Amanda H. Abbott

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.

Central nervous system imaging in Crouzon's syndrome

Although the need to prevent the secondary effects of craniosynostosis on the central nervous system is fundamental to the practice of craniofacial surgery, the detailed structural anatomy of the central nervous system in the syndromal craniosynostoses has become the subject of recent interest. A clinical and radiographic review of a population of 59 patients with Crouzons syndrome determined the frequency of central nervous system deformities. Twelve percent of patients had evidence of decreased mental function. Ventriculomegaly on computed tomographic scan was present in 51% and found to be of three grades: mild, moderate, and severe (hydrocephalus). This was nonprogressive in 7 of the 11 patients with follow-up computed tomographic scans. Ten patients underwent surgical release to increase intracranial space; however, 6 of these patients showed no progression in ventricular size. Nonventricular anomalies were found less frequently (14%). Central nervous system findings show fewer nonventricular anomalies than in Aperts syndrome patients, with a corresponding higher mental function. The principal anomaly of ventriculomegaly is not directly related to suture defect and may represent a primary brain abnormality. Recommendations are made for the assessment and management of patients with Crouzons syndrome with reference to these areas.

Noncraniofacial manifestations of Crouzon's disease.

Although most interest centers on the craniofacial region in Crouzons disease, noncraniofacial manifestations are important because they may complicate both diagnosis and management. A population of 59 patients with Crouzons disease was reviewed to determine the frequency of these deformities. Stylohyoid ligament calcification (50%) and cervical spine (40%) and elbow (18%) abnormalities were the most common. Minor hand deformities (10%), other musculoskeletal deformities (7%), and visceral anomalies (7%) were also seen. Acanthosis nigricans was not present in this population. Recommendations are made for the assessment and management of Crouzons disease with reference to these areas.

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.

Extradural Deadspace After Infant Fronto-orbital Advancement in Apert Syndrome

Infant fronto-orbital advancement is presently a management cornerstone of the craniosynostosis in Apert syndrome. This procedure is based on the premise that the expanding brain rapidly advances in support of, and to remodel, the new frontal facade. This series of infant patients with Apert syndrome undergoing fronto-orbital advancement with early postoperative computerized tomography assessment reveals a large extradural deadspace persistent through the first postoperative week, not obliterated consistently until the fourth week. Early deadspace effacement results from expansion of the prefrontal subarachnoid space, without any significant change in size or shape of the frontal brain substance or ventricles. Brain growth or expansion was particularly slow with brain shape distortions still evident at late follow-up.

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.