A 66-Year-Old Man Comes to the Office with Diplopia That

question 231

Multiple Choice

A 66-year-old man comes to the office with diplopia that progressively worsens toward the end of the day.  The patient has no shortness of breath, trouble swallowing, or generalized weakness.  He is currently receiving low-dose pyridostigmine for treatment of his condition and claims good compliance without significant side effects.  Physical examination reveals fatigable asymmetric ptosis and binocular horizontal diplopia.  Infusion of edrophonium elicits a significant improvement in his symptoms.  Which of the following is the best next step in management of this patient?

• A)Add atropine
• B)Administer pralidoxime
• C)Change long-term therapy to edrophonium
• D)Increase pyridostigmine dosage
• E)Stop pyridostigmine temporarily

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Definitions:

Excitatory Postsynaptic Potential

An excitatory postsynaptic potential (EPSP) is a temporary increase in membrane potential in a postsynaptic neuron, making it more likely to fire an action potential, usually in response to neurotransmitter release.

Neuronal Membrane

The cell membrane surrounding a neuron, which controls the movement of substances in and out of the cell and facilitates electrical signaling.

Saltatory Conduction

Fast propagation of an action potential at successive nodes of Ranvier; saltatory means “leaping.”

Nodes Of Ranvier

Gaps in the myelin sheath around nerve fibers where the axon is exposed and action potentials are regenerated.