GPAtlas🧭 When to suspect
Suspect an abnormal head shape when parents describe their baby’s head as asymmetrical, ‘flat’, or ‘squashed on one side’. Since the ‘Back to Sleep’ campaign (which roughly halved sudden infant death), positional (deformational) plagiocephaly has become very common – affecting up to half of babies under a year to some degree. The skull is simply moulded by outside pressure; the sutures are normal and brain development is not affected.
The clinical task is one of calibration: confidently reassure the many with benign positional moulding, while never missing the few with craniosynostosis (premature fusion of one or more cranial sutures). The single most useful discriminator is the trajectory: positional flattening is absent at birth, appears at 6 weeks–3 months, and improves as the baby becomes mobile, whereas craniosynostosis is present at or near birth and worsens over time.
| Head shape (from above / clinically) | Most likely diagnosis |
|---|---|
| Parallelogram – back of head flat on one side, same-side ear pushed forward, same-side forehead bulging | Positional plagiocephaly (benign, deformational) |
| Symmetrical flattening across the whole back, broad/tall head, forehead bossing | Positional brachycephaly (benign, deformational) |
| Long and narrow, ‘boat-shaped’, ridge along the midline (sagittal) | Sagittal synostosis → scaphocephaly (the commonest synostosis) |
| Triangular forehead, ridge down the middle of the forehead, eyes close-set | Metopic synostosis → trigonocephaly |
| One-sided forehead/brow flattening with opposite-side bossing, ‘harlequin eye’ | Unicoronal synostosis → anterior plagiocephaly |
| Broad, short, tall (‘towering’) forehead, both brows flattened | Bicoronal synostosis → brachycephaly |
| Trapezoid – back of head flat on one side, same-side ear pushed back and down, mastoid bulge | Lambdoid synostosis → posterior plagiocephaly (rare; the great mimic) |
|
🧠 Clinical pearl It is the trajectory, not a single snapshot, that tells you the diagnosis. Deformational flattening is absent at birth, appears around 6 weeks to 3 months, and gets better as the baby starts to move. A head that was abnormal from birth, or one that is worsening rather than improving, is craniosynostosis until proven otherwise – refer it, however subtle it looks. |
Source: NICE NG127 · NHS · GOSH
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