How many Botox treatments will I need to reduce enlarged glabella? (Photos)

It's difficult to tell from your pictures, but this may be bone. If it is due to muscles, a series of treatments with Botox is needed. I suggest following up with a cosmetic dermatologist. Hope this helps.

Botox is not used with the specific purpose of reducing muscle bulk; its function is to weaken (temporarily) the muscle function. Of course, it's possible that over time with consistent injections for maintenance, the muscle bulk may atrophy from disuse but that would likely take at least 4-6 injections over the course of over a year to see visible change in the bulk. 

If this is caused by the strong muscles of your glabella area, then yes, botox (over time) will help these decrease in size. I would recommend an in person assessment with an experienced injector to discuss your options and for a more comprehensive assessment. Good luck!