lecture 3
What is the structure of a peripheral nerve?
Peripheral nerve consist of parallel bundles of axons, surrounded by 3 connective tissue sheaths.
- endoneurium: surrounds each axon
- perineurium: surrounds each fascicle (bundle of axons)
- epineurium: surrounds all the fascicles (entire nerve)
What are the brachial plexus?
-formed from the ventral rami of C5-T1
Rami, Trunk, Divisions, Cords, Branches
What are the major nerves of the hand/ arm?
-Musculocutaneous
- median
- radial
- ulnar
What are the sensory and motor functions of the musculocutaneous nerve?
motor
- elbow flexion
Sensory
-lateral forarm
Polyneuropathy
Etiology: can be toxic, metabolic or autoimmune
Pathology: damage to many nerves
Symptoms: typically presents distally and symmetrically. It progresses distal to proximal, involving sensory motor and autonomic fibers. The trophic changes in severe cases.
What are the sensory and motor functions of the median nerve?
motor
- wrist and finger flexion, forearm pronation, thumb movement
sensory
- lateral half of the hand ventrally, nailed of index, middle and lateral half of the ring finger dorsally
What are the motor and sensory functions of the ulnar nerve?
motor
- wrist and finger flexion
sensory
- medial half of the hand ventrally and dorsally
What are the motor and sensory functions of the radial nerve?
motor
-elbow, wrist, hand extension, and supination
sensory
- medial half of the dorsal surface of the hand
What is an avulsion injury?
What is a rupture injury?
What is a neuroma injury?
What is a stretch injury?
Avulsion= the nerve is torn from its attachments to the spinal cord- most serious type
Rupture= the nerve is torn, but not at the spinal cord
Neuroma= these injuries result from scar tissue that forms and puts pressure on the nerve
stretch= also known as neuroplaxia, nerve is damaged but not torn
Erb's palsy
Etiology: birth injury, motorcycle accident, contact sports
Pathology: damage to upper part of brachial plexus (C5-C6)
Symptoms: difficulty/ loss of shoulder abduction, external rotation and elbow flexion
*waiters tip position
Prognosis: Variable
What are the possible symptoms for peripheral nerve injuries?
- motor
- sensory
- autonomic
- trophic
motor changes
- paresis (weakness) or paralysis
- muscle atrophy
- muscle fibrillations
sensory
- loss or decreased sensation
- impaired proprioception
- atypical sensations
autonomic
- dizziness
- incontinence
- blurred vision
- digestive changes
trophic
- skin becomes shiny, nails brittle, subcutaneous tissue thickens
- ulceration of tissues
- poor healing of wounds and infections
What is retrograde?
What is orthograde?
retrograde is degeneration of a proximal axon
orthograde or wallerian is degeneration of distal axon
What is neuropathy?
What is mononeuropathy?
What is polyneuropathy?
Neuropathy is a disease or dysfunction of one or more peripheral nerves
Mononeuropathy is a single nerve. It is a final dysfunction. It presents in the distribution of injured nerve.
* multiple mononeuropathies are several individual nerves; presents as asymmetrical involvement of nerves
Polyneuropathy is many nerves. It typically presents distally and symmetrically.
What is neuropraxia?
Etiology: repeated mechanical stimuli (pressure, stretch, vibration) nerve entrapment
Pathology: Impingement or compression leads to a loss of myelin at the site of the injury (no damage to axon)
Prognosis: recovery tends to be complete
It is a class I
Klumpke's Palsy
Pathology: damage to lower part of brachial plexus (C8-T1)
Symptoms: paralysis and atrophy of the hand intrinsic muscles and long flexors/ extensors of fingers. Loss of sensation along the medial aspect of the arm.
Prognosis: Variable
What is axonotmesis?
Etiology: usually from crushing of nerve (after dislocation/ closed fracture)
Pathology: axon cut but surrounding myelin and connective tissues intact; degeneration occurs distal to the lesion
Prognosis: good
What is neurotmesis?
Etiology: excessive stretch or laceration
Pathology: entire nerve cut (axons and surrounding tissues)
Prognosis: variable
What is sprouting?
The nerve has been transected and Wallerian degeneration has begun. Proximal nerve terminals send sprouts toward the Schwann cell tubes. some of the sprouts make it into the correct tube and reinnervate the muscle, but others may reach the incorrect end organs.
Diabetic Polyneuropathy
- sensory: glove/ stocking distribution (proper diabetic foot care is important)
-motor: balance and coordination problems
-autonomic: impaired sweating; orthostatic hypotension; bowel/ bladder digestive dysfunction Prognosis: variable
Carpal Tunel Symptoms
Etiology: gripping vibrating tools, repetitive use of flexor/ extensor muscles
Pathology: compression of the median nerve in carpal tunnel (space between the carpal bones and flexor retinaculum)
Symptoms:
- sensory: numbness. tingling, burning in the median nerve distribution
-motor: paresis and atrophy of the thenar muscles
Prognosis: variable
Will I sleep tonight
probably not
Do we drop out
maybe
List the cranial nerves on the white board
I don't know them
how are you feeling
I hate neuro
Guillain Barre Syndrome
Demyelination of the PNS
more severe motor than sensory effects