Plexus brachialis
The brachial plexus is a network of nerve fibers formed by the ventral branches of the last three cervical (C6-C8) and first thoracic (T1) spinal nerves. It is located in the axillary region between the scapula and the first rib. From this plexus emerge all the peripheral nerves that innervate the forelimb: the suprascapular, musculocutaneous, axillary, radial, median, and ulnar nerves. The radial nerve is the largest and most clinically significant, as it innervates all the extensor muscles of the elbow, carpus, and digits.
The brachial plexus is formed by the ventral branches of spinal nerves C6, C7, C8, and T1 (with variable contributions from C5 and T2). It gives rise to all major forelimb nerves: suprascapular, subscapular, musculocutaneous, axillary, radial, median, ulnar, and lateral thoracic. Electrodiagnostics (EMG, nerve conduction velocity) can help localize and grade severity.
Traumatic injury to the brachial plexus from forelimb hyperextension (e.g., falling into a ditch, foaling injury). May involve avulsion of nerve roots from the spinal cord.
Injury to the suprascapular nerve as it crosses the cranial border of the scapula, typically from direct trauma (collision with doorframes, trees). Causes denervation atrophy of the supraspinatus and
Injury to the radial nerve, most commonly from prolonged lateral recumbency during general anesthesia (compression neuropathy) or humeral fracture.
Traumatic injury to the brachial plexus from forelimb hyperextension (e.g., falling into a ditch, foaling injury). May involve avulsion of nerve roots from the spinal cord. Signs include: Complete forelimb paralysis (flaccid); inability to advance or bear weight on affected limb; dropped elbow; loss of sensation distal to shoulder; rapid muscle atrophy of shoulder and forelimb
Injury to the suprascapular nerve as it crosses the cranial border of the scapula, typically from direct trauma (collision with doorframes, trees). Causes denervation atrophy of the supraspinatus and infraspinatus muscles. Signs include: Characteristic lateral shoulder instability ('shoulder slip') during weight bearing; rapid atrophy of supraspinatus and infraspinatus creating a visible hollow above the scapular spine; lateral subluxation of the shoulder during weight bearing; Rapid dramatic wasting of the muscles on either side of the scapular spine; the scapular spine becomes extremely prominent; shoulder instability; the shoulder may pop laterally during weight bearing; often from running into a solid object.; Visible wasting along one side of the neck; asymmetric neck musculature; may follow trauma or prolonged pressure on the neck.; Obvious muscle wasting below the scapular spine; shoulder visibly slips laterally during walking; angular shoulder appearance; often recovers spontaneously over months if nerve not severed.
Injury to the radial nerve, most commonly from prolonged lateral recumbency during general anesthesia (compression neuropathy) or humeral fracture. Signs include: Inability to extend the elbow, carpus, and digit; 'dropped elbow' with knuckling of the fetlock; inability to bear weight on the limb; dragging the dorsal surface of the hoof
The brachial plexus is formed by the ventral branches of spinal nerves C6, C7, C8, and T1 (with variable contributions from C5 and T2). It gives rise to all major forelimb nerves: suprascapular, subscapular, musculocutaneous, axillary, radial, median, ulnar, and lateral thoracic. Electrodiagnostics (EMG, nerve conduction velocity) can help localize and grade severity.
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