What is Megalencephaly?
Megalencephaly, also called macrencephaly, is a condition in which an infant
or child has an abnormally large, heavy, and usually malfunctioning brain. By
definition, the brain weight is greater than average for the age and gender of
the child. Head enlargement may be evident at birth or the head may become
abnormally large in the early years of life. Megalencephaly is thought to be
related to a disturbance in the regulation of cell production in the brain. In
normal development, neuron proliferation - the process in which nerve cells
divide to form new generations of cells - is regulated so that the correct
number of cells is produced in the proper place at the appropriate time. In a
megalencephalic brain, too many cells are produced either during development or
progressively as part of another disorder, such as one of the neurofibromatoses
or leukodystrophies. Symptoms of megalencephaly include delayed development,
seizures, and corticospinal (brain cortex and spinal cord) dysfunction.
Megalencephaly affects males more often than females. Unilateral megalencephaly
or hemimegalencephaly is a rare condition that is characterized by the
enlargement of one side of the brain. Children with this disorder may have a
large, asymmetrical head accompanied by seizures, partial paralysis, and mental
retardation. Megalencephaly is different from macrocephaly (also called
megacephaly or megalocephaly), which describes a big head, and which doesn’t
necessarily indicate abnormality. Large head size is passed down through the
generations in some families.
Is there any treatment?
There is no standard treatment for megalencephaly. Treatment will depend upon
the disorder with which the megalencephaly is associated and will address
individual symptoms and disabilities.
What is the prognosis?
The prognosis for infants and children with megalencephaly depends upon the
underlying cause and the associated neurological disorders. The prognosis for
children with hemimegalencephaly is poor.
What research is being done?
The National Institute of Neurological Disorders and Stroke (NINDS) and other
institutes of the National Institutes of Health (NIH) conduct research related
to megalencephaly in laboratories at the NIH and also support additional
research through grants to major medical institutions across the country. Much
of this research explores the complex mechanisms of normal brain development.
The knowledge gained from these fundamental studies will provide a foundation
for developing ways to prevent megalencephaly and the other cephalic disorders.
March of Dimes Foundation
1275 Mamaroneck Avenue
White Plains, NY 10605
Tel: 914.428.7100 888.MODIMES (663.4637)
Source: National Institutes of Health; National Institute of
Neurological Disorders and Stroke