PALEOPATHOLOGICAL FINDINGS OF DRY SKULLS WITH PLAGIOCEPHALY

Summary: In literature, plagiocephaly is defined as abnormal asymmetrical head shape with unilateral flattening of the anterior and/or posterior part of the skull. It is classified as synostotic or deformational. Synostotic plagiocephaly is the result of premature unilateral fusion of neurocranim sutures. Positional plagiocephaly is caused by asymmetrical intrauterine and/or postnatal external forces. The authors report findings of both types of plagiocephaly in the dry skull collection from pertaining Broumov Ossuary (13 th – 18 th century), Czech Republic. In the paper, the incidence of paleopathological asymmetrical skull deformities is discussed in the context with recent clinical data.


Introduction
Plagiocephaly is a general term for abnormal asymmetrical cranium shape with unilateral flattening of the anterior or posterior part of the skull. The term meaning "oblique head" ("lopsided skull") derives from the Greek word roots "plagios" and "kefalê". Pathogenically, plagiocephaly can be classified as synostotic (organic) or deformational (positional, functional, postural, nonsynostotic) (21). Synostotic plagiocephaly is caused by premature unilateral fusion of the coronal suture (frontal or anterior synostotic plagiocephaly), lambdoid suture (occipital or posterior synostotic plagiocephaly, true occipital plagiocephaly) or lateral skull sutures (1,4,17,21). In the literature, the term "hemicranial plagiocephaly" is sometimes used for deformities associated with multiple unilateral sutural fusions (1). Deformational occipital (posterior) plagiocephaly is caused by intrauterine and/or postnatal external forces on the one side parietooccipital region of the developing skull (13).
Morphological characteristics of the frontal plagiocephaly (Figs. 1, 2) are following (5,10,18,19): asymmetrical "rhombdoid" skull shape (in vertex view), asymmetry of the skull base (predominantly of the anterior cranial fossa), ipsilateral flattening of the forehead and ipsilateral compensatory occipital bossing, contralateral compensatory bossing of the forehead (asymmetrical "pointed" forehead), asymmetry of the nose root (it is deviated towards fused coronal suture), asymmetry of the orbits (ipsilateral orbit is enlarged and elevated), and asymmetrical position of the ears (the ear of the affected side is situated anterior and superior). Three forms of frontal plagiocephaly are defined: mild form (with minimal frontal flattening, symmetrical orbits, and a midline nose), moderate form (with ipsilateral flattening, compensatory contralateral bossing, and nasal root deviation), and severe form (with vertical orbital dystopia, severe ipsilateral flattening, contralateral bossing, and deviation of the nose root) (19). Occipital synostotic plagiocephaly ( Fig.  1) is characterized by the asymmetrical "trapezoid" skull shape (in vertex view), ipsilateral flattening of the forehead and bulging of the mastoid process (it is pathognomotic for unilambdoid synostose), compensatory contralateral bossing of the forehead and occiput: "pointed" occiput, asymmetry of the ears (ipsilateral ear is situated posterior); facial asymmetry is not mostly severe (12,16,21). Occipital positional plagiocephaly ( Fig. 2) is associated with asymmetrical "parallelogram" skull shape, unilateral parieto-occipital flattening, ipsilateral frontal bossing, contralateral frontal flattening and occipital bossing, asymmetry of external nose (nasal root is in a midline position but nasal bones and piriform aperture are deviated on the contralateral side), asymmetry of the orbits (contralateral orbit is situated low then ipsilateral orbit), asymmetry of the ear position (ipsilateral ear is situated anterior and superior) (9,11,13,16,21). Positional plagiocephaly can be classified as mild (without facial asymmetry) or severe (with facial asymmetry) (3).

Discussion
Presented paleopathological study is focused on the incidence of synostotic and/or deformational plagiocephaly in the dry skull collection from the Broumov Ossuary (13 th -18 th century), Czech Republic. Although asymmetrical skull deformities are quite common today, not many cases have been described in the paleopathological literature (1).
In the literature, the craniosynostosis is defined as a premature fusion of one or more of cranial sutures (8). It can occur as an isolated defect (nonsyndromic) or as a part of the syndrome (e.g. Crouzon, Apert, Pfeifer, Cole-Carpenter). It may affect the coronal, sagittal, metopic, lambdoid and/or lateral sutures in isolation or in combinations (14). The skull growth is restricted predominantly in a direction perpendicular to the premature fused suture. In response to the closed suture, the remaining sutures undergo compensatory growth. Uncorected craniosynostosis may be associated with deformity of the craniofacial skeleton and it can also cause serious constriction of the developing brain (craniostenosis), eyes (orbitostenosis), and facial viscera (faciostenosis) (14). Craniosynostosis is classified into two main categories: "simple" (or unisutural) when only one suture is involved (Fig. 11), and "complex" (compound) when two or more sutures are involved. It is usually more severe when more than one suture closes too early. The occurrence of the various types of simple craniosynostosis is approximately as follows: sagittal 50-55%, coronal 20-29%, metopic 4-10%, and lambdoid 2-4% (8).
Although the etiology of craniosynostosis is currently unknown, animal experiments and a recent interest in molecular biology point toward interplay between the dura mater and the underlying brain (14). The cranial suture fate is programmed by the dura derived paracrine signals. The dura  Republic. All skulls were minutely investigated by cranioscopy and craniometry. Positive findings of plagiocephaly were documented by the digital camera Camedia 3030 ZOOM, Olympus. In the part of them, X-ray and/or computed tomography (CT) examination was performed. acts as a regionally specialized endogenous tissue engineering and provides the osteogenic factores (e.g. fibroblast growth factors). These factors regulate fetal osteogenic growth and possibly influence fetal suture patency (20). Mutations in the gene coding for fibroblast growth factors cause some syndromes with craniosynostosis (2). In the contemporaneous population, craniosynostosis has been reported to occur approximately once per 2,000 live births (8). Unicoronal craniosynostosis -scarce form of craniosynostosis -happens in approximately one out of every 2,500 live birth (2), rare unilambdoid craniosynostosis happens in approximately three out of every 100,000 births (6). In contradistinction to recent clinical studies, in Broumov historical populations dating to the 13 th -18 th centuries, the incidency of synostotic plagiocephaly was rather high (1.74 %): unicoronal craniosynostosis was present in 0.27 % skulls, unilambdoid craniosynostosis in 0.13 % skulls, synostotic plagiocephaly with asymmetrical fusions of some skull sutures in 0.94 % skulls, and combination of synostotic plagiocephaly with another form of synostotic skull deformity in 0.40 % skulls. Kabbani and Raghuveer (8) assume that the true incidence of craniosynostosis in population is higher then clinical studies assert. The present report supports the assumption of these authors.
Positional plagiocephaly is the most common cause of plagiocephaly (15). It results from asymmetrical cranial growth without craniosynostosis. The practice of artificial skull deformation by pressure to an infnant's head dates back to 2000 BC when several ancient civilizations have used head-molding to produce desired skull shape. Positional occipital plagiocephaly is caused by constant external pressure on the one side parieto-occipital region of the developing skull (3). Risk factors associated with the positional head deformity are prolonged exposure to traditional "back" sleeping position, premature birth, congenital muscular torticollis, and intrauterine constraint (e. g. in multiple gestation or oligohydramnion) (13). Following the American Academy of Pediatrics recommendation (in 1992) that babies sleep in supine position to reduce the risk of Sudden Infant Death Syndrome, the incidency of deformational plagiocephaly has increased dramatically. Before 1992, the incidency was one of every 300 healthy born infants. Nowadays, the condition occurs in one of every 60 live birth (7). High positional plagiocephaly occurrence (12.48%) in skulls of Broumov historical populations was probably pre-dominately caused by traditional back sleeping position of newborns and suckling infants in past centuries.