Update Post Avastin, 18 months post diagnosis

My husband, diagnosed May 2015, with inoperable tumor in his right frontal lobe, had the usual radiation/temodar protocol, post radiation chemo only four months. Important to note; 60% of his brain was radiated because of the placement of the tumor(s). After much urging from his UCLA neuro-onc, he had four infusions of Avastin, starting end of August 2016. The results were not what we had hoped, he got weaker after each infusion, to the point that he was back in his wheelchair after being ambulatory post shunt in early July. He is just now clawing his way back from the effects of Avastin, which also include fatigue, and fogginess. It is too soon to tell if Avastin will have any beneficial effects for him. His post Avastin MRI showed a sizable reduction of his tumor and much less inflammation. It also showed possible necrosis.  Two weeks ago he had a major seizure, his neuro-onc can't explain it. I also asked my husband's neuro-onc if he was experiencing aphasia and her response said no, that the EEG showed a slowness of the brain. I'm not sure what that means.  I asked if conflating thoughts, ideas, imagining experiences that didn't occur, word confusion be defined as slowness? And doesn't an EEG just map one moment of time? Would the results of an EEG be different without medication, morning vs afternoon, etc? I need help understanding and also to set my expectations on remapping and what I thought was a pliable brain.  I thought these symptoms would have been a left temporal lobe issues, not right. Does anyone have a similar experience to share?
BTW, his tumor is MGMT methylated and IDH1 non-mutated.