Plexus brachialis
The brachial plexus is a network formed by the ventral branches of spinal nerves C6, C7, C8, and T1 (with variable contributions from C5 and T2). It lies in the axilla between the scapula and first rib, medial to the scalenus muscles. From it arise all major nerves of the forelimb: suprascapular, subscapular, musculocutaneous, axillary, radial, median, and ulnar. The radial nerve is the largest and most important clinically because it innervates the elbow, carpal, and digital extensors; damage produces a dropped elbow and inability to bear weight or advance the limb properly. Clinically, trauma (falls, collisions), stretching injuries, or compressive lesions from caudal cervical or first-rib pathology can affect the plexus or its roots. Electrodiagnostics (EMG, nerve conduction) help localize and grade lesions.
Radial nerve paralysis is the classic severe presentation. Proximal lesions may also affect musculocutaneous or axillary function. EMG and nerve-conduction studies aid localization. Prognosis depends on the degree of axonal loss.
## Overview Brachial plexus avulsion or neuropathy is traumatic injury to the network of nerves that supply the forelimb. The plexus can be compressed between the scapula and ribs or stretched by ext
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
## Overview Radial nerve paralysis is loss of function of the radial nerve, most commonly from compression during general anesthesia or from humeral fracture. The horse cannot extend the elbow, carpu
A front leg that cannot bear weight, has a dropped elbow, or shows rapid muscle wasting after a fall or trauma needs immediate veterinary attention. Support the limb carefully during transport.
## Overview Brachial plexus avulsion or neuropathy is traumatic injury to the network of nerves that supply the forelimb. The plexus can be compressed between the scapula and ribs or stretched by extreme limb abduction. The result is partial or complete loss of motor and sensory function to the limb, often producing a non-weight-bearing leg with a dropped elbow and muscle atrophy. ## Causes Falls, collisions, or being cast with a limb trapped are typical. Traction during anesthetic recovery or hobble use has also been implicated. Fractures of the first rib can damage the plexus secondarily. ## Diagnosis Clinical signs of radial, suprascapular, or more extensive nerve deficits (inability to extend the elbow, shoulder instability, knuckling) after trauma are characteristic. Electrodiagnostics and advanced imaging can confirm the extent of injury; radiographs rule out fractures. ## Treatment Anti-inflammatory medication, physical therapy, neuromuscular electrical stimulation, and protective bandaging or splinting to prevent contracture are the mainstays. Surgical exploration is rarely beneficial. Many cases are managed supportively while waiting to see how much function returns. ## Recovery and Prognosis Prognosis is guarded. Some horses regain useful limb function over weeks to months; others remain non-weight-bearing and require euthanasia. Early, intensive rehabilitation improves the chance of a functional outcome. ## Prevention Careful handling during anesthesia and avoidance of situations that trap a forelimb reduce risk. Signs include: non-weight-bearing forelimb; dropped elbow; shoulder instability or lateral rotation; muscle atrophy of the shoulder and arm; knuckling of the fetlock
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.; 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.
## Overview Radial nerve paralysis is loss of function of the radial nerve, most commonly from compression during general anesthesia or from humeral fracture. The horse cannot extend the elbow, carpus, or digit, resulting in a dropped elbow, knuckling, and inability to bear weight normally. Dragging of the dorsal hoof is typical. ## Causes Compression neuropathy or trauma. ## Diagnosis Neurologic examination and radiographs to rule out fracture. ## Treatment Splinting, nursing care, and time. Fracture cases require different management and have a poor prognosis. ## Recovery and Prognosis Fair to good for pure compressive lesions. Grave with humeral fracture. ## Prevention Careful anesthetic positioning. Signs include: inability to extend the elbow, carpus, and digit; dropped elbow with knuckling; inability to bear weight; dragging the dorsal hoof
Radial nerve paralysis is the classic severe presentation. Proximal lesions may also affect musculocutaneous or axillary function. EMG and nerve-conduction studies aid localization. Prognosis depends on the degree of axonal loss.
A front leg that cannot bear weight, has a dropped elbow, or shows rapid muscle wasting after a fall or trauma needs immediate veterinary attention. Support the limb carefully during transport.
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