What is Megalencephaly?

Megalencephaly is a condition in which a person's brain is abnormally large. An average adult brain weighs between 1,300 and 1,400 grams, or between 2.87 pounds and 3.09 pounds. According to The Gale Encyclopedia of Neurological Disorders, the brain of an adult with megalencephaly weighs more than 1,600 grams, or 3.53 pounds.

Megalencephaly may be present at birth. It can also develop over time. In some cases, your brain may reach twice the normal weight.

Megalencephaly can occur alone. It may not occur with any symptoms. It can also occur with a wide range of neurological problems or birth defects. It’s sometimes confused with macrocephaly. This is a condition in which your head is large but not necessarily abnormal.

Three broad types of megalencephaly exist:

Primary Megalencephaly, or benign familial megalencephaly

Secondary Megalencephaly, which occurs as the result of another disorder

Unilateral Megalencephaly, or hemimegalencephaly, which occurs when half the brain is enlarged


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