Her condition has drastically changed

Hello, my mother was diagnosed with stage 4 lung cancer with metastasis to different areas. She is a 50 year old lady (non smoker). Our oncologist at UCSF put her on Tagrisso when she was first diagnosed, in which it has reduced the tumor by a lot in her lung. About 4 months ago, her symptoms, behaviors and body functions have drastically changed and continuously get worse. Our oncologist also doubled her tagrisso dose about a month ago, to ensure treatment. Lately, she has had impaired speech, her motor movement have weakened and has loss of balance. It’s hard to move some of her body parts. She needs a caregiver (our family) practically 24/7. She has also became very nervous and hard to sleep. Our oncologist was a bit nervous recently that it could possibly be or not be Leptomingeal spread. They have not diagnosed it yet, but she has done her Lumbar puncture and blood tests about a week ago. The blood work in her CSF looked all to be normal, but the cytology report has not come out yet. Will be in by this week. Her brain MRI and CT did not show any cancerous cells or tumors. Any insight on this would be great, as we’re trying to figure out the best way to manage her symptoms as of time being. There seems to be a neurological issue and it seems like her CNS is affected. But our oncologist has yet to diagnose any of that. He is well aware of all her symptoms and was not too sure about what’s going on. He is awaiting the cytology results for her spinal fluid. Thank you!