Axon +

Endoneurium+

Perineurium+

Epineurium

Type A

Type B

Sunder

land1951

I II III IV V

Seddon

1942


Axonotmesis


)


Non-degenerative

Degenerative



Lundborg

1988

Physiological

conduction block

Myelindamage

Axonal disruptio

n

Axon +

Endo

Axon +

Endo +

Peri

Axon +

Endoneurium+

Perineurium+

Epineurium

Type A

Type B

Sunder

land1951

I II III IV V

Seddon

1942


Axonotmesis


)



Sunderland ‘VI’

Grabb & Smith’s Plastic Surgery 6th edition. Chapter 9


Nerve in Danger!

Pain, Pain, Pain• Burning• Severe

Autonomic dysfunction• Absence of sweating• Smoothness & dryness of skin

Tinel’s sign• Distal to Proximal• Regenerating touch fibres


In clinical practice, how do you distinguish?

Axonotmesis versus Neurotmesis

Nature of injury

Serial observations

Exploration

Seddon BMJ 1942

(Imaging)


George Bonney 1986


Nerve Surgery

Neurolysis

Nerve repair

Nerve grafting

Nerve transfer


Neurolysis

ExternalInternal


Nerve repair


Prerequisites for Nerve Repair

Skeletal stability

Healthy tissue bed

Healthy nerve ends

No undue tension

Adequate soft tissue coverage


Epineurial versus Group Fascicular Repairs

EpineurialLess exactSimple

Group FascicularBetter alignmentMore dissection (scarring)

The functional results of group fascicular repair has not been shown to be more superior than that of epineurial repair.



Which of the following is false regarding fibrin glue?

a) Fibrin glue is nontoxic and does not block axon regeneration

b) It may be used in combination with suture repair

c) The outcome of fibrin glue repair is inferior to that of suture repair

d) The common components of fibrin sealants include fibrinogen, thrombin and calcium chloride e) It has low tensile strength

Tse & Ko. Nerve glue for upper extremity reconstruction. Hand Clinics 2012


Prognostic Factors of Outcomes

•AgePatient factor

• Level of injury (distal vs proximal)

• Type of nerve (pure vs mixed functions)

• Condition of nerve ends

Injury factors

• Delay to repair• Length of gap

Surgical factors


Nerve Grafts/Conduits

Autologous SourceNerve autograftVein (+/- muscle)

Off-the-shelfType I collagenCaprolactonePolyglycolic acid (PGA)

Processed nerve allograft

Lin et al. Nerve Allografts & Conduits in Peripheral Nerve Repair. Hand Clinics 2013Kaushik & Hammert. Options for Digital Nerve Gap. JHSAm 2015


A 35 year-old male presented with numbness along the radial border of his right index finger 9 months after he sustained a cut in his first web. After surgical exploration and debridement, there is a 3.5cm nerve defect in the radial digital nerve.

What is the most appropriate surgical reconstructive option?

a) Flexion of digit to achieve primary repair before gradual distraction

b) Type I collagen nerve conduit

c) Autologous vein graft

d) Posterior interosseous nerve graft

e) Polyglycolic acid (PGA) conduit


Principles of Motor Nerve Transfers

Donor nerve near target motor end platesExpendable donor nervePure motor donor nerveDonor-recipient size matchDonor function synergy with recipient functionMotor re-education improves function

Mackinnon SE, Novak CB. Hand Clin 1999


Thank you!

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@CY_Hand

peripheral nerve injuries

Health & Medicine

nerve brain

peripheral nerve injury

peripheral nerve injury

adapting skin

lesion loss of conduction

adapting pressure

adapting sensitive

site distal conduction