peripheral nerve injuries Flashcards
What is another name for motor root
ventral root
What is another name for a sensory root
dorsal root
Where do the cell bodies of motor units lie
The grey matter of the spinal cord
Where do the cell bodies of sensory units lie
dorsal root ganglia
What forms a spinal nerve
Ventral and dorsal root combining
Where do the spinal nerves leave the spine
Intervertebral foramen
What surrounds peripheral nerves
schwann cells
Describe the structure of a peripheral nerve
Axons that are covered in endoneurium - grouped into fascicles (nerve bundles) which are covered in perineurium - these are grouped into nerves which are covered in epineurium
What is the fastest type of neuron fibre
Alpha
What is the slowest type of nerve fiber
C
What is the correlation between size and speed of transmission
the larger the fibre, the faster the speed of transmission
What can compress nerves and give examples
Entrapment
Carpal tunnel syndrome - median nerve compression
Sciatica - intervertebral disc compresses sciatic nerve
Morotons neuroma - digital nerves in web space are compressed
What is neurapraxia
Reversible conduction block caused by trauma which causes local ischaemia and demyelination which then leads to the neurapraxia
What is wallerian degeneration
Degeneration of the distal end of an axon
Does the tube remain intact in axonotmesis
Yes because the endoneurium is intact
What happens in neurotmesis
division of the nerve
What are closed nerve injuries associated with
the nerve is still continuous and intact
Neuropraxis and axonotmesis
When is surgery indicated in closed nerve injuries
If no recovery has been identified after 3 months
What nerves commonly get damaged with closed nerve injuries
Brachial plexus and radial nerve
What type of injury are Open nerve injuries associated with
Associated with nerve division - neurotemesis
What is a common cause of open nerve injury
Accidental cut of the hands with knife
What is the treatment for open nerve injury
Early surgical intervention
What are the sensory clinical features of nerve injury
Dysaethesiae - disordered sensation - anaesthetic, hypo and hyper-aesthetic or paraesthesia(pins and needles)
What are the motor clinical features of nerve injury
Paresis - weakness
Dry skin - nerve not stimulating sweat glands in skin
Diminished or Absent reflexes due to no preipheral nerve
How fast is the regeneration of a nerve
1mm/day
What is the first function to return in nerves
pain
Does a pure or mixed nerve have better recovery and why
Pure because it is all one type of nerve (sensory or motor) so they all regenerate back to one end plate
Is nerve healing better for a distal or proximal injury
distal - due to degeneration of the end plates when it is further which is why proximal is not as fast at healing
What is tinnel’s sign
Tap over sign and paresthesia will be felt as far distally as regeneration has progressed
How can nerve injury be assessed and healing can be monitored
Electrophysiological nerve conduction studies
What injuries require direct repair
laceration
no loss of nerve tissue
When is nerve grafting done
When there is nerve loss - due to damage or retraction where the nerve endings cannot be pulled together
What happens in nerve grafting
unuseful nerve such as the sural nerve is used and stitched at either end to the nerve endings - provides a passage for the axons to grow down
What is the rule of three
The surgical timings of traumatic peripheral nerve injury
Describe the rule of three
Immediate surgery within 3 days for clean and sharp injuries
Early surgery within 3 weeks for blunt/contusion injuries
Delayed surgery within 3 months for closed injuries
What are the signs in upper motor neuron lesions (central)
Still have peripheral nerves therefore
decreased strength
Increased tone and deep tendon reflex
present clonus and babinski
no atrophy
What are the signs in lower motor neuron lesions (peripheral nerve)
decreased strength, tone and deep tendon reflex
Absent clonus and babinski
Atrophy is present
