History
Mrs. Cheung was a 70-year-old lady with a history of diabetes.
She presented with a 3-week history of right-sided ptosis without headache.
Physical examination
Neurological examination was pertinent for a right partial ptosis with some variability but no definite fatiguability and equivocal ice pack test. The curtain sign was negative. Pupils were of equal size with normal light reflex. There was no ophthalmoplegia with normal intorsion.
There were no neurological signs over the contralateral limbs.
Investigations
Baseline blood work and CT brain were unremarkable.
Thought process
Given the variability of the right ptosis, the pathology was likely localized to the neuromuscular junction.
A right oculomotor nerve palsy, even medical in etiology, was deemed less likely as the presentation is typically ophthalmoplegia with ptosis (rather than ptosis without ophthalmoplegia).
A strategic midbrain lesion may result in a nuclear oculomotor nerve palsy with ptosis and no ophthalmoplegia, but would typically be accompanied by neurological deficits over the contralateral limbs.
The sparing of the ipsilateral 4th, 5th, and 6th cranial nerves would speak against a cavernous sinus localization.
The most common etiology would be myasthenia gravis.
Next steps
Blood was sent for anti-AChR antibody. A trial of Mestinon was initiated.