Abstract
A large number of intelectually engaging and potentially serious neuromuscular diseases have been presented. The emergency medicine physician must be able to recognize those entities that have the potential to clinically deterioration. The evaluation of weakness requires a comprehensive, broad -based differential that is driven by the history and physical. Diagnostic testing is determined by the clinical suspicion as is the urgency for further work-up. The following are the final diagnoses of the eight illustrative cases that were presented at the beginning of this article. Case 1. This unfortunate woman had a metabolic myopathy that was only diagnosed after enzymatic analysis of a muscle biopsy. Her genetic defect, carnitine palmitoyltranferase deficiency, is unusual as it does not present until late in adolescence or slightly later in life. It is a defect in lipid metabolism in which long-chain fatty acids are unable to gain entrance into the mitochondrion for oxidative degradation. The defect is apparent only after prolonged exercise or fasting. In this patient, rhabddomyolysis led to acute renal failure that resolved without requiring temporary dialysis. Case 2. This patient had an elevated CPK-MM. Her EMG showed myopathic changes and her nerve conduction studies were normal. She had a positive test for antinuclear antibodies. A biopsy of her quadriceps muscle revealed lymphocytic infiltration of the muscle fibers that showed some focal myocyte degeneration. The diagnosis of dermatomyositis was made based on the findings noted previously and the heliotrope hue of her periorbital skin. A search for an occult neoplasm was negative. She responded moderately to a course of high-dose prednisone. Case 3. The laboratory test that confirmed this diagnosis was the potassium of 2.4 mEq/L. The remainder of the electrolytes were normal. Infusion of 20 mEq of potassium over 2 hours led to a prompt return of normal muscle strength. The final diagnosis was hypokalemic periodic paralysis. In this disease there is an inherited defect in the ability of the myocyte to maintain a normal transmembrane potential. The defect is latent until there is a precipitating factor, such as an high carbohydrate meal or prolonged immobility. There is also a form seen with thyrotoxicosis and is essentially cured when the patient becomes euthyroid. The disease is seen most frequently in Asian males, although it is reported in most ethnic groups. Prophylaxis in these patients is with acetazolamide which raises the serum potassium indirectly by causing a metabolic acidosis. Triamterene and spironolactone have also been successfully used on occasion. This patient turned out to have thyrotoxicosis as well. Case 4. This man had both cranial motor and peripheral muscular dysfunction. There was no evidence of nonmotor cranial nerve dysfunction, nor was there evidence of any peripheral sensory deficits. The diagnosis of myasthenia gravis was established by the rapid and transient response of this patient to 2 mg of edrophonium. He was found to have antiacetylcholine receptor antibodies and was also thyrotoxic. He had a stormy course requiring intubation and prolonged ventilation. Eventually, he underwent thymectomy and is stable on pyridostigmine. Case 5. Initially suspected to be hysteria, this patient and his relatives had botulism from home-canned peppers. The index case required prolonged intubation and ventilation. The patients were treated with polyvalent antiserum and gastric lavage to remove the residual contaminated food which was still in their stomachs due to the gastric atony seen with this disease. The botulinus toxin prevents the release of acetylcholine molecules from their storage vesicles in nerve terminals. Thus, this disease is the opposite of the cholinergic syndrome seen with organophosphate insecticide poisonings except that cognitive functioning is not impaired in botulism. Case 6. This is a celebrated case that took a great deal of sleuthing to unravel. The patient entered with what appeared to be pulmonary edema but that was actually bronchorrea associated with muscle weakness and a cholinergic crises. His signs and symptoms fulfilled the acronym SLUD (salvation, lacrimation, urination, defecation). Once it was realized that this was a possibility the family was queried about insecticides; the patient was an inveterate gardener who had just sprayed his greenhouse with an organophosphate pesticide. The patient's pseudocholinesterase level came back very low several days after admission. He was treated with huge doses of atropine, requiring over 100 mg in the first 24 hours to control his bronchorrhea. He was intubated and received pralidoxime as well. He survived to continue his hobby but reverted to organic gardening. Case 7. This case of Guillain-Barre syndrome was obvious by the time the patient was seen. The patient had a mild sensory component and was areflexia and this helped place the lesion in his peripheral nerves. Testing for HIV and EB virus were subsequently negative. He had a protracted course and was treated with plasmapheresis and was not totally recovered six months following his diagnosis. Case 8. Although this patient was felt to have a nonorganic cause of her weakness, she fulfills the criteria for the fibrositis syndrome. This is a condition of heightened sensitivity to painful stimuli in patients with multiple somatic complaints and depression. The debate goes on whether it is truly a rheumatologic disorder or a functional psychiatric illness. At any rate, the emergency physician must realize that there is nothing available at this time for these patients other than support.