Interpretation of positive edrophonium (Tensilon) test in patients with end-stage renal disease

[A case of Miller Fisher syndrome with a false-positive edrophonium test]

A 69-year-old woman presented with acute bilateral ptosis, ophthalmoplegia, ataxia, and hyporeflexia in the extremities following an antecedent upper respiratory infection. We suspected that she had Miller Fisher syndrome (MFS) and performed an edrophonium test (ET) to rule out myasthenia gravis (MG). Edrophonium chloride improved the patient's bilateral ptosis, but not her ophthalmoplegia. Given the absence of the waning phenomenon on electrophysiological examination, the anti-acetylcholine receptor antibody, and a diurnal variation of symptoms, we concluded that the ET result was a false-positive. A diagnosis of MFS was confirmed by the presence of a positive anti-GQ1b antibody. To our knowledge, this is the first case report of MFS with a false-positive ET.

Advances in the diagnosis of neuromuscular junction disorders

Disorders of the neuromuscular junction have a wide range of clinical presentations, which frequently poses a diagnostic challenge to evaluating clinicians. This article describes the tests used in the diagnosis of diseases of the neuromuscular junction, reviews the evidence supporting the use of each test, and proposes guidelines for their efficient utilization. A focused review of the literature was employed. Reports from four main categories of diagnostic tests (pharmacologic, electrodiagnostic, immunologic, and miscellaneous tests) were reviewed, and the sensitivity and specificity of each test in the diagnosis of specific neuromuscular junction diseases were examined. The clinical presentation determines which diagnostic tests should be utilized in individual cases of suspected neuromuscular junction disease. However, knowledge of the sensitivity and specificity of each test can help to focus the diagnostic evaluation and maximize the diagnostic yield of each test.

Mechanisms of antibiotic neurotoxicity in renal failure

Neurological complications of antibiotics are relatively common in renal failure. Central nervous system neurotoxicity due to penicillin and beta-lactam antibiotics is best documented with fewer accounts of ototoxicity, peripheral nerve toxicity and neuromuscular blockade. In the context of risk stratification, the goal of this review is to explore the mosaic of factors in renal impairment that may contribute to susceptibility to antibiotic neurotoxicity. Improved knowledge of the pathogenesis of these formidable adverse events among the renal failure subjects should help prevent antibiotic neurotoxicity in the future.