Is it permissible for the debtor to receive his mother's zakat money, she being afflicted with Alzheimer's, to pay off her debt to him?

If a person reaches a state where they are unable to manage their own wealth, their case is brought before a judge to appoint someone to administer their wealth in a way that serves their best interest. If a judge is unavailable, the family may appoint someone to invest the money, disburse its Zakat, and settle its due obligations. The money may not be disposed of in a way that does not serve their interest. If you are the guardian of your mother's wealth and pay its Zakat, and you are among those eligible for Zakat due to a debt you cannot repay, there is no harm in you taking Zakat for yourself to settle your mother's debt to you.