Imaging Quiz Answer: A Soldier's Neck and Shoulder Pain
Carlos E. Jiménez, MD; Elmer J. Pacheco, MD; Albert J. Moreno, MD; Alan L. Carpenter, DOTHE PHYSICIAN AND SPORTSMEDICINE - VOL 24 - NO. 6 - JUNE 96
The patient's radiographs were normal. The bone scans demonstrated bilateral increased activity in the soft tissue in the supraclavicular regions, corresponding to the location of the trapezius muscles (figure 3). These findings suggested rhabdomyolysis, which was confirmed by the patient's serum creatine phosphokinase (CPK) level of 877 U/L (the normal range is 20-110 U/L). The serum and urinary myoglobin levels and renal function parameters were within normal limits.
Treatment. The patient was treated with rest, analgesics, and increased fluids. Three days later his symptoms were almost resolved, and his CPK level had returned to normal. Treatment of this condition mainly consists of maintaining an adequate circulating fluid volume, correcting any metabolic disturbances, and ensuring sufficient diuresis to prevent renal complications (1). The etiology of this muscle injury most likely was the heavy bilateral pressure from the soldier's backpack shoulder straps during the long training march.
Rhabdomyolysis, the disintegration of skeletal muscle tissue, can result from numerous causes, including trauma, overexertion, pressure necrosis, heatstroke, and frostbite (2). Rhabdomyolysis appears to be a relatively common sequela of diverse training and competitive sports involving strenuous exercise (3,4). Contributing factors include lack of training, lack of heat acclimatization, profuse sweating, insufficient intake of salts, and high ambient temperature (1).
Clinically, the patient can present with many different symptoms—from mild myalgia to severe muscle pain and weakness with involvement of multiple organ systems. Other signs and symptoms include confusion, malaise, tachycardia, hyperthermia, nausea, vomiting, muscle stiffness, and contractures. Acute renal failure, life-threatening cardiac dysrhythmia, and compartment syndrome are the major complications of severe rhabdomyolysis.
The most suggestive laboratory abnormality seen in rhabdomyolysis is elevated serum CPK that is at least five times the normal value. A rise in serum myoglobin precedes the serum CPK elevation, but because the level returns to normal within 6 hours of muscle injury, this finding is helpful only for an early diagnosis of rhabdomyolysis.
Bone scintigraphy involves the intravenous injection of a bone-seeking radiopharmaceutical (in this case, technetium 99m labeled diphosphonate). Regional bone blood flow rate and bone formation rate are two of the major factors that influence the uptake of bone-seeking agents. Soft-tissue uptake of these radiopharmaceuticals will occur in certain instances. In rhabdomyolysis, uptake is believed to be secondary to cell death. This results in an intracellular influx of calcium and the formation of various calcium phosphate complexes, providing sites for radionuclide deposition. The bone scan pattern for rhabdomyolysis usually features increased activity in the muscle groups involved. The scintigraphic images are usually most prominent from 24 to 48 hours after injury and typically resolve within 1 week.
Although in most cases a bone scan is not necessary to diagnose rhabdomyolysis, it is extremely helpful when rhabdomyolysis is suspected but the serum CPK has normalized and there is unexplained renal insufficiency. In these instances, the bone scan may well be the imaging test of choice. It will not only confirm the diagnosis, but will also determine the extent of muscle injury (5).
The opinions or assertions presented here are the private views of the authors and are not to be construed as official or as reflecting the views of the US Department of the Army or Department of Defense.
Dr Jiménez is a second year fellow, Dr Pacheco is a staff physician, Dr Moreno is chief, and Dr Carpenter is a staff physician, all in the Nuclear Medicine Service in the Department of Medicine at William Beaumont Army Medical Center in El Paso, Texas. All are members of the Society of Nuclear Medicine. Address correspondence to Carlos E. Jiménez, MD, 7453 B O'Reilly St, El Paso, TX 79930-4226.