Megalencephaly (also called macrencephaly) is a condition in which there is an abnormally large, heavy brain that usually fails to function. The brain weight is more than what is normal for the age and gender of the person.


Megalencephaly is thought to be related to a disturbance in the regulation of cell reproduction or proliferation. Proliferation is the process in which nerve cells divide to form new generations of cells. In normal development, neuron growth is regulated so that the correct number of cells is formed in the right place at the right time.


Symptoms of megalencephaly may include:

  • Head enlargement at birth. The head may become abnormally large in the early years of life.

  • Delayed development.

  • Convulsive disorders.

  • Corticospinal (brain cortex and spinal cord) dysfunction.

  • Convulsions (seizures).

This condition affects males more often than females.


There is no certain treatment for megalencephaly.