Bulging Fontanelle: Causes, Treatment & When To See A Doctor

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A bulging fontanelle in infants is characterized by the outward appearance of their soft spot (fontanelle). Under normal conditions, the fontanelle is curved inwards. But when the pressure inside the brain increases or if there is a fluid buildup, the tension within leads to the protrusion and formation of the dome-shaped fontanelle.

The condition could be accompanied by fever and may require medical care. Read on to know more about the causes of bulging fontanelle, its diagnosis, and treatment.

In This Article

What Is Fontanelle In Infants?

Fontanelle supports the brain’s growth during infancy

Image: Shutterstock

The skull consists of several bones, of which eight bones enclose and protect the brain. Each bone meets at a joint called a suture. In adults, the sutures are closed, but in infants, there is a space between the sutures filled with a membranous tissue. The space between the sutures is called a fontanelle or soft spot.

The function of fontanelle is to allow the baby’s head to mold during delivery and support the brain’s growth during infancy. The sutures fuse over time due to the addition of minerals, and the soft spot eventually disappears without any distension or bulging.

Since the skull has multiple bones, a baby has multiple fontanelles that close at different stages of infancy and toddlerhood (1). The following are the most notable fontanelles and the age at which they usually close.

  • Posterior fontanelle, situated in the back of the head, closes by one to two months of age.
  • Anterior fontanelle, on top of the head, closes between seven and 19 months after birth.

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A newborn has six fontanelles at the time of birth (2).

Normally the fontanelles feel firm and slightly curved inward to the touch. It is normal for fontanelles to bulge when an infant cries, vomits, or lays down. They return to normal when the infant is calm, in a head-up position. However, bulging fontanelle in other situations can be an indication of a pathology. A tense or bulging fontanelle occurs when fluid builds up in the brain or the brain itself swells – in any condition leading to increased pressure inside the skull.

Causes Of Bulging Fontanelle

It is important to note that bulging fontanelle is not a disease itself but rather a sign of an underlying disease or condition. An infant may have bulging fontanelle due to the following reasons (2).

  • Hydrocephalus, a condition that causes fluid buildup in the skull

A mom of four, Vicky Herbert, shares about her youngest son, Ethan, who was diagnosed with hydrocephalus that led to the bulging of his fontanelle. She writes, “Ethan was born nine weeks early, weighing 3lbs 10oz, and following a traumatic birth, where the umbilical cord was wrapped tightly around his neck, he suffered a bleed on the brain… Hydrocephalus was mentioned during this conversation, more to make us aware than anything else… He was still in the special care baby unit at this time, and one week later, I arrived at the unit and knew instantly that he had developed Hydrocephalus. His fontanelle was full and bulging, making his head appear cone-shaped. I had read a little about Hydrocephalus since it was mentioned last week and immediately recognized the signs (i).”

  • High intracranial pressure
  • Encephalitis, swelling of the brain tissue commonly due to infections
  • Meningitis, an inflammation of the brain membranes
  • Intracranial hemorrhage
  • Head trauma
Head trauma can cause bulging fontanelle in infants

Image: Shutterstock

  • Hypoxic-ischemic injury due to deprivation of oxygen to the brain
  • Congenital hypothyroidism
  • Tumors

You may seek medical care to identify and begin treatment of causes since brain anomalies may lead to severe complications.

protip_icon Be watchful
Several metabolic, hematologic, and cardiovascular disorders can cause bulging fontanelles in newborns (2).

When To See A Doctor?

Prompt medical care is required if your baby has bulging fontanelle. Fever and drowsiness, along with bulging and enlargement of soft spots, can be an indication of bulging fontanelle and you should seek emergency care.

Contact the doctor if the fontanelle is protruding, even if the baby remains calm and has no other symptoms.

Diagnosis Of Bulging Fontanelle

Medical history and physical examination may help to identify raised or expanded bulging fontanelle and its causes. The following tests may be done (3).

  • Lumbar puncture or spinal tap
  • Blood tests
  • CT scan of the head
  • MRI scan of the head
protip_icon Things to know
The physical examination of the fontanelles should be done when the baby is calm and is being supported in supine and upright positions (2).
MRI scans can detect the cause of bulging fontanelle in infants

Image: Shutterstock

Treatment For Bulging Fontanelle

Brain infections are treated with antibiotics or antivirals

Image: Shutterstock

The treatment options may vary according to the cause and may include the following.

  • Brain infections are treated with antibiotics or antivirals, depending on the etiologic agents.
  • Surgical procedures may be performed to create shunts in hydrocephalus to drain excess fluid
  • Surgical removal of tumors is done if present
  • Thyroid hormone replacement therapy could help infants with thyroid abnormalities
  • Intracranial pressure is managed with medications if present

Frequently Asked Questions

1. Does bulging fontanelle go away?

If an underlying condition or pathology is causing a prominent bulging fontanelle, it does not go away on its own. It warrants immediate medical attention.

2. Does bulging fontanelle mean dehydration?

No, dehydration in babies causes a sunken fontanelle. A bulging fontanelle usually occurs due to increased intracranial pressure or intracranial or extracranial tumors (2).

3. How big should the fontanelle be at three months?

The fontanelle of a healthy three-month-old may measure between 0.8 and 6.9cm (4).

4. Can a virus cause a bulging fontanelle?

Yes. A viral infection, such as COVID-19, can cause a bulging fontanelle, or “soft spot,” in an infant (5).

5. What happens if fontanelle is pressed?

Pressing into the “soft spot” or fontanelle of an infant is generally not recommended because it can cause discomfort, tenderness, or throbbing sensation to the baby and may also cause damage or injury.

A bulging fontanelle could be caused due to multiple reasons. However, you need not worry as there are several ways of treating it. To ensure that you are opting for the right type of treatment, it is advisable to consult your child’s pediatrician and understand the process that they suggest to treat the bulge. Usually, they examine the signs and will perform a complete medical checkup before coming up with a treatment plan. Ensure not to delay the process for your child’s safety and well-being.

Infographic: Bulging Fontanelle And Its Causes

Bulging fontanelle may require prompt medical treatment but it is helpful to know its causes. Check this infographic to have a glance at the condition and its causes.

causes of bulging fontanelle (Infographic)

Illustration: Momjunction Design Team

Get high-quality PDF version by clicking below.

Download Infographic in PDF version Download Infographic
Download Infographic in PDF version

Key Pointers

  • An infant may develop a bulging fontanelle due to tumors or trauma, among other reasons.
  • Congenital hypothyroidism, meningitis, and high intracranial pressure could also lead to bulging fontanelle.
  • Fever and bulging soft spots are an indication you should visit the doctor.

View this incredible video of a cute baby with an extremely bulging fontanelle to understand the significance of this condition and the subsequent procedures to be followed.

Personal Experience: Source


MomJunction's articles are written after analyzing the research works of expert authors and institutions. Our references consist of resources established by authorities in their respective fields. You can learn more about the authenticity of the information we present in our editorial policy.

1. Fontanelles-Bulging; MedlinePlus; US National Library of Medicine
2. The Abnormal Fontanel; The American Academy of Family Physicians
3. What Causes a Bulging Anterior Fontanelle?; Pediatric Education
4. Mohammad Esmaeili et al.; Fontanel Size from Birth to 24 Months of Age in Iranian Children; National Library of Medicine
5. Jared Schiff and Courtney Brennan; Covid-19 presenting as a bulging fontanelle; The American journal of emergency medicine; NCBI

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