Soft spots on a baby’s head, known as fontanelles, are flexible areas where the skull bones have not yet fused. They serve a vital purpose, allowing a baby’s brain to grow rapidly during infancy and facilitating passage through the birth canal during delivery. Parents often feel apprehension about these delicate areas, wondering about their normal appearance and what might signal a concern. Understanding typical characteristics is important for identifying deviations.
Understanding the Fontanelle
A baby’s skull consists of several bony plates connected by fibrous joints (sutures), with wider gaps forming the fontanelles. Two primary fontanelles exist: the large anterior fontanelle, on the top front of the head, and the smaller posterior fontanelle, near the back. The anterior fontanelle typically measures 0.8 to 2.8 inches (2-7 cm) and usually closes between 12 and 18 months. The smaller posterior fontanelle often closes by 2 to 3 months. These areas are covered by a tough, protective membrane, not exposed brain tissue.
Normal vs. Bulging Fontanelle Sensation
When gently touched, a normal fontanelle should feel soft and relatively flat against the contours of the baby’s skull. It may exhibit a slight, rhythmic pulsation, which is normal and corresponds with the baby’s heartbeat. Checking the fontanelle when the baby is calm and upright is important, as crying, straining, or lying down can temporarily cause it to appear slightly raised.
In contrast, a bulging fontanelle feels tense, firm, and raised above the surrounding skull bones. The skin over the area might appear taut and stretched. While a normal fontanelle might show a subtle pulse, a bulging one could either pulsate more prominently or, in some cases, show no pulsation at all due to increased pressure. This persistent elevation, especially when the baby is relaxed, indicates a significant change.
Potential Causes of a Bulging Fontanelle
A fontanelle bulges due to increased pressure inside the skull, known as intracranial pressure. This can stem from various medical conditions. One common cause is hydrocephalus, an abnormal accumulation of cerebrospinal fluid within the brain’s ventricles. This fluid buildup exerts pressure on the brain.
Infections of the central nervous system, such as meningitis or encephalitis, can also cause a bulging fontanelle. These infections lead to swelling and fluid accumulation, increasing intracranial pressure. Head trauma, even minor impacts, can sometimes result in bleeding or swelling within the skull. Certain medications or metabolic disorders can also contribute to increased pressure.
When to Seek Medical Help
A persistently raised, firm, and tense fontanelle is a serious medical sign requiring immediate professional evaluation. This is especially true if accompanied by other concerning symptoms.
Accompanying signs that necessitate immediate medical consultation include fever, excessive crying, irritability, or unusual lethargy. Vomiting, poor feeding, a stiff neck, or seizures are warning signs that, with a bulging fontanelle, indicate an emergency. Even without these additional symptoms, a persistently bulging fontanelle requires prompt assessment.