Hi and welcome to the Chiari forum.
May I ask where your melanoma is located? I was told, to protect the scar and not allow the sun to burn the skin in that area. I always wore a hat, and when I went in a pool in addition to the hat I wore a sleeveless shirt with a stand up collar to help cover my neck. I have not heard of anyone else saying they developed a melanoma post op.
It is possible the increase of symptoms could be scar tissue creating yet another CSF obstruction. OR it could be a related condition you were not aware of before surgery.
Do you know what type of dura patch was used for your duraplasty?