Microcephaly is a rare condition in which the head is
abnormally small. Compare microcephaly to
head is abnormally large.
HOW SMALL DOES THE HEAD HAVE TO BE TO
QUALIFY AS MICROCEPHALY?
Technically, any head in which the skull is not able to hold more than 1349 milliliters
(equal to about one fourth of a gallon) qualifies as microcephaly. A milliliter is one
thousandth of a liter, meaning that it takes one thousand milliliters to equal one liter.
One liter is equal to about one fourth of a gallon. Now that you know how much is in a
liter, you can tell that a milliliter is a very small amount of liquid. The normal range for the
amount of milliliters that can fit in the skull is 1350 to 1450 milliliters. Heads in this range
The head of an individual with microcephaly is two or more standard deviations below
the average head size of a normal individual that is the same age, race, and sex. A
standard deviation is a measure of the degree in which something varies from the
average. Not all people have the exact same head sizes. However, most people's head
sizes fall within a normal range. The normal range is typically defined as falling within
one standard deviation below the average and one standard deviation above the
average. The more standard deviations away from the average that something gets, the
more abnormal it is.
WHEN DOES MICROCEPHALY DEVELOP AND WHAT CAUSES
Microcephaly is usually present at birth, but it can also develop
during the first few years of life. Thus, it is possible for the head to
be normal in size at birth, but to stop growing at a normal rate,
causing it to be too small. Microcephaly can be caused by brain
damage before birth due to an illness known as German measles.
German measles is characterized by fever, difficulty breathing, a red
rash, joint pain, and enlarged lymph nodes (small egg-shaped
structures in the body that help fight infection).
Brain damage during birth can also lead to microcephaly, as can disease or any trauma. Trauma is most
likely to lead to microcephaly during the last three months of pregnancy or when the child is a young infant.
Microcephaly can also be caused if the mother has an infection while pregnant or if she is exposed to
harmful substances during early pregnancy, such as x-rays (a type of energy) or chemicals. Another
cause of microcephaly is if the bones of the skull come together too early. For genetic (inherited) causes
of microcephaly, see the next section.
CAN MICROCEPHALY BE INHERITED FROM PARENTS?
Yes. There is rare form of microcephaly (known as microcephaly vera) in which the head is extremely
reduced in size and is inherited from the genes of parents. Genes are units of material contained in a
person's cells that contain coded instructions as for how certain bodily characteristics (such as eye color)
will develop. A cell is the smallest, most basic unit of life, that is capable of existing by itself. All of a
person's genes come from his/her parents. This is why people have physical characteristic of their
Microcephaly can also be caused by an abnormality in a person's chromosomes. Chromosomes are
structures in a person's cells that contain naturally occurring substances known as proteins and a
substance known as DNA (an abbreviation for deoxyribonucleic acid). DNA is a chain of many connected
genes (see prior paragraph).
BESIDES APPEARING SMALL, WHAT ELSE DOES THE HEAD OF A PERSON WITH
MICROCEPHALY LOOK LIKE?
Besides appearing small, the head of a person with microcephaly generally appears flat in the back, the
front of the head slants backwards, and the top of the head is pointed. The scalp (skin covering the head)
is loose and often wrinkly. The small size of the child's head will become more obvious as the child gets
WHAT ARE THE BRAINS AND INTELLIGENCE LIKE OF PEOPLE WHO HAVE MICROCEPHALY?
In microcephaly, the brain is underdeveloped and brain functioning is usually abnormally slow. This results
in some degree of mental retardation (slowness), and thus low intelligence. Hyperactivity (abnormally
increased activity of the body) commonly occurs. The degree of mental retardation and hyperactivity
varies with each child. Speech and motor movement may be delayed or seriously impaired. The person
with microcephaly may be clumsy or may have a condition known as spastic quadriplegia. In spastic
quadriplegia, there is a decreased ability to move and spasms (sudden, involuntary muscle movements)
occur in the legs and arms. Convulsions can also occur, which are abnormal, severe, involuntary muscle
movements. However, vision, hearing, and the sense of touch are spared.
WHAT ARE THE FACIAL FEATURES LIKE OF PEOPLE WITH MICROCEPHALY?
The facial features of people with microcephaly are usually normal. This is because the face grows at a
normal rate in people with microcephaly, while the rest of the head does not. This means that the face will
appear large when compared with the head.
IS THE REST OF THE BODY SMALL IN PEOPLE WITH MICROCEPHALY?
Yes. The body is often underweight and dwarfed looking in people who have microcephaly, although the
head is smaller when compared to the rest of the body.
CAN MICROCEPHALY BE TREATED?
Unfortunately, there is no form of treatment for microcephaly. Nursing care generally focuses on treating
specific symptoms, providing support, help, and education to parents so they can learn how to take care
of a brain-damaged child.
WHAT IS THE LIFE EXPECTANCY OF PEOPLE WITH MICROCEPHALY?
The life expectancy of people with microcephaly is generally low. The exact life expectancy varies
depending on the presence of associated abnormalities.
WHAT OTHER WORDS ARE RELATED TO MICROCEPHALY?
Microcephaly is also known as microcephalia, microcephalism, nanocephalia, and nanocephaly. This is
why nanocephalic, nanocephalous, microcepahlic, and microcephalous means relating to or characterized
WHY IS IT CALLED MICROCEPHALY?
Microcephaly comes from the Greek word "mikros" meaning "small," and the Greek word "kephale"
meaning "head." Put the two words together and you get "small head."