DLA to PIP Transfer

Hi This my First post,
I have been in receipt of DLA Lower rate for personal help and higher rate Mobility since 2006. I must now transfer to PIPs. I have read in some of the information in your guides that the assessors do not have to take any notice of what medical reports I have from my consultants and GP that have been received whilst claiming DLA. I have 4 letters from different medical professionals stating that operations done to my brain stem, spinal decompression will not improve thus stopping me from having surgery on my knee and also any further back operation.
I do not see how they could disregard these reports as none of my treatment or their decisions would change one bit.

Thank you Gorden.
The latest letter from my Neurosurgeon consultant was a few days after the clinic date of 18/04/2019. He sent a report following on from an MRI scan to my spine surgery that he asked for in december 2018, to my GP and a copy to me. In this he details the condition of my spine, says that I have significant arthritis of both feet and left knee.
He goes on to list previous cerebellar abscess which required surgery, then lists 10 other points that he recommends as well as pointing out that after discussing all options with me, that ant benefit from any further surgery at all on me as its unlikely and too much of a risk.
The other reports I have are from the last six months in 2018 where I was examined by the consultants who have came to the decisions that have been fed into that report.