Cranial features of the spotted seal, Phoca largha, in the Nemuro Strait, considering age effects

Cranial features (development, individual variation, and sexual dimorphism) were examined from the 23 metrical characters and 2 nonmetrical characters (the degree of closure of the 9 cranial sutures and the presence of sagittal crest) in the two spotted seal specimen groups at the Nemuro Strait, Hokkaido. One specimen group was incidentally taken in the salmon trap nets between 1982 and 1983 (n = 70), and the other was randomly sampled by damage control kill between 1997 and 1998 (n = 82). The development of morphometrical characters of skulls ceased at 5.6, 10.7, 7.9, and 11.9 yr. old, for 1982-83 male, 1982-83 female, 1997-98 male and 1997-98 female, respectively. The sutures were half ankylosed till approximately 10 yr. old in both sexes. The sagittal crest began from about 5 yr. old in male. Individual variation of skull was large in the feeding, breathing, and facial-expression apparatus. On the other hand, the variation of braincase, and skull concerning to the movement of head/neck tended to be small. Only 1997-98 specimens exhibited a sexual dimorphism in skull characters except for the braincase, whereas the dimorphism was not found in 1982-83 specimens. We could not detect the significant difference between two specimen groups, although there were a few differences in characters related to the rostrum and mandible.

[Relationships between the coronal suture and the sulci of the lateral convexity of the frontal lobe: neurosurgical applications]

An anatomical study of the relationships between the coronal suture and the sulci of the convexity of the frontal lobe was accomplished in seven cephalic segments. The pre-central and central sulci are, respectively, 26,5 mm and 40,5 mm behind the bregma and 15,0 mm and 35,5 mm behind the pterion. The use of the coronal suture as point of reference, and especially, its relationship with the sulci of the lateral surface of the frontal lobe, allows to determine the projection on the cranium of the superficial cerebral lesions with the purpose to delimit the surgical access and to guide the approach to the cerebral convexity.

Sagittal suture as an external landmark for the superior sagittal sinus

OBJECT

Historically, the sagittal suture has been used as an external landmark to indicate the middle portion of the superior sagittal sinus (SSS). The goal of this study was to verify this relationship.

METHODS

The authors examined 30 adult cadavers to reveal the location of the SSS with respect to the sagittal suture. Their findings demonstrated that the SSS is deviated to the right of the sagittal suture in the majority of observed specimens, although the maximum displacement to the right side was never more than 11 mm.

CONCLUSIONS

This information should be useful to the neurosurgeon who must be aware of the SSS and its relationship with superficial skull landmarks.

Frequency variations of discrete cranial traits in major human populations. II. Hypostotic variations

Five discrete hypostotic cranial traits, tympanic dehiscence, ovale-spinosum confluence, metopism, transverse zygomatic suture vestige, and biasterionic suture, were investigated in 81 human population samples. Except for ovale-spinosum confluence, marked asymmetric occurrences of the bilateral traits were not detected in the majority of the samples. Significant intertrait association was observed mainly between the biasterionic suture and other sutural variations including accessory ossicles. The traits showing relatively consistent sex differences across diverse populations were tympanic dehiscence, which is predominant in females, and biasterionic suture in males. On a world scale, the 5 hypostotic cranial traits showed distinctive patterns of geographical variation. Different clinal variations within and between macrogeographical areas such as western and eastern parts of the Old World were found for the frequencies of the traits. The Ainu may be the most distinct outlier in the eastern Asian region on the basis of the incidence of the traits, especially the transverse zygomatic suture vestige. The interregional variation without reasonable adaptive value and nonadaptive shift of the possible outliers presented in this study suggest that the genetic background for the occurrence of these traits cannot be excluded completely.

A comparison of cranial base growth in Class I and Class II skeletal patterns

The purpose of this retrospective longitudinal study was to compare 7 cephalometric measurements of the cranial base in subjects with Class I and Class II skeletal patterns at ages 1 month, 2 years, and 14 years. A sample of 22 Class I and 21 Class II subjects was selected; the inclusion criteria were overjet, ANB, and Harvold unit difference. Analyses of head circumference, crown-rump length, and weight revealed no significant (P >.15) differences between the Class I and Class II infant subjects at the initial age (1 month). One angular and 6 linear measurements were first compared with a multivariate analysis of variance, which revealed significant effects for age (P <.0001) and the age by skeletal pattern interaction (P =.0266) but not for skeletal pattern (P =.3705). Analyses of variance showed significant (P <.0001) age effects for each of the cephalometric variables but no significant skeletal pattern effects (P >.10). The anterior cranial base measurement of nasion to sphenoethmoidal suture was the only variable found to have a significant age by skeletal pattern interaction (P <.006), which revealed a difference in the timing of its growth spurt that occurred between 1 month and 2 years in the Class I subjects and between 2 years and 14 years in the Class II subjects. There were no significant differences between the skeletal classes at any of the 3 ages evaluated. Conclusions from this study indicate that cranial base growth patterns are similar for Class I and Class II subjects and that the premise of a more obtuse "saddle angle" or cranial base angle in Class II skeletal patterns was not supported.

The mid-palatal suture in young adults. A radiological-histological investigation

The aim of the present study was to analyse which histological-histomorphometric findings correspond to a radiologically diagnosed open (group I) or closed mid-palatal suture (group II) on occlusal radiographs. For this purpose, 30 radiological regions of interest (rROI) from specimens obtained from 10 subjects ranging in age from 18 to 38 years were evaluated, and compared with the suture morphology, mean sutural width, and degree of suture closure on stained sections (3/rROI). The results showed that whether or not a radiologically visible suture can be classified as 'open' depends predominantly on the main oronasal suture course in relation to the X-ray path, rather than on factors such as suture width and degree of obliteration. The mean sutural width was 231 microns in group I (n = 10 rROI) and 201 mu in group II (n = 20 rROI). The degree of obliteration in relation to the total oronasal suture length was 0.45 in group I and 1.30 per cent in group II. No significant differences were found between the corresponding parameters of the two groups. The term 'suture obliteration' or 'fusion' should be avoided if a suture is radiologically not visible, since in 11 of the 20 rROI in which the suture was not visible no obliteration was recorded morphometrically.

New fossil hominid calvaria from Indonesia--Sambungmacan 3

A morphologically distinct partial calvaria of Homo cf. erectus from Java, Indonesia is described. The fossil hominid Sambungmacan 3 (Sm 3) was first discovered in 1977 from the banks of the Solo River near the village of Poloyo, Sambungmacan district, in central Java. It was later recovered in a New York City natural history establishment in 1999 and quickly returned to the Indonesian authorities. Examination of Sm 3 shows that the calvaria is well preserved with only portions of the cranial base missing. The most striking characteristics of Sm 3 include: the presence of a vertically rising forehead, more open occipital/nuchal and frontal angles, a more globular vault, and a cranial capacity within the Homo erectus range. Most notably absent in Sm 3 are a number of the classic characters attributed to Homo erectus, such as a strongly expressed angular torus and a continuous supratoral sulcus. The absence of such characters would normally place the calvaria outside the range of Homo erectus (sensu stricto), however, overall quantitative and qualitative morphological assessments of Sm 3 place it within the Homo erectus spectrum. The combination of the morphological characters in Sm 3 may be interpreted in several ways: 1.) the known cranial variation of H. erectus from Indonesia and China is extended; 2.) this calvaria shows evidence of evolutionary change within H. erectus; or 3.) more than one species of Homo existed in the (presumed) Middle Pleistocene of Java.)

The roughness of the supranasal region--a morphological sex trait

The supranasal region often attracts attention by a remarkable rough and jagged quality of the bony surface caused by an irregular supranasal suture and additional holes and pores. Some authors point out that there is a positive relation between the supranasal suture, the superciliar arches, and the forehead contour. For this a relation to sex is conceivable. This present study was done to prove the value of this morphological trait for sexing skulls.A total of 80 human skulls of known sex (40 females, 40 males) were collected from autopsy material used in anatomy teaching classes and from forensic cases. The mean age of the female sample was 70.98 years (minimum 38, maximum 93), that of the male sample was 74.10 years (minimum 57, maximum 99). To quantify the roughness of the supranasal region the calculation of the box-counting dimension was used. The results were normally distributed in both, the male and female group. The male dimension values were well grouped (maximum 1.51111, minimum 0.98765, mean 1.26159, S.D. 0.12268, 95% CI 1.22236-1.26604) whereas the female showed a wide range (maximum 1.46744, minimum 0.44755, mean 1.15052, S.D. 0.21388, 95% CI 1.08212-1.21892), widely overlapping the male range. Statistical analysis showed that there was a less than 1% probability that the female box-counting dimension was lower than the male by chance (P-value 0.00593). For this results the admission of the trait 'quality of the supranasal region' into a catalogue of features regarding morphognostic sex determination following the scheme: hyperfemininity: very smooth and regular--femininity: more smooth and regular--indifferent--masculinity: more rough and irregular--hypermasculinity: very rough and irregular, seems to be justified.

[The sulci and gyri localization of the brain superolateral surface in computed tomography and magnetic resonance imaging]

The knowledge of the superolateral surface brain anatomy is fundamental to localize and to approach the cerebral lesions. A literature review of the signs and landmarks for the identification of its sulci and gyri in computed tomography and magnetic resonance imaging had been done. The combined use of these several signs makes possible the sulci and gyri identification and its cerebral lesions localization in almost all cases.

Is the asterion a reliable landmark for the lateral approach to posterior fossa?

An anatomical study was conducted to gain orientation regarding the posterolateral approaches. The asterion is defined as the junction of the lambdoid, parietomastoid, and occipitomastoid sutures. This anatomical point has been widely used as a landmark in lateral approaches to posterior fossa. Although there are many common practices in posterolateral approaches, studies providing accurate anatomical knowledge as to what is the correct point to start a craniotomy are limited in number. Therefore, this study was conducted in an attempt to determine the reliability of the asterion for the posterolateral approaches as surgical landmark.

Cranial sutures as intramembranous bone growth sites

Intramembranous bone growth is achieved through bone formation within a periosteum or by bone formation at sutures. Sutures are formed during embryonic development at the sites of approximation of the membranous bones of the craniofacial skeleton. They serve as the major sites of bone expansion during postnatal craniofacial growth. For sutures to function as intramembranous bone growth sites, they need to remain in an unossified state, yet allow new bone to be formed at the edges of the overlapping bone fronts. This process relies on the production of sufficient new bone cells to be recruited into the bone fronts, while ensuring that the cells within the suture remain undifferentiated. Unlike endochondral growth plates, which expand through chondrocyte hypertrophy, sutures do not have intrinsic growth potential. Rather, they produce new bone at the sutural edges of the bone fronts in response to external stimuli, such as signals arising from the expanding neurocranium. This process allows growth of the cranial vault to be coordinated with growth of the neurocranium. Too little or delayed bone growth will result in wide-open fontanels and suture agenesis, whereas too much or accelerated bone growth will result in osseous obliteration of the sutures or craniosynostosis. Craniosynostosis in humans, suture fusion in animals, and induced suture obliteration in vitro has been associated with mutations or alterations in expression of several transcription factors, growth factors, and their receptors. Much of the data concerning signaling within sutures has been garnered from research on cranial sutures; hence, only the cranial sutures will be discussed in detail in this review. This review synthesizes classic descriptions of suture growth and pathology with modern molecular analysis of genetics and cell function in normal and abnormal suture morphogenesis and growth in a unifying hypothesis. At the same time, the reader is reminded of the importance of the suture as an intramembranous bone growth site.

Comparative analysis of cranial suture complexity in the genus Caiman (Crocodylia, Alligatoridae)

The variation in degrees of interdigitation (complexity) in cranial sutures among species of Caiman in different skull regions was studied by fractal analysis. Our findings show that there is a small species effect in the fractal dimension of cranial sutures, but most variation is accounted for by regional differentiation within the skull. There is also a significant interaction between species and cranial regions. The braincase sutures show higher fractal dimension than the facial skull sutures for all three species. The fractal dimension of nasal-maxilla suture is larger in Caiman latirostris than in the other species. The braincase sutures show higher fractal dimensions in C. sclerops than in the other species. The results suggest that different regions of the skull in caimans are under differential functional stress and the braincase sutures must counteract stronger disarticulation forces than the facial sutures. The larger fractal dimension shown by C. latirostris in facial sutures has probably a functional basis also. Caiman latirostris is known to have preferences for harder food items than the other species.

Infant skull and suture properties: measurements and implications for mechanisms of pediatric brain injury

The mechanical properties of the adult human skull are well documented, but little information is available for the infant skull. To determine the age-dependent changes in skull properties, we tested human and porcine infant cranial bone in three-point bending. The measurement of elastic modulus in the human and porcine infant cranial bone agrees with and extends previous published data [McPherson, G. K., and Kriewall, T. J. (1980), J. Biomech., 13, pp. 9-16] for human infant cranial bone. After confirming that the porcine and human cranial bone properties were comparable, additional tensile and three-point bending studies were conducted on porcine cranial bone and suture. Comparisons of the porcine infant data with previously published adult human data demonstrate that the elastic modulus, ultimate stress, and energy absorbed to failure increase, and the ultimate strain decreases with age for cranial bone. Likewise, we conclude that the elastic modulus, ultimate stress, and energy absorbed to failure increase with age for sutures. We constructed two finite element models of an idealized one-month old infant head, one with pediatric and the other adult skull properties, and subjected them to impact loading to investigate the contribution of the cranial bone properties on the intracranial tissue deformation pattern. The computational simulations demonstrate that the comparatively compliant skull and membranous suture properties of the infant brain case are associated with large cranial shape changes, and a more diffuse pattern of brain distortion than when the skull takes on adult properties. These studies are a fundamental initial step in predicting the unique mechanical response of the pediatric skull to traumatic loads associated with head injury and, thus, for defining head injury thresholds for children.

The reliability and variability of SN and PFH reference planes in cephalometric diagnosis and therapeutic planning of dentomaxillofacial malformations

Various interpretations of clinical and cephalometric data lead to different diagnostic and surgical planning in the study of dentoskeletal malformations. Many authors have identified this discrepancy as an incorrect positioning between the skeletal structures and the Frankfurt plane (PFH)--a plane that is used routinely for the sagittal measurement of the upper and lower jaw. The aim of this study was to establish a control method to verify the correct positioning of the sella-nasion point plane (SN) and the PFH. To find a reference plane, the authors concentrated their attention on measuring the intersecting angles between these two planes and the vertical posterior maxillary (PM) plane. Fifty patients (33 women and 17 men), all of whom were aesthetically and structurally harmonious class I dentoskeletal types, were analyzed using this method. Student's t-test, the Kolmogorov-Smirnov test, and Fisher's F-test were used for statistical analysis. The results were compared with those proposed by the University of Michigan. To achieve a correct diagnosis and to obtain good functional and cosmetic results in the treatment of these kinds of malformations, it is necessary to make use of the PM vertical plane during cephalometric analysis.

Implant-borne suture expansion in rabbits: a histomorphometric study of the supporting bone

Osseointegrated implants have a large potential for diverse clinical applications, including support for sutural expansion and facial prostheses. The objectives of this study were to evaluate: (1) the histomorphometric response of thin cortical bone to implant placement and (2) whether loading of the bone surrounding these implants affects osseointegration as evaluated by histomorphometry. Eighteen New Zealand White rabbits had two titanium implants placed bilaterally in the anterior surface of their nasal bones. The rabbits were divided into an unloaded control group, one experimental group loaded at 1 Newton (N), and another loaded at 3 N. Fluorescent labels were used to mark areas of active bone formation. All rabbits were euthanized after 12 weeks of loading. Stereological point-hit and line-intercept methods were used to measure bone volume, direct bone-implant contact, new bone volume, and bone turnover rate in the bone surrounding the implants. All the implants remained stable during the loading period. A factorial ANOVA with repeated measures was used to compare the variables. The only significant difference among the three groups was a higher bone volume in the lateral coronal far region in the control group (p < 0. 05). Within all groups, bone volume (p < 0.002), turnover rate (p < 0.001), and percent of new bone (p < 0.05) were higher within 1 mm of the implant compared to 1-3 mm away. This may be due to the increased stress and strain in the bone adjacent to the implant. This study indicates that there are no detrimental effects of loading on osseointegration when implants placed in the thin facial cortices are used as anchors for sutural expansion.

Magnetic resonance images and histology of the spheno-occipital synchondrosis in young monkeys (Macaca fuscata)

Magnetic resonance images and the histology of spheno-occipital synchondrosis were examined in young monkeys in order to compare the magnetic resonance images with their histologic observations. In serial magnetics resonance images of posterior cranial base, the spheno-occipital synchondrosis showed a low signal zone with unclear boundaries, running through the posterior cranial base perpendicularly to the clivus. The zone was always interposed between nonsignal zones. These observations were the same as those in young juvenile human beings. The histologic sections also revealed that the low signal zone was really the spheno-occipital synchondrosis, which consisted of hyaline cartilage and that the nonsignal zones were bone tissues. The chondroblasts in the spheno-occipital synchondrosis were arranged bipolarly. Intense alkaline phosphatase activity was located in the areas along the bone. Tetracycline labeling was also noticed in the bone formed in the endochondral ossification. These results suggest that magnetic resonance imaging enables us to observe the spheno-occipital synchondrosis in the posterior cranial base and also to elucidate its influences on the growth of maxilla and mandible in the future.

Comparison of macroscopic cranial methods of age estimation applied to skeletons from the Terry Collection

A total of 963 skeletons (408 Whites and 555 Blacks) from the Terry Collection were studied to examine macroscopic cranial methods of age estimation. The methods of Acsádi and Nemeskéri, Masset, Baker and Meindl and Lovejoy were applied to every skull. The results indicate that the most accurate techniques in this application were those that consider endocranial suture closure. The methods of Acsádi and Nemeskéri and Masset were the most accurate in all the subsamples (by population, sex, sex within population and in total), although the relative accuracy could vary in application to other populations.

[The evolution of the lower jaw and the jaw joint, from reptiles to man]

The evolution of the mandible shows two characteristic features: transformation of the angular, articular and square bones in reptiles into the tympanic bone, malleus and incus of the middle ear respectively; and specific volume expansion of the tooth-bearing bone which in mammals comprises the entire mandible. Posture, locomotion and mastication are the basic evolutionary factors which simultaneously provoked 1) a displacement of the temporal regions, 2) a transformation of the face lowering and widening the lower jaw and 3) an elongation of the sutures uniting the different bones in the reptile jaw bone, progressively leading to their separation and transversal orientation. These transformations were accentuated in the biped. Thus in man the temporomandibular joint is in a very lateral and elevated position near the mastoids. The mandibular condyls are elongated transversally with a medial cantilever. The medial part of the meniscus is drawn medially by the lateral pterygoid while the lateral part is drawn laterally by the temporal and masseter fibers. The ramus is oriented vertically and lies close to the cervical spine. The dental arches are displaced posteriorly on the bone and have lost their anterior abutment. The strongest occlusal forces are displaced to the posterior part of the arches and are transmitted vertically to the intra-articular meniscus. All these phenomena are termed extreme adaptations and the temporomandibular joint would (apparently) suffer if the evolution continued. The architectural features of temporomandibular joint overload can be deducted by comparison with the "ideal" architectural conditions for the craniofacial equilibrium.

Morphological aspects of the mid-palatal suture in the human foetus: a light and scanning electron microscopy study

Morphological features of the mid-palatal suture were studied in human foetuses from 4 to 9 months of intra-uterine life. The foetuses were divided into three age groups, GI (16-23 weeks), GII (24-31 weeks) and GIII (32-39 weeks). The mid-palatal suture in GI foetuses is rectilineal in form with a wide space between the palatal processes of the maxilla. The suture has a sinuous nature in GII and GIII foetuses due to growth of the bone processes crossing the mid-line. A wide zone of cellular proliferation observed in GI narrows in GII and GIII foetuses. The imbricating nature of the suture in GII and GIII is caused by bone growth adjacent to the mid-palatal suture. Sharpey's fibres, emerging from the bone processes, run to the median region of the mid-palatal suture and are observed from GI foetuses onwards. The collagen fibres of the mid-palatal suture are orientated transversely under the oral epithelium and exhibit a regular meshwork with a predominance of sagittal fibres in the median region of the suture. These fibres are orientated transversely and obliquely at the junction with the nasal septum.

Anatomic position of the asterion

OBJECTIVE

The asterion is defined as the junction of the lambdoid, parietomastoid, and occipitomastoid sutures. The asterion has been used as a landmark in lateral approaches to the posterior fossa. However, its reliability as a landmark comes into question considering the apparent variability of its position. This study was performed to determine the reliability of the asterion as a surgical landmark.

METHODS

One hundred dried skulls were obtained for study. A 2-mm drill hole was placed at the asterion on each side. The position of the drill hole on the inner surface of the skull was next determined and recorded.

RESULTS

The asterion was located over the posterior fossa dura in 32% on the right and 25% on the left. Its position was over the transverse or sigmoid sinus complex in 61% on the right and 66% on the left. The landmark was located above the transverse-sigmoid sinus complex in 7% on the right and 9% on the left.

CONCLUSIONS

The asterion is not a strictly reliable landmark in terms of locating the underlying posterior fossa dura. Its location is very often directly over the transverse-sigmoid sinus complex. Burr holes placed at the asterion may often open the bone directly over the sinus, leading to potential damage.

Direct current stimulation of the coronal suture in rabbits

The purpose of this investigation was to determine whether a constant direct current stimulation applied at the coronal suture would alter sutural morphology and selected cephalometric parameters of the cranial vault and cranial base. In each of six rabbit litters (N = 36), animals were randomly assigned to control, sham, and experimental groups. At 21 days of age, the sham and experimental groups had thin titanium wire cathodes surgically positioned between the fascial layers of the scalp overlying the coronal suture. On this same day and on day 70, all animals had standardized lateral and dorsoventral cephalograms taken and also received lead acetate vital stain injections. The following results were demonstrated: (1) a significantly greater flexure in the cranial base angle (P < 0.01) for the experimental group at day 70; (2) no statistically significant differences for percentage changes (day 70/day 21) in cranial vault length or cranial vault width among the control, sham, and experimental groups (P < 0.05); (3) alterations in sutural morphology at day 70 for the experimental group, including lengthened collagenous fibers, abundant cartilage in the suture, and a twofold increase in the bony modeling of the ectocranial surface. This study concludes that, although the exact mechanisms of action for direct current stimulation remain unknown, this manipulation can indeed alter some parameters of the cranial skeleton and suture morphology.

Palatal thickening and facial form in Paranthropus: examination of alternative developmental models

Paranthropus is distinctive among hominoids in its possession of a greatly thickened hard palate. Although traditionally considered a structural adaptation to counter high-magnitude masticatory stress, alternative developmental models are equally viable. Three models of palatal thickening were evaluated in this study. A mechanical model interprets palatal thickening as a compensatory response to increased instability of the midpalatal suture effected by an anterior placement of the masseteric muscle mass. This model predicts that palatal thickness is correlated with the length of the palate posterior to the masseteric tubercle. Two non-mechanical models consider the thickness of the hard palate to be structurally related to and therefore correlated with either 1) the degree to which the premaxilla overlaps the hard palate in the subnasal region or 2) the height of the posterior facial skeleton. The correlation of craniofacial variables was assessed intraspecifically in ontogenetic series of great ape and human crania. Tests of correlation were performed for each comparison using both residuals calculated from reduced major axis regression of the variable of interest against a measure of cranial size and shape ratios. A significant correlation of palatal thickness with posterior facial height in Pan suggests that the unusually thick hard palate of Paranthropus is directly related to the increased posterior facial height characteristic of this taxon. Further evaluation suggests that extreme palatal thickening in these specimens occurred by virtue of their possession of a nasal septum morphology in which the vomer extends onto the superior and nasal surface of the premaxilla. Such a morphology would have constrained the palatal nasal lamina to maintain the approximate level of the premaxillary nasal lamina throughout the growth process thereby promoting palatal thickening.

Why do we fail in aging the skull from the sagittal suture?

The controversy over the reliability of ectocranial suture status (open vs. closed) as an age estimation stimulated the pursuit of Meindl and Lovejoy's suggestion (Meindl and Lovejoy [1985] Am. J. Phys. Anthropol. 68:57-66) for large scale analysis. The extent of the sagittal suture closure was assessed in 3,636 skulls from the Hamann-Todd and Terry collections. The debate over whether cranial suture ossification represents a pathologic or an age-predictable pathologic process also stimulated a comparison with age and two stress markers, hyperostosis frontalis interna and tuberculosis. Sagittal suture closure was found to be age-independent and sexually biased. The wide confidence intervals (for age) appear to preclude meaningful application of suture status for age determination. No correlation was found with the tested biological stressors.

Stimulatory effects of low-power laser irradiation on bone regeneration in midpalatal suture during expansion in the rat

The purpose of this study was to investigate the effects of low-power laser irradiation on bone regeneration during expansion of a midpalatal suture in rats. Gallium-aluminum-arsenide diode laser 100 mW irradiation was applied to the midpalatal suture during expansion carried out over 7 days (3 or 10 minutes per day), 3 days (7 minutes per day for day 0-2 or 4-6), and 1 day (21 uninterrupted minutes on day 0). The bone regeneration in the midpalatal suture estimated by histomorphometric method in the 7-day irradiation group showed significant acceleration at 1.2- to 1.4-fold compared with that in the nonirradiated rats, and this increased rate was irradiation dose-dependent. Irradiation during the early period of expansion (days 0 to 2) was most effective, whereas neither the later period (days 4 to 6) nor the one-time irradiation had any effect on bone regeneration. These findings suggest that low-power laser irradiation can accelerate bone regeneration in a midpalatal suture during rapid palatal expansion and that this effect is dependent not only on the total laser irradiation dosage but also on the timing and frequency of irradiation. We suggest laser therapy may be of therapeutic benefit in inhibiting relapse and shortening the retention period through acceleration of bone regeneration in the midpalatal suture.

Epigenetic variation in the Nigerian skull: sutural pattern at the pterion

The variation of pterion articulation was assessed in 212 north-eastern Nigerian dried skulls. Four sutural variants were recorded. Sphenoparietal articulation was present in 82.1%, frontotemporal articulation in 23.6%, stenocrotaphia in 1.9% and epipteric articulation in 5.7% of the skulls. Symmetry of articulation was predominant in sphenoparietal (86.7%), frontotemporal (58.0%) and stenocrotaphia (100.0%) articulations. Epipteric articulation was 100.0% unilateral. In cases of unilateral presence, the occurrence on the right side was predominant for sphenoparietal (65.2%) and epipteric (66.7%) articulations. Frontotemporal articulation was more frequently seen on the left side of the skull (73.9%). These variants, when combined with some other non-metrical and metrical variants, may become useful anthropological tools for the identification of the north-eastern Nigerian skull.

Surface and superficial surgical anatomy of the posterolateral cranial base: significance for surgical planning and approach

We have performed an anatomic study, 15 using fixed cadaveric preparations, with the goal of identifying surface landmarks that will reliably locate the underlying transverse and sigmoid sinus complex. Simple morphometric relationships were first determined on both sides of each specimen to yield 30 sides measured. The following relationships were determined: 1) zygoma root-asterion, 2) asterion-mastoid tip, 3) zygoma root-suprameatal spine (Henle's spine), 4) asterion-suprameatal spine, 5) mastoid tip-suprameatal spine. The relationship of the asterion to the transverse-sigmoid junction was determined by bone removal. Also, the distances from the asterion to the sigmoid sinus-superior petrosal sinus junction and the superior margin of the transverse sinus were studied. Surface and marks were found to have definitive relationships to underlying anatomic substrates in all specimens studied. The critical relationships that were concluded from this study can be described in terms of two easily identified lines between bony surface structures. A line drawn from the zygoma root to the inion, i.e., the superior nuchal line, reliably located the rostrocaudal level of the transverse sinus in all specimens. Although the asterion did not consistently fall on this line, the transverse-sigmoid junction could reliably be placed at the anteroposterior level of the asterion. Further, a line drawn from the squamosal-parietomastoid suture junction to the mastoid tip reliably defined the axis of the sigmoid sinus through the mastoid. We also found that the junction of the squamosal and parietomastoid sutures lay over the anterior border of the upper curve of the sigmoid sinus. The anterior portion of the supramastoid crest correlated with the level of the middle fossa. These surface relationships all have significance for posterolateral approaches to the cranial base. Since performing this study, these relationships have been found reliable for operative planning in our clinical cases.

Effects of buccal shields on the maxillary dentoalveolar structures and the midpalatal suture--histologic and biometric studies in rabbits

The mechanism of the buccal shields with regard to regulating the transversal relationship of the maxillary dental arch is uncertain. The periosteal pull theory, growth at the midpalatal suture and changes in equilibrium have all been proposed as explanatory factors. The aim of the study was to investigate the transversal development of the dental arch and the osseous remodeling at the lateral surfaces of the maxillary alveolar process and in the midpalatal suture after stretching the bucca (cheek) with buccal shields in the vestibulum. Ten New Zealand white male rabbits 12 weeks old were used. The animals were divided into two groups (control and experimental). Initial and final impression had been taken from the two groups and plaster models were made using biometric analysis in all animals of each group. Transversal measurements were taken of the distances between the maxillary right and left teeth. Tetracycline hydrochloride and Alizarin complexone were used to label the mineralizing tissues. After the animals had been killed, the biopsies from the midpalatal suture, the alveolar wall, and the periosteum were studied under a microscope. The results from the biometric analysis showed maxillary dental arch expansion in the two groups that was significantly larger in the experimental group. Microscopically, the growth at the midpalatal suture was also significantly larger in the experimental group, while no significant differences were found at the maxillary alveolar bone in the two groups. The conclusions drawn from this study are that the vestibular buccal shields bring about an increased expansion of the maxillary dental arch and increased growth at the midpalatal suture. No increased bone deposition was found at the buccal dentoalveolar wall, inducing doubts as to the accuracy of the periosteal pull theory for widening of the dental arch.

Growth of the cranial vault: influence of intracranial and extracranial pressures

The cranial vault is composed of several flat membranous bones whose growth is mainly a result of the activity in the interposing sutures. The reactions of the calvarium and cranial base to provoke stimuli of the sutures differ depending on their developmental stage. In this report the effects of pressure, exerted extracranially by means of mechanical forces or intracranially by means of hydrodynamic fluctuations, are described.

Basicranial synchondroses and the mandibular condyle in craniofacial growth

Basicranial synchondroses are remnants of the fetal chondrocranium and thus represent primary cartilage, whereas the chondral part of the mandibular condyle, for example, develops unattached to the chondrocranium, as secondary cartilage. The two cartilage groups show differences in structure and cell proliferation pattern, and yet both are endowed with tissue-separating qualities.

The role of sutures in normal and abnormal craniofacial growth

The paper is a shortened version of a paper read at the symposium on craniofacial growth, in which the literature on various aspects of sutures was reviewed. Suture development, structure, growth, and closure are covered, and the response of sutures to orthopedic forces and their role in craniosynostosis exemplified. Rather than being an extensive review, references are included preferably to present diversity in results and methods within the subtitle of the symposium, 'mechanisms and study methods'.

[Angles among main cranial sutures in Japanese]

To examine a relation of angles among the coronal, sagittal and lambdoid sutures to the size of the calvaria as well as to the remains of the metopic suture, 158 adult Japanese calvae or calottes were observed. The calvae used consisted of four groups: group M composed of 74 male calvae without the metopic suture; group F, of 41 female calvae without the same suture; group Un, of 27 sex-unknown calvae without the same suture; and group Um, of 16 sex-unknown calvae with the same suture. The angles among the sutures were measured at both bregma and lambda. The size of the calvaria was represented by bistephanic arc and breadth (distance between the stephanions), and by parietal sagittal arc and chord (distance from the bregma to the lambda). Results obtained were as follows. The distances both between the stephanions and from the bregma to the lambda were larger in M than in F, though these distances in M, F and Un were much the same as those in Um. The bistephanic index (breadth/arc) was higher in Um than in F, whereas the sagittal parietal indices (arc/chrod) in M, F and Um were similar to one another. Apical angle of the frontal squama was larger in M than in F, and was larger in Um than in M and F. However, apical angle of the occipital squama showed no difference among M, F and Um.(ABSTRACT TRUNCATED AT 250 WORDS)

Comparative cephalometric study of nasal cavity growth patterns in seven animal models

Although primates have been the craniofacial growth models of choice, recent circumstances have stimulated the search for nonprimate models. In a series of studies we have described changes in various regions of the craniofacial complex for seven commonly used animal models. The present study examined the bony nasal cavity. One hundred and forty-four serial and cross-sectional lateral head x-rays were obtained for unoperated controls from previous growth studies. The sample consisted of data from 26 rats, 21 rabbits, 21 domestic cats, 23 domestic dogs, 17 baboons, 16 rhesus monkeys, and 20 chimpanzees. Comparative human data was taken from the Bolton Standards. The samples were divided into three age categories based on dental and somatic development. Midsagittal nasal cavity measurements included length, height, shape index, and area. Analysis was based on the percent increase in measures from the infant condition. Three major shapes were discerned at adulthood (1) vertical quadrangles (humans and cats); (2) triangles (chimpanzees, rhesus monkeys, and baboons), and (3) horizontal quadrangles (rabbits, rats, and dogs). Results showed that overall shape was best modeled by the chimpanzee and, as a nonprimate model, the laboratory cat. Rabbits and rats also showed similar percent changes for length or height dimensions at different ages, suggesting that these animals may be acceptable, inexpensive alternatives to primates in some experimental situations.

Thyroid hormone action on rat calvarial sutures

To clarify the effect of thyroid hormone on the calvarial sutures, the morphology, histology, and bone mineral density were analyzed in thyroid hormone-injected rats. A total of 80 female Wistar rats at the age of 10 days were divided into 2 groups; the triiodothyronine (T3)-treated rats (n = 40, T3 100 micrograms/kg body weight/day) were maintained under the same conditions as controls (n = 40, saline-vehicle only), and both were sacrificed at 50, 80, and 200 experimental days, respectively. T3-treated animals showed smaller values of lambda-asterion and pterion-bregma distances at the various periods of examination, resulting in smaller sizes in right-left direction of the skull. The sagittal suture distance in the skull specimens observed by Goldner's staining (fibrous tissue content) appeared smaller and the osseous margin widths greatly increased in the T3-treated rats. Fluorescent microscopy revealed that the tetracycline-calcein double labelings were not interrupted from the periosteal to the endosteal areas in any specimens indicating the scantiness of osteoclastic activity in the suture areas. Mineral apposition rates at the osseous edges of the suture were significantly increased in the T3-treated rats (p < 0.01 at the age of 90 days). The distance between the second labels and the distance between the first labels were significantly larger in the T3-treated rats. Bone mineral density (BMD) measurement showed that the T3 administration decreased only the calvarial BMD at the age of 210 days (p < 0.01), but did not decrease lumbar or femur BMD. This experiment demonstrated clear evidence of excess thyroid hormone action on the early narrowing of the sagittal suture in infantile hyperthyroid rats, probably due to the enhanced osteogenic activity caused by the hormone.

Thickness and resistivity variations over the upper surface of the human skull

A study of skull thickness and resistivity variations over the upper surface was made for an adult human skull. Physical measurements of thickness and qualitative analysis of photographs and CT scans of the skull were performed to determine internal and external features of the skull. Resistivity measurements were made using the four-electrode method and ranged from 1360 to 21400 Ohm-cm with an overall mean of 7560 +/- 4130 Ohm-cm. The presence of sutures was found to decrease resistivity substantially. The absence of cancellous bone was found to increase resistivity, particularly for samples from the temporal bone. An inverse relationship between skull thickness and resistivity was determined for trilayer bone (n = 12, p < 0.001). The results suggest that the skull cannot be considered a uniform layer and that local resistivity variations should be incorporated into realistic geometric and resistive head models to improve resolution in EEG. Influences of these variations on head models, methods for determining these variations, and incorporation into realistic head models, are discussed.

Sutural biology and the correlates of craniosynostosis

The purpose of this paper is to provide a new perspective on craniosynostosis by correlating what is known about sutural biology with the events of craniosynostosis per se. A number of key points emerge from this analysis: 1) Sutural initiation may take place by overlapping, which results in beveled sutures, or by end-to-end approximation, which produces nonbeveled, end-to-end sutures. All end-to-end sutures occur in the midline (e.g., sagittal and metopic) probably because embryonic biomechanical forces on either side of the initiating suture tend to be equal in magnitude. A correlate appears to be that only synostosed sutures of the midline have pronounced bony ridging. 2) Long-term histologic observations of the sutural life cycle call into question the number of layers within sutures. The structure varies not only in different sutures, but also within the same suture over time. 3) Few, if any, of the many elegant experimental research studies in the field of sutural biology have increased our understanding of craniosynostosis per se. An understanding of the pathogenesis of craniosynostosis requires a genetic animal model with primary craniosynostosis and molecular techniques to understand the gene defect. This may allow insight into pathogenetic mechanisms involved in primary craniosynostosis. It may prove to be quite heterogeneous at the basic level. 4) The relationship between suture closure, cessation of growth, and functional demands across sutures poses questions about various biological relationships. Two conclusions are provocative. First, cessation of growth does not necessarily, or always lead to fusion of sutures. Second, although patent sutures aid in the growth process, some growth can take place after suture closure. 5) In an affected suture, craniosynostosis usually begins at a single point and then spreads along the suture. This has been shown by serial sectioning and calls into question results of studies in which the affected sutures are only histologically sampled. 6) Craniosynostosis is etiologically and pathogenetically heterogeneous. Known human causes are reviewed. Is craniosynostosis simply normal suture closure commencing too early?(ABSTRACT TRUNCATED AT 400 WORDS)

Pediatric cochlear implantation. Radiologic observations of skull growth

We investigated the effects of long-term implantation of auditory prostheses on skull growth in young animals. Four monkeys were implanted with dummy cochlear implants at 6 months of age. To simulate implantation in children, the bed for the receiver-stimulator or interconnecting plug was drilled across a calvarial suture down to the underlying dura. Plain skull roentgenograms were periodically taken to monitor head growth for up to 3 years after implantation. These longitudinal measurements revealed no significant asymmetric skull growth. Postmortem measurements using computed tomographic scans confirmed these results and showed no significant difference in the intracranial volumes between the implanted and control sides of each animal or between experimental and nonimplanted control monkeys. These results suggest that long-term cochlear implantation in very young children will not cause any significant deformity of the skull.

Differential growth among components of the palate in rhesus monkeys (Macaca mulatta)

To understand the etiology of maxillary hypoplasia better, which is common in individuals with cleft palate and other craniofacial anomalies, the relative growth and contribution of the maxillary and palatine segments to enlargement of the hard palate was examined in rhesus monkeys. The purpose of the study was to identify and evaluate sites of differential growth of the palatine and maxillary segments as they contribute to the development of the midface and facial prognathism. One hundred and eight male and 107 female skulls ranging from 1.0 to 7.0 years of age were examined. Measurements of the maxillary and palatine lengths, palatal width, midface depth, canine length, and molar surface areas in the ontogenetic sample were collected. Univariate and bivariate statistics were used to describe dimensional changes and evaluate region-specific sex differences. The relative growth of palatal dimensions was evaluated using allometric analysis methods. Significant sex differences were observed (t-test, p < or = .05) for all palatal dimensions by 4 years of age. However, proportions of the maxillary and palatine segments to overall palate length appeared to be similar throughout growth for both sexes. The results suggest that sutures of the midface, in particular the transverse palatine suture, may be important in the bony development of the palate during growth. These sutures may contribute to the overall modulation of palatal development.(ABSTRACT TRUNCATED AT 250 WORDS)

Sutural complexity in artificially deformed human (Homo sapiens) crania

The pattern of complexity of cranial sutures is highly variable both among and within species. Intentional cranial vault deformation in human populations provides a controlled natural experiment by which we were able to quantify aspects of sutural complexity and examine the relationship between sutural patterns and mechanical loading. Measures of sutural complexity (interdigitation, number, and size of sutural bones) were quantified from digitized tracings of 13 sutures and compared among three groups of crania (n = 70) from pre-European contact Peru. These groups represent sample populations deformed in 1) anteroposterior (AP) and 2) circumferential (C) directions and 3) an undeformed population. Intergroup comparisons show few differences in degree or asymmetry of sutural interdigitation. In the few comparisons which show differences, the C group is always more interdigitated than the other two while the AP group has more sutural bones. The sutures surrounding the temporal bone (sphenotemporal, occipitotemporal, and temporoparietal) most frequently show significant differences among groups. These differences are related to the more extreme binding of C type deformation and are consistent with hypothesized increases in tension at coronally oriented sutures in this group. The larger number of sutural bones in the AP group is consistent with the general broadening of the cranium in this group and with experimental evidence indicating the development of ossicles in areas of tension. We suggest that so few changes in sutural complexity occurred either because the magnitude of the growth vectors, unlike their direction, is not substantially altered or because mechanisms other than sutural growth modification are responsible for producing the altered vault shapes. In addition, the presence of fontanelles in the infant skulls during binding and the static nature of the binding may have contributed to the similarity in complexity among groups.

Relationship of squamosal suture to asterion in pongids (Pan): relevance to early hominid brain evolution

Based on 244 measurements of the relationship of the squamosal suture to the landmark asterion in 49 chimpanzee skulls, it is shown that in the normal lateral view the squamosal suture is very rarely inferior to asterion. In hominid crania, the squamosal suture is always well superior to asterion. Even in Pan, that part of the squamosal suture most homologous with the remnant found on the Hadar AL 162-28 Australopithecus afarensis hominid cranial fragment is very rarely inferior to asterion. Such variability suggests that Falk's (Nature 313:45-47, 1985) orientation of the Hadar specimen is incorrect; she places asterion superior to the position of the squamosal suture if projected endocranially. The implication for the brain endocast is that, however the fragment is oriented, the posterior aspect of the intraparietal (IP) sulcus is in a very posterior position relative to any chimpanzee brain. The distance from the posterior aspect of IP to occipital pole is twice as great in chimpanzee brain casts than on the Hadar AL 162-28 endocast, even though the chimpanzee brain casts are smaller in overall size. This suggests that brain reorganization, at least as exemplified as a reduction in primary visual striate cortex (area 17 of Brodmann), occurred early in hominid evolution, prior to any major brain expansion.

Dimensional variation of craniofacial structures in relation to changing masticatory-functional demands

A reduction in masticatory stress has been an important factor in the evolution of the human skull. Similarly, the recent increase in the occlusal variation has been related to a change in masticatory activity. The present study investigates short-term variation in craniofacial dimensions by examining cephalometrically two Finnish samples, one exposed to a hard and the other to a soft diet. The samples comprised 32 skulls, derived from the 16th and 17th centuries, and 50 living individuals. Out of 18 dimensions measured, 12 showed only non-significant differences between the samples. In the present-day sample, the cranial length and the anterior cranial base were significantly longer, and the upper incisors segment significantly higher. In the skull sample, the posterior facial height, the height of the mandibular ramus, and the antero-posterior width of the pharynx were significantly larger. The results suggest that hard diet, which requires more chewing force and time, promotes vertical growth of the ramus and anterior translocation of the maxilla. The greater posterior face height and greater height of ramus are in accordance with the earlier finding that the mandible shows more anterior growth rotation in an attritive environment. These findings support the hypothesis that the growth of the craniofacial skeleton is regulated by masticatory stress. It is suggested that both the dimensional changes and the lack of dental attrition may have contributed to the higher occlusal variation of modern individuals.

Fractal dimensions of cranial sutures and waveforms

Two quite different shapes of cranial sutures ostensibly yield fractal dimensions. The rare, intricate sutures yield the more valid fractal dimensions because self-similar scaling provides a double-log plot of negative slope. These sutures are fractals over a range of several r values. Some of the highly folded, wavy sutures in humans also fill space except at very tiny values of r, but are nonfractal. A great deal depends on whether the dimension D is > 1 and by how much, whether the curve yields a false fractal dimension, whether the curve scales and shows self-similarity, and whether the scaling occurs regularly in the same pattern. We suggest careful attention to the inverse power law equations, which when misused can yield false fractal values. Cranial sutures vary from the simple wavy sutures to the complex folded ones, and, in rare instances, evolve and develop to the self-similar, scaling, elaborate ones called intricate sutures. The main thing is to express the biology precisely, whether waveform regularity or irregularity or scaling elaboration conserving space and the original shape. D values may not in themselves reliably allow such a distinction, by whatever method used.

Interrelationship between size and tissue-separating potential of costochondral transplants

The aim was to determine whether the reportedly unpredictable outcome of the use of costochondral grafts in reconstructive surgery is related to variation in growth potential between the transplanted cartilages. A rib fragment including the costochondral junction was transplanted across the interparietal suture in 10-day-old rats. The transplants contained either a short, intermediate, or long cartilaginous end and a constant length of bone. The animals were killed 25 days later and the width of the neurocranium was measured from dry skulls. The neurocranium was wider the longer the cartilaginous end of the transplant. It is concluded that costochondral transplants have an intrinsic potential for separating skeletal components and that this capacity is closely related to the amount of cartilage in the transplant.

Altering the angulation of a curved osteotome--does it have effects on the type of pterygomaxillary disjunction in Le Fort I osteotomy? An experimental study

A standard Le Fort I osteotomy was performed on 12 cadavers to determine whether the incidence of pterygoid plate fractures could be reduced by increasing the angle of the curved osteotome relative to the sagittal plane. In the group where an osteotome with the usual angulation was employed, fractures occurred on 9 of 12 sides. In the increased angulation group, 5 of 12 pterygoid plates were fractured. All fractures were restricted to the level of the horizontal osteotomy cut. It is concluded that increased angulation of a curved osteotome can decrease the incidence of fractures of the pterygoid plates. This procedure, however, is not recommended because it can cause fracture of the palatine bone or displacement of the fractured pterygoid plate fragment posteriorly.

Skull dysfunction

Individuals commonly report a multitude of factors or triggers as the cause for the onset of a headache or facial pain. The challenge has always been to understand the many triggers, the diverse symptoms, the chronological characteristics, and the variability of location associated with headache and facial pain. Part I of this article presents theories and hypotheses proposing that the etiology of the final common pathway of headache and facial pain is from pain signals generated within the skull's joints. The model proposes to explain the variability in the triggers, symptoms, chronological aspects, and location known to be associated with headache and facial pain. The evidence to support these theories is clinical and anecdotal at this time. These theories need controlled investigation. A review of the anatomy of the skull's joints is provided. Part II of this article is a step-by-step description of the use of a nasal balloon device for the treatment of skull joint dysfunction. A review of the history and use of this and other methods of skull joint treatment is provided.