Hi, thanks for the query. I would like to know what are the symptoms in your sister & how the symptoms/deficits have progressed (gradual/rapid) to ascertain whether or not she has a dementia process. Later on we can dig deeper by means of various investigations like MRI Brain, Neuropsychological assessment, test for Vitamin B12, folate levels, thiamine deficiency; test for neurosyphilis etc. to name a few causes of dementia 9Since you have already tested & ruled out Lyme s disease). If treatable; for example Vitamin B12 deficiency, neurosyphilis etc. we can use appropriate drugs to reverse these conditions & halt further damage to brain. But the damage already occured can not be reversed. Irrespective of all these causes; basic treatment modality of dementia is by drugs named cholinestrase inhibitors+ NMDA antagonist drugs (Donepezil+ memantine) which help to slow the dementia progress & allow more functional & fruitful life. In addition there are certain behavior techniques named as cognitive remediation taught by Psychologist & Psychiatrists to help these patients utilize their depleted brain reserves more effectively. Hope this helps. Good Luck