In this video we demonstrate a case of a patient presenting with a two-year history of muscle weakness. The patient had been previously diagnosed with seronegative myasthenia gravis after negative laboratory workup and imaging studies. We used the Tensilon test in an unusual manner to further evaluate for potential neuro-ophthalmologic disorder. We discuss how to approach diagnostic uncertainty in patients presenting with features atypical for myasthenia gravis and how to exclude a diagnosis of organic disease.