Major clinical features of synostotic occipital ...

Major clinical features of synostotic occipital plagiocephaly: mechanisms of cranial deformations Hamilton Matushita, Nivaldo Alonso, Daniel Dante Cardeal & Fernanda Gonçalves de Andrade Child's Nervous System ISSN 0256-7040 Childs Nerv Syst DOI 10.1007/s00381-014-2414-7

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Author's personal copy Childs Nerv Syst DOI 10.1007/s00381-014-2414-7

ORIGINAL PAPER

Major clinical features of synostotic occipital plagiocephaly: mechanisms of cranial deformations Hamilton Matushita & Nivaldo Alonso & Daniel Dante Cardeal & Fernanda Gonçalves de Andrade

Received: 2 January 2014 / Accepted: 27 March 2014 # Springer-Verlag Berlin Heidelberg 2014

Abstract Purpose The clinical diagnosis of most common single-suture craniosynostosis is easily set, based on the stereotype of deformities and knowledge of the mechanisms of cranial deformations. However, synostosis of unilateral lambdoid suture, probably due to its lower incidence and similarity with other non-synostotic deformities affecting the posterior portion of the skull, makes its clinical diagnosis more difficult and imprecise. The aim of this study is to evaluate the most easily and accurate clinical characteristics to be recognized in the synostotic occipital plagiocephaly. Methods This study consisted of clinical evaluation of eight patients with synostotic occipital plagiocephaly, whose diagnosis was further corroborated by computed tomography. Results We identified the following: unilateral occipital flattening in eight out of eight patients (100 %), bulging of ipsilateral mastoid process in eight out of eight (100 %), “edge effect” of ipsilateral lambdoid suture in eight out of eight (100 %), inferior deviation of the ear in eight out of eight (100 %), H. Matushita : D. D. Cardeal : F. G. de Andrade Department of Neurosurgery, Division of Pediatric Neurosurgery, University of São Paulo, São Paulo, Brazil D. D. Cardeal e-mail: [email protected] F. G. de Andrade e-mail: [email protected] N. Alonso Department of Plastic Surgery, Craniofacial Unit, University of São Paulo, São Paulo, Brazil e-mail: [email protected] H. Matushita (*) Rua Barata Ribeiro 237, Cj 43/44/46, Bela Vista, São Paulo 01308-000, Brazil e-mail: [email protected] e-mail: [email protected]

“Dumbo” ears in eight out of eight (100 %), horizontal slant of the bimastoid line in seven out of eight (87.5 %), tilt of the head viewed from behind in seven out of eight (87.5 %), trapezoidal contour of the skull in top view in six out of eight (75 %), contralateral parietal bossing in six out of eight (75 %), and bossing of the contralateral forehead three out of eight (37.5 %). Conclusions The most important clinical features specific to the clinical diagnosis of synostotic occipital plagiocephaly, not present in the positional posterior plagiocephaly, were bulging of the ipsilateral mastoid process, edge effect of the synostotic lambdoid suture, tilt of the head, and slant of the bimastoid line viewed from behind, inferior deviation of the ear, and contralateral parietal bossing. Keywords Plagiocephaly . Synostotic occipital plagiocephaly . Unilateral lambdoid . Synostosis . Craniosynostosis . Skull deformity . Mechanisms

Introduction Fusion of the lambdoid suture in isolation is considered to be an exceedingly rare form of craniosynostosis. Populationbased studies have demonstrated that the overall incidence of craniosynostosis ranges from 3.1 to 6 cases per 10,000 births, and lambdoid synostosis is the rarest of all types of craniosynostosis, corresponding to less than 1 to 5.5 % of all cases of craniosynostosis, and in the population, less than 0.3 in 10,000 births [1–6]. Among cases of single-suture craniosynostosis, those involving unilateral closing of the lambdoid suture do not present well-defined clinical characterization because of their rarity. This diagnosis can often be confounded with positional plagiocephaly (PP), a type of deformity that is much more common than unilateral lambdoid synostosis (ULS). The

Author's personal copy Childs Nerv Syst

estimates of the prevalence of PP associated with positional brachycephaly have been reported to be as high as 18 to 19.7 % in healthy infants [7]. A study by Mulliken et al. [8] demonstrated that out of 115 infants presenting with unilateral posterior cranial flattening, only one had ULS. Both conditions give rise to asymmetry of the posterior occiput, with flattening of one side. It can be challenging to make a clinical diagnosis of ULS, even for the most experienced pediatric neurosurgeons or craniofacial surgeons. Rekate [3] stated that radiological assessment is essential for the precise differentiation between these two conditions. Fearon et al. [9] reported that among all the types of isolated monosutural craniosynostosis, physical examination may fail in diagnosing ULS. Liu et al. [10] reported the cases of three patients with true ULS who were originally diagnosed as having positional occipital plagiocephaly. In 1996, Huang et al. [2] proposed clinical criteria for diagnosing ULS that aid in differentiating it from PP, which have been widely used in the literature. The objective of this study was to investigate which of the clinical features of synostotic plagiocephaly are more consistently found in ULS and whether the diagnosis can be based on physical examination alone.

Patients and methods In our institution, we identified ten patients who were diagnosed as ULS cases. Two of these patients were excluded because of inadequate data. Thus, the study group was narrowed down to a smaller population of eight patients, who formed a subset for which all data points were available. We analyzed the clinical data, the photographic documentation (Fig. 1), and computed tomography (CT) scans on eight patients with ULS who were treated at our institution between January 1990 and January 2010.

Further data analysis was then conducted based on these cases. All of the patients underwent 3-D CT scans of the skull to define the suture anatomy and skull deformities. All the patients presented lambdoid suture fusion that was confirmed by means of computed tomography. All the cranial deformities that could be related to synostosis were observed independently, by two pediatric neurosurgeons belonging to the staff of our institution. The features were considered positive when the observations coincided between the two observers, and divergences between the observers were adjudicated by the senior author. Descriptive clinical findings were not compared with three-dimensional CT scans before the clinical photographs, or the patients had been examined by the observers. The clinical features analyzed in this study included the following: a. b. c. d. e. f. g. h. i. j.

Unilateral occipital flattening Trapezoidal head shape (viewed from the vertex) Ipsilateral mastoid bulging Downward slanting of the ipsilateral skull base Displacement of the ipsilateral ear Ipsilateral “Dumbo” ear Bossing of the forehead Contralateral parietal bossing Tilt of the head Overriding of the lambdoid suture.

The final results are displayed in Table 1.

Results The ages of the patients ranged from 5 months to 4 years and 5 months (mean age=21.1 months). Regarding gender, there were five males and three females. The right side was involved in six cases and the left in two cases. Two patients

Fig. 1 Case 5 clinical photographs. a Frontal view. b View from behind. c View from the top

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+ + + + + + + −

+ + + + + + + +

presented later in life, i.e., after reaching the age of 4 years, and they did not receive surgical treatment. In these two children, the skull was only mildly affected. Six children underwent an operative correction of the synostosis at a mean age of 12.3 months (range 5 to 21 months). The decision to pursue surgical treatment was based on the severity of the deformities. Analysis of the 3-D CT scans provided proof of ULS in all cases (Fig. 2). The most commonly recognized physical features, which were associated with synostotic plagiocephaly in all of the patients were as follows: unilateral occipital flattening, ipsilateral mastoid bulging, low-set ears, ridging of the lambdoid suture, and Dumbo ear. The following clinical features were less consistently recognized: downward slanting of the cranial base, viewed from behind (seven out of eight), tilting of the head (seven out of eight), trapezoidal head shape (six out of eight), contralateral parietal bossing (six out of eight), anterior displacement of the ear (three out of eight), and bossing of the forehead (three out of eight) (Fig. 3).

+ Contralateral + Ipsilateral Symmetrical Symmetrical + Contralateral Symmetrical Symmetrical Symmetrical + + + + + + + +

+ + − + + + + −

Bossing of the forehead Ipsilateral “Dumbo” ear

Contralateral parietal bossing

Tilt of the head

Overriding of the lambdoid suture

Childs Nerv Syst

Inf. Inf. Ant-inf. Ant-inf. Inf. Ant-inf. Inf. Inf. + + + − + + + + + + + + + + + + Inf. inferior, Ant-inf. anteroinferior

+ + + + + + + + 1 2 3 4 5 6 7 8

+ − + + + + + +

Displacement of the ipsilateral ear Downward slanting of the ipsilateral skull base Ipsilateral mastoid bulging Trapezoidal head shape (viewed from above) Unilateral occipital flattening Patients

Table 1 Clinical features analyzed in the physical examinations and/or on clinical photographs of the patients

Discussion Clinical examination of infants with single-suture synostosis is an essential element in establishing the diagnosis. Each type of craniosynostosis causes a predictable morphological change that results from arrested cranial growth perpendicular to the affected suture and continued compensatory growth at the sutures in the neighborhood that remain open [11]. This combination of arrested growth in one region and compensatory overgrowth of adjacent sutures may explain how unilateral suture involvement results in bilateral deformity and how fusion of the sutures within the posterior cranial convexity produces a deformity that affects the entire anteroposterior dimension of the cranium. An examiner who is familiar with these remarkable growth patterns and the characteristic dysmorphology specific to each type of synostosis is able to consistently establish an accurate clinical diagnosis [12]. The diagnosis of single-suture craniosynostosis should be made fundamentally on the basis of careful clinical examination and understanding of the mechanisms of cranial changes. The most difficult clinical diagnosis to make is ULS, because it is the least familiar form of all single-suture craniosynostosis cases, and it is frequently misdiagnosed as positional occipital plagiocephaly. ULS in isolation is thought to have been defined as a clinical entity by Muakkassa et al. [13] in 1984, although premature fusion of the lambdoid suture had previously been mentioned in the literature by Bertelsen [14] in 1958 and Knudson et al. [15] in 1960. The descriptions of the clinical features of lambdoid synostosis in Muakkassa’s


Fig. 2 Three-dimensional CT scans of the patients

cases were, in fact, what is now recognized as PP and not true synostotic plagiocephaly. The proportion of synostotic plagiocephaly reported in their series was much higher than that has been reported more recently. Fig. 3 Photographs of four cases demonstrating the main phenotypic characteristics of ULS. The most important clinical features were as follows: bulging of the mastoid, overriding of the fused lambdoid suture, bossing of the contralateral parietal region, tilting of the head, low-set ears, slanting of the cranial base or bimastoid line, and “Dumbo” ear

Pople et al. [16] reported on the clinical presentation of 100 infants with occipital plagiocephaly and recognized three different clinical, radiological, and pathological circumstances: (1) lambdoid synostosis, (2) lambdoid


ridging (“locked” lambdoid), and (3) skull base asymmetry with open sutures (“lazy” lambdoid). The diagnosis of lambdoid synostosis was incorrectly based only on the clinical appearance. It was accepted that in contrast with other forms of synostosis, radiological signs of suture fusion may often be missing. One radiological indicator of synostosis was endocranial ridging of the suture or effacement of the suture itself, which was described as a sclerotic suture. These findings were interpreted as an isolated fusion of the internal table at the lambdoid suture [17]. Since the radiological findings were not related to the clinical findings, the term functional lambdoid synostosis was used for a synostotic lambdoid suture. The suture may have appeared radiologically patent but may not have been functioning normally. Thus, it was accepted that the unilateral synostotic plagiocephaly could represent a distinctive type of craniosynostosis, in which the suture might be patent in radiological evaluations. Because of previous controversies and confusions regarding the exact diagnosis and treatment for true ULS, the rarity of the disease, and the much greater prevalence of PP, the diagnosis of true lambdoid synostosis based only on clinical features is still not well known even today and remains controversial. As the incidence of PP increases, it might be asked whether these patients should undergo tomographic examination. The prevalence of PP has been reported to vary according to the children’s age at diagnosis, ranging from 3.3 % at 2 years of age to 19.7 % at 4 months of age [6]. Referrals of infants presenting with PP have increased sixfold since the recommendations of the “Back to Sleep” campaign were issued by the American Academy of Pediatrics in 1992 [18]. The ionizing radiation associated with CT has negative effects on the developing brain. The impact of such exposure is controversial; however, studies suggest that even low-dose CT used on an infant can increase the risk of lethal brain cancer and leukemia [19–21]. Brenner et al. [19] estimated

Fig. 4 a Diagram showing mild PP with trapezoid-shaped outline of the head. b Diagram showing severe PP with parallelogramshaped outline of the head

that the cancer mortality risk of 1-year-old children who were exposed to a single CT head examination was 1:1,500. Recently, the American National Cancer Institute [22] raised concerns about the hazards of ionizing radiation with regard to inducing tumors and developmental delays in children. In addition to the risk of cancer development, the ionizing radiation might have negative consequences for cognitive function. A retrospective study conducted by Hall et al. [23] reported that there was an adverse effect on adult cognitive performance among children who received low doses of ionizing radiation for treatment of vascular lesions of the scalp while they were younger than 18 months. Because the overwhelming majority of infants with cranial asymmetry will have PP and not synostosis, it is inadvisable to have every child with cranial flattening undergoes imaging. Therefore, these processes have to be distinguished by means of history taking and physical examination, so that a decision regarding whether radiological imaging is necessary can be made. True ULS presents several features of cranial deformity that are different from those produced by PP. Knowledge of the mechanisms of cranial dysmorphology secondary to premature unilateral fusion of the lambdoid suture is critical in understanding all the clinical features that may be regarded as a characteristic of this craniosynostosis. The most frequently used clinical criterion for making a diagnosis of lambdoid synostosis is to analyze the cranial deformation caused by premature fusion of the suture, but the age of onset of the deformities may offer some hints. Because craniosynostosis is congenital, parents often report that the deformity was observed immediately after birth. On the contrary, in cases of PP, the history is that the child’s head was wellrounded at the time of birth, and the occipital flattening was noted 3 to 6 months later, which suggests postnatal deformation [6]. Differences in skull characteristics between positional flattening and true lambdoid synostosis were proposed by Huang


Fig. 5 Axial view of case 2 demonstrating the ipsilateral compensatory bulging of the frontal region, instead of contralateral bulging, as would be expected in ULS, thus resulting in a parallelogram-shaped outline of the head

et al. [2]. Based on a clinical examination of four children with ULS, in comparison with 102 children with PP, they concluded that the following clinical signs were distinctive features of synostosis: (a) trapezoid-shaped head viewed from the vertex, (b) ipsilateral occipitomastoid bossing, (c) contralateral parietal bossing, (d) downward slanting of the ipsilateral skull base, (e) low-set and posteriorly positioned ipsilateral ear, (f) unilateral occipital flattening, and (g) contralateral frontal bossing. However, some divergences from Huang’s criteria have been reported in the literature. The head outline viewed from above has been described as a trapezoid in cases of synostotic plagiocephaly and as a parallelogram in PP. This description may be corrected only in those cases with complete and severe deformations, either of synostotic or PP type. In the early stages of PP, when the deformity does not involve the frontal area, the cranial shape is a trapezoid, rather than a parallelogram [23] (Fig. 4). In addition, the forehead prominence that helps to give the outline of a parallelogram is present in only 57 %, as reported by Dias et al. [24]. This is probably related to the severity of the plagiocephaly. When the frontal bossing is not equal to the degree of occipital flattening, the shape of the head is really more trapezoidal [25]. On the contrary, in the vertex view of patients with ULS, the head may have a parallelogram shape rather than a trapezoidal shape, when associated with ipsilateral PP [8]. In one of our cases, the frontal bossing was ipsilateral, thus probably representing concomitant synostosis of the lambdoid suture and deformational plagiocephaly (case 2) (Fig. 5).

Furthermore, Ehret et al. [26] observed that a trapezoidshaped head can be seen in rare cases of the following: (a) combined anterior and posterior positional molding, (b) unicoronal synostosis with positional molding, and (c) unicoronal synostosis with lambdoid synostosis. Our findings demonstrated that a trapezoidal head shape viewed from above was not recognized in one of the eight patients (12.5 %), with a diagnostic accuracy of 87.5 %. The specificity will be low because of the many variations of the head outline present under other circumstances. These data present some discrepancies in comparison with the results regarding forehead deformation that we could identify. In five out of eight cases, the forehead was symmetrical, which means that even when the forehead is symmetrical, the shape of the head may be trapezoidal. Frontal bossing is not a striking finding, but when present, it is contralateral instead of ipsilateral, as would be the case of deformational plagiocephaly. In addition to the controversies described above, Smartt et al. [27] reported that six out of nine patients presented true ULS, with contralateral frontal retrusion, in their digital photographs and 3-D CT scans in the vertex view. Another finding reported by these authors was contralateral frontofacial deficiency, which was seen in all cases. We observed that the most consistent clinical findings associated with ULS were signs arising from compensatory growth at the sagittal and contralateral lambdoid suture, which resulted in contralateral parietal bossing, and from compensatory growth at two small sutures, the occipitotemporal and parietotemporal sutures, thus resulting in ipsilateral mastoid bulging, low-set ears, and Dumbo ears. Metabolic hyperactivity of most of the adjoining sutures is responsible for the morphological changes most consistently found in ULS. Even at the earliest ages, these skull

Fig. 6 Illustration of the hyperactivity of the sagittal and contralateral lambdoid sutures and of the occipitomastoid and parietomastoid sutures. Large arrow indicates the resulting vector of dislocation of the external auditory meatus and mastoid


deformations are easily diagnosed, as in one of our cases, in which the diagnosis was made as the child was born. Contralateral parietal bossing is best evaluated when viewed from behind the patient, which leads to a tilted calvarial outline. Our data agree with the consistency of these clinical features and should be the main clinical characteristic to be pursued in cases of suspicion of synostotic plagiocephaly. We noted that in cases of ULS, bulging of the ipsilateral mastoid process can assist in making a non-radiological diagnosis of the sutures that originate posterior plagiocephaly. Such children present marked asymmetry of the calvaria, which results in bossing of the ipsilateral mastoid process and contralateral parietal region. All our data corroborated the findings of Huang et al. [2], with the exception of displacement of the external auditory meatus (EAM). In the literature, there have been divergences and variations in descriptions of the positioning of the EAM. Huang et al. [2] postulated that the ipsilateral ear in children with synostotic plagiocephaly was usually observed to be displaced posteriorly instead of anteriorly. According to the mechanisms of compensatory growth at the parietomastoid and occipitomastoid sutures, the positioning of the ear is more probably displaced away from the sutures, rather than towards them (Fig. 6). The ipsilateral mastoid has to have a lower position in relation to the other side, since metabolic hyperactivity of the occipitomastoid and parietomastoid sutures moves down the mastoid process, and the positioning of the ipsilateral EAM should be anterior and inferior, compared with the opposite side, because the hyperactive sutures are located above and posteriorly to the EAM. Mulliken et al. [8] described the anterior displacement of the ipsilateral EAM in three cases: symmetrically in all three and slightly posteriorly in one. David and Menard [28] also reported one patient in whom the ipsilateral EAM was displaced anteroinferiorly; they argued that true lambdoid synostosis more likely determines the anterior displacement of the ear, rather than posterior. Dias et al. [24] reported that 60 % of their patients presented anterior displacement of the ear. Lin et al. [29] observed one case with a unilateral synostotic lambdoid suture, with the EAM displaced downwards and posteriorly, instead of forward displacement as seen in positional occipital plagiocephaly. However, displacement of the EAM is not a discriminatory sign between synostotic and positional plagiocephalies, because anterior displacement can be found in both conditions. In patients with lambdoid synostosis, the severity of displacement is of significantly greater magnitude [30]. A Dumbo ear on the same side of the synostotic suture is not an important clinical feature, because the ear may have a deformed appearance even in PP cases, and anterior positioning can occur in both types of cases. Furthermore, changes to the anterior cranial vault may be variable and inconsistent and are therefore less accurate as a clinical feature of synostotic plagiocephaly. According to the mechanisms of cranial deformation, this characteristic is probably only present in the most severe cases.

At the same time, we observed a prominent ridge that can be recognized in the area of the mastoid bone and along the fused suture. This edge effect of the synostotic suture was identified in all the patients, and we interpreted this as a phenomenon that occurred due to elevation and elongation of the synostotic suture. By comparing the physical signs with CT data, we observed that cranial deformities secondary to craniosynostosis were sharper radiologically. We also noted from CT that there was an elongation of the fused lambdoid suture. This deformity was very similar to what is seen in synostosis of the sagittal suture, i.e., elongation of the sagittal suture and the entire cranium, and frontal and occipital compensatory bossing due to an increased metabolic activity of the coronary and lambdoid sutures, respectively. In ULS, the increased parietal bossing and the mastoid bulging corresponded to an increased activity of the contralateral lambdoid and sagittal sutures and of the occipitomastoid and parietomastoid sutures, respectively (Fig. 6). When all these changes were viewed from behind, it was possible to appreciate the tilted appearance of the head, with the so-called “wind effect”. We recognize that the present study has limitations, since it was retrospective and examination of photos is a twodimensional view and not a 3-D live study. Difficulties in evaluating the anterior displacement of the ear were one of the main features that could have affected the result from this study, but there was little impact on the final characterization of the clinical stereotype of the ULS.

Conclusion Findings of unilateral occipital flattening associated with bulging of the mastoid, ridging of the fused lambdoid suture and an ipsilateral low-set ear on one side, and bossing of the parietal region on the other side, in children, are a very strong indicator of a synostotic lambdoid suture. This range of clinical findings can usually lead to a correct diagnosis without the need for computed tomography scan evaluation. Careful physical examination can accurately diagnose this uncommon single-suture craniosynostosis, and the computed tomography scan is almost always more of a confirmatory tool than a diagnostic one. These clinical features alone allow a clear distinction between synostotic and positional plagiocephalies. As a consequence, more appropriate treatment may be offered. A unilateral synostotic lambdoid suture can be determined by means of phenotypic diagnosis and does not require computed tomography.

Funding Authors received no financial support for this work. Conflict of interest disclose.

The authors have no conflicts of interest to


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