Lower Motor Neuron Injuries Flashcards
What is a motor unit?
Anterior horn cell, motor axon and muscle fibres
Where do sensory units lie?
Outside the spinal cord where cell bodies lie in posterior root ganglia
What is a peripheral nerve?
The part of a spinal nerve distal to the nerve root
What are axons?
Long processes of neurones are coated with endoneurium
What are fasicles?
Nerve bundles covered by perineurium
What are fasicles grouped to form?
Nerves which are covered by epineurium
Give examples of direct and indirect trauma?
Direct - blow or laceration
Indirect -Avulsion or traction
What is neurapraxia?
Nerve in continuity
Stretched or bruised
Reversible conduction block - local ischaemia and demyelination
Prognosis good (weeks or months)
What is axonotmesis?
Endoneurium remains intact but axons are disrupted
Caused by stretching, crushed or direct blow
Wallerian degeneration follows
Prognosis is fair - sensory often recovers better than motor
What is Neurotmesis?
Complete nerve division via laceration or avulsion
No recovery unless repaired (by direct suturing or grafting)
- Endoneural tubes are disrupted so no guidance on nerve regrowth = neuroma formation
prognosis is poor
What are closed nerve injuries?
Associated nerve injuries in continuity
Spontaneous recovery possible
Surgery indicated after 3 months if there is no evidence of clinical recovery
Axonal growth rate is 1-3mm/day
What are open nerve injuries?
Frequently related to nerve division
Treated with early surgery
Distal portion of nerve undergoes Wallerian degeneration
What are sensory clinical features of nerve injury?
Dysaethesiae
-anaesthetic, hypo or hyper aesthetic and paraesthetic
What are motor clinical features of nerve injury?
Paresis, paralysis, wasting, dry skin
What is nerve healing dependent on?
Whether the nerve is pure or mixed, how distal the lesion is
