The problematic symmetry between brain birth and brain death.

The possible symmetry between the concepts of brain death and brain birth (life) is explored. Since the symmetry argument has tended to overlook the most appropriate definition of brain death, the fundamental concepts of whole brain death and higher brain death are assessed. In this way, a context is provided for a discussion of brain birth. Different writers have placed brain birth at numerous points: 25-40 days, eight weeks, 22-24 weeks, and 32-36 weeks gestation. For others, the concept itself is open to question. Apart from this, it needs to be asked whether a unitary concept is an oversimplification. The merits of defining two stages of brain birth, to parallel the two definitions of brain death, are discussed. An attempt is then made to map these various stages of brain birth and brain death onto a developmental continuum. Although the results hold biological interest, their ethical significance is less evident. Development and degeneration are not interchangeable, and definitions of death apply specifically to those who are dying, not those who are developing. I conclude that while a dual concept of brain death has proved helpful, a dual concept of brain birth still has problems, and the underlying concept of brain birth itself continues to be elusive.