This document discusses the history and techniques of peripheral nerve repair. It notes that peripheral nerves have the ability to regenerate after injury, unlike the central nervous system. The key points covered include: - The timeline of discoveries and advances in peripheral nerve repair from the 17th century to present day. - The anatomy of peripheral nerves and the different layers (epineurium, perineurium, endoneurium) - Grading systems for peripheral nerve injuries. - Pre-operative evaluation techniques like nerve conduction studies and EMG. - Surgical techniques for different types of injuries like transection, avulsion or neuroma in continuity. - Microsurgical techniques like

1. From – DR Parth Jani
Senior resident, Neurosurgery,
PGIMER.

2.  Axons of the peripheral nervous system have the potential
for regeneration, after they are severed.
 The CNS environment doesn’t support regeneration, infact
actively inhibits it.
 So, anatomically disconnected peripheral axons have the
chances of reinnervating their target end organs.

3. First traumatic
median nerve
repair
Laugier (1864)
First
successfu
l human
nerve
suture
following
excision of
painful
median
nerve
neuroma
Nelaton (24th
April 1863)
First
successfu
l nerve
repair in
fowl.
Flourens (1828)
Demonst
rated
ability of
peripher
al nerves
to
regenera
te
Results
not
believed
by
editors.
Cruikshank
(1776)
Antony
van
Leeuwen
hoeck
(1675)
•Describ
ed
structu
re of
real
nerve
tracts
Antony van
Leeuwenhoeck
(1675)
“The
paralysis
which
proceeds
from a
severed
or
exceedin
gly
bruised
nerve
cannot be
cured,
because
the path
of the
animal
spirit is
cut”
Ambroise Pare’
(1575 AD)
Nerve
repair
thought
to be
impossi
ble
Claudio Galen
(130-201 AD)

4. MESONEURIUM
EPINEURIUM
PERINEURIUM
ENDONEURIUM
NERVE FIBRE
AXON

6.  Condensation of a loose areolar connective tissue that surrounds a
peripheral nerve and binds its fascicles into a common bundle.
 Interfascicular or inner epineurium -extends between the fascicles.
 Epifascicular or external epineurium - surrounds the entire nerve
trunk, comprises 30%–75% of the nerve cross-sectional area but varies
along the nerve.
 Arrangement of facicles-
MEDIAN NERVE IN
DISTAL FOREARM- 3
consistent fascicular groups
1. Anterior fascicle-PT &
FCU.
2. Medial fascicle-HAND
INTRINSICS AND FDS
3. Posterior fascicle-AIN
br & PL.
‘GROUPED FASCICULAR
REPAIR POSSIBLE”

7.  Surrounds individual fascicles- smallest structural component amenable to
suturing.
 Strongest tensile strength-less tolerant to elongation than the epineurium.
 Blood nerve barrier- formed by perineurium- alternating layers of flattened
polygonal cells-which interdigitate along extensive tight junctions. Each layer of
cells, enclosed by basal lamina
 Innermost layer which surrounds indivisual
nerve fibres or subdivide nerve fascicles.
 Endoneurial fluid pressure is slightly higher
than that of the surrounding epineurium-this
pressure gradient minimizes endoneurial
contamination by toxic substances external to the
nerve bundle.
In dissection- Endoneurium appears
as gelatinous material that bulges
out of the sectioned ends of nerve
fascicles.
This is indication that surgeon has
reached a sufficiently healthy level
of section of stump during repair.

8. “coiled blood supply from segmental
blood vessels protect compromise in
supply during gliding’
 In endoneurium- only capillaries
present.
 Anastomosing vessels between
epineurium and endoneurium
pass obliquely through
perineurium in a VALVE LIKE
mechanism
Increased endoneural pressure
due to
contusions/traction/avulsion
lead to longer segment
ischemia than anticipated.

9. • Neurapraxia- is a reduction
or complete block of
conduction across a
segment of a nerve with
anatomical continuity
preserved eg torniquet
palsy.
• Axonotmesis- result of
damage to the axons with
preservation of the neural
connective tissue sheath
(endoneurium), epineurium,
Schwann cell tubes, and
other supporting structures
• Neurotmesis- axon, myelin,
and connective tissue
components are damaged
and disrupted or
transected.
Conduction block
+/- myelin injury
Gr1 + axonal
disruption
Gr 2
+endoneurial
disruption
Gr3+perineural
disruption
Gr4+ epineural
disruption
Grade 6 sunderland injury- mixed injury

10. Nerve
injury
High
energy
Low
energy
Complex
injury
Transection Avulsion Contusion
Stretch
-
•Entrapment
-
•Compartment
-
•Injection
Neuroma in continuity
Blun
t
shar
p
Pre-
ganglio
nic
Electrical
Chemical
Thermal
Radiation

11. SHARP TRANSECTION-
 30% following soft tissue lacerations.
 Sharply transected nerve is classified neurotmetic-sunderlands grade 5.
 Partial transection- non transected fibres may be having gr 2,3,4 injury.
 Epineurium is cleanly cut, there is minimal contusive injury or hemorrhage leading to
LESS SCARRING.
BLUNT TRANSECTION- ragged tear of epineurium acutely, irregular longitudinal
segment of nerve injured.
 Retraction and proliferation leads to more severe scars around the stumps, may form
neuromas in continuity.

12. Contusive injuries leave nerve in continuity but damage the
vasculature.
LIC can be either focal, diffuse or multifocal.
Clinical and electrophysiological clues guide the
completeness of injury. Perineurium endows tensile strength, however
“8% stretch leads to disturbance in intraneural circulation and blood nerve barrier
function. And 20% stretch if applied acutely can lead to structural failure.”
 Stretch forces may leave nerve lesions(neuroma)in continuity with epineurium
intact and grade 4>3>2 lesions from within.

13.  Common mode of injury for brachial plexus injury.
 Extremes of movement at the shoulder joint, with or without
actual dislocation or fracture.
 Spinal nerves and roots-avulsed from spinal cord or more
laterally from truncal or more distal outflows.
 combination of neurapraxia, axonotmesis, and neurotmesis
may coexist.
 unfortunately, these mixed grades of injuries have
significant neurotmetic components.

14. Anatomical factors-
• Spinal nerves run in the gutters of the foramina
in the cervical vertebrae.
• AT THIS INTRAFORAMINAL LEVEL-nerves are
tethered by mesoneurium-like connections to the
gutters.
A &B-bony “chutes” of the lower trunk spinal nerves
are abbreviated in comparison
with those transmitting the upper trunk spinal
nerves, and the lower trunk spinal nerves
traversing these bony “chutes” are less bound to the
bone by connective tissue (A and B).
C &D-C8 and T1 nerves are prone to preganglionic
injury (C), whereas the spinal nerves (C5 and C6)
contributing to the upper trunk are prone to
postganglionic injury

15.  Clinical-SUBJECTIVE
1. Motor-specific MYOTOMES
EXAMINED.
Test range of motion, functionality,
and strength in the muscles
supplied by the nerve
2. Sensory- map areas of
altered/absent sensations.
 Moving touch-tests meissner and
paccinian corpuscles-radr
 PRESSURE- tests slowly
adapting merkel cells.
 Two point discrimination- tests
innervation density
 Vibration-paccinian corpuscles-
radr

16. 1. NERVE CONDUCTION STUDIES
2. ELECTROMYOGRAPHY
3. Additional studies:
 Late responses: F wave , H wave
 Repetitive stimulation studies
 Single-fiber EMG.
NERVE CONDUCTION STUDIES
 MOTOR NERVES- the nerve is stimulated supramaximal at two
points (or more) along its course, and a recording is made of the
electrical response of one of the muscles that it
innervates.(compound muscle action potential-CMAP)
 SENSORY NERVES-stimulating supramaximally the nerve
fibers at one point and recording the nerve action potentials from
them at another. (SNAP)

17. Amplitude(milli/microvolts): height of evoked
response on supramaximal stimulation-
proportional to number of axons conducting
impulses. Direct relationship to clinical
symptoms-weakness/sensory loss.
Duration(milliseconds): time interval during
which evoked response occurs, reflects the
conduction rate of impulses-expressed in
inversely linked to amplitude
Latency: interval between the moment of nerve
stimulation and onset of CMAP or SNAP
Conduction velocity: measures the speed of the
fastest conducting fibres
SNAP- number of functioning large myelinated
axons present
CMAP amplitude- number and density of
innervated muscle fibers, not the number of
axons innervating them

18. Insertional activity: electrical
activity present as the electrode
is passed through muscle cells
Spontaneous activity:
electrical activity present when
the muscle is at rest and the
electrode is not being moved
Motor unit action potential
(MUAP) shape and amplitude
Motor unit recruitment (MUR)
patterns

19.  Electrodiagnostic methods-cannot reveal a specific location for MAS.
Mrn-neuroma located precisely on image- amenable to mas.
 Intraoperative use of nerve action potentials SOLVES THE DILLEMA in
areas of severe nerve injury- while confrontation of NEUROMA IN
CONTINUITY.
 But 2 issues-
1.optimum length to be tested-10cm
2.imaging-surgical nerve action potential discordance.
 Delay in Approach after Blunt Trauma-distal muscle degeneration and
atrophy
After 6 months, muscles show develop fatty degeneration-unreceptive to
returning regrowing nerve fibers.

20. Axial T2 Spectral Adiabatic
Inversion Recovery (SPAIR) image
through cubital tunnel.
Larger arrows- muscle strains of
PT,flexors.
Smaller arrows- mild t2
hyperintensity-
NEUROPRAXIA/SUNDERLAND
GRADE 1
A. shows moderate diffuse enlargement of the right brachial
plexus with abnormal hyperintensity and no neuroma or
discontinuity.
B. Sagittal STIR-mild diffuse enlargement of median (small
arrow),ulnar (medium arrow), and radial (large arrow) nerves
Double arrows-edema-like signal of the infraspinatus muscle.
Moderate stretch injury/Sunderland grade II/III injury

21. 3D DW-PSIF (three-
dimensional diffusion-
weighted reversed
fast
imaging with steady
state free precession.
A. fusiform
enlargement
(small arrows) of the
median nerve (large
arrows).
B. enlarged
heterogeneous median
nerve in keeping with
multifocal fascicular
disruption and internal
fibrosis (arrow).
C. confirmed
Sunderland grade IV
injury with a
neuroma-in-continuity.
NEUROMA IN CONTINUITY
(SUNDERLAND GRADE 4)

22. complete discontinuity of
the right brachial plexus
(large
arrow) with bundling of the
lacerated nerve roots and
trunks (medium
arrow) in the right axilla
Intraoperative
electrophysiology confirmed
lack of conduction in the
enlarged right C5 nerve
root (double small
arrows), lacerated distally.
SUNDERLAND GRADE
5/NEUROTMESIS

23. Wound care first nerve care after that!
‘You cannot expect the nerve to heal primarily when the
wound over it does not heal in that fashion’
- George Omer
Quantitative assessment of motor and sensory systems pre-
operatively and post-operatively
Timing
 Primary (<3 Days) Delayed Primary (>3 Days < 3weeks)
Secondary (> 3 week)
Proper microsurgical technique
Early post-op mobilization
Post-op physiotherapy

24.  Transection/laceration
 Sharply transected nerve(30%)- microsurgical repair within 72
hours if no gross wound contamination and patients are stable
for surgery.
 Partial transection(70% have partial connectivity/20% may
show a neuroma with lesion in continuity)-
Microsurgical repair is always required.
But, Urgent repair is not required- delayed primary repair
after 2-3 weeks.
 Blunt transection/contused nerve +/- ragged epineurium- tack
the nerve ends to adjacent planes f/b secondary repair after 3
weeks.

25.  “Neuroma in continuity” ( contusions,stretch,compression,ischaemic,injection,iatrogenic)-
Should be evaluated first with clinical, electrodiagnostic studies and preop MRI.
 In case of no evidence of regeneration/recovery by atleast 4-6 weeks.
 If focal lesion- ‘likely to regenerate’- followup for 3 months.
 If lengthy lesion- ‘less likely to regenerate’- follow up for 4-5 months
Check for regeneration by NAP recording or directly explore.
NAP(REGENERATIVE)- NEUROLYSIS/IF PREGANGLIONIC-
NERVE TRANSFER.
NAP(NON REGENERATIVE)- RESECTION AND NERVE REPAIR
directly.

28.  General anesthesia with SHORT ACTING MUSCLE RELAXANT.
 Potential graft donor sites should be draped.
 Intraoperative nerve conduction studies- “NEUROMA IN CONTINUITY”
No conduction- resection and nerve repair
Conduction across neuroma- INTERNAL NEUROLYSIS.
“brachial plexus injuries in infants- resection of neuroma is
preferred despite conduction due to relative benefit of resection vs neurolysis”
 Nerve repair is done after repair of other tissues.
 Hemostasis (bleeding from epineural vessels) –
1. BIPOLAR DIATHERMY- CURRENT CONTROLLED –LOW HEAT SYSTEM(eg-
codman malis system)
2. Microsuture-monofilament nylon10-0/9-0.
3. Collagen sealents.
Epineurectomy
with removal of
interfascicular
scar tissue.

29.  Most commonly used method.
 Sine qua non for successful
regeneration is to perform
debridement of both the ends, resect
the scar tissue till endoneurium
bulges out.
 UNIFORM COAPTATION-
o trim perpendicular to the long axis
of nerve,
o appropriate orientation of the nerve.
o Inspect the longitudinal blood vessel
on the epineurium.
o Fascicular topography from
proximal and distal ends to be
understood.

30.  Technique-
 Two initial sutures placed 180degrees
apart as stay slightly away from edge.
 Two 180 degree apart sutures from edge.
 At the anterior side 3rd suture to bisect the
two stays , f/b two more anteriorly.
 Repeat same steps on posterior sides after
turning over.
 “moderate tension”- more traction l/t
axonal malalignment,
 Total:4-10 sutures in all.
 more suture-more scarring.
 Suture less Techniques
 Fibrin Glue
 Laser –Carbon dioxide,and argon
(Problems of tensile strength and excessive
thermal effects)

31. Term epineural sleeve is
introduced because after
distal nerve stump
dissection, the
epineurium is pulled as
a sleeve over the
proximal nerve end,
covering the coaptation
site

32.  More specific nerve repair technique
 Nerve topography must be well understood.
 Individual injured fascicles from the proximal stump
are connected to specifically selected fascicles from the
distal stump
 Tension-free coaptation must- 1-2 perineurial sutures
per fascicle.
 Epineurium of both stumps is incised longitudinally
up to 5 mm
 Fascicles are then dissected free from the main nerve
trunk, with
 Do not to cut any interfascicular communications
 Avoid internal endoneurial contents in sutures.
 Maximum 5 fascicles –o/w TOO MUCH
SUTURE,TRAUMA TO FASCICLES AND
SCARRING.

33. “no persuasive clinical trial proves its superiority to epineurial suture. In terms of practicality, too much
manipulation and extra stitches left within the nerve have the potential of producing a greater amount of
scar tissue, and those unfavorable factors may counteract the advantage of fascicular repair”
Indications-
1. Median nerve at the wrist-fascicular repair on the motor component(of thenar
musculature) + epineurial repair of rest nerve.
2. Oberlin operation, one fascicle of ulnar nerve is transferred to the biceps
branch of the musculocutaneous nerve for reconstruction of elbow flexion in
C5-C6 avulsion of the brachial plexus.
3. Donor nerve is much finer than the recipient nerve; eg-in intercostal nerve
transfer-two to four intercostal nerves are coapted to a larger main fascicle of
the musculocutaneous nerve at the level of the axilla.

34.  a group of fascicles is used as a
suturing unit.
 Coaptation-between internal
epineurium or of perineurium.
 Uncommonly indicated.
 Indications-
1. Median nerve (distal half of the arm)
-three fascicular groups defined.
2. Nerve injury in which continuity of
only a subset of fascicles is
maintained.
- In this INTERNAL NEUROLYSIS
PLUS GROUPED FASCICLE REPAIR
can be planned.

35.  coaptation of the distal end of
an injured nerve to the side of
a normal nerve acting as the
donor.
 Side of the donor nerve can
be- incised through
epineurium/perineurium/not
incised at all/cutting a
fraction of axons.
 2 indications-
1. proximal stump is not
salvageable
2. long-length nerve defect- as
alternative to nerve
grafting.

36.  Gold standard for long nerve gaps(>2.5cm).
 Technique same-just 2 repair sites.
 After debridement of scar and neuroma, healthy
fascicular tissue identified at prox and distal
ends.
 In severely scarred wounds, scarring zone is left
in situ.nerve identified proximal and distal to
lesion.
 Must be Absolutely no tension on suture lines.
 Graft length- 15-25% more than the deficit
length.
 MAX LENGTH-8-10CM, more than that-
 unfavourable for motor recovery.
CABLE GRAFTING
INTERFASCICULAR
NERVE GRAFTING
“Millesi advocated primary nerve repair for defects
upto 2.5 cm,nerve grafting of defects >6cm”

37. Nerve type No. of nerve strands
Sciatic nerve 10-12
Tibial/
peroneal
7-8
Radial 6-7
Ulnar/
Median
5-6
Axillary/MC 3-4
digital nerves,
the spinal
accessory nerve,
or the
suprascapular
Single strands
INTERFASCICULAR
GRAFTING -epineurium of
the graft is sutured to the
interfascicular epineurium
or perineurium of the
fascicular group

38.  Preferred sites-
1. Sural nerve- most common
2. The medial antebrachial
cutaneous nerve
3. Lateral antebrachial
cutaneous nerve.
4. The superficial sensory branch
of the radial nerve.
 From the popliteal fossa to the
level of the ankle, about 30 to
 50 cm of this nerve can be
obtained
• Limited
donor site
morbidity
• Superficial
location
• Limited
functional
morbidities
.

39.  Nerve grafts with identifiable vascular pedicles.
 Advocated for extreme grafting situations like ,
1. Poorly vascularized bed
2. Massive skin defects
3. Extensive gaps->8-10cm
 Donor sites- sural and ulnar nerves.
 Nerve regrowth in excess of 1.5 mm/ day

40.  Disadvantages of nerve grafts- limited
sources of cutaneous nerves, painful
neuroma.
 Synthetic tubes made of bioabsorbable
material have the theoretical advantage
of providing a chamber in which
neurotrophic and neurotropic factors are
accumulated from migrating schwann
cells and from both nerve stumps.
 3 main types available-
1. Collagen conduits containing type I or
type IV collagen.
2. Polyglycolic acid conduits.
3. Caprolactone conduits.

41.  Early mobilisation indicated
 Neurolysis:2-3 days of immobilisation
 Nerve repair or transfer:2-3 wks of immobilisation followed by
active,active assisted and passive range of motion
 Electromyography at 3-6 months intervals
 Massage the scar, follow with tinel sign
 Prevent joint contractures
 Prevent muscle wasting
“We just have to keep the house in order till the master arrives.”

42.  Refrences-
1. Youmans & Winn Neurological Surgery 7th ed.-2017
2. Mathes Plastic Surgery
3. Grabb and Smiths Plastic Surgery.