Plagiocephaly: What Causes Flat Head Syndrome and What a Cranial Chiropractor Can Do

When a new parent notices that their baby's head is flat on one side, the response from most pediatricians follows a familiar script: do more tummy time, reposition the head during sleep, and if it doesn't improve by four months, consider a helmet.

This is not bad advice, exactly. Repositioning helps. Helmets can reshape a growing skull. But there is something fundamental about plagiocephaly that these interventions never address: the underlying cranial bone displacement from birth that caused the flatness in the first place.

As someone who has worked with infants since the early years of my practice — and as someone who personally experienced torticollis as a child and understands what it means to carry a structural problem that nobody identified — I want to offer a different perspective on flat head syndrome.

What Plagiocephaly Actually Is

Plagiocephaly refers to asymmetric flattening of the skull. "Positional plagiocephaly" describes flattening that develops after birth due to a preferred head position — the baby consistently turns their head to the same side, and the constant pressure on one area gradually flattens it.

But the preferred head position itself has a cause. Infants don't randomly develop a preference for one side. Most commonly, it's because turning the head to the other side is uncomfortable or restricted. And that restriction almost always traces back to what happened during delivery.

Birth as a Physical Event

Labor and delivery are physically demanding for the baby, not just the mother. During a vaginal birth, the baby's head must navigate the birth canal through a combination of compression, rotation, and extension — forces that can be significant, and become even more so when vacuum extraction or forceps are used, when delivery is prolonged, or when the baby was in a difficult position (occiput posterior, asynclitic, breech).

The cranial bones of a newborn are soft and mobile — by design, to allow them to compress and overlap during delivery. But that same softness means they can also be displaced or held in a compressed position by the forces of delivery. When the occiput or one of the temporal bones is compressed or torqued, the infant will instinctively avoid the position that creates discomfort. They turn their head to the comfortable side. The uncomfortable side gets less time against surfaces, recovers less, and eventually the side that carries more resting contact time begins to flatten.

The flattening is a downstream consequence. The cranial bone displacement is the upstream cause.

Why Helmets Often Miss the Root Cause

Cranial remolding helmets work by creating space on the flat side of the head and gentle contact on the rounded side, using the pressure of a growing skull to gradually encourage a more symmetric shape. They can be effective at changing the shape of the skull — which matters for cosmetic reasons and may matter for brain development, though the research on that latter point is ongoing.

What helmets do not do is address the position and mobility of the underlying cranial bones. A helmet can reshape the exterior contour of the skull. It cannot restore normal sutural motion to a compressed temporal bone, release an occipital condyle that is jammed against the atlas, or normalize the cranial rhythmic impulse on the restricted side.

This is why some children complete a full course of helmet therapy and show cosmetic improvement but still have the underlying mechanical dysfunction — which may contribute to ongoing neck asymmetry, developmental delays, sensory integration challenges, or other issues that nobody connects to the original birth trauma.

The Critical Intervention Window

Cranial bones are most responsive to treatment in the first months of life, when they are still relatively soft and the cranial sutures are at their most mobile. The ideal window for cranial chiropractic assessment and treatment in a plagiocephalic infant is under six months of age — ideally, under three months.

This does not mean that older infants or even toddlers cannot benefit. It means that the earlier we begin, the less work is required to achieve correction, and the more fully the developing brain has access to a symmetric cranial environment during its most rapid period of growth.

If your pediatrician mentions plagiocephaly at the two-month well visit, that is the time to also seek a cranial evaluation — ideally before the helmet recommendation comes at four months.

What a Cranial Session for an Infant Looks Like

I understand that parents are understandably cautious about bringing a small baby to a chiropractor. Let me describe exactly what happens.

The infant remains in the parent's arms or lies comfortably on a padded table — whichever the baby prefers. I begin with observation: head shape, spontaneous head position, eye level asymmetry, facial symmetry. Then I use gentle palpation — fingertip contacts — to assess the position and mobility of each cranial bone.

The treatment itself involves contacts so light that many babies sleep through the entire session. I am not manipulating the spine. I am not applying any force. I am applying sustained, gentle, precisely directed fingertip pressure that encourages restricted cranial bones to resume their normal motion. A session typically lasts 15-20 minutes and most infants find it calming.

Parents sometimes describe visible changes after the first session: the baby turns their head more freely to both sides, settles more easily during nursing, or sleeps more peacefully.

Associated Conditions That Often Resolve Alongside

Plagiocephaly rarely appears alone. The same cranial bone displacement from birth that creates the head shape asymmetry frequently also contributes to:

Torticollis — persistent head tilt or rotation preference, which may be positional (from the cranial restriction) or involve the sternocleidomastoid muscle directly.

Nursing difficulty — difficulty achieving a deep latch, preference for nursing on one side, poor suction, and gas/colic symptoms that may relate to suboptimal jaw and palate mechanics.

Infant colic — while colic has many causes, cranial and upper cervical restriction affecting the vagus nerve is a meaningful contributor in some infants. When vagal tone is normalized through cranial adjustment, digestive comfort often improves.

I had torticollis as a child, and I know what it's like to grow up with a structural problem that shapes how you carry yourself for years before anyone identifies it. That personal history is part of why this work with infants matters so much to me. Catching these patterns early changes a child's trajectory in ways that are genuinely difficult to quantify.

Key Takeaways

• Positional plagiocephaly is usually caused by a preferred head position, which itself is caused by cranial bone displacement from birth.
• Helmets reshape the exterior of the skull but do not address the underlying bone position or sutural mobility.
• The ideal intervention window for cranial chiropractic is under six months, before the bones lose their maximum plasticity.
• Cranial treatment for infants is extremely gentle — fingertip pressure only, with no thrusting or manipulation.
• Plagiocephaly frequently coexists with torticollis, nursing difficulty, and colic, all of which may improve alongside the cranial correction.

If your baby has been diagnosed with plagiocephaly or if you've noticed a head shape asymmetry or consistent head-turning preference, please don't wait for the four-month helmet appointment. Call Pura Vida Chiropractic at (210) 685-1994 and bring your baby in for a cranial evaluation with Dr. Dan Foss. Early intervention makes all the difference. We serve San Antonio families in English and Spanish — hablamos español.