De novo PS1 Mutation (Pro436Gln) in Very Early-Onset Posterior Variant of Alzheimer's Disease Associated with Spasticity: a case report Manuscript Number: 21-0420R2 Author(s): Pablo Agüero, Guillermo García-Ribas, Estrella Gómez-Tortosa, Isabel Lorda, Patricia Paredes Rodríguez, María José Sainz, Raquel Téllez, Almudena Ávila