Nerve injury (1).ppt nerve neurophysiology

ppt nerve injury

1. AIPAS
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NERVE INJURY
MSc (MP)
Eman Masood

2. AIPAS Introduction
When a nerve fiber is injured, various changes
occur in the nerve cell body. All these changes
together are called degenerative changes.
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3. AIPAS Causes of Injury
•Obstruction of blood flow.
•Local injection of toxic substances.
•Crushing of nerve fiber.
•Translocation of nerve fiber.
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4. AIPAS Degrees Of Injury
Sunderland has classified the injury to nerve
fibers into five categories depending upon the
order of severity.
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5. AIPAS First Degree
•Most common type of injury to the nerve.
•It is caused by applying pressure over a
nerve for a short period leading to occlusion
of blood flow and hypoxia.
•Axon is not get destroyed but mild
demyelination occurs.
•Temporary conduction block.
•Function returns within few hours to few
weeks.
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6. AIPAS Second Degree
•Due to prolonged severe pressure, which
causes Wallerian degeneration.
•Endoneurium is intact.
•Repair and restoration of function takes
around 18 months.
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7. AIPAS Third Degree
•Endoneurium is interrupted.
•Epineurium and perineurium is intact.
•Recovery is slow, poor an incomplete.
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8. AIPAS Fourth Degree
•More severe.
•Epineurium an perineurium are also
interrupted.
•Fasciculi of nerve fibres are disturbed and
disorganized.
•Regeneration is poor and incomplete.
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9. AIPAS Fifth Degree
•Involves complete transaction o nerve trunk
with loss of continuity.
•Useful regeneration is not possible unless
the cut ends are rearranged and
approximated quickly by surgery.
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10. AIPAS Degenerative Changes in
the Neuron
Degeneration refers to deterioration or pathological
changes of an injured tissue. When a peripheral nerve
fiberis injured, the degenerative changes occur in the
nerve cell body an the nerve fiberof same neuron and
the adjoining neuron.
Degenerative changes are classified into three types:
•Wallerian degeneration
•Retrograde degeneration
•Transneuronal degeneration
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11. AIPAS Wallerian Degeneration
Wallerian degeneration is the pathological change that
occurs in the distal cut end of nerve fiber(axon). It
starts within 24hrs of injury. Changes occur throughout
the length of distal part of nerve fibersimultaneously.
•Axis cylinder swells and breaks into small pieces.
After few days, the broken pieces appears as debris
in the space occupied by axis cylinder.
•Myelin sheath is slowly disintegrated into fat
droplets. The changes in myelin sheath occurs from
8
th
-35
th
day.
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12. AIPAS
•Neurilemmal sheath is unaffected, but the Schwann
cells rapidly multiply. Macrophages invade from
outside and remove the debris of axis cylinder and
fat droplets of disintegrated myelin sheath. So, the
neurilemmal sheath becomes empty. Later it is filled
by the cytoplasm of Schwann cells. All these
changes take place for about 2 months from the day
of injury.
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13. AIPAS Retrograde Degeneration
Pathological changes that occur in the nerve cell and
axon proximal to the cut end.
Changes occur within 48hrs
•First, Nissl granules disintegrate into fragments by
chromatolysis.
•Golgi apparatus is disintegrated.
•Nerve cell body swells due to accumulation of fluid
and becomes round.
•Neurofibrils disappear followed by displacement of
the nucleus towards the periphery.
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14. AIPAS
•Sometimes, the nucleus is extended out of the cell.
In this case, death of the neuron occurs and
regeneration of the injured cell is not possible.
•Changes in the axon proximal end-In the axon,
changes occur only up to first node of Ranvier from
the site of injury. Degenerative changes that occur
in proximal cut end of axon are similar to those
changes occurring in distal cut end of nerve fiber.
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15. AIPAS Transneuronal Degeneration
If an afferent fiber is cut, the degenerative changes
occur in the neuron with which the afferent nerve fiber
synapses. It is called transneuronal degeneration.
Example:
•Chromatolysis in the cells of lateral geniculate body
occurs due to sectioning of optic nerve.
•Degeneration of cells in dorsal horn of spinal cord
occurs when the posterior nerve root is cut.
•Degeneration of cell in ventral horn of spinal cord
occurs when there is tumor in cerebral cortex.
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16. AIPAS
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17. AIPAS Regeneration of Nerve
Fiber
The term regeneration refers to regrowth of lost or
destroyed part of tissue. The injured and degenerated
nerve fiber can regenerate. It starts as early as 4th day
after in injury, but becomes more effective only after 30
days and is completed in about 80 days.
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18. AIPAS Criteria for Regeneration
•Gap between the cut ends of nerve should
not exceed 3mm.
•Neurilemma should be present a,
neurilemma is absent in CNS regeneration
does not occur in CNS.
•Nucleus must be intact, if it is extended from
nerve cell body, the nerve is atrophied and
the regeneration does not occur.
•Two cut eds should remain in same line.
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19. AIPAS
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20. AIPAS
THANK YOU
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