Plagiocephaly vs Brachycephaly: Key Differences



Plagiocephaly vs Brachycephaly: Key Differences Explained

Quick answer: Plagiocephaly is an asymmetric flattening on one side of the head (parallelogram shape), while brachycephaly is a symmetric flattening across the entire back of the skull. Both are types of positional flat head syndrome and can appear together.

• Plagiocephaly: One-sided; ear displaced forward, facial asymmetry visible.
• Brachycephaly: Bilateral; head appears wide and high, forehead may bulge forward.
• Combined: Both deformities frequently co-exist in the same baby.

Plagiocephaly and brachycephaly are two of the most commonly diagnosed types of flat head syndrome. Although they share the same causes, the two conditions produce very different head shapes — and distinguishing between them is important for finding the best treatment for your baby.

What Is Brachycephaly?

Brachycephaly presents as a noticeably wide and tall head shape.

If your baby has brachycephaly, you may notice flattening across the back of the skull appearing around eight weeks of age, causing the head to look much wider than normal. The back of the head may also appear taller than normal, and in some cases this can lead to a bulging forward of the skull at the forehead.

Brachycephaly typically develops during the first few months of life when the skull is still soft, malleable, and susceptible to external pressures. Active steps must be taken to prevent the deformity from worsening or becoming permanent.

What Is Plagiocephaly?

Plagiocephaly is the most common type of flat head syndrome and refers to flattening on one side of the head, producing an asymmetric skull shape. Often compared to the shape of a parallelogram, the flattening appears on the left or right side of the skull — creating a lopsided appearance.

Clinical signs of plagiocephaly beyond the flattening include:

• Ear misalignment. The ear and cheek on the flatter side are pushed forward.
• Facial asymmetry — one eye may sit lower or appear smaller than the other, and the brow ridge may protrude on that side.
• Combined plagiocephaly and brachycephaly — a wide, asymmetric head shape that is very common.

What Causes Plagiocephaly and Brachycephaly?

Despite their differences, many babies we see at CranioWell show a combination of both. The terms are clinical descriptions of the characteristics of the flattening — not two separate diseases. Both conditions are most commonly caused by one or more of the following factors:

• Soft skull — Babies are born with extraordinarily soft skulls that allow them to pass through the birth canal and accommodate rapid brain growth in the first months. Because the skull plates have not yet fused, they are highly susceptible to reshaping under pressure.
• Multiple births — Flat head syndrome is more common in multiples because there is less space in the uterus, placing extra pressure on the soft skull bones.
• Premature birth — Premature babies are particularly vulnerable because they miss out on the bone mineralization that occurs in the final weeks of pregnancy. They also tend to rest with their heads to one side because they cannot yet move them.
• Positional pressure after birth — Time spent with the head resting on flat, hard surfaces is one of the most common causes. This is compounded by torticollis (one-sided neck muscle tightness).

What Treatments Are Available?

As soon as flattening begins to appear, we recommend parents start repositioning techniques. This can help prevent plagiocephaly and brachycephaly from worsening — and may even reverse mild cases, typically before the baby is about four months old.

• During sleep — Alternate which end of the cot the baby's head points toward each night. Move the night light to different sides of the room (babies follow light with their eyes and head). Ensure the baby's head position is checked and adjusted as needed.
• During play — Practice tummy time to strengthen neck and trunk muscles. This takes pressure off the back of the head.
• During feeding and carrying — Alternate the side on which you hold your baby to encourage equal movement on both sides of the head.
• While travelling — Where possible, limit time spent in car seats and prams with the head resting against a hard, flat surface. Use a sling or baby carrier instead of transporting in a car seat.

Next Steps for Plagiocephaly and Brachycephaly

We aim to provide reassurance and clear guidance rather than alarm. We assess each baby's head shape objectively — because without knowing where you are starting from, it is impossible to know where you are going.

Our experience shows that if plagiocephaly and brachycephaly have not self-corrected by five months of age, they are unlikely to improve without further help. In these cases, CranioWell's HKM Pro helmet therapy can be used to gradually guide the skull back toward a more normal, symmetrical shape.

Related: Plagiocephaly Guide, Brachycephaly Guide, Torticollis in Babies.