<s>[INST] When my mother passed away, she had been diagnosed with "water on the brain".  I saw the cat scan.  The neurologist said it was not there, but always refused to operate.  Why would he do this.  Many of her symptoms were similar to alsimers (sp), according to my family doctor. [/INST] The term refers to a condition known as HY Chat Doctor.  A CT scan is sometimes able to pick this condition up but not always and even if it does rarely do it ever lead to surgery and rarely SHOULD it lead to surgery.  If the neurologist did not believe she suffered from this condition then, that is why no surgery was performed.  By the way, neurologists don't operate on brains...neurosurgeons do.  Alzheimer's disease is also not a reason to operate. </s>