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What causes bulging fontanelle? 4 possible conditions

What Is a Bulging Fontenelle?

A fontanelle is more commonly known as a soft spot. When a baby is born, he or she typically has several soft spots where the bones of the skull have not yet fused. A newborn has fontanelles on the top, back, and sides of the head.

It is important for new parents to understand what a fontanelle should look and feel like. According to the National Institutes of Health (NIH), a baby’s soft spot should feel relatively firm. It should curve inward but only very slightly (NIH , 2011).

Changes in texture or appearance can at times be a sign of serious health issues. One problem parents should watch for is a soft spot that is curved outward. This is also known as a bulging fontanelle. It is a sign of brain swelling or fluid buildup on the brain. These can cause the pressure inside the skull to rise. The result may be damage to the baby’s developing brain.

A bulging fontanelle is an emergency. If your child is experiencing this symptom, seek medical attention right away.

What Are the Causes of a Bulging Fontanelle?

Common Causes

Some of the most common causes of a bulging fontanelle are:

  • encephalitis–brain inflammation caused by a viral or bacterial infection
  • hydrocephalus–excess brain fluid that is present at birth or occurs from injury or infection
  • meningitis–inflammation of brain and spinal cord tissue that results from a viral or bacterial infection
  • hypoxic-ischemic encephalopathy–brain swelling and damage that occurs when a baby’s brain is deprived of oxygen for a long period of time
  • intracranial hemorrhage–bleeding in the brain
  • head trauma

Other Causes

The conditions above are not the only explanations. A 2003 journal article in American Family Physician also identified the following conditions, along with numerous others, as possible causes:(Kiesler and Ricer , 2003)

  • brain tumor or abscess
  • Lyme disease–a bacterial infection you get from being bitten by an infected tick
  • Addison’s disease–your adrenal glands do not make enough hormones for your body to function properly
  • congestive heart failure–blood and fluid build up in parts of your body because your heart cannot not pump enough blood
  • leukemia–cancer of white blood cells
  • electrolyte disturbance–your blood’s levels of certain chemicals, such as sodium and potassium, are out of balance
  • hyperthyroidism–your thyroid makes more hormones than you need
  • maple syrup urine disease–your body can’t properly break down proteins
  • anemia–your blood does not contain enough oxygen

When Should I Seek Medical Care?

There are several factors that can make a soft spot appear to be bulging when, in reality, there is nothing dangerous happening. These factors include:

  • the baby lying down
  • the baby vomiting
  • the baby crying

To determine whether an infant actually has a bulging fontanelle, try to calm him or her down. Position the infant so that his or her head is in an upright position. If you succeed in doing this and one or more of the soft spots still appears to be bulging, seek medical attention immediately.

Do not wait to make a doctor’s appointment; go to the nearest emergency room. This is especially crucial if the baby has a fever or seems extremely sleepy.

What to Expect at the Hospital

Because there can be many explanations for this symptom, the doctor will collect as much information as possible about the child’s condition.

The doctor will perform a physical examination of the infant. He or she will also likely ask:

  • whether the bulge is constant or appears normal at times
  • when you first noticed the abnormal appearance of the soft spot
  • which soft spots appear to be bulging

You should also be sure to tell the doctor about any other symptoms you have observed, including marked drowsiness, an elevated temperature, or irritability that is beyond what is normal for your child.

Depending on the answers you provide and other symptoms that may be present, the doctor may order one or more tests to reach a diagnosis. According to the NIH, some of the most commonly used tests are computed tomography (CT) and magnetic resonance imaging (MRI) scans of the head.

Lumbar puncture (also called a spinal tap) may also be performed. This involves taking a sample of cerebrospinal fluid from the lower spine to check for disease and infection in the nervous system (NIH , 2011).

Treatment will depend on the underlying cause of the bulging fontanelle.

What Can Happen if a Bulging Fontanelle Is Not Treated?

A bulging soft spot can be a sign of several very serious conditions. The consequences of not seeking treatment right away can be dire. For instance, encephalitis (a common cause of bulging fontanelles) can lead to permanent brain damage or even death, in severe cases.

Is There Any Way to Prevent a Bulging Fontanelle?

There is no definite way to prevent fontanelles from bulging. This is in large part because the symptom has so many potential causes.

However, parents and other caregivers can avoid unnecessary hospital visits by learning how to distinguish between a soft spot that temporarily appears to be bulging and one that is actually protruding.

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See a list of possible causes in order from the most common to the least.



Hydrocephalus is a condition that occurs when fluid builds up in the skull and causes the brain to swell. The name literally means "water on the brain."

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This condition is considered a medical emergency. Urgent care may be required.

Encephalitis is an inflammation of the brain tissue. It's most often caused by viral infections. In some cases, bacterial infections can cause encephalitis.

Read more »



This condition is considered a medical emergency. Urgent care may be required.

Meningitis is an inflammation of the membrane that covers the brain and spinal cord. It may cause headache and fever in teens and adults, irritability in babies, and trouble breathing in young children.

Read more »


Shaken Baby Syndrome

This condition is considered a medical emergency. Urgent care may be required.

Shaken baby syndrome is caused by forcefully and violently shaking a baby. Other names for this condition include abusive head trauma, shaken impact syndrome, whiplash shake syndrome, and inflicted head injury. Shake...

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This feature is for informational purposes only and should not be used to diagnose.
Please consult a healthcare professional if you have health concerns.