|Year : 2014 | Volume
| Issue : 2 | Page : 79-82
A retrospective study of panoramic radiographs for zygomatic air cell defect in children
Srikanth H Srivathsa1, Suchetha N Malleshi2, Karthikeya Patil2, Mahima V Guledgud2
1 Department of Oral Medicine and Radiology, Annoor Dental College and Hospital, Perumattom, Muvattupuzha, Ernakulum, Kerala, India
2 Department of Oral Medicine and Radiology, JSS Dental College and Hospital, JSS University, Mysore, Karnataka, India
|Date of Web Publication||12-Aug-2014|
Dr. Srikanth H Srivathsa
Department of Oral Medicine and Radiology, Annoor Dental College and Hospital, Perumattom, Muvattupuzha, Ernakulum, Kerala
Source of Support: None, Conflict of Interest: None
Background and Aim: The aim was to determine the prevalence of zygomatic air cell defect (ZACD) among children of Indian origin and also to determine the dominant form of ZACD.
Materials and Methods: One thousand six hundred and eighty-eight routine panoramic radiographs of subjects between 7 and 18 years, processed between January 2006 and January 2009 were screened, recorded and analyzed for ZACD.
Results: Of the 1688 panoramic radiographs examined, 768 were of males and 920 of females. The radiographs were divided into two groups, Group I comprising of subjects in the age 7-12 years and other Group II in the age range 13-18 years. ZACD was found in 50 subjects, accounting for prevalence of 2.96%. Other occurrences found were unilateral 38 cases, bilateral 12, unilocular 20 and multilocular 42 respectively.
Conclusion: This study described the prevalence and characteristics of ZACD among selected Indian children. It is essential to know and determine this variant of normal anatomy and differentiate it from pathologies.
Keywords: Mastoid, panoramic radiography, temporal bone, zygomatic
|How to cite this article:|
Srivathsa SH, Malleshi SN, Patil K, Guledgud MV. A retrospective study of panoramic radiographs for zygomatic air cell defect in children. Saudi J Oral Sci 2014;1:79-82
|How to cite this URL:|
Srivathsa SH, Malleshi SN, Patil K, Guledgud MV. A retrospective study of panoramic radiographs for zygomatic air cell defect in children. Saudi J Oral Sci [serial online] 2014 [cited 2019 May 21];1:79-82. Available from: http://www.saudijos.org/text.asp?2014/1/2/79/138469
| Introduction|| |
Panoramic radiographs are useful in clinical practice as they delineate variations of normal anatomy along with the pathologies. A variant of normal anatomy evident on panoramic radiographs is zygomatic air cell defect (ZACD), also called as pneumatized articular tubercle (PAT). , ZACD has been defined as "accessory air cells in the zygomatic process and articular eminence of the temporal bone which appear similar to the mastoid air cells and which does not extend further anteriorly than the zygomatico temporal suture."  ZACDs appear radiographically as nonexpansile and nondestructive radiolucency in the zygomatic process of the temporal bone or the articular eminence and are clinically asymptomatic.  ZACDs have been classified as unilocular, multilocular and trabecular types.  Unilocular ZACD appears as an oval radiolucent defect with well-defined borders whereas; the multilocular variant demonstrates numerous small cavities within and resembles mastoid air cells. The trabecular variety is considered to be a multilocular entity with internal bony striations. 
It is pertinent that diagnosticians and surgeons recognize this entity as inadvertent breach into this air cell especially during surgical procedures such as eminectomy or eminoplasty can promote intra-cranial spread of infections and other possible complications.  Data regarding the prevalence of ZACD in children of Indian origin is lacking and hence this research aimed to determine the prevalence of the same and also to elaborate on the dominant location and type.
| Materials and Methods|| |
A retrospective study of 1688 panoramic radiographs was carried out in the Department of Oral Medicine and Radiology, JSS Dental College and Hospital. The subjects were aged 7 to 18 years and their panoramic radiographs were processed and screened for ZACDs between January 2006 and January 2009. These radiographs were made for diagnostic evaluation of various dental and maxillofacial complaints such as mixed dentition analysis, preorthodontic evaluation, etc. All radiographs were obtained with panoramic radiographic machine (Rotograph Eur 230, FIAD SpA-20094, Trezzano S/Naviglio, Villa, Italy) operating between 65 kVp and 75 kVp, 10 mA and 16 s using T-Mat G/Lanex medium film/screen combination (Eastman Kodak Co., Rochester, NY, USA). All the radiographs had been processed automatically using Promax 5 speed processor (Chayagraphics Co. Ltd., Bangalore, India).
Only those radiographs depicting the articular eminence bilaterally fairly well were selected. Exclusion criteria included radiographs not exhibiting the articular eminence, motion blur, improper images and images with artifacts, and central pathologies in the area of interest. Institutional Ethical Committee Clearance was obtained for the study.
All the 1688 radiographs were analyzed by four oral radiologists, in ambient viewing conditions. For descriptive purposes, the radiographs were divided into two groups, Group I comprising of subjects aged 7-12 years and Group II subjects aged 13-18 years. ZACDs were documented only if irrefutable and unified evidence meeting the defining criteria of ZACD as described in the literature  was recognized by all four oral radiologists. Following this, ZACDs were further classified based on the demographics, laterality (unilateral/bilateral) and locularity (uni/multilocular).
The data collected were tabulated and subjected to statistical analysis, namely descriptive statistics, frequencies/percentages, and standard deviation using Microsoft Office Excel 2007 (Microsoft Corporation, 2007, USA).
| Results|| |
The youngest subject with ZACD was 8 years and oldest was 18 years. There were 8 male (53.4%) and 7 female (46.6%) subjects in the Group I who exhibited ZACD with a mean age of 10.37 years and in Group II, there were 15 (42.8%) males and 20 (57.1%) females with the mean age of 15.20 years [Table 1].
Zygomatic air cell defect was discovered in 50 subjects who had a total of 62 ZACDs is shown in [Table 2].
Of 50 subjects who demonstrated ZACDs, 23 (46%) were found in males and 27 (54%) in females, with male to female ratio of 0.8:1. Unilateral occurrence was noted in 38 (76%) and bilateral in 12 (24%) and 20 presented with unilocular and 42 with multilocular appearance. [Figure 1] and [Figure 2] show cropped panoramic radiograph of ZACDs. The distribution of ZACDs with age, gender, locularity and laterality is summarized in [Table 3]. [Figure 3] depicts the distribution of laterality of ZACDs and [Figure 4] and [Table 4] depicts the distribution of locularity of ZACDs.
|Figure 1: Cropped panoramic radiograph showing left multilocular zygomatic air cell defect in a 16-year-old male subject|
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|Figure 2: Cropped panoramic radiograph showing left unilocular zygomatic air cell defect in a 9-year-old male|
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|Table 3: Distribution of ZACD with respect to age, gender, locularity, and laterality|
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| Discussion|| |
Air cells are series of communicating cavities within the bone lined by mucous membranes.  Pneumatization, noted mostly in para-nasal sinuses can also manifest in the temporal bone. These pneumatized air cells present in the zygomatic process of the temporal bone have been named ZACD.  Identification of this entity was made in 1934 by Tremble.  Tyndall and Matteson in 1985  termed it as pneumatized articular eminence/PAT and later in 1987 recoined it as ZACD. ,
Irrespective of demographics, prevalence of ZACD varies from 1% to 3.42%, based on the population studied. Orhan et al. were the first to study ZACDs in the pediatric population and they reported prevalence of 1.62%.  They later studied variations of ZACDs among pediatric and adolescents in association with malocclusions and found prevalence of 3.42%, which is the highest recorded prevalence.  In this study, the prevalence among Indian children was relatively higher, at 2.96%. The study which found the highest prevalence considered population with different kinds of malocclusions, whereas this study considered otherwise normal individuals. Two studies from India, found the prevalence of ZACD in the adult population to be 2.5% and 1.8% respectively. ,
The youngest patient to demonstrate ZACD in a study from Turkey was aged 7 years.  In this study, the youngest patient was 8 years old. Although our sample included subjects aged 7 years, none demonstrated ZACD. There is no consensus for the ZACD gender prevalence rates, with a few studies having reported a male predominance and others female preponderance. , The pediatric study also reports no gender difference. 
It is difficult to draw a consensus on the laterality of ZACDs. The pediatric study found unilateral ZACD to be more common than the bilateral type. This study is in accordance with the pediatric and other studies demonstrating dominance of unilateral variant (n = 38). ,, Most studies stated that ZACDs occurred more on the right side than the left side. , ZACDs were mostly noted on the left side (n = 20) in this study in contradiction to Orhan et al. study, who found equal number of ZACDs on right and left sides. 
Zygomatic air cell defects can be visualized as uni- or multi-locular radiolucencies. This study demonstrated dominance of the multilocular variant (n = 42). The pediatric study by Orhan et al. also found that multilocular variant to be prevalent. 
A variation among this aspect has been noted in a few studies. Previous studies from India , showed multilocular variant to be the dominant form, whereas one study found equal number of uni- and multi-locular ZACDs  and another found unilocular to be the dominant form.  This variation could be because of inter-observable variability as well as the difference in the population studied.
It is important to recognize the existence and significance of ZACD, as the ZACDs and other temporal pneumatic spaces can serve as a potential pathway for various pathologies. Previous studies have emphasized that pneumatizations exposed during eminectomies can serve as potential avenues for cranial sepsis and infection.  During surgeries, surgeons should take care to avoid accidental penetration through the defect, which may result in dural tear and leakage of cerebrospinal fluid.  Preoperative demonstration of ZACD serves as a contraindication for performing eminoplasty or eminectomy to treat recurrent mandibular dislocation and alternative surgical therapy is indicated. ,
These air spaces can be breached during maxillofacial trauma.  Fracture or dehiscence of the glenoid fossa may lead to herniation of soft tissue contents into the middle ear and further result in the middle ear infections and mastoid effusion. They may serve as an entry port for mastoid tumors to extend into temporomandibular joint (TMJ). Otitis or mastoiditis extending to the TMJ can result in ankylosis of TMJ. 
A few central pathologies such as the aneurysmal bone cyst, central hemangioma, central giant cell tumor, eosinophilic granuloma, fibrous dyspalsia and metastatic tumors have been recognized to have involved the zygomatic processes of the temporal bone and hence should be considered in the differential diagnosis for ZACD. ,,
| Conclusion|| |
Data is lacking with respect to the prevalence and characteristics of ZACDs in children. This study attempted to fill this vacuum and offers an insight into this less known anatomical variation. It is prudent for oral and maxillofacial radiologists to be aware of this entity owing to its significance and possible complications. Comparison of literature between adult and pediatric population shows a difference in prevalence, but the radiographic characteristics of this innocuous entity remains similar. A prospective longitudinal study may throw more light on the evolutionary pattern of the ZACDs.
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[Table 4], [Figure 1], [Figure 2], [Figure 3], [Figure 4]
[Table 1], [Table 2], [Table 3]