Macrocephaly: Causes, Symptoms, and Treatments

Macrocephaly is one of those medical words that sounds like it should come with a cape and a theme song. In real life, it simply means a head that’s larger than expected for a person’s age and sex. For some families, it’s a harmless “big head runs in the family” situation. For others, it can be an important clue that something inside the skull needs attention.

This guide breaks down macrocephaly causes, warning signs, how clinicians evaluate a large head circumference, and what treatments look like when treatment is needed. We’ll keep it accurate, practical, and just humorous enough to make the topic feel less intimidating (because worry doesn’t deserve a monopoly on your brain space).

What Is Macrocephaly?

Macrocephaly is typically defined as an occipitofrontal circumference (OFC)a fancy term for head circumferencegreater than about the 97th percentile for age and sex (or more than 2 standard deviations above the mean). Translation: compared with most kids the same age, the head measures bigger than expected.

Important nuance: macrocephaly is a description, not a diagnosis. It’s like saying “tall.” Being tall might be normal, or it might be part of a medical condition. A large head can be normal, or it can signal an underlying issue.

Macrocephaly vs. Megalencephaly (Not the Same Thing)

People often assume a big head means a big brain. Sometimes that’s true, but not always. Megalencephaly refers to an unusually large brain tissue volume. Macrocephaly can happen from:

• More brain tissue (megalencephaly)
• Extra fluid (like hydrocephalus or benign extra fluid spaces)
• Bleeding or fluid collections
• Bone/skull growth differences
• Masses (tumors or cysts)

When a “Big Head” Is Completely Normal

Some kids have macrocephaly and are otherwise perfectly healthy. Two common “this is probably fine, but let’s track it” patterns include:

Benign Familial Macrocephaly

If one or both parents (or several relatives) have larger heads, a baby may simply inherit that trait. In these cases, the child’s head circumference is large but growth follows a steady curve, development is typical, and exams are reassuring. The “treatment” is often just monitoring and reassuranceplus buying hats from the adult section sooner than expected.

Benign Enlargement of Subarachnoid Spaces (BESS)

Some infants develop macrocephaly due to extra cerebrospinal fluid (CSF) in spaces around the brain without pressure-related damage. Many children outgrow this pattern as the skull and fluid dynamics mature. Clinicians still monitor closely, because the key word here is “benign,” and medicine likes to earn that label before handing it out.

Causes of Macrocephaly: The Main Categories

When macrocephaly is not simply familial, clinicians look for patterns that suggest what’s driving head growth. Below are common causes (from more frequent to less common), with plain-English explanations.

1) Hydrocephalus (Too Much CSF Inside the Brain)

Hydrocephalus happens when CSF builds up in the brain’s ventricles, leading to enlarged spaces and potentially increased pressure. In infants, the skull bones haven’t fused yet, so the head can enlarge as pressure rises. Hydrocephalus can be congenital (present at birth) or acquired (from bleeding, infection, tumors, or other causes).

Why it matters: untreated increased intracranial pressure can affect vision, development, and brain function. The goal is to identify it earlyespecially if head growth is accelerating.

2) Bleeding or Fluid Collections (Including Subdural Hematomas)

Bleeding around the brain or chronic fluid collections can increase head size. Sometimes this is related to trauma, bleeding disorders, or other medical causes. Because the possibilities range from routine to urgent, this category typically triggers a careful history, exam, andwhen indicatedimaging.

3) Genetic Syndromes and Overgrowth Conditions

Macrocephaly can be part of certain genetic syndromes, especially those involving body overgrowth or changes in brain development. Examples include:

• Sotos syndrome (often includes overgrowth and developmental differences)
• PTEN hamartoma tumor syndrome (macrocephaly may occur with developmental differences and sometimes autism spectrum features)
• Neurocutaneous conditions (some include macrocephaly among other signs)

Key point: a genetics evaluation isn’t about slapping on a labelit can guide medical screening, developmental supports, and family planning information.

4) Brain Masses (Tumors or Cysts)

Some masses take up space inside the skull and may lead to macrocephaly, especially when they block CSF flow or increase pressure. This is less common than benign familial causes, but it’s a reason clinicians pay attention to symptoms like vomiting, headaches, neurological changes, or rapid head growth.

5) Bone and Skull Growth Differences

In some conditions, the skull bones grow differently or become thickened, contributing to a larger head size. This is usually identified by physical exam findings and imaging when needed.

6) Metabolic or Storage Disorders (Rare, But Important)

Rare disorders affecting how the body processes certain substances can lead to brain enlargement or changes that show up as macrocephaly. These are not the most common causes, but clinicians may consider them when macrocephaly is paired with developmental regression, seizures, unusual neurologic findings, or a concerning family history.

Symptoms of Macrocephaly: What to Watch For

Here’s the tricky part: macrocephaly itself may cause zero symptoms. Many children feel fine and develop normally. Symptoms usually come from the underlying causeespecially if pressure inside the skull rises or brain development is affected.

Common Signs in Infants

• Rapidly increasing head circumference (crossing growth percentiles)
• Bulging or tense “soft spot” (fontanelle)
• Vomiting, poor feeding, or unusual sleepiness
• Irritability that feels “not like your baby”
• Eyes that seem driven downward (“sunsetting” gaze)
• Seizures

Common Signs in Older Children

• Headaches (especially morning headaches)
• Nausea/vomiting
• Vision changes
• Balance or coordination problems
• Developmental delays, learning difficulties, or regression

Red Flags That Should Prompt Urgent Medical Care

If a child with macrocephaly has rapid head growth plus symptoms like repeated vomiting, lethargy, seizures, abnormal eye movements, or a markedly bulging fontanelle, seek urgent evaluation. This isn’t about panicit’s about not ignoring the body’s “check engine” light.

How Macrocephaly Is Diagnosed

Diagnosis starts with something refreshingly low-tech: a measuring tape. Clinicians measure head circumference and plot it on standardized growth charts.

Step 1: Measure, Plot, Repeat

The most useful clue is not a single big measurementit’s the growth trend. A head that stays consistently large may be normal. A head that starts average and then rapidly climbs percentiles may need workup.

Step 2: History and Physical Exam (The Detective Work)

Expect questions like:

• Was the head large at birth or growing quickly over time?
• Any family history of large head size, hydrocephalus, genetic syndromes, or developmental delays?
• Any prematurity, bleeding, infection, or trauma?
• How is the child meeting developmental milestones?

Clinicians also check for signs such as unusual facial features, skin findings, muscle tone differences, eye findings, or asymmetry that could suggest specific conditions.

Step 3: Imaging (When Indicated)

Imaging is not automatic for every child with a big head. It’s chosen based on risk factors and symptoms. Common options include:

• Head ultrasound (in infants with an open fontanelle; no radiation)
• MRI (high detail, no radiation; may require sedation in younger children)
• CT (fast and useful in emergencies, but uses radiation)

Step 4: Labs or Genetic Testing (Only When the Story Suggests It)

If macrocephaly appears to be part of an overgrowth syndrome or developmental condition, clinicians may recommend genetic testing. This can help with:

• Explaining why macrocephaly is happening
• Guiding screening for related health risks
• Informing prognosis and supportive services
• Offering genetic counseling for families

Treatments for Macrocephaly

There isn’t one universal macrocephaly treatment because macrocephaly isn’t one universal condition. Treatment targets the cause and the child’s needs.

Watchful Waiting and Monitoring

If a child has benign familial macrocephaly or another reassuring pattern, clinicians may recommend:

• Regular head circumference measurements
• Routine developmental screening
• Follow-up visits to ensure growth stays on a stable curve

In these cases, “doing nothing” actually means “watching carefully”a classic parenting skill, now medically endorsed.

Treating Hydrocephalus

If hydrocephalus is causing macrocephaly and symptoms, treatment focuses on restoring safer CSF flow or drainage. Options may include:

• Ventriculoperitoneal (VP) shunt: a device that drains excess CSF to another part of the body
• Endoscopic third ventriculostomy (ETV): a procedure that creates a new pathway for CSF flow in selected cases

After treatment, many children improve significantly, though ongoing follow-up is common to monitor development and watch for device or flow issues.

Addressing Bleeding or Fluid Collections

Treatment depends on the cause and severity. Some collections are monitored; others may require neurosurgical intervention. The plan is individualizedbecause brains are not “one-size-fits-all,” even if hats are.

Surgery for Tumors or Cysts

If imaging shows a mass affecting CSF flow or brain function, specialists may recommend surgery, sometimes combined with other therapies. The goal is to relieve pressure, treat the underlying lesion, and support long-term outcomes.

Supportive Therapies and Early Intervention

When macrocephaly is linked to developmental differences, therapies can be a major part of treatment:

• Physical therapy (motor skills, strength, coordination)
• Occupational therapy (daily skills, fine motor, sensory support)
• Speech-language therapy (communication, feeding when relevant)
• Behavioral and educational supports

Supportive care isn’t a consolation prizeit’s often what makes the biggest difference in day-to-day life.

Practical Tips for Parents and Caregivers

Track Growth Without Turning Into a Tape-Measure Influencer

It’s okay to be curious, but try not to measure head circumference at home every other day. Small differences can be technique-related and stressful. Let your pediatrician track the trend with consistent methods and standardized charts.

Focus on Function, Not Just Size

Ask: Is my child feeding well? Sleeping normally? Meeting milestones? Acting like themselves? A stable, thriving child with macrocephaly is often far less concerning than a child with rapid growth plus symptoms.

Know When to Escalate

Call your clinician promptly if you notice rapid head growth or new symptoms like persistent vomiting, unusual sleepiness, seizures, or abnormal eye movements.

Frequently Asked Questions

Can macrocephaly go away?

The head size itself usually doesn’t “shrink,” but the concern may fade if the child’s growth stabilizes and development is normal. In conditions like benign extra fluid spaces, the pattern often becomes less pronounced over time.

Does macrocephaly always mean hydrocephalus?

No. Hydrocephalus is one possible cause, but many children have macrocephaly from familial traits or other non-hydrocephalus reasons.

Is macrocephaly linked to autism?

Some children with autism have larger head sizes, and certain genetic conditions (such as PTEN-related syndromes) can involve both macrocephaly and neurodevelopmental differences. But macrocephaly alone does not diagnose autism or predict it.

Conclusion

Macrocephaly can be as harmless as inherited “family head size,” or as important as an early sign of hydrocephalus, genetic syndromes, or other neurologic conditions. The difference comes down to growth pattern, symptoms, and a careful clinical evaluation. If your child has macrocephaly, the goal is not to fear the measurementit’s to understand the story behind it and act when needed.

Medical note: This article is educational and not a substitute for professional medical advice. If you’re concerned about a child’s head growth or symptoms, contact a pediatric clinician promptly.

Real-World Experiences: What Families and Clinicians Often Notice (About )

When people talk about macrocephaly, the conversation often starts the same way: “We didn’t notice anything… until someone else did.” A grandparent makes a comment during a photo shoot (“He’s got that big, beautiful head like Uncle Mike!”). A daycare provider mentions the baby’s hat never fits. Or the pediatrician measures head circumference at a routine visit and says, calmly, “This is bigger than expectedlet’s take a closer look.”

For many families, the first emotional wave is not fearit’s confusion. The baby seems fine. They’re eating. They’re smiling. They’re doing baby things like staring intensely at ceiling fans, as if the fan is delivering a TED Talk. In those cases, clinicians often lean on two anchors: trend and function. Is the head growing steadily along a high percentile, or is it accelerating? And is the child developing skills on schedule?

One common experience in benign familial macrocephaly is the “measurement plot twist.” A parent gets told the baby’s head is large, and suddenly everyone in the family starts comparing foreheads like it’s an Olympic event. Then someone finds an old story: “Your dad needed an adult bicycle helmet at age eight.” When the family history is clear and the child is thriving, the plan may be simple: monitor, recheck, move on with life (and buy bigger beanies).

Another pattern: families describe a slow build of “something’s off” signals. The baby becomes unusually sleepy, feeding feels harder, vomiting becomes frequent, or the soft spot looks more tense. In these cases, the experience shifts from “interesting measurement” to “we need answers.” Imaging can feel scaryespecially MRI discussionsbut many parents report relief once a clear cause is identified. Even when the news is serious, uncertainty is often the most exhausting part.

For families navigating hydrocephalus treatment, the experience is often described as a mix of high-stakes stress and everyday logistics. Surgery may be followed by a period of careful observation: watching for symptom changes, learning what “normal” looks like again, and building confidence. Parents often become fluent in a new vocabulary: shunts, ventricles, pressure symptoms, follow-ups. They also learn something surprisingly empowering: most of the time, the child’s behavior is the best guide. “He’s acting like himself” becomes the gold standard sentence.

And then there’s the developmental-support sidephysical therapy appointments, speech sessions, early intervention evaluations. Families often say the emotional turning point comes when they stop asking “Why is this happening?” every day and start asking “What helps my child thrive?” Macrocephaly may be the reason the journey began, but in many real stories, it becomes just one detail in a much bigger narrative: growth, support, and a kid who’s more than a number on a chart.