Introduction to periphral nervous sys

1. I
Haneen Hassan Shaker
Baghdad University/Alkindy
college of medicine

2. INTRODUCTION / PATHOLOGY
Damage varies in severity from transient and quickly recoverable
loss of function to complete interruption and degeneration.
There may be a mixture of types of damage in the various fascicles
of a single nerve trunk.

3. Nerve injuries types
Neurapraxia
Axonotmesis
Neurotmesis

4. Nerve injuries types :
(SEDDON’S CLASSIFICATION )
1.Neuropraxia( Demyelination ) :
• a reversible physiological nerve conduction
block.
• It is due to mechanical pressure causing
segmental demyelination.
• spontaneous recovery after a few days or
weeks.

5. 1. Neuropraxia
 Endoneurium is intact
 Axon is intact
 pressure

6. 2. Axonotmesis ( Demyelination + Axon loss) :
• i.e. common in crash injuries ,closed
fracture and displaced bone.
• Spontaneous recovery is likely.

7. 2.Axonotmesis
 ( Demyelination + Axon loss)
Endoneurium is intact
Axon is damaged
 Distal end will
 undergo Wallerian
 Degeneration

8. 3. Neurotmesis ( Demyelination +
Axon loss + Endoneurium loss ) :
1.More severe injury ,open fracture &
traction injuries
2. No Spontaneous recovery

9. 3. Neurotmesis:
Endoneurium is
Damaged
Axon is damaged. Distal end will
undergo Wallerian
Degeneration

10. WALLERIANS CLASSIFICATION
• Axons and myelin sheath degenerate distal to the cut .
• Schwan cells grow into the gap.
• Proximal to the cut the axons sprout branches which grow into the gap.
• They enter the distal Schwann tube and acquire a new myelin sheath.
• The axon joins
• The speed of recovery is about 1-1.5mm a day.

11. WALLERIAN CLASSIFICATION

12.  Denervated muscle waste
 Joints become stiff and deformed
 The skin and nail undergo trophic changes.
 Brain forget the patterns of muscle behavior.
Other structures:

13. CLINICALLY

14. CLINICALLY
• Look for:
Scar of the causal wound
Smooth anesthetic skin
Shiny trophic ulcer.
Muscle wasting
• Feel:
 Anesthetic skin smooth , cool , and dry .
 Palpable and tender nerve bulp.

15. • Move:
The patients can not perform certain
movement Muscle tone and power are lost.
0 total paralysis
1 barely detectable contracture
2 Not enough power to act against gravity
3 Strong enough to act against the gravity
4 Still stronger but less than normal
5 Full power

16. Diagnosis
Is a nerve lesion present ?
At what level is a lesion?
Obvious from injury & individual muscles .
What type of lesion is present ?

17. Special investigations
• Nerve blocking
A local anesthesia is injected into the injured nerve , if
followed by sensory or motor loss ,the lesion is partial.

18. Special investigations
• Electrical test
The nature , the level and extent of recovery is obtained by :
1-the assessment of strength/duration curve
2-elctromyography study of voluntary action potential
3-the measurement of motor and sensory conduction
velocities at varying levels.

19. Treatment
Nerve repair indicated:
• 1-the nerve is known to be divided because the lesion
was seen at wound toilet operation
• 2-the nerve is likely to have been divided because of
the nature of injury ,eg; a knife wound
• 3-the nerve is presumed to be divided because
recovery of supplied muscles has not occurred in the
calculated time , or because of palpable nerve blub
• 4- for diagnostic purpose

20. Care of paralyzed part
• Skin protected .
• joint moved with full range to prevent stiffness
• splint .

21. Timing of nerve exploration
• Best too soon than too late
Advantage of primary suture
• Nerve ends have not retracted
• their relative rotation undisturbed and no fibrosis
Indication to postponed the suture :
• Dirty wound
• the nature of the lesion is uncertain.

22. prognosis
• Type of lesion
neuroapraxia recover fully , axonotmesis usually recover well ,neurtmesis worse
prognosis
• Level of lesion
the higher the lesion the worse the prognosis
• Type of nerve
pure motor or sensory better than mixed , because of axonal confusion
• Size
of gap above the critical resection length 7-10 cm suture not successful
• Age
in children prognosis better than adult
• Delay
in suture ,esp. after few months
• Associated lesions
damage to vessels , tendon or other structure . Dificult to obtain useful
limb