Bovine Neutology - Musculoskeletal Flashcards
A 4-year-old cow presents with an inability to bear weight on its right forelimb, a dropped elbow, and signs of Horner’s syndrome on the same side. What is the most likely diagnosis, and what are the key clinical signs supporting this diagnosis?
- A. Radial nerve paralysis; signs include dropped elbow and inability to extend the carpus.
- B. Brachial plexus avulsion; signs include inability to bear weight, dropped elbow, and ipsilateral Horner’s syndrome.
- C. Suprascapular nerve injury; signs include atrophy of the supraspinatus and infraspinatus muscles.
- D. Lumbosacral plexus injury; signs include hindlimb weakness and ataxia.
Answer: B. Brachial plexus avulsion; signs include inability to bear weight, dropped elbow, and ipsilateral Horner’s syndrome.
Explanation:
Brachial plexus avulsion in cattle is characterized by lower motor neuron paresis of the affected thoracic limb, resulting in an inability to bear weight and a dropped elbow. Ipsilateral Horner’s syndrome, presenting as ptosis, miosis, enophthalmos, and protrusion of the third eyelid, may also be observed due to disruption of sympathetic nerve fibers. These clinical signs are indicative of brachial plexus avulsion.
What are the common etiologies of brachial plexus avulsion in cattle, and how does the pathophysiology of this condition lead to the observed clinical signs?
- A. Metabolic disorders leading to nerve degeneration.
- B. Traumatic events causing overstretching or tearing of the C6–T2 nerve roots.
- C. Infectious diseases resulting in nerve inflammation.
- D. Congenital malformations affecting nerve development.
Answer: B. Traumatic events causing overstretching or tearing of the C6–T2 nerve roots.
Explanation:
Brachial plexus avulsion in cattle typically results from traumatic injuries, such as excessive traction or abduction of the forelimb during parturition, especially in cases of dystocia. These forces can overstretch or tear the nerve roots of the brachial plexus (C6–T2), leading to loss of motor and sensory function in the affected limb. The resultant nerve damage manifests clinically as an inability to bear weight, a dropped elbow, and potentially ipsilateral Horner’s syndrome due to disruption of sympathetic innervation.
In a cow suspected of having brachial plexus avulsion, what diagnostic steps should be taken to confirm the diagnosis, and what is the general prognosis for recovery?
- A. Perform electromyography; prognosis is excellent with surgical intervention.
- B. Conduct a thorough neurological examination; prognosis is guarded depending on injury severity.
- C. Utilize radiographic imaging of the limb; prognosis is poor without immediate treatment.
- D. Assess serum electrolyte levels; prognosis is favorable with medical management
Answer: B. Conduct a thorough neurological examination; prognosis is guarded depending on injury severity.
Explanation:
Diagnosis of brachial plexus avulsion in cattle is primarily based on a comprehensive neurological examination, focusing on motor and sensory deficits in the affected limb, as well as the presence of signs like Horner’s syndrome. Electromyography may assist in assessing the extent of nerve damage. The prognosis is guarded and largely depends on the severity of the injury. While mild nerve contusions may show partial recovery with supportive care, complete nerve root avulsions often result in permanent deficits, and in severe cases, amputation of the affected limb may be necessary due to non-weight-bearing and potential self-mutilation.
