Musculoskeletal Growth Injury and Repair – Peripheral Nerve Injuries Flashcards
What are the two units of a nerve…worded that weird but you know it
Motor and sensory units
What are the motor units (efferent) and where are they located?
Anterior horn cells found in grey matter of spinal cord
What are the sensory units (afferent) and where are they located?
Cell bodies in the posterior root ganglia i.e. outside of the spinal cord
Nerve fibres joint to form motor and sensory roots. Are the sensory roots anterior or posterior and ventral or dorsal?
Posterior/dorsal roots
Nerve fibres joint to form motor and sensory roots. Are the motor roots anterior or posterior and ventral or dorsal?
Anterior/ventral roots
What surrounds larger peripheral nerve fibres?
Myelin sheath which provides insulation
What are axons coated with?
Endoneurium - type of CT
What are axons grouped together to form?
A fascicle
What are fascicles grouped together to form?
Nerve
What type of CT covers nerves?
Epineurium
What cells surround neurones?
Schwann cells
RECAP- which type of fibres travel the quickest?
A alpha fibres
->these are the biggest fibres
RECAP- which type of fibres travel the slowest?
C fibres
->these are the smaller fibres
Which fibres transmit dull, aching or burning pain and temperature sensation?
C fibres
Which fibres transmit sharp pain and light touch?
A delta fibres
Which fibres transmit touch, pressure, vibration and join position sensory axons?
A beta fibres
Give some examples of direct trauma injuries.
Blow or laceration
Give some examples of indirect trauma injuries.
Avulsion or traction
List some common conditions caused by compression of a nerve.
Carpal tunnel syndrome
Sciatica
Morton’s neuroma
Which nerve gets compressed in carpal tunnel syndrome?
Median nerve
Which nerves get compressed in sciatica?
Spinal roots by IV discs
What nerve get compressed in Morton’s neuroma?
Digital nerve in 2nd or 3rd web space of forefoot
Neurapraxia?
Mild nerve injury in which nerve has been stretched or bruised
Causes conduction block and local ischaemia and demyelination
What is prognosis of neurapraxia?
Good as reversible, settles after weeks or month
Axonotmesis?
More severe than neuropraxia, nerve is more stretched
Wallerian degeneration follows
What is the prognosis of axonotmesis like?
Fair, sensory recovery is often better than the motor recovery but is still not normal but enough to recognise hot and cold, sharp and blunt etc
Neutrotmesis?
Worse than axonotmesis and neuropraxia.
Often caused by lactation or avulsion
What is the prognosis of neurotmesis like?
No recovery unless repaired by suturing or grafting
Poor porgnosis
Nerve injuries are be described as being open or closed. Closed nerve injuries are associated with nerve injuries in continuity (whole nerve is still in tact). Give examples
Neuropraxis
Axonotmesis
How long after closed nerve injuries in surgery indicated?
3 months after as spontaneous recovery in possible
What are open nerve injuries usually associated with?
Trauma e.g. knives or glass cutting through a nerve
How are open nerve injuries usually treated?
Early surgery
What are the clinical features of nerve injuries?
Sensory- numbness and paraesthesia
Motor- weakness, paralysis, wasting, dry skin
Diminished or absent reflexes
Do pure or mixed nerves tend to recover better?
Pure nerves (only sensory or motor)
Which sign can be used to monitor recovery in nerve injuries?
Tinel’s sign
->tap over nerve site and paraesthesia will be felt as far distally as nerve regeneration has progressed. We do this in clinical skills for carpal tunnel syndrome).
How quickly do nerves regenerate?
1mm/day
What are the two ways of surgically repairing a nerve?
Direct repair
Nerve grating
When can nerves be directly repaired?
In laceration if two nerve endings present
When is nerve grafting used?
When there is nerve loss of it’s a late repair after a few months after injury
Injuries to peripheral and central NS can both cause loss of motor or sensory function or both.
So how can we tell the difference clinically?
UMN vs LMN lesions as in UMN lesions, the peripheral nerve is still intact
RECAP- UMN lesion findings?
Decreased strength
Increased tone
Increased reflexes
Present Babinski’s sign
Clonus
REACP- LMN lesion findings?
Muscle atrophy
Decreased reflexes
Absent Babinski’s sign
