Final answer:
Based on the symptoms of lightheadedness and one-sided weakness, the potential diagnosis for the 26-year-old woman is a stroke, which is a medical emergency and calls for immediate treatment.
Step-by-step explanation:
The sudden onset of lightheadedness and generalized weakness of the left lower and upper extremities in a 26-year-old woman is concerning for a potential stroke. A stroke can manifest with neurological symptoms such as inability to move or feel one side of the body, problems with speech, confusion, and dizziness. It is a medical emergency caused by a disruption of blood flow to the brain, leading to neuronal death in the affected region. Strokes require rapid assessment and immediate medical attention, and treatment options may include medication to dissolve clots and prevent future strokes, as well as various forms of physical therapy.