What is a bulging fontanel?
A fontanel, also called fontanelle, is more commonly known as a soft spot. When a baby’s born, they typically have several fontanels where bones of their skull haven’t fused yet. A newborn has fontanels on the top, back, and sides of their head.
Usually, only the anterior fontanel, which is on the top of the head toward the front, can be seen and felt. This is the one called the soft spot. In some babies, the posterior fontanel, which is found toward the back of the head, can also be felt, though it’s much smaller.
It’s important for new parents to understand what a fontanel looks and feels like. A baby’s soft spot should feel relatively soft and curve inward very slightly.
Changes in texture or appearance can be a sign of serious health issues. Parents should watch for soft spots that are curved outward on their baby’s head and feel very firm. This is known as a bulging fontanel and may be a sign of brain swelling or fluid buildup in the brain.
A bulging fontanel is an emergency. It can be a sign of pressure rising inside the skull which may result in damage to the baby’s developing brain. If your child is experiencing this symptom, seek medical attention immediately.
Some of the most common causes of a bulging fontanel are:
- encephalitis, which is a brain inflammation caused by a viral or bacterial infection
- hydrocephalus, which is excess brain fluid that’s present at birth or occurs from injury or infection
- meningitis, which is inflammation of the brain and spinal cord tissue that results from a viral or bacterial infection
- hypoxic-ischemic encephalopathy, which is brain swelling and damage that occurs when your baby’s brain is deprived of oxygen for a long period
- intracranial hemorrhaging, which is bleeding in the brain
- head trauma
A bulging fontanel may be attributed to additional conditions, along with numerous others, as possible causes:
- a brain tumor or abscess
- Lyme disease, which is a bacterial infection you get from an infected tick
- Addison’s disease, which is a condition in which your adrenal glands don’t make enough hormones for your body to function properly
- congestive heart failure, which is when blood and fluid buildup in parts of your body because your heart can’t pump enough blood
- leukemia, which is cancer of the white blood cells
- an electrolyte disturbance, which is when your blood’s levels of certain chemicals, such as sodium and potassium, are out of balance
- hyperthyroidism, which is when your thyroid makes more hormones than you need
- maple syrup urine disease, which occurs when your body can’t properly break down proteins
- anemia, which is a condition in which your blood doesn’t contain enough oxygen
In most cases of these conditions, a baby would have other symptoms in addition to a bulging fontanel and would most likely be sick.
Also, it would be very uncommon, if not rare, for any of these — except brain tumor or abscess — to cause a bulging fontanel, either because the condition is rare in infancy or because the condition happens in infancy, but rarely causes a bulging fontanel.
There are several factors that can make a soft spot appear to be bulging when in reality there’s no danger. Common things babies do such as lying down, vomiting, or crying can be mistaken for your baby having a bulging fontanel.
To determine whether your infant actually has a bulging fontanel, first try to calm them down, and then position them so their head is upright. If you succeed in doing this and the soft spot still appears to be bulging, seek medical attention for your child immediately.
Don’t wait to make a doctor’s appointment. Go to the nearest emergency room. This is especially crucial if your baby has a fever or seems extremely sleepy.
If you don’t already have a pediatrician, the Healthline FindCare tool can help you find one in your area.
A bulging soft spot can be a sign of several very serious conditions that can even be life-threatening. For instance, encephalitis, a common cause of bulging fontanels, can lead to permanent brain damage or even death in severe cases.
Because there can be many explanations for these symptoms, your doctor will collect as much information as possible about your child’s condition.
Your doctor will perform a physical examination of your infant and will likely ask:
- about your baby’s medical history and any medications
- whether the bulge is constant or appears normal at times
- when you first noticed the abnormal appearance of the soft spot
Be sure to tell your doctor about any other symptoms you’ve observed, including:
- marked drowsiness
- an elevated temperature
- irritability beyond what’s normal for your child
Depending on the answers you provide and other symptoms that may be present, your doctor may order one or more tests, such as an MRI or CT scan, to make a diagnosis.
Lumbar puncture, or a spinal tap, may also be performed. This involves taking a sample of cerebrospinal fluid from your baby’s lower spine to check for disease and infection in their nervous system.
Treatment will depend on the underlying cause of your baby’s symptoms.
There’s no definite way to prevent fontanels from bulging. This is mostly because the symptom has so many potential causes.
With available information, parents and other caregivers can better understand this symptom. For example, it can help them distinguish between a soft spot that temporarily appears to be bulging and one that’s protruding.
However, though information is available, it’s important for parents and other caregivers to contact their child’s doctor if they have questions or concerns about bulging fontanel.