Memantine - worse headaches?

My neurologist started me on Memantine/Namenda for brain fog caused by long COVID. She also said it can help with migraines as well and as I have CFS it can help with fatigue from this. So we thought it could kill several birds with one stone.

Within 2 days of taking it, I got my first thunderclap headache (not ever, I had one in February after a concussion, but first with this medication) and ended up at the ER. The 10/10 pain lasted 10 minutes, causing me to vomit multiple times, but I was in 8.5-9/10 pain for 3 more hours until a Toradol shot and Fioricet broke it at the ER. I got a second thunderclap 3 days later, it woke me out of a dead sleep at 4am. This one lasted 5 hours. After that one broke, a migraine started that has not responded to any abortives. I had finally gotten to a place - after failing preventatives and abortives after a Covid infection last summer - where Botox had started working and allowed Reyvow to become a successful abortive. But not anymore.

I put the pieces together and realized the timing lined up with beginning Memantine and stopped taking it 2 nights ago and the severity of the migraine is reducing. Has anyone else experienced anything like this? It’s also possible it’s connected to having gotten COVID again but my Covid infection was over 4 weeks ago and the thunderclap headaches didn’t start until 2 weeks ago, right when I started Memantine.