Thanks for consulting HealthcareMagic!
May be your Dad's condition is due to progression of Alzheimer's. However, certain other neurological conditions like Dementia with lewy Bodies, Vascular Dementia
, Normal Pressure Hydrocephalus
etc need to be ruled out. For this he needs a complete neurological assessment.
Hope I have answered your query. Let me know if you have have any clarifications.
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Wish you good health!