What Causes Lightheadedness, Muscle Spasms And Fainting Spells While Standing?
Some blood tests necessary, anxiety may be a factor as well.
Detailed Answer:
I read your question carefully and I understand your concern.
The distribution of those symptoms is not really typical for any single organ, whether the brain or other systems, they do not anatomically correspond to a specific area. In a way that is reassuring as there is no indication of any brain lesion.
So that leaves the possibility of a metabolic or hormonal issue as the next possibility. Electrolyte, blood glucose or thyroid function alterations are some possibilities. Anemia is another possible cause as well. So some routine blood tests such as blood count, glucose, liver and kidney function, electrolyte panel, thyroid function are advised.
Also blood test measurement supine and standing by your doctor is advised to screen for possibility of orthostatic hypotension, an excessive drop in blood pressure when standing which may also cause some of those symptoms.
If all those are done and result normal then the possibility of anxiety being the source should be considered. It can commonly manifest with all of those symptoms you mention so a reconsideration of the medication choice or the lexapro dosage may be necessary.
I remain at your disposal for other questions.