Chiari I Malformation

Has anyone heard of this? I found out about this online and it seems to match a lot of my symptoms, such as the vision loss, dizziness, numbness and headaches at the base of the skull (feel kind of like lumbar puncture headaches), which appear in particular when sitting or lying in certain positions. Perhaps it would even explain the heart palpitations.

The only thing is, I have already had an MRI and it wasn’t spotted on that. But then it wasn’t looked at by a specialist. Also, the lumbar puncture I had last year did not suggest high CSF pressure. Maybe I’ll ask my doctor about it anyway.