58-year-old woman with double vision and unsteadiness
A 58-year-old woman presents to the emergency department with a 3-day history of double vision and unsteadiness. She is a librarian and first noticed symptoms as difficulty focusing on book spines. Her gait has become progressively clumsy, and she now requires assistance to walk. She reports a self-limited diarrheal illness 10 days ago. Her medical history is significant for hypertension. On examination, temperature is 37.1°C (98.8°F), blood pressure is 138/84 mm Hg, pulse is 88/min, and respirations are 18/min. She has bilateral ptosis and limitation of extraocular movements in all directions. Strength is 5/5 in all extremities. Sensation is intact. She has prominent truncal and limb ataxia. Deep tendon reflexes are absent in the arms and legs. Which of the following is the most appropriate next step in management?
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A
Explanation
Clinical Pearl:
Miller Fisher syndrome, a variant of Guillain-Barré syndrome, presents with the classic triad of ophthalmoplegia, ataxia, and areflexia. The most critical initial step is to assess for respiratory muscle weakness with spirometry to prevent acute respiratory failure.
Explanation:
This patient's presentation with acute ophthalmoplegia, ataxia, and areflexia following a diarrheal illness is classic for Miller Fisher syndrome, a variant of Guillain-Barré syndrome (GBS). The most important initial step in managing suspected GBS is monitoring for impending respiratory failure, a major cause of mortality. Measuring negative inspiratory force (NIF) and forced vital capacity (FVC) is the standard method to assess respiratory muscle strength. Although intravenous immunoglobulins are the definitive treatment, they should be administered after respiratory status is assessed and deemed stable. An MRI of the brain would assess for central mimics like a brainstem stroke, but the finding of global areflexia makes a peripheral neuropathy far more likely and this test is less urgent than respiratory assessment. Administering edrophonium is a test for myasthenia gravis, a diagnosis made unlikely by the presence of ataxia and areflexia. A lumbar puncture can provide diagnostic support but is not the most crucial initial step and does not guide immediate life-saving interventions.
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