Exam 2 Neurology Flashcards
Neuropraxia is…
Due to loss of blood supply, pressure from the weight of the animal during anesthesia, tourniquets, etc. There is no resulting degeneration of the nerves but myelin sheaths may degenerate and it may take days to months for full functional recovery.
Axonotmesis is….
Degeneration of axons but the endoneurium and Schwann cells remain intact allowing regeneration of the axon (1 mm/day) and return of function. Usually paresis and hypersthesia.
Neurotmesis is….
Complete severance of a nerve and degeneration of the distal portion and its Schwann cells. Regeneration usually does not occur. Usually anesthesia and paralysis.
These types of injuries typically come about as a result of motor car accidents, intra-muscular injections, blows, bullets, etc….
Peripheral nerve injuries
What are signs of a peripheral nerve injury?
Anesthesia and absence of peripheral reflexes in areas supplied by the affected nerve. There is usually also marked and rapid muscle atrophy–neurogenic atrophy.
How is diagnosis of peripheral nerve injuries made?
Based on history, and symptoms of non-progressive lower motor neuron (LMN) signs, that is hyp- or anesthesia, hypo- or areflexia, hypotonicity and neurogenic muscle atrophy.
How would you treat a peripheral nerve injury?
Glucocorticoids to decrease inflammation and protect the limb while recovery occurs. If possible, decompress the nerve surgically. If nerve regeneration does not occur, transplantation of tendons of unaffected flexor muscles to substitute for those of extensors may be attempted along with arthrodesis. Amputation if all else fails usually after 6 months.
This type of injury typically occurs after trauma that abducts the front limb and forces it cranially or caudally. This usually results in avulsion of the ventral nerve roots (any or all of those between C6-T2) and maybe the dorsal roots.
Brachial Plexus Avulsion
Disruption of nerve roots C8 and T1 leads to denervation of ….
The extensors and flexors of the elbow and carpus.
Also the lateral thoracic nerve to the cutaneous tranci muscle exits here and if it is involved there will be a loss of the panniculus reflex.
Injury to T1 ventral nerve roots often damages the preganglionic sympathetic nerve fiberss resulting in Horner’s syndrome (miosis is most common but there can be ptosis, enopthalmos and protrusion of the 3rd eyelid.)
Disruption of nerve roots C6 and C7 leads to denervation of…
The extensors and flexors of the shoulder.
How would you treat brachial plexus avulsion?
Physiotherapy will help prevent contracture of joints.
If no improvement in 6 months~amputate.
These types of tumors often (~80%) occur in the caudal cervical area where they are associated with the brachial plexus. They can however occur in any spinal or cranial nerve. Nerve root neoplasias usually originate peripherally and spread proximally into the spinal cord.
Nerve sheath tumor
What are 3 examples of nerve sheath tumors?
Neurofibromas, neurofibrosarcomas, Schwannomas=malignant peripheral nerve sheath tumors (MPNST).
These types of tumors may compress nerve roots or peripheral nerves and even invade their structures….
Meningiomas, lymphomas, or bony or soft tissue tumors (osteosarcomas, chondrosarcomas, fibrosarcomas, hemangiosarcomas and myelomas).
What are signs of nerve root or peripheral nerve neoplasia?
Chronic progressive monoparesis with neurogenic muscle atrophy and “root signature”- hyperasthesia with limb palpation or manipulation.
