Material and methods

From April 2012 to October 2016, 10 patients (6 boys, 4 girls; mean age, 9.9 years) ( Table I ) affected by Goldenhar syndrome with unilateral craniofacial involvement were examined via CBCT volumetric imaging. This study was approved by the research ethics committee of the University of Florence in Italy, and informed written consent was obtained from each patient. Scans were performed with NewTom 5G (QR srl, Verona, Italy), a horizontal CBCT unit equipped with an amorphous silicon flat-panel detector (20 × 25 cm). The patients lay in a supine position with competent lips and the mouth in habitual occlusion. The same protocol—called “standard regular” by the producer—was used for all examinations. It provided 110 kV, 3.39-5.38 mA, 18 × 16 cm FOV, 18-second scan time, and 3.6-second exposure time with the acquisition of 360 images (1 image for each rotation degree) at the lowest doable automatically set radiation dose. The largest FOV available was chosen to include both the facial skeleton and the vertebral spine up to the sixth cervical vertebra. All CBCT volumes were reconstructed with 0.3-mm isometric voxel size. The 0.4-mm thick axial sections were exported in DICOM format and analyzed by using OsiriX software (version 7.0; OsiriX, Geneva, Switzerland), implemented in a Macintosh operating system with a 21.5-in monitor (Power Macintosh G3; Apple, Cupertino, Calif).

The anatomic points chosen for the 10 linear measurements and the 6 calculated volumes are shown in Figures 1 and 2 , respectively. Gonion, pogonion, and zygomatic-facial foramen were identified on the 3D surface-rendering reconstructions. The identification of the remaining 7 points took place on the 2-dimensional reconstruction planes (coronal, sagittal, and axial) by using the 3D multiplanar reconstruction function that allowed the simultaneous display of any structure on those 3 planes. The distances between sella turcica and the other points, except for pogonion, were calculated by the 3D curved multiplanar reconstruction function. The distances between gonion and pogonion and between gonion and the condyle were calculated also. The last 2 corresponded with the length of the mandibular body and the mandibular ramus, respectively.

The 10 anatomic points used for the linear measurements: A and B, sagittal planes; C and D, axial planes; E, coronal plane; F, 3D volume rendering. Note the fusion of the vertebral bodies and os odontoideum ( circle ). ST , Center of sella turcica; PO , most anterior point of the mandibular symphysis or pogonion; GO , midpoint of the posterior margin of the mandibular angle or gonion; CO , most cranial point of the mandibular condyle; ZTS , midpoint of the zygomatic-temporal suture; ZFF , zygomatic-facial foramen; FZS , midpoint of the frontozygomatic suture; SPF , most caudal point of the sphenopalatine fossa; MF , mental foramen; MA , most caudal point of the mastoid.

Single-slice volume contouring drawn for volumetric measurements: A, coronal plane; B-D, axial planes. EEV , External ear canal volume, calculated from the inner border of the tragus to the tympanic membrane; MEV , middle ear volume, defined by the bone walls of the tympanic cavity; IAV , Internal auditory canal volume, calculated from the inner acoustic foramen to the sickle crest; CV , condyle volume, inferiorly delimited by a plane passing through the most caudal point of the mandibular notch and perpendicular to the tangent of the mandibular ramus; OV , orbit volume, defined by its bone borders and posteriorly by the optic foramen; MSV , maxillary sinus volume, defined by its bone walls.

Orbit, maxillary sinus, and condyle volumes were measured on the axial images, whereas the external ear canal, middle ear, and internal auditory canal volumes were measured on the coronal images. All volumes were calculated using the volume region of interest function after a region of interest surrounding the anatomic structures was depicted in each slice in which the same structures could be seen.

The cervical vertebrae anomalies were assessed by adaptation of the conventional x-ray classification of Sandham to CBCT. Sandham divided the vertebral anomalies into 2 groups: fusion anomalies and posterior arch deficiencies. Fusion anomalies were defined as incomplete separation with osseous continuities between 2 vertebral bodies or arches. Posterior arch deficiencies were represented by a discontinuity or interruption of the posterior arch of the vertebra due to incomplete ossification or dehiscence.

All examinations were evaluated by 3 skilled maxillofacial imaging observers (S.C., C.N., V.S.) (with 21, 10, and 4 years of experience, respectively). The assessment was carried out twice by each observer, with an interval of 3 months. Collected data were analyzed using SPSS statistical analysis software (version 23.0; IBM, Armonk, NY). Intraobserver and interobserver reliability values were determined for each designated parameter (affected side, nonaffected side, reduction factor, and differences between the nonaffected and the affected sides). For both linear and volumetric measurements, the intraclass correlation coefficient was used. According to Zidan et al, intraclass correlation coefficient values of 0.00 to 0.10, 0.11 to 0.40, 0.41 to 0.60, 0.61 to 0.80, and 0.81 to 1.0 represent no, slight, fair, good, and very good agreement, respectively.

The mean, median, standard deviation, and maximum and minimum values of each parameter were calculated for both linear and volumetric measurements among the 60 observations (2 evaluations by 3 observers for 10 patients). The reduction factor was the ratio between the nonaffected and affected sides as stated by Hirschfelder et al. Then, a descriptive analysis was performed. The differences between the nonaffected and affected sides for all linear and volumetric measurements were assessed by using the Wilcoxon signed rank test for paired data. For each analysis, a P value ≤0.05 was considered to be statistically significant.

Results

Alterations of bone development were detected on the affected side in all 10 patients ( Tables II and III ). Statistically significant differences (0.001 ≤ P value ≤0.043) between the nonaffected and affected sides were observed for all linear and volumetric measurements, except for maxillary sinus volume and the distances between gonion and pogonion, and between sella turcica and the fronto-zygomatic suture ( P = 0.5). Intraobserver and interobserver reliabilities for both linear and volumetric measurements were very good. The intraclass correlation coefficient values were 0.84 ± 0.26 and 0.83 ± 0.28 for the linear measurements, respectively, and 0.96 ± 0.08 and 0.91 ± 0.13 for the volumetric measurements, respectively.

Table II

Linear measurements

Distance	Parameter	Mean (cm)	Median (cm)	SD (cm)	Minimum (cm)	Maximum (cm)
GO-CO	NAS	4.96	4.86	0.79	4.09	6.25
	AS	3.69	3.77	0.90	2.42	4.94
	RF	1.40	1.29	0.36	1.08	2.02
	DIF	1.27	1.19	0.77	0.31	2.47
GO-PO	NAS	7.85	7.53	0.96	7.07	9.51
	AS	7.81	7.43	1.10	6.65	9.39
	RF	1.01	1.01	0.08	0.91	1.12
	DIF	0.04	0.10	0.57	−0.77	0.81
ST-CO	NAS	5.50	5.60	0.19	5.17	5.63
	AS	4.89	5.10	0.73	3.83	5.54
	RF	1.15	1.02	0.20	1.01	1.46
	DIF	0.60	0.12	0.76	0.07	1.77
ST-GO	NAS	7.68	7.37	0.85	6.75	9.03
	AS	7.09	6.84	0.92	6.11	8.60
	RF	1.09	1.08	0.05	1.04	1.16
	DIF	0.59	0.53	0.32	0.25	1.10
ST-ZTS	NAS	6.07	6.20	0.25	5.67	6.26
	AS	5.75	5.76	0.28	5.34	6.13
	RF	1.06	1.06	0.04	1.01	1.10
	DIF	0.31	0.32	0.20	0.07	0.55
ST-FZS	NAS	6.36	6.38	0.71	5.22	7.16
	AS	6.47	6.60	0.45	5.77	6.91
	RF	0.98	0.96	0.06	0.91	1.05
	DIF	−0.11	−0.24	0.39	−0.54	0.34
ST-ZFF	NAS	6.59	6.44	0.68	5.63	7.39
	AS	6.29	6.25	0.72	5.46	7.20
	RF	1.05	1.03	0.04	1.03	1.12
	DIF	0.31	0.19	0.22	0.17	0.68
ST-MA	NAS	7.53	7.55	0.17	7.38	7.78
	AS	6.82	7.13	0.66	5.72	7.35
	RF	1.11	1.05	0.11	1.03	1.29
	DIF	0.71	0.32	0.64	0.22	1.67
ST-MF	NAS	8.81	8.85	0.91	7.51	9.97
	AS	8.42	7.98	1.02	7.45	9.86
	RF	1.05	1.02	0.06	1.01	1.15
	DIF	0.40	0.15	0.46	0.06	1.14
ST-SPF	NAS	3.60	3.65	0.41	2.98	4.13
	AS	3.25	3.30	0.23	2.86	3.48
	RF	1.11	1.09	0.06	1.04	1.19
	DIF	0.35	0.30	0.21	0.12	0.65

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