A dementia or memory-loss N-648 needs more than a diagnosis label. USCIS usually looks for a clear connection between the medical condition, cognitive testing or treatment history, daily function, and why English or civics testing is not realistic for the applicant.
Sometimes, if the medical professional explains how the condition prevents the applicant from learning or demonstrating English or civics knowledge, not just that the applicant has a diagnosis.
They can help show daily-function examples, missed medication, safety supervision, memory problems, or communication limits, but they do not replace the medical professional’s N-648 explanation.
That risk should be anticipated. The medical record, caregiver examples, and any accommodation request should explain why unclear answers are part of the condition rather than a credibility problem.