31 - brachial plexus trauma Flashcards
The brachial plexus is formed from the dorsal or ventral branches of the spinal cord segments?
ventral
Which SC segments form the brachial plexus?
C6-T2
in how many % of dogs do C5 spinal cord segments, it spinal nerve root and spinal nerve also contrite to the brachial plexus?
24%
what structure do nerve roots lack that make them especially susceptible to traction?
nerve roots don’t have an epineurium
In partial injury is the caudal or cranial portion more commonly affected?
caudal
Axons orientate where?
neuronal cell bodies in gray matter of the SC.
Each axon is surrounded by ?
Endoneurium
endometrium is made of?
collagen fibrils, fibroblasts and vascular tissue
groups of axons are surrounded by ?
perineurium
perineurium is made of
collagen and elastic fibres
connective tissue surrounding entire nerve is? and is made of?
epineurium.
connective tissue and collagen fibrils
dorsal spinal nerve root provides?
sensory input in to SC via a spinal ganglion,
ventral nerve root is for?
motor function and autonomic innervation
dorsal and ventral nerve roots lie within the ….? and form together to form a ….? that lies within the ….?
vertebral canal
specific spinal nerve
intervertebral foramen
which mater are the dorsal and ventral spinal roots surrounded by near to the spinal cord?
the Pia mater and inner layer arachnoid membrane.
what happens the meninges as spinal ganglia becomes the spinal nerve
cont as epineurium
what structures do nerves pass from being branches of the spinal roots to reaching the brachial plexus?
inter-transverse musculature, scalenus muscle and axillary space
List the named nerves that are branches of the brachial plexus x 13
brachiocephalic suprascapular subscapular axillary musculocutaneous radial median ulnar dorsal thoracic lateral thoracic long thoracic pectoral muscular
BSS AMRMU TTTPM
brachial plexus injury is morally caused by what direction f movement/.
abduction and caudal displacement
where are spinal nerve roots weakest? why ?
intradural
lack epineurium
when can you see psi.ateral pelvic limb ataxia.plegia.paresus?
if injury is sever enough to damage spinal cord
are ventral or dorsal a roots more susceptible to this kind of trauma?
ventral (motor) but both may be affected
neuropraxia is?
Neurapraxia is the mildest form of nerve injury. It consists of loss of conduction without associated changes in axonal structure.
reversibel, improve in hours to 6 weeks
axonotmesis?
The axons and their myelin sheath are damaged in this kind of injury, but the endoneurium, perineurium and epineurium remain intact.
recovery normally good bu t can take weeks
neurotmesis?
axons, myelin sheath and digress of endometrium, perineurium and epineurium are disrupted.
what are the 3 different classes of brachial plexus injury? and what SC segments/nerves are involved in each ?
- cranial brachial plexus injury. C5/6 - C7 brachiocephalicus, supra scapular, subscaputlar, axillary, musculocutaneous
- caudal C8- T2. radial, medial, ulnar
- total avulsion
which nerve is most commonly affected in cases of brachial plexus injury > what is its main role
- radial nerve in 94% cases
2. elbow extensor therefore weight bearing.
why do dogs with caudal brachia plexus injury display horners
pre ganglion fibres from T1 project on ascending sympathetic innervation of the eye
what reflex is lost with injury to c8/t1 and which nerve is implicated?
cutaneous trunci, lateral thoracic nerve.
clinical signs seen with cranial brachial plexus injury?
minimal, los shoulder movement and elbow flexion.
clinical signs seen with caudal brachial plexus injury
leg may be flexed (as axillary, suprascapluar, musculocutaneous still inactivity) but unable to weight bear as no elbow extension (radial nerve)
what neurodiagnostic may help with diagnosis?
- electromyography
- nerve conduction velocity
- Evoked potentials and assessment of sensory nerve
what MRI changes might you see with brachial plexus injury?
Can identify 1.incomplete root injuries, intraforaminal root avulsion, root avulsion from the SC.
- preganglioninc injury may appear as contralateral displacement of the SC, SC oedema, myelomalacia, syringomyelia, foal ares of haemosiderin deposition (T@w hypo intense)
- post ganglionic injuries - stretch injury with nerve disruption – swollen nerve isointense in T1w and hyper intense on t2w.
What surgical options exist for brachial plexus injury?
- Neurotization (for example use lateral thoracic nerve and suture to the musculocutaneus)
- reimplantation
what are the major surgical complications with brachial plexus nerve injury?
- neurologic deterioration (can get significant ipsilateral and poss bilateral PL dysfunction)
- cutaneuosu trauma and self mutilation
how long should we give brachial plexus injury before assigning a grave prognosis
4- 6 weeks
