Seizures or syncope

smithdiane877, failing the tilt table test usually means a lack of blood flow to the brain. My childhood friend often had absence seizures where blood flow to the brain was interrupted by an epileptic seizure. She would more often stare, but occasionally would fall to the ground. The absence of blood and electrolytes can cause irregular rhythm in the heart resulting in syncope.
Do you remember if you had a seizure in conjunction, or prior to the syncope.
What were you doing immediately prior to the syncope.
You might look for a (or another) neurologist who specializes in epilepsy.
Failing the tilt table test indicates to this rank amateur that the syncopy may be unrelated to the seizure.
Though the physical cause/effect can be different. A seizure can set the stage for the irregular heartbeat resulting in syncope. You likely know way more than I do.

@smithdiane877
I've had thousands of seizures that I have no memory of compared to a syncopal episode that I recall clearly.
Do you have any memories of the episodes?
Differentiating between a syncopal episode and a seizure can certainly be challenging.
Fainting spells are usually shorter than seizures although this isn't always the case.
People generally recover from fainting spells quickly compared to seizures. Seizures often take longer to recover from because seizures frequently are followed by a state of confusion (post ictal state) then followed by sleep. Of course this scenario isn't always the case.
Do you know or did the doctor say what type of seizures they thought you may have had?
Did anyone witness your episodes?
Did you bite your tongue/cheeks, was your body sore or have a headache?

When I fainted I was at the grocery store. I first lost my vision, took a couple steps then passed out. I was out a very short time and remembered everything that happened compared to remembering nothing when I have seizures.
Take care,
Jake

@smithdiane877
You may also want to see a cardiologist to check heart/circulation since you failed the tilt table test. It would be good to share with them your previous imaging of brain. They may want to do an ultrasound of your carotid arteries.

Have you ever had a cervical spine MRI to see if there is any compression of spinal cord/nerve roots or blood vessels?

@smithdiane877
You may also be dehydrated and it would be good to drink at least 50% of your weight in ounces of water with electrolytes added (like LMNT brand). An example of amount would be you weigh 130 pounds and should drink a minimum of 65 ounces of water with electrolytes added.

That is a terrific idea. I am scheduled for an MRI and I will check if the doctor can include the spinal cord/ nerve roots. Thank you!