What Causes Pressure Headaches With Pressure Down Face And Neck?

When I stand up or stretch I get severe pressure headaches and pressure down my face and neck. I then lose my vision (sometimes my hearing aswell) and fall down and sometimes I will have some type of seizure. After this happens I'm usually a bit confused and can't remember all of it. After it's over I feel extremely weak and feel my heart pounding and blood will start to pool in my hands and feet.
I have had an MRI.. they found nothing but a retention cyst on the left maxillary antrum. Could this be what is causing my symptoms.