Growth, injury + repair - NERVE Flashcards
Growth of the MSK system skeleton and size determination; increase in skeletal size and its regulation; osteogensesis and its modulation; plasticity of muscular system in adapting to changing functional demands.
Injury and repair of bone,
Injury and repair of articular cartilage,
Injury and repair of muscle,
Injury and repair of peripheral nerves
These short lectures will briefy describe the anatomy of
bone, tendons and nerves and the function of tendons in relation to movement.
Basic fracture healing will be described and tendon problems such as degeneration, infammation, enthesiopathy and rupture will be described
Pathway of a peripheral nerve from spinal cord
Anterior + posterior nerve roots –> combine to form mixed spinal nerve –> exit spinal column via intervertebral foramen –> divide into anterior and posterior rami
Axons (the long processes of neurons) are coated in …
and bundled together to form … (nerve bundles) which are coated in …
which are then grouped to form the … which is finally coated in …
ENDONEURIUM
FASICLES coated in PERINEURIUM
NERVE coated in EPINEURIUM
See pain lecture about fibre types (Aa, Ab, A delta, C etc) + function of each
.
Injury to nerves can be from 2 ways
Compression
Trauma
- direct (blow, laceration)
- indirect (avulsion [torn off], traction [putting tension])
Describe neurapraxia
- what has happened to nerve structure
- causes
- prognosis
Temp loss of motor + sensory function due to blocked nerve conduction WITHOUT changes in axonal structure
Nerve is stretched or bruised
Relatively mild nerve injury; common; good prognosis
Describe axonotmesis
- what has happened to nerve structure
- causes
- resultant effects
- prognosis
Axons and myelin sheath are damaged but endoneurium, perineurium and epineurium are intact so tube is still in continuity
Nerve is stretched (quite a bit) or crushed or direct blow
Wallerian degeneration follows - active process of degeneration that results when a nerve is cut or crushed and the part of the axon distal to the injury degenerate
Prognosis fair - sensory > motor recovery
Describe neurotmesis
- what has happened to nerve structure
- causes
- resultant effects
- prognosis
Most serious nerve injury - both nerve and myelin sheath disrupted, nerve is completely divided –> complete paralysis and atrophy of muscles innervated
Caused by laceration or avulsion
Wallerian degeneration follows (see axonotmesis flashcard)
Poor prognosis - no recovery unless surgically repaired by direct suturing or grafting of the 2 ends of the nerve
Classic conditions of nerve entrapment
Carpal tunnel - median nerve compression at wrist
Cubital tunnel - ulnar nerve compression at elbow
Sciatica - spinal root compression by IV disc
Morton’s neuroma - benign thickening of one of the nerves leading to the toes (usually between 3rd and 4th toe) –> sharp pain in ball of foot
Peripheral nerves can …
Those in the CNS can’t do this
REGENERATE
Describe ‘closed’ nerve injuries
- refer to what
- recovery?
- examples
Refer to nerve injuries in continuity (i.e. neurapraxia & axonotmesis)
Spontaneous recovery is possible
Surgery indicated after 3 months if no improvement
Typically STRETCHING of nerve
- brachial plexus injuries
- midshaft humerus fracture –> radial nerve palsy
Describe ‘open’ nerve injuries
- refer to what
- recovery
Refer to nerve division/transection (i.e. neurotmesis), e.g. knife, glass injury
Needs to be treated with EARLY SURGERY
Distal part of nerve undergoes Wallerian degeneration
Clinical features of nerve injury
- sensory
- motor
Sensory
-dysaesthesia (abnormal sensation)
Motor -paresis or paralysis of muscles innervated \+/- wasting of muscles innervated -dry skin? -diminished or absent reflexes
Describe the healing of peripheral nerve injuries
- initially what happens
- rate of regeneration of nerve
- prognosis depends on
Starts with wallerian degeneration then proximal axonal budding about 4 days later
Regeneration occurs at rate of 1mm/day
Prognosis depends on whether nerve is pure sensory/motor or mixed AND how distal the lesion is (proximal = worse)
How can healing of nerve injuries be monitored
- examination tests
- investigations
Tinel’s sign
-tapping over site of nerve and paraesthesia will be felt as far as the regeneration has progressed
Nerve conduction studies - e.g. EMGs
