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cases-waxman-solutions - Case 1 Chapter 3 Six months before...

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Case 1, Chapter 3 Six months before presentation, a 35-year-old unmarried woman began to complain that she occasionally saw double when watching television. The double vision often disappeared after she had some bed rest. Subsequently, she felt that her eyelids tended to droop during reading, but after a good night's rest she felt normal again. Her physician referred her to a specialty clinic. At the clinic, the woman said she tired easily and her jaw muscles became fatigued at the end of the meal. No sensory deficits were found. A preliminary diagnosis was made and some tests were performed to confirm the diagnosis. What is the differential diagnosis? Which diagnostic procedures, if any, would be useful? What is the most likely diagnosis? Abnormal, gradual tiring of the muscles for eye movement and chewing is suggestive of fatigue at the neuromuscular junction. The neuromuscular junction can normally transmit at high frequencies so that this type of fatigue does not occur. The prominence of muscular fatigue suggested a diagnosis of myasthenia gravis in this patient. The absence of sensory deficits tends to confirm the diagnosis. Electromyography is a useful procedure for confirmation of the diagnosis; the muscle action potential, which provides a measure of the number of muscle cells that are contracting, decreases in size with repetitive stimulation in myasthenia gravis. In addition, antibodies to ACh receptors are often present and can provide a measure of the degree of disease activity. Injection of anticholinesterase drugs, such as neostigmine or edrophonium chloride, may reverse the fatigue and help to confirm the diagnosis. Treatment centers around the use of anticholinesterase drugs and immunosuppressants, including corticosteroids, which decrease the rate of anti-ACh receptor antibody production. In some patients, thymectomy is effective. Comment: Myasthenia gravis should not be confused with the myasthenic syndrome (Eaton-Larnbert syndrome), an autommiune disease seen in the context of systemic neoplasms (especially those affecting the lung and breast). In the myasthenic syndrome, abnormal antibodies directed against presynaptic Ca- channels, interfere with the release of ACh from the presynaptic ending at the neuromuscular junction. Case 2, Chapter 5 A 15-year-old girl was referred for evaluation of a weakness of the legs that had progressed for two weeks. Two years earlier, she had begun to have pain between the shoulder blades. The pain, which radiated into the left arm and into the middle finger of the left hand, could be accentuated by coughing, sneezing, or laughing. She had seen a chiropractor, who had manipulated the spine; however, mild pain persisted high in the back. The left leg and, more recently, the right leg had become weak and numb. In the last few days, the patient had found it difficult to start micturation.
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