Evidence and mechanisms of retrogenesis in Alzheimer's and other dementias: management and treatment import.

Retrogenesis is the process by which degenerative mechanisms reverse the order of acquisition in normal development. Alzheimer's disease (AD) and related conditions in the senium have long been noted to resemble "a return to childhood" Previously, we noted that the functional stages of AD precisely and remarkably recapitulated the acquisition of the same functional landmarks in normal human development. Subsequent work indicated that this developmental recapitulation also applied to the cognitive and related symptoms in AD. Remarkably, further investigations revealed that the same neurologic "infantile" reflexes, which mark the emergence from infancy in normal development, are equally robust indicators of corresponding stages in AD. Neuropathologic and biomolecular mechanisms for these retrogenic processes are now evident. For example, the pattern of myelin loss in AD appears to mirror the pattern of myelin acquisition in normal development. Also, recent findings indicate that mitogenic factors become reactivated in AD, and, consequently, the most actively "growing" brain regions are the most vulnerable. Because of this robust retrogenic process, the stages of AD can be translated into corresponding developmental ages (DAs). These DAs can account for the overall management and care needs of AD patients. A science of AD management can be formulated on the basis of the DA of the Alzheimer's patient, taking into consideration differences of AD from normal development as well as homologies.