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Neurological Emergencies

A 55-year-old alcoholic man is brought in to the emergency room in a confused but nonagitated state. Significant examination findings include ophthalmoparesis, nystagmus, and ataxia. Emergency administration of which of the following medications is appropriate in the treatment?

a. Glucose

b. Magnesium sulfate

c. Pyridoxine

d. Cyanocobalamin

e. Thiamine

The answer is e. Without rapid replacement of thiamine stores, the patient with acute Wernicke encephalopathy may die. Usually 50 to 100 mg of thiamine is given intravenously immediately. This is followed over the course of a few days with supplementary thiamine injections of 50 to 100 mg. Without thiamine, the patient will develop periaqueductal and mamillary body lesions, which will be clinically apparent as autonomic failure. With chronic thiamine deficiency, neuronal loss occurs in alcoholic persons at least partly because of this relative vitamin deficiency. Purkinje and other cells in the cerebellar vermis will be lost to the extent that gross atrophy of the superior cerebellar vermis will be evident.

A 66-year-old woman presents with weakness worsening over the past 3 hours. The weakness began in her face, but now involves most of her body. She had made her own jam several months before and tasted a sample of it early this morning prior to discarding it because it smelled rancid. On further electrophysiologic testing, which of the following abnormalities would be most characteristic of this patient's illness?

a. Abnormal visual evoked responses (VERs)

b. Abnormal brainstem auditory evoked potentials

c. Posttetanic potentiation of the compound muscle action potential

d. Conduction block

e. Fibrillation potentials

The answer is c. Botulism is a disorder of the neuromuscular junction (NMJ). The characteristic findings are decremental response of the muscles to repetitive stimulation of the nerve at a low frequency (2-5 Hz) and incremental response to repetitive stimulation at high frequency (20-50 Hz). Other disorders of the NMJ, such as myasthenia gravis and Lambert-Eaton myasthenic syndrome (LEMS), also manifest with decremental response to repetitive stimulation at low frequencies due to depletion of acetylcholine in the synaptic cleft. Higher rates of stimulation lead to increased calcium in the presynaptic terminal, which allows more acetylcholine to be released in presynaptic disorders such as botulism and LEMS, thereby increasing the response of muscle. However, in myasthenia gravis, which is characterized by loss of acetylcholine receptors postsynaptically, there is no increase in response at higher rates of stimulation, because there is already a maximal amount of acetylcholine ...

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