Peripheral nerve injuries Flashcards
what is a motor unit?
motor axon and the muscle fibres it innervates
describe the structure of a peripheral nerve.
axons covered in endoneurium and grouped into fascicles (nerve bundles)
these are covered in perineurium
they are grouped to form a nerve which is covered with epineurium
what is neurapraxia?
nerve is still in continuity - the nerve is stretched or bruised
temporary loss of motor and sensory function
usually lasts 6-8 weeks
what is axonotmesis?
axons and myelin sheath are damaged but the epi, peri and endo neurium remain intact
what is neurotmesis ?
both nerve and myelin sheath are damaged
most severe nerve damage in the sheddon’s classification of nerve damage
no recovery unless repaired by direct suturing or grafting
what is morton’s neuroma?
compression of the digital nerve in 2nd and 3rd web space of forefoot (by ligaments)
what is Wallerian degeneration?
when a nerve fibre is crushed or damaged, a part of the axon distal to the injury degenerates
how can you test the progress of nerve regrowth?
tunnels test
when you have reached the most distal part of the nerve and you tap on it it will cause a shooting pain up the arm
what nerve injuries are reversible?
neropraxis
axonotmesis
what’s the difference between closed and open nerve injuries?
closed = nerve in continuity i.e. neuropraxis & axonotmesis
open i.e. neurotmesis
what are the clinical features of a nerve injury?
sensory- dysthaesia (anaesthesia, hypo or hyperaesthesia, paraesthesia)
motor - paresis or paralysis, wasting, dry skin
reflexes decreased or absent
what is the rate of nerve regeneration?
1mm/day
possibly 3-5mm per day in children
how can the extent of the nerve injury be assessed ?
electrophysiology
nerve conduction studies
what is the rule of 3 in regards to treating nerve injuries?
immediate surgery in 3 days for clean and sharp wounds
early surgery within 3 weeks for blunt/contusion injuries
delayed surgery performed 3 months after injury for closed injuries
