RobNorth makes a good point at 00.06.
Your mother is 90 years of age, I would suspect that she has some short term memory loss which as Ratter and others have said could be due to "old age",....then what is the point of an MRI brain scan other than of academic value?
The scan plus other factors may differentiate Alzheimer's disease; , cortical basal degeneration; , Creutzfeldt-Jakob disease;, dementia with Lewy bodies;, frontotemporal dementia; , motor neuron disease;, progressive supranuclear palsy BUT...so what?, there is very little that can be done for any of the above disorders.
80% of dementias are due to Altzheimers for which little can be done from the point of view of treatment OR as Ratter said it is just "old age".
"Has anybody any information to pass on?" Not really.