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 bulging of the 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.

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.

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.

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
  • 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.

When To See A Doctor?

Prompt medical care is required if your baby has bulging fontanelle. Fever and drowsiness, along with bulging of soft spots, can be an indication of 2. Seek emergency care.

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

Diagnosis Of Bulging Fontanelle

Medical history and physical examination may help to identify 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
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 the 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).

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

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.


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
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Dr Bisny T. Joseph

Dr. Bisny T. Joseph is a Georgian Board-certified physician. She has completed her professional graduate degree as a medical doctor from Tbilisi State Medical University, Georgia. She has 3+ years of experience in various sectors of medical affairs as a physician, medical reviewer, medical writer, health coach, and Q&A expert. Her interest in digital medical education and patient education made...
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Dr. Pooja Parikh

Dr. Pooja Parikh is a pediatrician whose medical journey has taken her from Rajkot (PDUMC) to Vadodara (SSGH) to Mumbai (Hinduja & Breachcandy Hospital). Currently she is actively involved in critical, intensive and general care of 0 to 18-year-olds in the port town of Gandhidham, where she was born and brought up. She believes that a doctor should be involved...
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