Hello Judith and welcome to the forum,
There is a section on how to complete review forms in our PIP guides (the section on review forms in the same in both versions).
PIP resources When I am helping someone complete one of those forms I do both - I detail what has changed and itemise what is still the same. E.g. My arthritis is considerably worse now and I can no longer use a shower without grab handles. I still do not have the ability to wash the top half of myself due to pain in my shoulders.
I know the boxes in the forms are very small, and I frequently just type the answers to the 'free text' boxes on a separate sheet and put in the box on the form 'see separate sheet'. If you do that, make sure that you put your name and NI number on each sheet.
I hope that helps
Catherine