Anatomy is essential in imaging craniosynostosis. In this article we have depicted various types of craniosynostosis through radiographs and 3D reconstructed images.

Fig. 1: Anatomy of cranial sutures
References: Netter FH, Dalley AF. Atlas of human anatomy. 2nd ed. East Hanover, NJ: Novartis, 1997.

Sagittal synostosis 

Restriction of growth perpendicular to the sagittal suture results in a narrow and elongated cranium with frontal bossing, occipital protrusion and ridging of the fused, heaped suture. This deformity is characterized by scaphocephaly (inverted boat with a keel), clinocephaly (flat cranium due to loss of cranial convexity), and leptocephaly (tall and narrow cranium)

Fig. 2: Sagittal synostosis in an 11-month-old boy. The plain skull radiography (A : AP view, B : Lateral view) and 3-D CT images (C) show the absence of a radiolucent sagittal suture (A and C) and an elongated cranium with frontal bossing and occipital protrusion (B and C). The patent coronal and lambdoid sutures have a radiolucent, serrated and nonlinear appearance, and the fused metopic suture is normal in this 11-month-old baby.
References: Kim HJ, Roh HG, Lee IW. Craniosynostosis: Updates in radiologic diagnosis. Journal of Korean Neurosurgical Society. 2016 May;59(3):219.

Coronal synostosis 

Coronal synostosis causes restriction of growth in the anterior-posterior direction, perpendicular to the coronal suture with compensatory overgrowth in the parietal direction, perpendicular to the patent sagittal suture. Unicoronal synostosis results in anterior plagiocephaly (oblique cranium) and appears as a shallow ipsilateral anterior cranial fossa with contralateral frontal bossing, an elevated roof and lateral wall of the ipsilateral orbit ("harlequin appearance"), a hypoplastic supraorbital ridge, elevated ipsilateral sphenoid wings, a contralaterally shifted anterior fontanel and facial asymmetry. Bicoronal synostosis restricts skull growth in the anterior-posterior direction, which generally results in brachycephaly (short cranium).

Fig. 3: Unicoronal (right) synostosis in a 12-month-old girl. A : The plain skull radiography and 3-D CT AP view images show the fused right coronal suture as the absence of a suture and a bony ridge compared to the patent left coronal suture (C). The "harlequin eye" appearance of the right orbit, the elevated ipsilateral sphenoid wings (arrows), the facial asymmetry (deviation of the nose and chin to the contralateral side), and the contralaterally shifted anterior fontanel are also demonstrated. The 3-D CT images also show the contralateral frontal bossing and ipsilateral hypoplastic supraorbital ridge. B : The plain skull radiography and 3-D CT lateral and superior view images show the absence of the right coronal suture, shallow ipsilateral anterior cranial fossa (*) and contralateral frontal bossing (arrow). Anterior plagiocephaly due to the decreased AP dimension of the right cranium with shifted anterior fontanel and contralateral frontal bossing are demonstrated on the superior view image.
References: Kim HJ, Roh HG, Lee IW. Craniosynostosis: Updates in radiologic diagnosis. Journal of Korean Neurosurgical Society. 2016 May;59(3):219.

Fig. 4: Bicoronal synostosis in a 1-month-old boy. The fusion of both coronal sutures is demonstrated as sclerotic linear ridges (arrows). The patent metopic suture and anterior fontanel in this 1-month-old baby are normal. The plain radiography of this 1-month-baby does not show the wide open metopic suture. However, it demonstrates the sclerotic fused suture. Brachycephaly (short cranium by shortened AP and widened biparietal dimensions) and the bilateral "harlequin eye" deformity of the orbits combined with hypertelorism are characteristic of bicoronal synostosis.
References: Kim HJ, Roh HG, Lee IW. Craniosynostosis: Updates in radiologic diagnosis. Journal of Korean Neurosurgical Society. 2016 May;59(3):219.

Metopic synostosis 

Premature fusion of the metopic suture results in a palpable ectocranial ridge or omega-shaped notch and a small anterior cranial fossa with a triangular pointed forehead (trigonocephaly) and parieto-occipital bossing due to bilateral constriction of the frontal bones. Imaging findings include decreased interorbital distance (hypotelorism), hypoplastic ethmoid sinus, and medially upward slanted orbital roof ("quizzical eye" appearance).

Fig. 5: Metopic synostosis in a 12-month-old boy. A fused metopic suture is demonstrated as a linear sclerotic line on the plain radiography image and a bony ridge on the 3-D CT image (arrows). Trigonocephaly, hypotelorism, a small ethmoid sinus, and the "quizzical eye" appearance of the orbits are noted.
References: Kim HJ, Roh HG, Lee IW. Craniosynostosis: Updates in radiologic diagnosis. Journal of Korean Neurosurgical Society. 2016 May;59(3):219.

Lambdoid synostosis 

A unilateral premature fusion causes posterior plagiocephaly (oblique deformity of the posterior cranium), which is more commonly caused by positional problems compared to premature fusion of the cranial suture. Therefore, unilateral lambdoid synostosis should be differentiated from positional plagiocephaly. Images show ipsilateral occipitoparietal flattening, contralateral frontal and occipitoparietal bossing, a contralaterally shifted posterior fontanel, double contouring of the occipital margin due to a unilateral small posterior cranium, and a tilted skull base. Bilateral fusion of the lambdoid sutures results in turricephaly (tall cranium; also known as oxycephaly and acrocephaly), with bilateral occipitoparietal flattening that leads to a small posterior cranial fossa and unimpeded compensatory growth at bregma.

Fig. 6: Unilateral (left) lambdoid synostosis in an 8-month-old boy. The plain skull radiography and 3-D CT images show the fused suture as a partial absence of the suture with a linear ridge and perisutural sclerosis (L in A and B). Ipsilateral occipitoparietal flattening (posterior plagiocephaly), contralateral frontal and occipitoparietal bossing, and contralaterally shifted posterior fontanel are demonstrated. The cranium shows a trapezoidal configuration on the superior view image. The unilateral small posterior cranium makes a double contour of the occipital margin on the lateral view images (arrows in B), and the tilted skull base is noted in the AP and PA view images (dashed lines in A and B).
References: Kim HJ, Roh HG, Lee IW. Craniosynostosis: Updates in radiologic diagnosis. Journal of Korean Neurosurgical Society. 2016 May;59(3):219.

Multisuture synostosis 

Multisuture synostosis is often syndromic. The patterns are variable according to the combination of sutures. Pansynostosis involves the sagittal, coronal and lambdoid sutures and is the most severe form resulting in the cloverleaf deformity of the skull (bulging of the temporal regions and severe proptosis, also known as Kleeblattschäde) or oxycephaly (a narrow and towering cranium) .(2)

Fig. 7: Pansynostosis in a 10-month-old girl with Crouzon syndrome. The plain skull radiography (A) and 3-D CT (B) images show an absence of the coronal, sagittal and lambdoid sutures. The fontanels are also closed. The cranium is narrow and towered (oxycephaly). "Copper beaten" skull is also demonstrated on the plain radiography images (A) by gyral impressions on the inner table of the skull, which represents the increased intracranial pressure.
References: Kim HJ, Roh HG, Lee IW. Craniosynostosis: Updates in radiologic diagnosis. Journal of Korean Neurosurgical Society. 2016 May;59(3):219.