El documento detalla la anatomía, patología, características y tratamiento de las lesiones de nervios periféricos, describiendo la estructura del sistema nervioso y los tipos de lesiones que pueden ocurrir. Se analizan los mecanismos de degeneración y regeneración nerviosa, así como los métodos de diagnóstico y las opciones de tratamiento, incluida la cirugía. Se enfatiza la importancia de la intervención temprana y la alineación adecuada de los fascículos nerviosos para una recuperación efectiva.

1. Peripheral nerve injury:
pathology, features, and treatment
Dr. Kolang (G. surgeon)
surgery dept,
JUNE.2024

2. Outline
• Anatomy, histology overview
• Pathology: degeneration and regeneration
• Classification of nerve injury
• Clinical feature and diagnosis
• Treatment of peripheral nerve injury

3. 3
Organization
 The nervous system is divided into two parts
 The central nervous system (CNS)
• Brain and spinal cord
• Integrative and control centers
 The peripheral nervous system (PNS)
• Spinal and cranial nerves
• Communication lines between the CNS and the
rest of the body

4. Peripheral nerves – 31 pairs
• 8 cervical: C1-C7 exit above
named vertebra. C8 between C7
and T1
• 12 thoracic: exit below named
vertebra
• 5 lumbar: exit below named
vertebra
• 5 sacral: S1-S4 exit as anterior
division and posterior division,
through anterior and posterior
foramina respectively
• 1 coccygeal: S5 and Co1 exit
through sacral hiatus

5. Spinal nerve
• spinal nerve is formed by union
of dorsal root (sensory axons) ,
and ventral root (motor axons)
at intervertebral foramina
• Spinal nerve: two way road
(both efferent and afferent
pathways)
• Dorsal root: one way in, and cell
bodies located at dorsal root
ganglion (cluster of nerve cell
bodies)
• Ventral root: one way out, and
cell bodies located within grey
matter of spinal cord

6. Spinal nerve
• Spinal nerve then branches
into dorsal ramus and ventral
ramus
• Dorsal ramus, smaller, courses
backwards to supply paraspinal
muscles, and posterior skin of
trunk, neck, and head
• Ventral ramus, larger, exits
laterally, and either enters a
plexus, or becomes an
intercostal nerve

7. Spinal nerves
• C1 - C4 anterior rami =
cervical plexus
• C5 – T1 = brachial plexus (T1
intercostal gives fibers to
brachial plexus)
• T1 - T11 = intercostal nerves
(12th
in abdomen as
subcostal)
• L1-L3 + ½ of L4 = lumbar
plexus
• ½ of L4 – S3 = lumbosacral
plexus

8. Dermatomes
• Dermatome: area of
skin innervated by fibers
of single spinal root
• The pattern is preserved
in thoracic region
• In limbs, the
dermatomes are
displaced due to
migration of limb buds

9. Anatomy of nerve
• An axon is either
myelinated or
unmyelinated
• Unmyelinated are
wrapped by single
schwann cell
• In myelinated, the
schwann cell by rotation
forms multilayered
structure that encloses a
myelin sheath around a
single axon

10. Anatomy of nerve
• Internode: segment of
myelinated fiber
enclosed by single
schwann cell
• From one schwann
cell to the other is an
area sparse in myelin
called node of ranvier

11. Anatomy of nerve
• Epineurium: surrounds
fascicles – protection and
nutrition
• Perineurium surrounds
each fascicle – tensile
strength, and tight
junctions
• Endoneurium: surrounds
axons – protection and
nutrition. Clusters of it form
fascile

12. Blood supply
• Vasa nervorum
• Three arteries
– Major superficial
artery
– Major
intrafascicular
artery
– Minor longitudinal
artery
• Anastomosis

13. 13
INTERNAL TOPOGRAPHY OF
PERIPHERAL NERVES
• Fascicular arrangement of
nerves are complex network
of branching and
intermingling fascicles that
constantly change throughout
the course of the nerve

14. 14
• fascicular arrangement
is complex in the
proximal aspect than
the distal fascicles

15. Etiology
• Metabolic or collagen disease
• Malignancies
• Toxins
• Thermal
• Chemical
• Mechanical trauma

16. 16
• Traumatic injury could be
 Primary injury
 secondary injury
 displaced osseous fragments,
 manipulation
 infection, scar, callus, or vascular
complications( hematoma, arteriovenous
fistula, ischemia, or aneurysm).

17. Pathogenesis
• Low grade injury can cause temporary block of hours to days
• More vigorous injury can demyelinate axons, and cause
conduction block of weeks for myelin to regrow
• Greater degrees of stretch or compression can cause
axonotmetic injury, with axon destruction, which may take
months to years
• Nerve stretch and compression injuries can disrupt vasa
nervorum  ischemia  necrosis

18. Pathology – degeneration & regeneration
• Pathologic events
occur at
–Cell body
–Distal stamp
–Proximal stamp
–End organ

19. Pathology – cell body
• Injuries nearer make
biggest changes
• Swells
• Chromotolysis, nissl
substance disperse
• Nucleus move
eccentrically
• Evident by 7 days
• In 4 – 6 weeks death or
recovery is apparent
• At recovery: edema
subside, nucleus central,
nissle reaccumulate

20. Pathology – proximal stamp
• Primary, traumatic or
retrograde
degeneration
• Usually one node
proximal, but can go
up to cell body
• Regenerating sprouts
noted within 24 hours
• Several day later,
sprouts emerge

21. Pathology – distal stamp
• Wallerian degeneration by
2 – 3 days
• Myelin detoriorates
• Axon disorganize
• Fluid loss  fragment 
shrink
• By 7 days, Phagocytes eat
myelin and axon debris
• 15 – 30 days, no debris left
• Tight junctions disrupt –
proteins act as toxins and
worsen condition (reforms
in 1 week)

22. Pathology – distal stamp
• Schwann cell lamina
persisted
• Bungner band
columns formed to
support sprouts
• Cone sprouts through
the band, helped by
fibronectin
• Releases proteases
to clean route

23. Pathology – distal stamp
• Cone survival/growth
helped by NGFs
• If endoneural tube
intact – previous
course
• Tight junctions in 01
week, complete in 03
• Schwann cells, and
endoneural tubes
degenerate 18 – 24
mo – re-growth
ceases

24. Pathology – muscle
• Paralyzed
• Atrophic changes 2 – 4 weeks (fibrillations)
• 30% loss in 1 month
• 50-70% loss in 2 months
• 60-80% in 4 months – hold on
• Striations and motor endplate
configurations are retained for longer
than 12 months
• Complete fibrosis not complete until 3 years

25. Pathology – sensory
• Only small area of sensory loss
(autonomous zone)
• Can have anesthetic intermediate zone
• 30-40% of small diameter sensory nerves
apoptose
• Sensory receptors degenerate longer

26. Nerve injury classification

27. Sixth-degree (Mackinnon) or mixed injuries
• Nerve trunk is partially severed, and the remaining part of the
trunk sustains fourth-degree, third-degree, second-degree, or
first-degree injury
• Recovery pattern is mixed depending on the degree of injury
to each portion of the nerve.
• Surgical intervention to correct the fourth-degree and fifth-
degree components may sacrifice the function of lesser
injured fascicles
27

29. Diagnosis
• For each nerve, know
– The course of the nerve
– Level of origin of motor branches
– Muscles supplied: grade the power
– Zones of sensation
• Autonomouz zone
• Intermediate zone

30. Diagnosing a nerve injury
• Evaluate nerve injury on arrival of the traumatized
patient, as well as after manipulation, cast, or
operation
• Follow patient clinically, and electrodiagnostically, to
minimize delay in recognizing a nerve deficit that will
not resolve spontaneously.
• On arrival pain usually limits examination
• There are simple tests to conduct to detect injuries of
major nerves of extremities even if patient is in severe
pain

31. Diagnosis
• Loss of pain perception in tip of little finger =
ulnar nerve injury
• Loss of pain perception in tip of index finger =
median nerve injury
• Inability to extend thumb = radial nerve injury
(see if extensors are intact and look muscle
belly)

32. Diagnosis
• Loss of pain perception in sole of foot =
sciatic or tibial nerve
• Inability to extend great toe or foot = peroneal
or sciatic injury
• Look muscle bellies or tendon continuity to
rely on these tests – many movements are
done with trick

33. Diagnosis
• Thumb opposition to little finger can be
done even if OP is cut or paralyzed
• Wrist can be partially extended by finger
flexion
• Elbow can be forcefully flexed by using BR

34. Motor

35. Sensory loss
• Autonomous or
isolated zone
• Intermediate
zone
• Maximal zone

36. Sensation assessment

37. Autonomic
• There is loss of sweating, pilomotor response and vasomotor
paralysis in the autonomic zone
• Wrinkle test: 4c* for 30 minutes(no wrinkling in denervated skin)
• Initially there is vasodilatation, warm, and pink area, later on
pale, cyanotic or mottled beyond maximal zone
• Ulcers form due to trauma, and heal slowly, finger nails
become distorted or entirely lost

38. Sweat test
• Sympathetic fibers are resistant to mechanical trauma
• Sweating within autonomous zone shows the nerve
injury is incomplete
• +20 lens of ophthalmoscope can show sweat beads
• Sweat test, is another means of testing, where
quinizarin powder is poured to the area
– denervated area remains dry and light gray
– and innervated area becomes deep purple

39. Diagnostic tests
• Tinel sign
• Electrodiagnostics
– NCS
– EMG

40. Tinel sign
• Percuss along the course of the injuried nerve with
hammer or finger, from distal to proximal
• Patient feels transient tingling sensation (which
persists for few seconds) at the distribution of the
nerve rather than area percussed
• It’s the regenerating unmyelinated portion of the
nerve that when percussed produces the tingling
sensation

41. Tinel sign
• Grade 1 has no tinel sign, because there is no
degenerated axon that is regenerating
• Grade 2 and 3 have advancing tinel sign (means,
every month 1 inch of proximal portion of the
nerve will have negative tinel sign as it get
myelinated)
• Grade 4 and 5 have no advancing tinel sign, as
there is no axon regeneration

42. NCS/EMG
• If done in 2 weeks, conduction studies can differentiate
neuropraxia from axono/neurotmesis
• In neuropraxia, there is conduction or motor unit
potentials present in 2 weeks, but there is no
conduction or MUPS in the other two
• In 12 weeks, if there are MUPS, it shows grade 2 and
3, and recovery is expected
• If no MUPS in 12 weeks, it shows grade 4 and 5 and
need surgical intervention.

43. 43
EARLY MANAGEMENT OF NERVE
INJURIES
 General Considerations of Treatment
 Life and limb
 Systemic antibiotics and tetanus prophylaxis
 Assess PN injury

44. Management of PNI
• Possible scenarios
–Clean laceration
–Contaminated laceration
–Blast or crushing
• Without a gap
• With a gap

45. Management of PNI
• Primary repair: within 6 to 8 hours
• Delayed primary: within 1 week
• Secondary repair: after 1 week
• These timings are arbitrary

46. Management of PNI
• Primary repair has two main benefits
 Shortens time of end organ denervation
 Improves fascicular alignment as there is
minimal excision of ends
• In war wounds, early secondary suture is
preferred

47. Management of PNI
• Clean laceration
 Clean and debride thoroughly
 Do primary repair, if patient condition allows and if
personnel and equipment are available
 If not possible at the first debridement, do it in 3 to 7
days
 Suture, dress, and follow for infection

48. Management of PNI
 Contaminated laceration
 Debride thoroughly
 Apply sterile dressing
 Do delayed primary repair in 7 – 18 days
 Contamination increases risk of scarring

49. When to operate
• For nerve lacerations, due to glass or knife,
operation can be done in 72 hours, as both
ends are healthy
• Delay results in retraction of nerve stamps,
and increased gap which necessitate grafting
– outcome is not guaranteed there on
• End-to-end neurorhaphy is operative option

51. Management of PNI
 Blast or crush injury
Clean and debride
If there is no gap, appose loose end-to-end for later easier
repair and prevent retraction
If there is gap, suture ends to soft tissues to prevent
retraction
Do soft tissue coverage, if necessary
 Let the soft tissues heal & do secondary repair in 3 – 6
weeks

52. When to operate
• If injury is uncertain, like blunt trauma, or fracture,
re-innervation is followed clinically and EMG
• Demyelination corrects in 8-12 weeks: if no re-
innervation noted then there is axonal damage
which needs intervention
• If no innervation is noted in 3 months, exploration
is indicated

54. When to explore
 Sharp injury nerve transection
 Avulsion or blast, to identify and tag
 No regeneration noted after blunt or closed trauma
– appropriate time passed
 No regeneration after low velocity gunshot
 Nerve deficit immediately after manipulation and
casting
 Delay exploration if there is progressive
regeneration – clinical and electrodiagnostic

55. Why surgical timing matters
• Muscle completely atrophies in 12-18 months, when
denervated
• The nerve must reach that muscle, before it
atrophies after that period even re-innervation has
no benefit
• You calculate how long it will take a nerve to reach
the end organ by travelling 1mm/day or 1
inch/month starting from day of operation
• 3/5 muscle function is a good outcome

56. Surgical options
• Neurorrhaphy
• Neurolysis
• Partial neurorrhaphy
• Methods to close the gap

57. Neurorrhaphy
 Done as long as nerve ends can come together
without tension
 Tension results in scarring or breakdown at repair site
 Mild tension stimulates nerve growth
 Problems with fancy joint positions
 Dehiscence of repair with early motion
 Joint stiffness

58. Neurorrhaphy
 Tension free repair
 Reasonable
 8-0 nylon suture
 Withstand normal joint motions
 Key goals for repair
 Avoid tension
 Avoid zone of injury
 Align
 Early controlled motion for neural gliding

59. Neurorrhaphy
 Epineurial repair is
preferred by some
 Align vessels on surface
and fascicles
 Big nerves may need
perineural repair to align
individual big fascicles
 Perineural needs
extensive dissection
down which can lead to
increased fibrosis

60. Neurorrhaphy
• End-to-end
• Side-to-end
• Distal stamp of injuried
nerve is attached to donor
nerve
• Neurectomy is done on
donor
• Collateral sprouts exit
epineurium of donor and
enter the distal stamp
• Good for long distance
injuries, and if no proximal
stamp to do end to end

61. TECHNIQUES OF NEURORRHAPHY
• No evidence to support one technique
over other
• Depends on experience and training
• Every incision should extend well proximal
and distal
• Handling of the nerve during mobilization
is easier by the use of moist umbilical tape
or pieces of rubber tissue

62. Instruments
• Handling and dissecting instruments
• Pneumatic tourniquet, suction apparatus,
and electrocautery
• Thrombin if vailable for end bleeding
• 8-0, 9-0, and 10-0 nylon sutures
• General anesthesia is better for UE, or SA for
lower extremity

63. Technique of neurorrhaphy
• Incision extends proximal and distal to nerve and follows course
• Extensile encisions are necessary if needed, sometimes from axilla to wrist for
a large ulnar or median nerve defect
• To make dissection and exposure simple, expose proximal to lesion, then distal
to lesion, and then the lesion site
• Remove scar tissues, and do stimulation to see any normal branches
• To prevent rotation, apply sutures in the epineureum proximal to and distal to
lesion for orientation, before mobilizing
• To prevent rotation, longitudinal epineurial vessles are also inspected for
alignment

64. Technique of neurorrhaphy
• Use moist tape or rubber tissue drain to handle nerve
• Cover parts of nerve not being operated with most
sponges
• Have a nerve stimulator, to know which one is sensory
and which one is motor
• If there is neuroma in continuity, and motor and sensory
responses to stimulation are not good, explore deeper

65. PERINEURIAL (FASCICULAR)
NEURORRHAPHY
• Incise the epineurium
longitudinally to dissect and
expose the fasciculi
• Align
• Identify corresponding groups
of fasciculi in the stumps
• approximate them individually
• If loose, close epineurium as
well

66. Epineurial Neurorrhaphy
• Place the first suture in the
posterior or deep
epineurium of the nerve
• Place the next three
sutures in the remaining
three quadrants
• Determine as possible that
no kinking or deviation of
the fasciculi

67. Epi-perineurial Neurorrhaphy
• Includes the epineurium
and perineurium
• Aligns large group of
fascicles in bigger nerves
• Epineurial repair adds
strength

68. Factors that affect neurorrhaphy
• Age
– Children are more successful than adults
– Reason unknown
– Example: after median and ulnar nerve repair
• Age affects 2 point descrimination
• 20-40 years: 3 cm
• 11-20 years: 1.5 cm
• <10 years: 1 cm

69. Factors that affect neurorrhaphy
 Gap
 Whenever gap increases, the funicular pattern changes
 The upper limit of gap beyond which results deteriorate is 2.5 cm
– nerves differ however
 Mobilization, Transposition, joint flexion, nerve grafting and
Sometimes bone can be shortened to overcome the gaps

70. Factors that affect neurorrhaphy
 Delay between injury and repair
 Delay of repair affects motor recovery more
profoundly than sensory recovery
 Satisfactory reinnervation of muscles can occur
after denervation up to 12 months
 Irreversible changes develop in muscle after 24
months
 No time limit known for sensory recovery

71. Factors that affect neurorrhaphy
 Level of injury
 Greater proportion of cross sectional area of nerve
trunk is occupied by fibers to the proximal muscles
 Re-growing axons disorientate, and axons are lost
more for distal muscles than for proximal

72. Endoneurolysis
 For intraneural scars resulting nerve deficit
 Relieves pain and restores conduction
 Feel gross changes with finger, and 0.5 cm
from these area incise the epineurium
 Take flaps to either side with suture
 Dissect carefully through fasciuli
 If fasciculi can be seperated, and stimulation noted =
nothing is done
 If fasciculi can’t be sepearted, and no stimulation =
neuroma is removed, and neurorrhaphy done

73. Partial neurorrhaphy
Usually large nerves like sciatic
Indicated for one half severing
If motor response to stimulation is good better to
defer repair( peroneal, ulnar nerves)
If most of the fascicles are severed, and there is
no stimulation, complete neurorrhaphy is done

74. Partial neurrhaphy
• Release epineurium
few centimeters on
each side
• Dissect normal funiculi
at the same distance
• Resect injuried parts
until normal tissue
noted
• Do end to end
neurorrhaphy
• Suture epineurium
back

75. Methods to close nerve gap
Mobilization
Transposition
Joint positions
 Nerve autograft
 Nerve allograft
 Conduits
 Nerve transfer

77. Autologous nerve graft
 Acts as a guiding tube
 Sural nerve is most commonly used, MABC, LABC
nerves can be used
 Small cable grafts are preferred, as they revascularize
early compared to large, and survive better
 Can close up to 20 cm of gap
 Use vascularize grafts for gap > 6 cm

78. Nerve graft
• Avoid tension at both
repair ends
• Make it redundant on the
repair sites, to allow early
motion of the joints
• Allografts need
immunosuppresion of 18
months, also prevention
of infections

79. Nerve graft
• Incise epineurium
• Dissect for each fasciculi,
and remove neuroma
• Now you have fascicles of
different levels
• Bring the nerve graft, and
section it around 10-15%
longer than needed portion
• Suture perineurium of the
donor to the perineurium of
the recipient fascicle with
10-0

80. NERVE CONDUITS
Bridging tube
As primary conduit or nerve wrap
Only for sensory gaps < 3 cm
Biologic: nerve, bone, vein, artery
Synthetic: silicon
As a wrap: if repair site dehisces still nerve can
go through the conduit canal

81. NERVE TRANSFER

82. Post operative care
Immobilize for 1-2 weeks
Consider associated injury(tendon or bone)
Start gentle ROM in 3 days to help gliding –
depends on intra-op tolerated motion
Pain management – paresthesia and electric
shock, may need narcotics, neuroleptics

83. POSTOPERATIVE MANAGEMENT
In 1 – 2 week, inspect wound and remove
sutures
6 to 12 weeks after surgery, careful attention
should be paid to the avoidance of fixed
contractures
8 to 12 weeks after surgery, progressive
strengthening exercises are begun

84. References
• S. Terry Canale James Beaty. Campbell's Operative
Orthopaedics. Pp3346-3413
• Steve K. Lee, MD, and Scott W. Wolfe, MD. Peripheral Nerve
Injury and Repair. J Am Acad Orthop Surg 2000;8:243-252
• Deal DN et. Nerve conduits for nerve repair or reconstruction.
Al J Am Acad Orthop Surg. 2012
• Campbell, William W., "Evaluation and management of
peripheral nerve injury" (2008). Uniformed Services University
of the Health Sciences. 3.http://digitalcommons.unl.edu/usuhs/3
• S. Hall. The response to injury in the peripheral
• nervous system. Review article. Society of Bone and
• Joint Surgery. 2005