Thank you for your question. The most common cause for unilateral ptosis (drooping) would be due to paralysis of the third cranial nerve. The third cranial nerve (CNIII) supplies muscles around the eye and eye lid. When CNIII is affected it can lead to drooping of the eyelid on one side.
CNIII paralysis can be caused by several different conditions. More commonly, CNIII paralysis can be caused by a vascular infarct (stroke) within various areas of the brain. We strongly recommend that you take your grandmother to the emergency department to be evaluated for a possible stroke. The sooner this is determined, the faster treatment can be started, which will facilitate her recovery in a more successful manner.
Thank you and AskTheDoctor.com wishes your grandmother a speedy recovery.
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