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

AbstractPurpose The clinical diagnosis of most common single-suturecraniosynostosis is easily set, based on the stereotype ofdeformities and knowledge of the mechanisms of cranialdeformations. However, synostosis of unilateral lambdoidsuture, probably due to its lower incidence and similarity withother non-synostotic deformities affecting the posterior por-tion of the skull, makes its clinical diagnosis more difficult andimprecise. The aim of this study is to evaluate the most easilyand accurate clinical characteristics to be recognized in thesynostotic occipital plagiocephaly.Methods This study consisted of clinical evaluation of eightpatients with synostotic occipital plagiocephaly, whose diag-nosis was further corroborated by computed tomography.Results We identified the following: unilateral occipital flat-tening in eight out of eight patients (100 %), bulging ofipsilateral mastoid process in eight out of eight (100%), “edgeeffect” of ipsilateral lambdoid suture in eight out of eight (100%), inferior deviation of the ear in eight out of eight (100 %),

“Dumbo” ears in eight out of eight (100%), horizontal slant ofthe bimastoid line in seven out of eight (87.5 %), tilt of thehead 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 tothe clinical diagnosis of synostotic occipital plagiocephaly,not present in the positional posterior plagiocephaly, werebulging of the ipsilateral mastoid process, edge effect of thesynostotic lambdoid suture, tilt of the head, and slant of thebimastoid line viewed from behind, inferior deviation of theear, and contralateral parietal bossing.

Keywords Plagiocephaly . Synostotic occipitalplagiocephaly . Unilateral lambdoid . Synostosis .

Craniosynostosis . Skull deformity .Mechanisms

Introduction

Fusion of the lambdoid suture in isolation is considered to bean exceedingly rare form of craniosynostosis. Population-based studies have demonstrated that the overall incidenceof craniosynostosis ranges from 3.1 to 6 cases per 10,000births, and lambdoid synostosis is the rarest of all types ofcraniosynostosis, corresponding to less than 1 to 5.5 % of allcases of craniosynostosis, and in the population, less than 0.3in 10,000 births [1–6].

Among cases of single-suture craniosynostosis, those in-volving unilateral closing of the lambdoid suture do not pres-ent well-defined clinical characterization because of their rar-ity. This diagnosis can often be confounded with positionalplagiocephaly (PP), a type of deformity that is much morecommon than unilateral lambdoid synostosis (ULS). The

H. Matushita :D. D. Cardeal : F. G. de AndradeDepartment of Neurosurgery, Division of Pediatric Neurosurgery,University of São Paulo, São Paulo, Brazil

D. D. Cardeale-mail: dcardeal@yahoo.com.br

F. G. de Andradee-mail: fernanda_andrade87@yahoo.com.br

N. AlonsoDepartment of Plastic Surgery, Craniofacial Unit, University of SãoPaulo, São Paulo, Brazile-mail: nivalonso@uol.com.br

H. Matushita (*)Rua Barata Ribeiro 237, Cj 43/44/46, Bela Vista, SãoPaulo 01308-000, Brazile-mail: matushita@uol.com.bre-mail: neurosp@uol.com.br

Childs Nerv SystDOI 10.1007/s00381-014-2414-7

estimates of the prevalence of PP associated with positionalbrachycephaly have been reported to be as high as 18 to19.7 % in healthy infants [7]. A study by Mulliken et al. [8]demonstrated that out of 115 infants presenting with unilateralposterior cranial flattening, only one had ULS. Both condi-tions give rise to asymmetry of the posterior occiput, withflattening of one side.

It can be challenging to make a clinical diagnosis of ULS,even for the most experienced pediatric neurosurgeons orcraniofacial surgeons. Rekate [3] stated that radiological as-sessment is essential for the precise differentiation betweenthese two conditions. Fearon et al. [9] reported that among allthe types of isolated monosutural craniosynostosis, physicalexamination may fail in diagnosing ULS. Liu et al. [10]reported the cases of three patients with true ULS who wereoriginally diagnosed as having positional occipitalplagiocephaly.

In 1996, Huang et al. [2] proposed clinical criteria fordiagnosing ULS that aid in differentiating it from PP, whichhave been widely used in the literature. The objective of thisstudy was to investigate which of the clinical features ofsynostotic plagiocephaly are more consistently found inULS and whether the diagnosis can be based on physicalexamination alone.

Patients and methods

In our institution, we identified ten patients who were diag-nosed as ULS cases. Two of these patients were excludedbecause of inadequate data. Thus, the study group wasnarrowed 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 documenta-tion (Fig. 1), and computed tomography (CT) scans on eightpatients with ULS who were treated at our institution betweenJanuary 1990 and January 2010.

Further data analysis was then conducted based on thesecases. All of the patients underwent 3-D CT scans of the skullto define the suture anatomy and skull deformities. All thepatients presented lambdoid suture fusion that was confirmedby means of computed tomography. All the cranial deformi-ties that could be related to synostosis were observed inde-pendently, by two pediatric neurosurgeons belonging to thestaff of our institution. The features were considered positivewhen the observations coincided between the two observers,and divergences between the observers were adjudicated bythe senior author. Descriptive clinical findings were not com-pared with three-dimensional CT scans before the clinicalphotographs, or the patients had been examined by theobservers.

The clinical features analyzed in this study included thefollowing:

a. Unilateral occipital flatteningb. Trapezoidal head shape (viewed from the vertex)c. Ipsilateral mastoid bulgingd. Downward slanting of the ipsilateral skull basee. Displacement of the ipsilateral earf. Ipsilateral “Dumbo” earg. Bossing of the foreheadh. Contralateral parietal bossingi. Tilt of the headj. 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 and5 months (mean age=21.1 months). Regarding gender, therewere five males and three females. The right side was in-volved 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 twochildren, the skull was only mildly affected. Six childrenunderwent an operative correction of the synostosis at a meanage of 12.3 months (range 5 to 21 months). The decision topursue surgical treatment was based on the severity of thedeformities. Analysis of the 3-D CT scans provided proof ofULS in all cases (Fig. 2).

The most commonly recognized physical features, whichwere associated with synostotic plagiocephaly in all of thepatients were as follows: unilateral occipital flattening, ip-silateral mastoid bulging, low-set ears, ridging of thelambdoid suture, and Dumbo ear. The following clinicalfeatures were less consistently recognized: downwardslanting of the cranial base, viewed from behind (sevenout of eight), tilting of the head (seven out of eight),trapezoidal head shape (six out of eight), contralateral pa-rietal bossing (six out of eight), anterior displacement of theear (three out of eight), and bossing of the forehead (threeout of eight) (Fig. 3).

Discussion

Clinical examination of infants with single-suture synostosisis an essential element in establishing the diagnosis. Each typeof craniosynostosis causes a predictable morphologicalchange that results from arrested cranial growth perpendicularto the affected suture and continued compensatory growth atthe sutures in the neighborhood that remain open [11]. Thiscombination of arrested growth in one region and compensa-tory overgrowth of adjacent sutures may explain how unilat-eral suture involvement results in bilateral deformity and howfusion of the sutures within the posterior cranial convexityproduces a deformity that affects the entire anteroposteriordimension of the cranium. An examiner who is familiar withthese remarkable growth patterns and the characteristicdysmorphology specific to each type of synostosis is able toconsistently establish an accurate clinical diagnosis [12].The diagnosis of single-suture craniosynostosis shouldbe made fundamentally on the basis of careful clinicalexamination and understanding of the mechanisms ofcranial changes.

The most difficult clinical diagnosis to make is ULS,because it is the least familiar form of all single-suturecraniosynostosis cases, and it is frequently misdiagnosedas positional occipital plagiocephaly. ULS in isolation isthought to have been defined as a clinical entity byMuakkassa et al. [13] in 1984, although prematurefusion of the lambdoid suture had previously been men-tioned in the literature by Bertelsen [14] in 1958 andKnudson et al. [15] in 1960. The descriptions of theclinical features of lambdoid synostosis in Muakkassa’sTa

ble1

Clin

icalfeatures

analyzed

inthephysicalexam

inations

and/or

onclinicalphotographsof

thepatients

Patients

Unilateralo

ccipital

flattening

Trapezoidalhead

shape(viewed

from

above)

Ipsilateral

mastoid

bulging

Dow

nwardslantin

gof

theipsilateral

skullb

ase

Displacem

ent

oftheipsilateralear

Ipsilateral

“Dum

bo”ear

Bossing

ofthe

forehead

Contralateral

parietalbossing

Tilt

ofthe

head

Overriding

ofthelambdoid

suture

1+

++

+Inf.

++Contralateral

++

+

2+

−+

+Inf.

++Ipsilateral

++

+

3+

++

+Ant-inf.

+Sy

mmetrical

−+

+

4+

++

−Ant-inf.

+Sym

metrical

++

+

5+

++

+Inf.

++Contralateral

++

+

6+

++

+Ant-inf.

+Sy

mmetrical

++

+

7+

++

+Inf.

+Sym

metrical

++

+

8+

++

+Inf.

+Sym

metrical

−−

+

Inf.inferior,A

nt-inf.anteroinferior

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cases were, in fact, what is now recognized as PP andnot true synostotic plagiocephaly. The proportion ofsynostotic plagiocephaly reported in their series wasmuch higher than that has been reported more recently.

Pople et al. [16] reported on the clinical presentation of100 infants with occipital plagiocephaly and recognizedthree different clinical, radiological, and pathologicalcircumstances: (1) lambdoid synostosis, (2) lambdoid

Fig. 2 Three-dimensional CT scans of the patients

Fig. 3 Photographs of four casesdemonstrating the mainphenotypic characteristics ofULS. The most important clinicalfeatures were as follows: bulgingof the mastoid, overriding of thefused lambdoid suture, bossing ofthe contralateral parietal region,tilting of the head, low-set ears,slanting of the cranial base orbimastoid line, and “Dumbo” ear

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ridging (“locked” lambdoid), and (3) skull base asym-metry with open sutures (“lazy” lambdoid).

The diagnosis of lambdoid synostosis was incorrectlybased only on the clinical appearance. It was accepted thatin contrast with other forms of synostosis, radiological signsof suture fusion may often be missing. One radiologicalindicator of synostosis was endocranial ridging of the sutureor effacement of the suture itself, which was described as asclerotic suture. These findings were interpreted as an isolatedfusion of the internal table at the lambdoid suture [17]. Sincethe radiological findings were not related to the clinical find-ings, the term functional lambdoid synostosis was used for asynostotic lambdoid suture. The suture may have appearedradiologically patent but may not have been functioning nor-mally. Thus, it was accepted that the unilateral synostoticplagiocephaly could represent a distinctive type of craniosyn-ostosis, in which the suture might be patent in radiologicalevaluations. Because of previous controversies and confu-sions regarding the exact diagnosis and treatment for trueULS, the rarity of the disease, and the much greater prevalenceof PP, the diagnosis of true lambdoid synostosis based only onclinical features is still not well known even today and remainscontroversial.

As the incidence of PP increases, it might be asked whetherthese patients should undergo tomographic examination. Theprevalence of PP has been reported to vary according to thechildren’s age at diagnosis, ranging from 3.3 % at 2 years ofage to 19.7 % at 4 months of age [6]. Referrals of infantspresenting with PP have increased sixfold since the recom-mendations of the “Back to Sleep” campaign were issued bythe American Academy of Pediatrics in 1992 [18].

The ionizing radiation associated with CT has negativeeffects on the developing brain. The impact of such exposureis controversial; however, studies suggest that even low-doseCT used on an infant can increase the risk of lethal braincancer and leukemia [19–21]. Brenner et al. [19] estimated

that the cancer mortality risk of 1-year-old children who wereexposed to a single CT head examination was 1:1,500.Recently, the American National Cancer Institute [22] raisedconcerns about the hazards of ionizing radiation with regard toinducing tumors and developmental delays in children. Inaddition to the risk of cancer development, the ionizing radi-ation might have negative consequences for cognitive func-tion. A retrospective study conducted by Hall et al. [23]reported that there was an adverse effect on adult cognitiveperformance among children who received low doses of ion-izing radiation for treatment of vascular lesions of the scalpwhile they were younger than 18 months. Because the over-whelming majority of infants with cranial asymmetry willhave PP and not synostosis, it is inadvisable to have everychild with cranial flattening undergoes imaging. Therefore,these processes have to be distinguished by means of historytaking and physical examination, so that a decision regardingwhether radiological imaging is necessary can be made.

True ULS presents several features of cranial deformitythat are different from those produced by PP. Knowledge ofthe mechanisms of cranial dysmorphology secondary to pre-mature unilateral fusion of the lambdoid suture is critical inunderstanding all the clinical features that may be regarded asa characteristic of this craniosynostosis. The most frequentlyused clinical criterion for making a diagnosis of lambdoidsynostosis is to analyze the cranial deformation caused bypremature fusion of the suture, but the age of onset ofthe deformities may offer some hints. Because craniosyn-ostosis is congenital, parents often report that the deformitywas observed immediately after birth. On the contrary, incases of PP, the history is that the child’s head was well-rounded at the time of birth, and the occipital flatteningwas noted 3 to 6 months later, which suggests postnataldeformation [6].

Differences in skull characteristics between positional flat-tening and true lambdoid synostosis were proposed by Huang

Fig. 4 a Diagram showing mildPP with trapezoid-shaped outlineof the head. b Diagram showingsevere PP with parallelogram-shaped outline of the head

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et al. [2]. Based on a clinical examination of four children withULS, in comparison with 102 children with PP, they conclud-ed that the following clinical signs were distinctive features ofsynostosis: (a) trapezoid-shaped head viewed from the vertex,(b) ipsilateral occipitomastoid bossing, (c) contralateral parie-tal bossing, (d) downward slanting of the ipsilateral skull base,(e) low-set and posteriorly positioned ipsilateral ear, (f) uni-lateral occipital flattening, and (g) contralateral frontalbossing. However, some divergences from Huang’s criteriahave been reported in the literature.

The head outline viewed from above has been described asa trapezoid in cases of synostotic plagiocephaly and as aparallelogram in PP. This description may be corrected onlyin those cases with complete and severe deformations, eitherof synostotic or PP type. In the early stages of PP, when thedeformity does not involve the frontal area, the cranial shape isa trapezoid, rather than a parallelogram [23] (Fig. 4).

In addition, the forehead prominence that helps to give theoutline of a parallelogram is present in only 57 %, as reportedby Dias et al. [24]. This is probably related to the severity ofthe plagiocephaly. When the frontal bossing is not equal to thedegree of occipital flattening, the shape of the head is reallymore trapezoidal [25]. On the contrary, in the vertex view ofpatients with ULS, the head may have a parallelogram shaperather than a trapezoidal shape, when associated with ipsilat-eral PP [8]. In one of our cases, the frontal bossing wasipsilateral, thus probably representing concomitant synostosisof the lambdoid suture and deformational plagiocephaly (case2) (Fig. 5).

Furthermore, Ehret et al. [26] observed that a trapezoid-shaped 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 shapeviewed from above was not recognized in one of the eightpatients (12.5 %), with a diagnostic accuracy of 87.5 %. Thespecificity will be low because of the many variations of thehead outline present under other circumstances. These datapresent some discrepancies in comparison with the resultsregarding forehead deformation that we could identify. In fiveout of eight cases, the forehead was symmetrical, whichmeans that even when the forehead is symmetrical, the shapeof the head may be trapezoidal.

Frontal bossing is not a striking finding, but when present, itis contralateral instead of ipsilateral, as would be the case ofdeformational plagiocephaly. In addition to the controversiesdescribed above, Smartt et al. [27] reported that six out of ninepatients presented true ULS, with contralateral frontal retrusion,in their digital photographs and 3-D CT scans in the vertexview. Another finding reported by these authors was contralat-eral frontofacial deficiency, which was seen in all cases.

We observed that the most consistent clinical findings associ-ated with ULS were signs arising from compensatory growth atthe sagittal and contralateral lambdoid suture, which resulted incontralateral parietal bossing, and from compensatory growth attwo small sutures, the occipitotemporal and parietotemporalsutures, thus resulting in ipsilateral mastoid bulging, low-set ears,and Dumbo ears. Metabolic hyperactivity of most of the adjoin-ing sutures is responsible for the morphological changes mostconsistently found in ULS. Even at the earliest ages, these skull

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

Fig. 6 Illustration of the hyperactivity of the sagittal and contralaterallambdoid sutures and of the occipitomastoid and parietomastoid sutures.Large arrow indicates the resulting vector of dislocation of the externalauditory meatus and mastoid

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deformations are easily diagnosed, as in one of our cases, inwhich the diagnosis was made as the child was born.Contralateral parietal bossing is best evaluated when viewedfrom behind the patient, which leads to a tilted calvarial outline.Our data agree with the consistency of these clinical features andshould be the main clinical characteristic to be pursued in casesof suspicion of synostotic plagiocephaly. We noted that in casesof ULS, bulging of the ipsilateral mastoid process can assist inmaking a non-radiological diagnosis of the sutures that originateposterior plagiocephaly. Such children present marked asymme-try of the calvaria, which results in bossing of the ipsilateralmastoid process and contralateral parietal region.

All our data corroborated the findings of Huang et al. [2],with the exception of displacement of the external auditorymeatus (EAM). In the literature, there have been divergencesand variations in descriptions of the positioning of the EAM.Huang et al. [2] postulated that the ipsilateral ear in childrenwith synostotic plagiocephaly was usually observed to bedisplaced posteriorly instead of anteriorly. According to themechanisms of compensatory growth at the parietomastoidand occipitomastoid sutures, the positioning of the ear is moreprobably displaced away from the sutures, rather than towardsthem (Fig. 6). The ipsilateral mastoid has to have a lowerposition in relation to the other side, since metabolic hyperac-tivity of the occipitomastoid and parietomastoid suturesmoves down the mastoid process, and the positioning of theipsilateral EAM should be anterior and inferior, comparedwith the opposite side, because the hyperactive sutures arelocated above and posteriorly to the EAM.

Mulliken et al. [8] described the anterior displacement of theipsilateral EAM in three cases: symmetrically in all three andslightly posteriorly in one. David and Menard [28] also reportedone patient in whom the ipsilateral EAM was displacedanteroinferiorly; they argued that true lambdoid synostosis morelikely determines the anterior displacement of the ear, rather thanposterior. Dias et al. [24] reported that 60 % of their patientspresented anterior displacement of the ear. Lin et al. [29] observedone case with a unilateral synostotic lambdoid suture, with theEAM displaced downwards and posteriorly, instead of forwarddisplacement as seen in positional occipital plagiocephaly.However, displacement of the EAM is not a discriminatory signbetween synostotic and positional plagiocephalies, because ante-rior displacement can be found in both conditions. In patients withlambdoid synostosis, the severity of displacement is of signifi-cantly greater magnitude [30]. A Dumbo ear on the same side ofthe synostotic suture is not an important clinical feature, becausethe ear may have a deformed appearance even in PP cases, andanterior positioning can occur in both types of cases. Furthermore,changes to the anterior cranial vault may be variable and incon-sistent and are therefore less accurate as a clinical feature ofsynostotic plagiocephaly. According to themechanisms of cranialdeformation, this characteristic is probably only present in themost severe cases.

At the same time, we observed a prominent ridge that can berecognized in the area of the mastoid bone and along the fusedsuture. This edge effect of the synostotic suture was identifiedin all the patients, and we interpreted this as a phenomenon thatoccurred due to elevation and elongation of the synostoticsuture. By comparing the physical signs with CT data, weobserved that cranial deformities secondary to craniosynostosiswere sharper radiologically. We also noted from CT that therewas an elongation of the fused lambdoid suture. This deformitywas very similar to what is seen in synostosis of the sagittalsuture, i.e., elongation of the sagittal suture and the entirecranium, and frontal and occipital compensatory bossing dueto an increased metabolic activity of the coronary and lambdoidsutures, respectively. In ULS, the increased parietal bossing andthemastoid bulging corresponded to an increased activity of thecontralateral lambdoid and sagittal sutures and of theoccipitomastoid and parietomastoid sutures, respectively(Fig. 6). When all these changes were viewed from behind, itwas possible to appreciate the tilted appearance of the head,with the so-called “wind effect”.

We recognize that the present study has limitations, since itwas retrospective and examination of photos is a two-dimensional view and not a 3-D live study. Difficulties inevaluating the anterior displacement of the ear were one ofthe main features that could have affected the result from thisstudy, but there was little impact on the final characterizationof the clinical stereotype of the ULS.

Conclusion

Findings of unilateral occipital flattening associated with bulgingof the mastoid, ridging of the fused lambdoid suture and anipsilateral low-set ear on one side, and bossing of the parietalregion on the other side, in children, are a very strong indicator ofa synostotic lambdoid suture. This range of clinical findings canusually lead to a correct diagnosis without the need for computedtomography scan evaluation. Careful physical examination canaccurately diagnose this uncommon single-suture craniosynosto-sis, and the computed tomography scan is almost alwaysmore ofa confirmatory tool than a diagnostic one. These clinical featuresalone allow a clear distinction between synostotic and positionalplagiocephalies. As a consequence, more appropriate treatmentmay be offered. A unilateral synostotic lambdoid suture can bedetermined by means of phenotypic diagnosis and does notrequire computed tomography.

Funding Authors received no financial support for this work.

Conflict of interest The authors have no conflicts of interest todisclose.

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