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Jan Regelsberger, Tobias Schmidt, Björn Busse, Julia Herzen, Michael Tsokos, Michael Amling, and Felix Beckmann

Object

Both CT and high-frequency ultrasound have been shown to be reliable diagnostic tools used to differentiate normal cranial sutures from suture synostosis. In nonsynostotic plagiocephaly, overlapping of the bony plates and the so-called “sticky suture” is still controversial and is believed to represent a pathological fusion process. Synchrotron–microcomputed tomography (SRmCT) studies were undertaken to determine whether positional head deformities can be assumed to be true suture pathologies.

Methods

Morphological features and growth development of 6 normal cranial sutures between the ages of 3 and 12 months were analyzed histologically. Additionally 6 pathological sutures, including sagittal synostosis and nonsynostotic plagiocephaly (NSP), were compared with the group of normal sutures by histological and SRmCT studies. Synchrotron-microcomputed tomography is a special synchrotron radiation source with a high photon flux providing a monochromatic x-ray beam with a very high spatial resolution. Morphological characteristics of the different suture types were evaluated and bone density alongside the sutures was measured to compare the osseous structure of the adjacent bony plates of normal and pathological sutures.

Results

Histologically jointlike osseous edges of the normal sutures were seen in the 1st month of life and interlocking at the age of approximately 12 months. During this 1st year, bone thickness increases and suture width decreases. The SRmCT studies showed that: 1) sutures and adjacent bones in NSP are comparable to normal sutures in terms of their morphological aspects; 2) bone densities in the adjacent bony plates of NSP and normal sutures are not different; 3) thickening of the diploe with ridging of the bone in sagittal synostosis is associated with significantly higher bone density; 4) synostotic sutures are only partially fused but vary in their extent; and 5) nonfused sections in sagittal synostosis behave like normal sutures without any signs of pathological bone formation.

Conclusions

Sutures in patients with NSP were found without any morphological irregularities or different osseous structures alongside those compared with normal sutures. Thus, a true suture pathology or osseous change of the adjacent bony plates is highly unlikely in NSP. Even though the number of specimens is limited in this series, cranial suture fusion seems to start at one undetermined point and spread along the suture, whereas other parts of the same suture are not involved according to morphological aspects and bone density measurements of the adjacent bones. This theory may represent a dynamic fusion process completed over time but just starting too early.

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Jan Regelsberger, Günter Delling, Michael Tsokos, Knuth Helmke, Gertrude Kammler, Heidi Kränzlein, and Manfred Westphal

Object

Positional plagiocephaly has become an increasing problem for pediatricians and craniofacial specialists. Diagnosis is commonly based on history and clinical features, but may be difficult in some cases when characteristic features are missing and radiographic studies seem to be necessary. Near-field high-frequency ultrasound has been used to evaluate the sonographic findings of suture anatomy and confirm the diagnosis of positional plagiocephaly as well as provide information of prognostic value.

Methods

The authors report on 100 pediatric patients between the ages of 2 and 13 months, who were admitted to their department since 2004 with an abnormal head shape suggesting nonsynostotic plagiocephaly (NSP). Suture anatomy was examined using a 7.5-MHz linear transducer and a Siemens Elegra ultrasound scanner by two independent investigators. Measurements of suture width and bone thickness were obtained, and the findings were correlated with clinical data as well as sonographic and histopathological findings in both normal and fused cranial sutures. Interobserver variability was assessed by means of paired t-tests. Linear regression analyses were used for correlating patient age with suture width and bone thickness.

Patency of lambdoid sutures was confirmed in 99 cases in which the clinical findings suggested NSP. Morphological characteristics of the sutures—interosseous hypoechoic areas between hyperechoic bone plates—were comparable to those of normal cranial sutures. In one patient, partial synostosis was diagnosed. Overlapping hyperechoic bone plates were found in 51 patients on the affected side of the skull and in 36 patients on the unaffected side. Suture width decreased over time from 6.5 to 2 mm, and thickness of bone in the affected area increased from 0.6 to 1.2 mm until the age of 13 months. The method was found to be limited by age (upper limit 13 months) and anatomical variations but did not show any interobserver variability (p < 0.05).

Conclusions

High-frequency ultrasound is a relatively inexpensive, safe, and easy-to-use tool for confirming the diagnosis of positional plagiocephaly and excluding true synostosis. Overlapping bone plates may be seen on the affected side of the skull in a majority of plagiocephalic patients, but this finding seems to have no prognostic value regarding early fusion of sutures and therefore should not affect treatment decisions. With its lack of interobserver variability and the advantage of not involving ionizing radiation, sonography has the potential to be a standard modality for investigating plagiocephaly in infants and should be offered in craniofacial outpatient clinics.