Does anyone know?? The experts sure don't

My wife has meningeal carcinomatosis, cancer in the cerebral spinal fluid that has not so far attatched in the brain. She has chemo through her omayrra resevoir in her head. She has frequent and severe headaches. Her oncologist said the headaches should be lessening and by this time gone due to chemo. He said the cancer cell count is negative to very low and cannot explain the headaches. Question 1: does the chemo irritate the meningeal linings around the brain? Question 2: is there a fluid or surfactant between the layers like the lungs have? if there is a fluid or lubricant between layers is the chemo effecting the fluid/surfactant like with pleurisy in the lungs? could her headaches be the same as a friction rub like pleurisy? her headaches start when she moves her hef head. I am racking my brain to come up with an explanation since the experts do not know.