Learning Issues: 1) How long does it take for muscle atrophy? Two types of muscle atrophy could be occurring in this case. Deinnervation atrophy may occur in association with suprascapular nerve or radial nerve paralysis. This type of muscle atrophy can be detected as early as within one week of which the nerve was injured. Disuse atrophy could also be a occurring alone or in conjunction with the nerve damage. If it were simple disuse atrophy, this would be slower in onset and progression and less severe. For instance, if there was a muscle or attachment injury of the triceps muscle in which it was severed, the elbow would drop and there would be nothing for the muscle to work against, therefore causing atrophy. 2) No signs of lameness after trailer trip? No, it has been 4 or 5 weeks since the horses returned from the trailer trip and foal didn't show signs of lameness until two weeks ago. 3) How long for nerve deficits to cause muscle necrosis? Muscle necrosis will probably not occur unless the colt was spending excessive amounts of time lying on one side, thereby causing ischemia, decreased tissue perfusion and hypoxia of the muscle tissue. 4) Can you get contracture of muscle just by lack of use? This is possible but more likely by lack of innervation occurring simultaneously with disuse. In this case muscle shortening/contracture is a big problem. 5) How long does limb edema and swelling typically last after a traumatic incident? Typically, edema and swelling should subside within 1 week of injury. If swelling is greater than one week and causing nerve deficits, then nerve damage can be permanent. 6) Is the dropped shoulder just from pain of a partial fracture of the humerus? Most likely, something else is going on in the shoulder. If it was just the fracture, pain would be very evident and the colt would probably be flexing his shoulder muscle to keep the foot from bearing too much weight. 7) Is there a pain response in any part of the limb? Including hoof? Need to include in plan of action to determine if there are other sources of pain. 8) Why isn't there any elevation in temperature and respiration? Is it a chronic injury now, or is there just a lack of pain? Probably no infection, two week injury, most likely nerve damage or the foal would be in severe pain if only due to a fracture. In this case you would see the elevated vital signs (TPR). 9) Why is he weight bearing? Is it a fracture or nerve deficit? See question #6. 10) Could a kick alone have severed the nerve? What else could have caused paralysis? Paralysis may have been caused by a kick, or direct trauma alone. The radial nerve runs on the lateral side of the arm whaere it emeres from the lateral head of the triceps. This makes the nerve more succeptible to damage from blunt external trauma to the shoulder area. 11) Low lateral radial nerve paralysis? Is this possible? Possible, but the history indicates muscle atrophy and misuse in shoulder area, therefore indicating the problem is probably not in the lower limb. 12) Did the penicillin have any effect? Complications? Much too low dose to cause much of an effect or adverse side effect in this colt. Commonly found on horse farms as the cure-all to anything. 13) Is there any chance of septicemia? How about from the small nicks and scrapes found on limbs? Unlikely, because the colt does not seem febrile or depressed. However, complete work-up will be included in the plan of action to check for inflammation and/or septicemia