What Is Brachycephaly and What Causes It?

Quick answer: Brachycephaly is the symmetric flattening of the back of a baby’s skull (occiput) with associated widening of the head. It is defined when the cephalic index exceeds 86. The most common cause is prolonged time spent lying on the back. Early repositioning and, in moderate-to-severe cases, helmet therapy are the main treatment approaches.

What Is Brachycephaly?

Brachycephaly comes from the Greek words brachy (short) and kephale (head). It describes a skull shape in which the front-to-back (anteroposterior) diameter is shorter than normal relative to the width, giving the head a wide, flat appearance when viewed from above.

The key measurement used to identify brachycephaly is the cephalic index (CI):

CI = (Head Width ÷ Head Length) × 100

• Normal range: 76–86
• Mild brachycephaly: 87–90
• Moderate brachycephaly: 91–95
• Severe brachycephaly: CI > 95

Brachycephaly is a positional (deformational) condition, meaning it develops due to external pressure on the skull. It is distinct from craniosynostosis (premature fusion of skull sutures), which requires surgical treatment.

What Causes Brachycephaly?

The primary cause is prolonged pressure on the back of the skull while the bones are still soft and malleable. Contributing factors include:

• Supine sleeping position: The "Back to Sleep" recommendation (introduced to reduce SIDS) means babies spend significant time on their backs, increasing pressure on the occiput.
• Extended use of bouncers, car seats, and pushchairs: These maintain the baby in a semi-reclined position with the back of the head resting against a surface.
• Limited active movement: Babies with low muscle tone or reduced spontaneous movement are at higher risk.
• Multiple births: Twins or triplets may have had less room to move in the womb, which can pre-dispose the skull to flattening.
• Prematurity: Premature babies spend more time in incubators in one position, and their skulls are softer.
• Family history: A naturally wider skull shape can be genetic.

Note: Brachycephaly that develops after birth is almost always positional. True brachycephalic skull shapes (without flattening) may also be an inherited ethnic or family characteristic and are not a medical concern.

How to Recognise Brachycephaly

Signs that may indicate brachycephaly:

• The back of the head appears flat when viewed from the side.
• The head appears unusually wide when viewed from above.
• The forehead may be prominent or bulge slightly forward.
• The head height may be increased (compensatory upward growth).
• Unlike plagiocephaly, the flattening is symmetric (both sides are equally affected).

Treatment Options

Mild Brachycephaly

Repositioning therapy and tummy time are the first-line interventions. These reduce sustained pressure on the back of the head and encourage the skull to grow in a more balanced direction.

• Repositioning therapy: changing the baby’s head position regularly during sleep and awake periods.
• Tummy time: supervised time on the tummy to strengthen neck and shoulder muscles and relieve occipital pressure.

Moderate to Severe Brachycephaly

Helmet therapy (cranial orthosis) is recommended for moderate to severe cases, ideally starting between 4 and 6 months of age. The helmet works by relieving pressure on the flattened areas while allowing unrestricted growth in the restricted directions, gradually reshaping the skull towards a more normal cephalic index.

CranioWell’s HKM Pro cranial remodelling helmet is custom-fabricated using 3D scanning technology, ensuring precise fit for each individual baby’s head measurements. It is registered in the ÜTS (Turkish Medical Device Tracking System) and EUDAMED (European Database on Medical Devices) databases.

For a comprehensive overview of all treatment methods, see our Head Shaping Methods for Babies guide.

Does Brachycephaly Cause Brain Problems?

Positional brachycephaly does not restrict brain growth or cause neurological problems. The brain continues to grow normally within the wider-shaped skull. However, in severe untreated cases, structural asymmetries in the face, jaw, and ears may develop over time, potentially affecting dental occlusion or ear canal positioning.

Frequently asked questions

Is brachycephaly the same as flat head syndrome?

In everyday language, "flat head syndrome" is used to describe both brachycephaly (symmetric back-of-head flattening) and plagiocephaly (asymmetric oblique flattening). Medically they are distinct: brachycephaly involves a high cephalic index without significant asymmetry.

At what age does brachycephaly need to be treated?

The optimal window for helmet therapy is 4–6 months, when skull bones are still highly malleable. Repositioning exercises can start from birth. After 12 months, the bones harden significantly and the potential for correction diminishes.

Will my baby outgrow brachycephaly?

Mild cases may improve as the baby begins rolling and sitting (around 6 months), reducing back-of-head pressure. Moderate and severe cases are unlikely to self-correct and benefit from early intervention.

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