Does the obligation to recite aloud during prayer cease for a person afflicted with Alzheimer's who forgets, stutters, and struggles with reciting the Qur'an, and is it permissible for him to recite silently what he can from Al-Fatiha or other surahs?

Reciting aloud in prayer is a Sunnah according to the majority of scholars. Whoever omits it forgetfully must perform the prostration of forgetfulness (sujud al-sahw) according to the Maliki and Hanbali schools. Whoever omits it intentionally does not have to perform prostration, and their prayer is valid. If a person cannot recite Al-Fatihah aloud due to forgetfulness, they must recite it silently, because the prayer is not valid without it.