Megalencephaly is a condition in which there is an abnormally large brain. It is usually functioning abnormally. Megalencephaly is, by definition, when the brain weight

Weight

In science and engineering, the weight of an object is the force on the object due to gravity. Its magnitude , often denoted by an italic letter W, is the product of the mass m of the object and the magnitude of the local gravitational acceleration g; thus:...

 is greater than average for the age

Ageing

Ageing or aging is the accumulation of changes in a person over time. Ageing in humans refers to a multidimensional process of physical, psychological, and social change. Some dimensions of ageing grow and expand over time, while others decline...

 and sex

Sex

In biology, sex is a process of combining and mixing genetic traits, often resulting in the specialization of organisms into a male or female variety . Sexual reproduction involves combining specialized cells to form offspring that inherit traits from both parents...

 of the infant

Infant

A newborn or baby is the very young offspring of a human or other mammal. A newborn is an infant who is within hours, days, or up to a few weeks from birth. In medical contexts, newborn or neonate refers to an infant in the first 28 days after birth...

 or child

Child

Biologically, a child is generally a human between the stages of birth and puberty. Some vernacular definitions of a child include the fetus, as being an unborn child. The legal definition of "child" generally refers to a minor, otherwise known as a person younger than the age of majority...

. Head enlargement may be evident at birth or the head may become abnormally large in the early years of life.

Symptoms

Symptoms of megalencephaly may include delayed development, convulsive disorders, corticospinal (brain cortex and spinal cord

Spinal cord

The spinal cord is a long, thin, tubular bundle of nervous tissue and support cells that extends from the brain . The brain and spinal cord together make up the central nervous system...

) dysfunction, and seizures.

Prognosis and treatment

The prognosis for individuals with megalencephaly largely depends on the underlying cause and the associated neurological disorders. Treatment is symptomatic. Megalencephaly may lead to a condition called macrocephaly

Macrocephaly

Macrocephaly , occurs when the head is abnormally large; this includes the scalp, the cranial bone, and the contents of the cranium.-Causes:...

. Unilateral megalencephaly or hemimegalencephaly is a rare condition characterized by the enlargement of one-half of the brain. Children with this disorder may have a large, sometimes asymmetrical head. Often they suffer from intractable seizures and mental retardation. The prognosis for those with hemimegalencephaly ranges from poor to highly functioning. In some cases, children with hemimegalencephaly are severely mentally retarded and must undergo a hemispherectomy

Hemispherectomy

Hemispherectomy is a very rare surgical procedure where one cerebral hemisphere is removed or disabled. This procedure is used to treat a variety of seizure disorders where the source of the epilepsy is localized to a broad area of a single hemisphere of the brain...

to stop seizure activity. In others, seizure activity can be controlled by medication; and the affected child develops mentally and physically trailing normal development by 1–2 years.

External links

• Cleveland Clinic
• http://www.news.com.au/couriermail/story/0,23739,24457932-952,00.html