Macrocephaly

What is Macrocephaly?

Measuring the size of your child’s head (specifically, the distance around the forehead from the back of the head), often called OFC, allows doctors to monitor their growth and development. Generally, the head circumference increases by about 2 cm each month for the first three months of life, 1 cm per month from three to six months, and then by 0.5 cm each month for the second half of the first year. In the first year of life, the average total increase is about 12 cm. The head continues to grow after one year, although at a slower pace of 1 cm every six months until the age of three, and then 1 cm per year until the age of five.

However, measuring the head circumference accurately can be a bit tricky, especially in younger infants who may be fidgety or have thick hair. Doctors must be careful to correctly position the measuring tape. Regular measurements at every routine health check-up are needed up to 24 to 36 months to check growth speed. It’s also important to monitor head size more frequently in high-risk cases, like premature babies or those suffering from bacterial meningitis, subdural hematoma (bleeding outside the brain), or hydrocephalus (build-up of fluid in the brain). If the measurements seem abnormal, they should always be verified.

Macrocephaly is a condition where a child’s head size is significantly larger than average (more than two standard deviations above the average for their age and sex), in the top 97% percentile. Often confused with macrocephaly, megalencephaly is a separate term that points to enlarged brain structures. Macrocephaly is a broader term that includes both megalencephaly and other reasons for an increased head size, like fluid collection around the brain.

It’s necessary to understand that different causes can lead to macrocephaly. This information aids in distinguishing harmless macrocephaly from conditions that need urgent investigation and treatment to avoid long-term brain damage and developmental delays.

What Causes Macrocephaly?

Macrocephaly is a condition where a person has a larger than normal head size. This change in head size can happen in children before the soft spots (fontanelles) and natural seams in the skull (sutures) close up. The causes of macrocephaly can vary. It may be due to an increase in brain tissue, known as megalencephaly, or an increase in the fluid that surrounds the brain (cerebrospinal fluid or CSF). Other times, macrocephaly can be caused by a rise in blood, thickened bone, or from increased pressure inside the skull.

Megalencephaly could be anatomic or metabolic. Anatomic megalencephaly is usually genetic and not harmful. Infants with this condition usually have a large head size at birth compared to their body size which continues to grow quickly, but they generally do not face health issues. However, there are also situations where megalencephaly is associated with genetic conditions, such as tuberous sclerosis, neurofibromatosis, autism, or achondroplasia, which can also cause macrocephaly.

There are also syndromes that can cause megalencephaly. For example, Sotos syndrome, also called cerebral gigantism; Fragile X syndrome, which is caused by a specific genetic issue and causes intellectual disability; Nevoid basal cell carcinoma syndrome or Gorlin syndrome, which increases the risk of skin cancer; and Cowden syndrome, which increases the risk of thyroid or breast cancers. All these conditions can cause an individual to have an enlarged head size.

In metabolic megalencephaly, the brain tissue increases due to the accumulation of certain products inside the brain tissue. Conditions that can cause this type of megalencephaly include certain genetic diseases like Alexander disease or Tay-Sach disease.

Macrocephaly could also be due to an increase in cerebrospinal fluid. In a condition called hydrocephalus, there is an excessive amount of CSF in the brain which increases the pressure and size of the fluid chambers in the brain. This can sometimes lead to developmental issues, and may require surgery to relieve the pressure.

The head size can also increase due to the presence of a clot or malformation in the blood vessels, or if there is an increase in the thickness of the skull. These conditions can affect the overall size of a person’s head. If there is bleeding within the skull, it may be related to an intentional injury, and further investigation would be needed. On physical examination, the patient may have other injuries or bleeding inside the eye. They might also have symptoms such as seizures, nausea/vomiting, tiredness, or irritability.

Finally, when the skull’s thickness increases, it can be due to an expansion of the bone marrow – as seen in a condition known as thalassemia major – or from specific bone conditions that affect the skull’s shape and size.

Risk Factors and Frequency for Macrocephaly

Macrocephaly, a condition where the head is abnormally large, is found in about 2% to 3% of the population. It occurs equally in both males and females. The occurrence of macrocephaly, such as where in the world it happens the most, often depends on the specific underlying cause of the condition.

Signs and Symptoms of Macrocephaly

Macrocephaly, or having a larger than normal head size, can be identified using a standard head measurement. This involves using a measuring tape to measure the circumference of the head, going above the eyebrows in front and over the most noticeable part of the back of the head . This measure, known as the occipital frontal circumference (OFC), is then compared to international growth charts. If a child under two years old has a head circumference at or above the 97th percentile for their age and sex, they meet the criteria for macrocephaly.

To understand if the macrocephaly is a symptom of another condition or syndrome, doctors take a detailed history. This includes information about birth measurements and growth over time, other medical conditions, developmental milestones, and any family history of macrocephaly. Any past brain trauma or infection, like meningitis or bleeding inside the brain during the newborn period, could lead to a condition known as hydrocephalus. These patients need to be closely monitored.

Alongside measuring the head, doctors also examine the baby’s overall appearance and facial features, and perform a thorough neurologic exam to look for signs of any underlying condition or genetic syndrome. They also check the eyes, as an increase in pressure inside the skull can sometimes cause a condition called papilledema, although this might not be visible in babies with still open ‘soft spots’ on their heads. Other specific tests include shining a light through the scalp to check the skull, checking for signs of bone disorders, and listening to the skull with a stethoscope.

Testing for Macrocephaly

If your child’s development is normal and they do not show any neurological issues or signs of a genetic condition, and there’s no family history of developmental or neurological problems, then a tool known as Weaver curves can be used. This tool uses both parents’ head sizes to create a standard range. If your child’s head size is within this range, then there’s no need for further evaluation.

However, if your pediatrician finds that your child’s head size is above the 97th percentile in their growth chart, meaning it’s larger than 97 percent of other children their age, they may recommend further tests. Similarly, if the child’s head size is growing significantly faster than expected for their age, or if they are less than six months old and their head size has increased by more than 2 cm in a single month, more tests may be needed.

Imaging of your child’s head may be necessary to understand why the head size is larger than normal. This could involve several methods. A head ultrasound can be a simple and cost-effective option, if the child’s soft spot (anterior fontanelle) is still open. A CT scan is faster, but it does expose your child to radiation, so it is usually avoided unless absolutely necessary. An MRI provides a detailed view of the brain’s structure without using radiation, but it’s more expensive than an ultrasound or CT scan, and it might require your child to be sedated.

If your child has benign macrocephaly – a harmless condition where the head is larger than average – the imaging might show dilation of the spaces between brain tissues (subarachnoid spaces). Other findings could include slightly larger fluid-filled spaces in the brain (ventricles), and visible spaces at the base of the brain (basilar cisterns).

Treatment Options for Macrocephaly

Macrocephaly, or a larger than average head size, requires different approaches of treatment depending on the underlying cause. If the large head size is due to a buildup of fluid in the brain, a condition known as hydrocephalus, then the patient may need to consult a neurosurgeon, who may perform surgery. This surgery is particularly crucial if there are signs of increased pressure in the brain – it can not only save lives, but can also improve the patient’s quality of life.

This operation typically involves draining the excess cerebrospinal fluid (CSF), which is causing the pressure increase. This has traditionally been accomplished via two methods: either placing an extraventricular drain (EVD), which is a temporary solution to divert the fluid away from the brain, or a ventriculoperitoneal (VP) shunt, which is a long-term solution that redirects the fluid from the brain to the abdominal area.

If the cause of the larger head size isn’t due to fluid buildup, then consultations with genetic counselors, pediatric development specialists, or pediatric neurologists might be necessary. For children with macrocephaly who also have epilepsy, they could potentially be prescribed antiepileptic medications to help control seizures.

In cases where the macrocephaly is benign, meaning it isn’t harmful and is likely inherited (a.k.a benign familial macrocephaly), treatment might not be necessary. Doctors will typically just observe the child’s head growth over time and reassure the parents that this condition generally doesn’t lead to future health problems.

If a baby’s head is larger than usual (a condition called macrocephaly), it’s important to know that this can be due to different reasons and the baby’s head can take different shapes as a result. Here are some potential explanations:

Plagiocephaly – This is when one area of the skull becomes flat, often because the baby has been lying in the same position for a long time.
Craniosynostosis – This happens when the gaps between the bones in the baby’s skull close earlier than they normally would, which can alter the shape of the head.
Brachycephaly – The baby’s head is broad and the forehead appears pushed back. This results from the early closure of a specific gap in the skull (the coronal suture).
Trigonocephaly – An early closure of another gap in the skull (the metopic suture) results in a triangular forehead.
Scaphocephaly – This is when the skull elongates from front to back with a narrowing at the sides. It happens due to the early closure of the sagittal suture.

Other birth defects of the skull can be due to injuries or pressures on the head while the baby is still in the womb. This can happen because of twins or multiple births, an abnormal position of the baby in the womb, or low levels of amniotic fluid surrounding the baby (oligohydramnios).

What to expect with Macrocephaly

The outcomes for babies with an unusually large head, or macrocephaly, depend on what’s causing this condition. In situations where a baby is growing and developing normally and passing neurological exams, macrocephaly often isn’t a cause for concern. Babies in these circumstances generally have good developmental outcomes.

Medical imaging may show that these infants have an enlarged space beneath the outer covering of their brain (called subarachnoid space). This might persist in the long term, but in these cases, no intervention is necessary.

Possible Complications When Diagnosed with Macrocephaly

Although benign familial macrocephaly, or having a larger than normal head due to genetics, doesn’t usually come with any problems, other reasons for head enlargement can have severe consequences. For instance, macrocephaly caused by hydrocephalus (a condition where there’s too much fluid in the brain) can lead to serious issues, including death unless treated quickly. People with macrocephaly might also suffer from seizures, developmental delays, and nervous system impairments.

Common possible complications:

Death if not treated swiftly (in the case of hydrocephalus-induced macrocephaly)
Seizures
Developmental disabilities
Nervous system deficits

Preventing Macrocephaly

If there’s an existing underlying reason or related condition causing macrocephaly (a condition where the head is abnormally large), it’s crucial to identify it. However, when macrocephaly runs in the family and is harmless with no other associated conditions, there’s no need for extensive tests. In these cases, the caregivers can be reassured that everything is okay.

Frequently asked questions

Macrocephaly is a condition where a child's head size is significantly larger than average (more than two standard deviations above the average for their age and sex), in the top 97% percentile.

Macrocephaly is found in about 2% to 3% of the population.

Signs and symptoms of Macrocephaly include: - Larger than normal head size, which can be identified using a standard head measurement. - Head circumference at or above the 97th percentile for age and sex in children under two years old. - Detailed history of birth measurements, growth over time, other medical conditions, developmental milestones, and family history of macrocephaly. - Past brain trauma or infection, such as meningitis or bleeding inside the brain during the newborn period, which could lead to hydrocephalus. - Overall appearance and facial features are examined for signs of any underlying condition or genetic syndrome. - Thorough neurologic exam is performed to look for signs of any underlying condition or genetic syndrome. - Eyes are checked for signs of increased pressure inside the skull, which can sometimes cause papilledema. - Specific tests may include shining a light through the scalp to check the skull, checking for signs of bone disorders, and listening to the skull with a stethoscope.

Macrocephaly can be caused by various factors, including an increase in brain tissue (megalencephaly), an increase in cerebrospinal fluid, an increase in blood or thickened bone, increased pressure inside the skull, the presence of a clot or malformation in the blood vessels, or an increase in the thickness of the skull. It can also be associated with genetic conditions, syndromes, or metabolic disorders.

The doctor needs to rule out the following conditions when diagnosing Macrocephaly: 1. Plagiocephaly - when one area of the skull becomes flat due to prolonged lying in the same position. 2. Craniosynostosis - when the gaps between the bones in the baby's skull close earlier than normal, altering the head shape. 3. Brachycephaly - when the baby's head is broad and the forehead appears pushed back due to the early closure of a specific gap in the skull (the coronal suture). 4. Trigonocephaly - when the early closure of another gap in the skull (the metopic suture) results in a triangular forehead. 5. Scaphocephaly - when the skull elongates from front to back with narrowing at the sides due to the early closure of the sagittal suture. 6. Other birth defects of the skull caused by injuries or pressures on the head while the baby is in the womb, such as twins or multiple births, abnormal position of the baby in the womb, or low levels of amniotic fluid (oligohydramnios).

The types of tests that may be needed for Macrocephaly include: - Weaver curves to determine if the child's head size is within the standard range based on the parents' head sizes - Imaging tests such as a head ultrasound, CT scan, or MRI to understand why the head size is larger than normal - Consultations with genetic counselors, pediatric development specialists, or pediatric neurologists to determine the underlying cause of the larger head size - If there are signs of increased pressure in the brain, a neurosurgeon may perform surgery to drain the excess cerebrospinal fluid (CSF) using either an extraventricular drain (EVD) or a ventriculoperitoneal (VP) shunt - For children with macrocephaly and epilepsy, antiepileptic medications may be prescribed to control seizures.

Macrocephaly, or a larger than average head size, can be treated in different ways depending on the underlying cause. If the large head size is due to a buildup of fluid in the brain, known as hydrocephalus, a neurosurgeon may perform surgery to drain the excess cerebrospinal fluid. This can be done through either an extraventricular drain (EVD) or a ventriculoperitoneal (VP) shunt. If the cause of the larger head size is not due to fluid buildup, consultations with genetic counselors, pediatric development specialists, or pediatric neurologists may be necessary. In cases where the macrocephaly is benign, treatment may not be necessary, and doctors may simply observe the child's head growth over time.

The side effects when treating Macrocephaly can include: - Death if not treated swiftly (in the case of hydrocephalus-induced macrocephaly) - Seizures - Developmental disabilities - Nervous system deficits

The prognosis for macrocephaly depends on the underlying cause of the condition. In cases where a baby is growing and developing normally and passing neurological exams, macrocephaly is often not a cause for concern and babies in these circumstances generally have good developmental outcomes. Medical imaging may show an enlarged space beneath the outer covering of the brain, but no intervention is necessary in these cases.

Neurosurgeon, genetic counselor, pediatric development specialist, or pediatric neurologist.