Paediatric skull—suspected NAI

A skull X-ray (SXR) continues to have an important role when there is suspicion of non-accidental injury (NAI) in an infant or a toddler . The primary indication for a SXR in these patients is forensic .

Be careful:

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Accessory sutures are common.
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Calling an accessory suture a fracture may lead to an incorrect suggestion of NAI.
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Dismissing a fracture as an accessory suture can have serious clinical consequences.
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To avoid mistakes:
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  Be aware of the positions of the common accessory sutures.
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  Assess and interpret an infant's or toddler's radiographs in a systematic step-by-step manner.

The standard radiographs

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Lateral.
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AP frontal view.
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Towne's view.

The precise SXR views to be obtained will be specified by the local protocol for NAI assessment in infants and toddlers .

Abbreviations

the sutures

C, coronal;
In, innominate;
L, lambdoid;
M, mendosal;
Met, metopic;
O, occipitomastoid;
P1 and P2, accessory parietal;
Sa, sagittal;
Sq, squamosal.

NAI, non-accidental injury.

Normal anatomy

Infants and toddlers—normal accessory sutures

Evaluating the SXR in an infant or toddler presents unique problems. Diagnostic confusion between sutures and fractures may have serious consequences. A basic understanding of the locations and variable appearances of these sutures will help to reduce the likelihood of misdiagnosis .

A basic classification of skull sutures in infants and toddlers

Grouping	Notes	Sutures
The normal sutures	Visible on the SXR in all infants and toddlers – persisting in all adults	Sagittal, coronal, lambdoid, squamosal, and smaller sutures around the mastoid
A normal developmental suture	Visible on the SXR in all infants and many toddlers – but not in adults	Innominate
The most common accessory sutures	Visible on the SXR in some infants and toddlers – occasionally persisting to adulthood	Metopic, accessory parietal, mendosal

Normal accessory sutures and the radiographs on which they are seen

Suture	Most commonly seen on	Notes
Metopic suture	Frontal √ √ Towne's √	The commonest accessory suture. It is also the one that most commonly persists in older children, and even in a few adults.
Accessory parietal suture	Towne's √ √ Frontal √ Lateral √	May be complete or incomplete. Occurs in vertical, horizontal or oblique orientations. Most commonly vertical.
Mendosal suture	Lateral √ √ Towne's √	Extends posteriorly from the lambdoid suture on the lateral view. Passes medially on Towne's view.
Innominate suture	Lateral √ √	Sometimes classified as an accessory suture but best regarded as a normal developmental suture because it is always present in infants. As the child matures this suture disappears.

The lateral SXR

The normal sutures. L = lambdoid suture; C = coronal suture; M = mendosal; O = occipitomastoid suture; Sq = squamosal suture; In = innominate suture

Accessory parietal sutures. Can appear in various positions (P).

Accessory parietal sutures vary in position. This drawing does not correspond to any radiographic projection. It shows the general positions and direction of the more common incomplete accessory parietal sutures (P1 and P2) when looking down from above the cranium.