Infant skulls have soft spots, called fontanelles, which are flexible membrane-covered gaps between the skull bones. These allow the skull plates to overlap during birth and provide space for rapid brain growth after birth. While a normal fontanelle is typically soft and flat, a bulging fontanelle can signal an underlying medical issue that requires prompt attention.
Understanding Fontanelles
There are typically six fontanelles, but the most prominent are the anterior and posterior fontanelles. The anterior fontanelle, on the top front of the head, is diamond-shaped and usually measures between 0.6 cm and 3.6 cm at birth. It generally closes between 7 and 19 months of age, though it can remain open up to 26 months.
The posterior fontanelle, at the back of the head, is smaller and triangular. This fontanelle typically closes within 2 to 3 months after birth. A normal fontanelle should feel soft and flat, possibly exhibiting a slight pulsation due to blood flow. This flexibility allows for the brain growth that occurs during infancy.
Recognizing a Bulging Fontanelle
A bulging fontanelle presents as a tense, taut, or firm area that protrudes noticeably above the surrounding skull bones. This appearance differs from the normal soft, flat, or slightly concave feel of a healthy fontanelle. It is important to distinguish a true bulging fontanelle from a temporary protrusion.
A baby’s fontanelle may temporarily bulge when crying, coughing, vomiting, or lying down. However, a true bulging fontanelle remains outwardly curved even when the baby is calm, upright, and not straining. If the soft spot does not return to its normal flat or slightly indented state after the baby calms down, it warrants closer examination.
Potential Causes of a Bulging Fontanelle
A bulging fontanelle indicates increased pressure inside the skull, known as elevated intracranial pressure. This pressure can result from various medical conditions. One common cause is hydrocephalus, an excessive accumulation of cerebrospinal fluid (CSF) within the brain’s ventricles. This fluid buildup can be congenital or acquired due to injury or infection.
Infections affecting the brain and its surrounding membranes are another frequent cause. Meningitis, an inflammation of the membranes covering the brain and spinal cord, and encephalitis, an inflammation of the brain itself, can both lead to a bulging fontanelle. These infections cause swelling and increased pressure. Bleeding within the brain, known as intracranial hemorrhage, or head trauma can also cause the fontanelle to bulge.
Less common causes include brain tumors or abscesses, which increase intracranial volume. Certain medications, such as tetracyclines, and excessive vitamin A intake have also been linked to bulging fontanelles. Rare conditions like Lyme disease, Addison’s disease, or leukemia can also present with this symptom.
When to Seek Medical Attention
A bulging fontanelle, especially with other symptoms, is a medical emergency. Seek urgent medical evaluation if the bulging persists even when the baby is calm and upright. It is concerning if accompanied by a fever, which can indicate an infection like meningitis or encephalitis.
Other symptoms requiring immediate medical consultation include extreme irritability, lethargy, or excessive sleepiness. Persistent vomiting, poor feeding, a high-pitched cry, or seizures also warrant urgent care. Changes in consciousness, a stiff neck, or eyes that appear fixed downward are additional signs needing professional medical evaluation.
Diagnosis and Treatment
Upon presentation with a bulging fontanelle, medical professionals conduct a physical examination and neurological assessment. This evaluation helps determine the extent of bulging and associated neurological signs. To identify the underlying cause, imaging tests are often performed.
A head ultrasound may be used while the fontanelle is open to visualize the brain and detect fluid accumulation. More detailed imaging, such as a computed tomography (CT) scan or magnetic resonance imaging (MRI), might be necessary to view brain structure and identify masses, bleeding, or inflammation. A lumbar puncture, collecting cerebrospinal fluid, may be performed to check for infections like meningitis.
Treatment strategies depend on the specific diagnosis. Bacterial infections may require antibiotics, while hydrocephalus might be managed with surgical placement of a shunt to drain excess fluid. Addressing medication-induced causes typically involves discontinuing the offending drug.