Value of high-resolution ultrasound in the differential diagnosis of scaphocephaly and occipital plagiocephaly

Abstract

Secondary to the increase in deformational plagiocephaly a growing number of infants with cranial deformity present to craniofacial teams. Computed tomography (CT) is diagnostic, but uses ionizing radiation. The purpose of this study was to evaluate ultrasound as a screening test for the patency of cranial sutures in scaphocephaly and occipital plagiocephaly. The cranial sutures of 54 infants with this cranial deformity were assessed by ultrasound. Sutures were read as patent or fused if a hypoechoic gap could or could not be demonstrated between the hyperechoic clavarial bones, respectively. Seven children suffered from true craniosynostosis of either the sagittal or the lambdoid suture. In five cases the ultrasound findings were diagnostic for a fused suture, in two cases the results were inconclusive. Forty-seven infants presented with deformational plagiocephaly. Ultrasound examination demonstrated patent sutures in 45 cases and was inconclusive in two cases. Sonography of the cranial sutures is a good screening tool to distinguish fused from patent cranial sutures in scaphocephaly and occipital plagiocephaly and avoids the radiation exposure associated with CT examinations.

Cranial deformity in infants may result from premature fusion of one or multiple cranial sutures or may result from external moulding forces to the malleable and growing cranium.

The clinical appearance of children with suspected craniosynostosis is often characteristic. Although a few surgeons argue that computed tomography (CT) scans should be reserved for infants with suspected craniosynostosis in whom the physical examination is not clearly diagnostic, most surgeons think that radiographic imaging is necessary to confirm the diagnosis.

In children with posterior plagiocephaly the distinction between true fusion of the lambdoid suture and positional moulding of the back of the head may be difficult. The distinction is critical, however. Lambdoid synostosis, although rare, requires occipital surgical advancement. Positional plagiocephaly has to be treated conservatively with physical therapy and/or corrective helmet therapy.

The gold standard in radiographic imaging of the head with regard to cranial deformity is CT, but it is expensive, involves radiation exposure and frequently necessitates sedation of the children. The radiation effects are a matter of concern, as they are reported to be associated with an increased lifetime risk of cancer and influence the cognitive development of children.

In the recent literature, ultrasound (US) is described as a reliable alternative examination technique to evaluate the patency of the cranial sutures in children with an atypical head shape.

The purpose of this retrospective study was to determine the sensitivity and specificity of US in distinguishing true craniosynostosis from positional head deformity.

Materials and methods

Fifty-four infants were referred to the authors’ interdisciplinary craniofacial clinic and plagiocephaly clinic because of plagiocephaly and scaphocephaly between May 2008 and April 2009. Their age ranged from 0.8 to 11.7 months (median 6.0 months). Children with suspected synostosis of the coronal or metopic suture or complex craniosynostosis underwent CT examination for presurgical planning and were excluded from the study. Clinical examination was followed by standardized near-field high-frequency US imaging of all cranial sutures (Siemens Elegra, 13.5 MHz linear scanner). The scanner was positioned perpendicular to the assumed course of the suture. A suture was interpreted as patent if a hypoechoic gap could be found between the hyerechoic calvarial bones ( Fig. 1 ). The US images were read as showing a fused suture if a hypoechoic gap could not be seen in the expected course of the affected suture ( Fig. 2 ).

Fig. 1
Ultrasound and CT imaging of a 6-month-old child with positional posterior plagiocephaly. (a) US image with hypoechoic gap between hyperechoic calvarial bones. (b) Axial CT scan with left occipital flattening and patent lambdoid sutures. (c) Vertex view of 3D CT demonstrates parallelogram appearance of the skull. (d) Posterior view of 3D CT reconstruction shows patent lamboid sutures and a horizontal skull base.

Fig. 2
US and CT imaging of a 7-month-old child with unilateral lambdoid synostosis on the right side. (a) US image with an absent hyopechoic gap, but ridging and continuous hyperechoic calvarian bones. (b) Axial CT scan with right occipital flattening and fused lambdoid suture. (c) Vertex view of 3D CT demonstrates trapezoid appearance of the skull. (d) Posterior view of 3D CT reconstruction demonstrates fused lambdoid suture and an ipsilateral downward tilt of the skull base.

Results

Seven children had true craniosynostosis. In five children, US examination demonstrated premature closure of either the sagittal (four cases) or the lambdoid (1 case) suture. In two infants, the ultrasound findings were inconclusive. In one case additional plain radiographs, in the other a three dimensional (3D) CT examination was performed demonstrating partial fusion of the sagittal and the lambdoid suture, respectively. For preparation of the occipital advancement 3D CT was performed in the two lambdoid cases with the classical findings for craniosynostosis. The children with characteristic head shape and positive US for sagittal synostosis were operated on without additional imaging studies. The surgical findings confirmed the premature fusion of the sagittal or the lambdoid suture in all cases. In none of the children with craniosynostosis the US images were read as patent sutures ( Table 1 ).

Table 1
Ultrasound findings in 54 children referred with cranial deformity.
Cranial deformity Ultrasound diagnosis
Total Fused suture Patent suture Inconclusive
Craniosynostosis 7 5 0 2
Sagittal suture 5 4 1
Lambdoid suture 2 1 1
Positional cranial deformity 47 0 45 2

Forty-five infants had normal appearance of the cranial sutures on US. None of them had additional imaging for the evaluation of the sutures. In two children with posterior plagiocephaly the US images were inconclusive. CT examination revealed normal patent sutures in these cases. All 47 children diagnosed with positional cranial deformity had clinical follow-up of 3–10 months with no further evidence of craniosynostosis. Head shape improved or normalized with conservative physical or helmet therapy.

Under the premise, that the inconclusive US findings are regarded as false-positive and false-negative results, the method had at least a sensitivity of 71.4% (95% confidence interval: 35.5%, 100%), a specificity of 95.7% (89.9%, 100%), a positive predictive value of 71.4% (35.5%, 100%) and a negative predictive value of 95.7% (89.9%, 100%).

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Jan 26, 2018 | Posted by in Oral and Maxillofacial Surgery | Comments Off on Value of high-resolution ultrasound in the differential diagnosis of scaphocephaly and occipital plagiocephaly
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