David J. Netherway

Mandibular lengthening by distraction for airway obstruction in Treacher-Collins syndrome.

Mandibular lengthening by distraction was performed in a 6-year-old tracheostomy-dependent Treacher-Collins syndrome patient. Detailed preoperative imaging revealed an occluded retrotongue base pharyngeal airway, which, following mandibular distraction, became patent and permitted tracheostomy removal. Mandibular distraction as a technique must be targeted toward clinical problems—management of upper-airway obstruction may be one such scenario.

CT-determined intracranial volume for a normal population.

Intracranial volume comparisons of patients with craniosynostosis and normal have been contrary to expectations, leading to questioning of the validity of the current normal reference material. Computed tomography-determined intracranial volume is presented for a white normal population. Specifically, intracranial volumes for 157 subjects (82 female and 75 male) were measured from computed tomography data using the Cavalieri estimator: volume determination was based on measuring the area in each computed tomography section. Monomolecular and Gompertz models were applied to find curves of best fit to the intracranial volume as a function of the age. The best fit was obtained using the monomolecular model when the response variable was the logarithmically transformed intracranial volume, and the independent variable was the logarithm of the age from conception. For example, the mean (standard deviation) for male subjects at 1 year and 20 years were 1,125.6 (89.6) ml and 1,472.9 (117.2) ml, respectively, and for female subjects 1,024.9 (84.0) ml and 1,321.7 (108.3) ml, respectively. Although the shape and rate of increase of the female and male curves is similar, the female mean is 1.3 standard deviations below the male mean at 20 years. These curves were compared with the commonly referenced curves of Blinkov (1941), Lichtenberg (1960), and Dekaban (1977). Our male curve is substantially higher than these curves in the age range 8 months to 4 years. Our female curve, however, is approximately 1 standard deviation below Lichtenbergs curve from birth to 7 months. There are then only minor differences between our female curve and Lichtenbergs curve until his curve crosses ours at 41 months, where they significantly diverge from approximately 4.5 years. Our curves indicate that 95% of the final intracranial volume has been attained by 42 months for girls and 46 months for boys.

Intracranial volume measurement of metopic craniosynostosis

The authors report 32 patients with nonsyndromic isolated metopic synostosis who have undergone evaluation of their intracranial volumes. Twenty-five were male and seven were female. The measured intracranial volumes were compared with normal age-corrected values established in the authors’ unit, and any differences were noted.The authors found that, although there was a range of intracranial volumes, in the male patients, intracranial volumes were significantly smaller than those found in the normal population (P < 0.05). However, this result was not found in the smaller female sample.These results contrast with those of smaller earlier studies, but the authors conclude that intracranial volumes are smaller than average for age-corrected normal values; this finding highlights the need for volume expansion in conjunction with cranial reshaping.

Mandibular lengthening by distraction for airway obstruction in treacher-collins syndrome: the long-term results.

Mandibular lengthening by distraction was performed in a 6-year-old severely affected Treacher-Collins syndrome patient who was tracheostomy dependent. As previously reported, this procedure permitted tracheostomy removal once distraction was complete. Now that the patient is skeletally mature, the long-term results of this intervention are reported with regard to his clinical outcome and an assessment of the anatomical changes in the upper airway during growth. Although the distraction could be considered a success in that it enabled permanent decannulation and improved the minimum cross-sectional area of the upper airway, there was no further increase in the minimum cross-sectional area of the upper airway during childhood growth. It is significant that the abnormal growth pattern of the mandible, which is characteristic of this syndrome, did not alter from its preoperative pattern once distraction was completed.

Intracranial volume measurement of sagittal craniosynostosis

We report 41 cases of non-syndromic isolated sagittal synostosis in which evaluation of intracranial volumes was undertaken. Twenty-six were male and fifteen were female. The measured intracranial volumes were then compared with normal age-corrected values. We have found that intracranial volumes were significantly larger than the normal population intracranial volumes in both sexes. However the statistical significance of this finding was much greater in females, (p<0.00002), than males (p<0.040), which was only of borderline significance. The results confirm smaller, earlier studies that intracranial volumes in sagittal synostosis patients are larger than average for age-corrected normal values. Analysis of a sub-set of six patients with sagittal synostosis who were found to have a common polymorphism 294C>T (Asn294Asn) in FGFR3 (fibroblast growth factor Receptor 3) on genetic testing were compared to age and sex matched cases of non-syndromic sagittal synostosis (without an underlying mutation) which confirmed that there were no discernable differences in intracranial volumes between the two groups. We conclude that this investigation supports the role of cranial re-shaping to improve cosmesis as the primary aim of surgical correction in this condition, in the absence of raised intracranial pressure.

Bilambdoid and posterior sagittal synostosis: The Mercedes Benz Syndrome

A consistent pattern of craniosynostosis in the sagittal and bilateral lambdoid sutures is described in three patients. The external cranial ridging associated with fusion of these sutures produces a characteristic triradiate, or “Mercedes Benz,” appearance to the posterior skull. Locally marked growth restriction is evident in the posterior fossa with compensatory secondary expansion of the anterior fossa manifesting a degree of frontal bossing which mimics bicoronal synostosis. Although this appearance could lead to inadvertent surgery in the frontal region, attention to the occipital region with wide early suture excision and vault shaping is indicated.

Analysis of Intracranial Volume in Apert Syndrome Genotypes

Objective: Apert syndrome is caused by a mutation of the fibroblastic growth factor type 2 gene and in nearly all of the cases where the mutation has been identified it occurs in one of two adjacent sites of the gene, either position 252 or position 253. There is currently uncertainty whether a worse neurosurgical outcome occurs in association with a particular genotype. We investigated whether there were clinically subtle (but relevant) morphological differences in the craniofacial skeleton, which would result in differences in the intracranial volume, which might account for apparent differences in surgical outcome. Method: Three-dimensional CT scans of pre-operative Apert syndrome whose genotype had been identified had the intracranial volume measured using the Cavalieri estimator with correction for partial voluming effects. The values were compared to age and sex normals and then the two genotypes compared. Results: Intracranial volumes were measured for 22 cases, 16 with the 252 mutation and 6 with the 253 mutation. Conclusions: All cases except two had greater than their sex- and age-adjusted mean normal intracranial volumes. For the 252 and 253 genotypes there were no discernible differences in intracranial volumes between the two genotypes.

Application and comparison of techniques for three-dimensional analysis of craniofacial anomalies.

Traditionally, cephalometric analysis has been limited to data determined from two-dimensional (2-D) cephalograms. With imaging facilities such as CT and biplanar radiography now available, the natural extension has been towards the use of three-dimensional (3-D) coordinate positions of landmarks for comparative purposes. While these data have been potentially available for several years, the accurate and reproducible extraction of anatomic landmarks suitable for comparative purposes has been limited. This paper presents results of the application of traditional comparative techniques to well determined 3-D coordinate data acquired from biplanar radiography and CT for a patient with Treacher Collins syndrome and further provides a comparison with the technique of strain analysis, often referred to as finite element analysis, which has been applied recently to craniofacial data. Comparisons of distances and angles between landmarks, landmark coordinate positions, and strains of the patient relative to experimental reference standards reveal that the essential skeletal features of Treacher Collins syndrome have been identified and quantified by the analysis techniques. Further, a measure of the significance of the deviations has been determined by comparisons with the experimental reference standards.

Scanning electron microscope and micro-CT evaluation of cranial sutures in health and disease.

Current knowledge of suture biology has been ascertained as a result of morphological studies of normal cranial sutures (and rarely those undergoing craniosynostosis). These were initially undertaken often using histological investigations, or more recently using CT scans, as investigative tools, but have often used animal models. However, recent technological advances have provided the potential to refine our understanding of the ultrastructure by the use of new advanced scanning technology, which offers the possibility of more detailed resolution. Our aim was to undertake detailed scans of normal, fusing and fused sutures from patients with craniosynosotosis affecting different sutures, to study the detailed structure at different stages of the fusion process using a modern micro-CT scanner and a microanalytical scanning electron microscope. We wished to include in our study all the human sutures because previous studies have mostly been undertaken using the sagittal suture. Ten sutures from seven patients have revealed a complex ultra-structural arrangement. The different patterns of bone ridging seen on the ectocranial and endocranial surfaces of the fused sagittal suture were not repeated on closer inspection of either fused coronal or lambdoid sutures. Elemental analysis confirmed that the amount of calcium increased and the amount of carbon decreased as sampled areas moved away from the suture margin. We conclude that scanning allowed detailed assessment and revealed the complex arrangement of the structure of the human cranial sutures and those undergoing the process of craniosynostosis, with some differences in final structure depending on the affected suture.

Computer tomography determined intracranial volume of infants with deformational plagiocephaly : a useful "normal"?

Over the last 10 years, children with deformational (nonsynostotic) plagiocephaly have undergone computed tomography scans using the same protocols as children with lambdoid craniosynostosis because of their similarly distorted head shapes. These children are believed to have normal intracranial volume. Given the recent questioning of what is the normal range of intracranial volume in human populations, the authors have undertaken a comparison of the intracranial volume of children with deformational plagiocephaly and Lichtenbergs normal population (Lichtenberg R. Radio-graphie du crane de 226 enfants normaux de la naissance a 8 ans: Impressions digitiformes, capacite, angles et indices [thesis]. Paris: University of Paris, 1960). The intracranial volume was determined for 20 females and 46 males with deformational plagiocepahly ranging in age from 2.5 to 20.7 months using computed tomography scan data. Although no significant differences were found for the females, the authors found that the intracranial volume of the males with deformational plagiocephaly were significantly larger than Lichtenbergs population. The authors conclude that this is because Lichtenbergs data do not adequately reflect the normal range of intracranial volume for males ranging in age from 2.5 to 20.7 months, rather than gender differences associated with deformational plagiocephaly. Further, until a more suitable normal becomes available, the deformational (nonsynostotic) plagiocephaly data could-be used as substitute normal reference material in the measured age range for assessment of the intracranial volumes of children with craniosynostosis.