Dentomaxillofacial Radiology (2011) 40, 110–1142011 The British Institute of Radiologyhttp://dmfr.birjournals.org

INVESTIGACIÓN

Neumatización de la eminencia articular en tomografía computarizada cone beam: prevalencia, características y una revisión de la literatura.O Miloglu*, AB Yilmaz, E Yildirim and HM AkgulDepartamento de Diagnostico Oral y Radiología, Facultad de Odontología, Universidad de Ataturk, Erzurum, Turquía

Objetivos: La meta de este estudio fue determinar la prevalencia y características de neumatización de eminencias articulares (NEA) con TC cone beam (TCCB) y para presentar una revisión de la literatura sobre esta.

Métodos: Un estudio retrospetivo fue realizado usando imagenes de TCCB sagitales y coronales de 514 pacientes en el Departamento de Radiologia Oral y Maxilofacial, de la Universidad Ataturk, Turquía. La edad y el sexo fueron recolectados para todos los pacientes y, en casos de NEA, también fueron registradas las lateralidades y tipos. Fue usado el Test x2.

Resultados: De 514 pacientes, 41 (8.0%) tuvieron NEA, de las cuales 25 fueron mujeres (61.0%) y 16 fueron hombres (39.0%). Esta diferencia no fue estadistiamente significante (P . 0.05). El rango de edad de los pacientes con NEA fue de15-62 años. De los 41 pacientes, 31 (75.6%) tenía NEA unilateral y el 10 (24.4%) tenia NEA bilateral. 17 (41.5%) NEA fue unilocular y 24 (58.5%) fue multilocular.

Conclusiones: Es posible que el NEA fuera una condición mas frecuente de lo que es comúnmente percibido. En casos con diagnósticos diferenciales o en casos en los que se planifica tratamiento quirúrgico, radiografías panorámicas deben ser complementadas con TCCB.

Dentomaxillofacial Radiology (2011) 40, 110–114. doi: 10.1259/dmfr/75842018

Keywords: pneumatized articular eminence; zygomatic air cell defect; temporomandibular joint; cone beam computed tomography

*Correspondence to: Assistant Professor Ozkan Miloglu, Department of Oral Diagnosis and Radiology, Faculty of Dentistry, Ataturk University, 25240, Erzurum, Turkey; E-mail: omiloglu@hotmail.comReceived 17 October 2009; revised 31 December 2009; accepted 4 January 201

IntroducciónNeumatizacion se refiere al desarollo de cavidades llenas de aire en el hueso. Temble1 reporto la distribucion de celulas de aire en el hueso temporal. Diez lugares donde celulas accesorias de aire podrían encontrarse en el hueso temporal fueron identificadas, incluyendo una area en el proceso cigomatico del hueso temporal 1,2. Tyndall y Matteson3 indicaron que la neumatizacion de la eminencia articular (NEA) del hueso temporal ha sido identificada como un defecto radiolucido asintomático en el proceso cigomatico del hueso temporal, con una apariencia similar a células de aire mastoideas. Carter et al4 re-enfatizo que la ocurrencia de este fenómeno y llamo a estas celulas como defectos de células de aire cigomáticas (zygomatic air cell defect) de la misma forma.

Las celulas de aire de la eminencia articular del hueso temporal pueden ser visibles en radiografias panomaricas y hay muchos casos de reportes y de estudios de prevalencia de NEA, basados en el uso de estas radiografias, en la literatura actual

3–22.Radiografías panoramicas fueron consideradas el metodo inicial para revisar estos defectos debido a que la radiografiapanoramica es mas ventajosa que la TC para la visualizacion de la eminencia articular, debido a su baja radiacion y bajo costo. Sin embargo, debido a que la TC no esta sujeta a la superimposicion, esta sobrepasa la exactitud del diagnositco de las radiografias panoramicas en la evaluacion de los espacios aereos temporales. Ademas, una lesión

noramic radiog

. However,since CT is not subjected to superimposition it exceedsthe diagnostic accuracy of panoramic radiographs inthe evaluation of temporal air spaces. Moreover, a lesssuperficially located region, such as the medial portionof the articular eminence, may only be visible on CT.To our knowledge, a systematic study of the prevalenceof PAT using cone beam CT (CBCT) has not previouslybeen performed. In this study, we have attemptedto determine the prevalence and characteristics

of PAT in an oral diagnosis and radiology clinicpopulation using CBCT, and to present a review of thePAT literature.Literature reviewA detailed search of the reported literature wasconducted using the Pubmed database for the years1976 to 2009. The search strategy used the keywords‘‘pneumatized articular eminence’’, ‘‘pneumatized articulartubercle’’, ‘‘zygomatic air cell defect’’, ‘‘air cells’’,‘‘zygomatic arch’’ and ‘‘zygomatic process’’. The citationlists from the included references were subsequentlyexamined in an attempt to identify additionalreports and a hand search was performed to find lettersto the editor and opinion letters in the journals(Tables 1 and 2).Materials and methodsWe designed a retrospective cohort study composed oftomography images of 514 patients who presented to theOral Diagnosis and Radiology service at the AtaturkUniversity Dentistry Faculty between March 2008 andSeptember 2009. Patients had been scanned with CBCT(NewTom FP QR-DVT 9000, 110 kVp, 15 mA, 36 sscan time, 5.4 s typical X-ray emission time, 17 cmdiameter–13 cm height scan volume, Verona, Italy).Cases in which the zygomatic arch was not adequatelyseen for technical or anatomical reasons and the casesthat had maxillofacial fracture history were not includedin this study. On one of the axial views, the long axis ofthe examined condyle was traced, and the softwaregenerated lateral and frontal cross-sectional reconstructionsperpendicular and parallel to the long axis of thecondyle, respectively. The thickness of the image sliceswas 1 mm and the distance between slices was 1 mm forboth lateral and frontal reconstructions. Images werereviewed on a digital imaging workstation. The imageswere examined by two investigators (one professor andone postgraduate dentomaxillofacial radiologist) at thesame time. To check for the diagnostic reproducibility of

the interreliability of the two investigators, 10% of the

radiographs assigned by them were randomly examinedeach day for three consecutive days. Examination ofresults using the Wilcoxon matched pairs signed-ranktest showed no statistically significant differencesbetween the two observers, indicating diagnostic reproducibility.In addition, 10% of the remaining radiographswere selected at random and re-evaluated twiceby the same examiners 6 weeks after the first evaluation.Intraexaminer reproducibility was found to be 96% and90%, respectively. Pneumatization of articular eminencewas determined on both sides.The age and gender were recorded for all patients and,for the cases of PAT, laterality and type were also noted.Diagnosis of PAT on the images was done only ifunequivocal pneumatization of the articular eminencecould be seen or if the defect was located in the articulareminence posterior to the zygomaticotemporal suture asa well-defined uni- or multilocular radiolucency. PATwas classified as unilocular or multilocular as in thestudy by Tyndall and Matteson.3 Unilocular PAT wasidentified as a single radiolucent oval defect with welldefinedbony borders. Multilocular PAT was identifiedas numerous radiolucent small cavities.The variables were analysed using the Statistical Packagefor Social Sciences (SPSS 11.5; Chicago, IL) program. Thex2 test was used to determine potential differences in thedistribution of lesions when stratified by gender. AP-value of ,0.05 was considered statistically significant.ResultsThe average age of the 514 patients who were included inthis study was 33.4 (SD 14.0) years and the age range was4–85 years. There were 298 females (58.0%) and 216males (42.0%) in the study population. The mean age ofthe females was 31.8 (SD 14.3) years with a range of 7–82years while the mean age of the males was 35.7 (SD 13.3)years with a range of 4–85 years. The gender and agedistribution of the study population is presented Table 3.41 (8.0%) of 514 individuals had PAT, of whom 25(61.0%) were females and 16 (39.0%) were males. Theages of the patients ranged from 5 to 62 years (mean30.6 ¡ 11.4 years). Mean age was 29.1 years for femalesand 33.0 years for males. 31 cases (75.6%) had unilateraland 10 (24.4%) had bilateral PAT. Of the 31 unilateral

cases, 14 (45.2%) were on the left and 17 (54.8%) were onthe right side. 17 (41.5%) of the PATs were uniloculartype, 24 (58.5%) were multilocular type (Table 3). Theyoungest patient with PAT was a 15-year-old female.Figures 1–3 show severalPATexamples in different images.DiscussionThe classification of temporal bone pneumatization iscomplex. It can be divided into five regions, which inturn are subdivided into areas. The primary regionsconsist of the middle ear, mastoid (squamomastoid),perilabyrinthine, petrous apex and accessory. Thesquamomastoid region comprises two key areas ofpneumatization, the mastoid antrum (including thecentral tract) and the periantral area. The tegmental

periantral cells lie superior to the mastoid antrum andmay pass upward into the squamotemporal region orextend into the zygomatic arch producing the PAT.4,2

The anatomical relationship of PAT to mastoid aircells is interesting. Perhaps PAT can be thought of asextensions of the mastoid air cells similar to extensionsof the paranasal sinuses. Dentists are aware of alveolarand tuberosity extensions of the maxillary sinuses andthe occasional extension of the sphenoid sinus superiorlyinto the dorsum sellae.3There have been only a few studies on PATs in theliterature. The prevalence of this phenomenon has beenreported to be between 1.0% and 2.6%.3–7,10,14 All ofthe current studies were carried out on panoramicradiographs. The use of conventional panoramic radiographsto screen for PAT is expedient because theradiographs are obtained during routine examinationof many patients. Conventional panoramic radiographs,however, have inherent problems, including awide focal zone and superimposition of adjacentstructures. High-resolution CT is considered themethod of choice for the assessment of bony structuresand air spaces in the base of the skull. Since CBCT isnot subject to superimposition, it exceeds the diagnosticaccuracy of panoramic radiographs in the evaluation oftemporal air spaces. Although the air cells adjacent tothe temporomandibular joint (TMJ) may be visibleon panoramic radiographs, a less superficially located

region such as the medial portion of the articulareminence may be visible on only CT.23,24 Therefore,CBCT images were used to ensure high accuracy in thisprevalence study of PAT. In our study, the prevalenceof PAT was detected as 8.0%, and this rate was higherthan suggested in literature. Groell and Fleischmann24

detected an articular eminence with air spaces in 12of 100 patients who had undergone high-resolutionaxial CT.Current reports in the literature reveal an averagefemale-to-male ratio of 1.1:1. The female-to-male ratioin the present study was found to be 1.6:1. However,the difference between females and males was notstatistically significant and this was consistent with theliterature. The mean age of patients with PAT found byCarter et al,4 Kaugars et al,14 Yavuz et al,5 Hoffmannet al10 and Orhan et al7 was 49.6, 45.9, 30.0, 43.2 and36.6 years, respectively. The mean age was 30.6 years inthe present study, similar to that found by Tyndall andMatteson’s3 (32.5 years), owing to the young adultpopulation in both investigations. The age range ofpatients with PAT was wide (4–85 years), similar toCarter et al4 (4–93 years), Yavuz et al5 (10–75 years),Hoffmann et al10 (7–87 years), Orhan et al7 (11–90years) and Tyndall and Matteson3 (15–74 years).However, Kaugars et al’s14 series was relatively moreconstricted (32–69 years). In our study, the youngestpatient reported with PAT was 15 years old.Hollingshead25 pointed out that the accessory air cellsbegin to pneumatize after puberty and achieve full size

after several years, as is the case with proper mastoid aircells. In contrast to this statement, Hoffman et al,10

Orhan et al7 and Yavuz et al5 detected cases of PAT inpatients aged 7, 11 and 10 years and therefore beforethe second half of the second decade of life. Orhan et al6found PAT in 9 patients before puberty with a meanage of 8.8 years and an age range of 7–11 years.Pneumatization of accessory air cells had begun beforepuberty, which is in contrast with general opinion.A current literature review revealed that the unilateralto bilateral ratio was 2.5:1. In the present study,a ratio of 3:1 was observed, which is close to thatreported in the literature. Tyndall and Matteson3 found

15 multilocular and 17 unilocular PAT cases, Orhan etal7 reported 16 multilocular and 10 unilocular PATcases, and Yavuz et al5 detected 66 multilocular and 44unilocular PAT cases in their series. In our study, wefound that 17 (41.5%) of PATs were unilocular and 24(58.5%) of PATs were multilocular.PAT must be differentiated from other radiolucencieswithin the zygomatic arch, including aneurysmal bonecyst, haemangioma, giant cell tumour, eosinophilicgranuloma, fibrous dysplasia and metastatic tumourdeposits.3,4,7,10,14,18,26 PAT can be detected incidentallyon radiographs as an asymptomatic radiolucency withnon-expansile characteristics. All of the other entities inthe differential diagnosis have been reported to becharacterized by painful enlargement of the cheek andseen radiographically as expansile, destructive lesions.CT images can be considered where there is adifferential diagnosis of suspected cases.PAT is important because it facilitates the spread ofvarious pathological processes into the joint such astumours, inflammation or fractures owing to minimalresistance. The presence of air in the TMJ has beenshown to be associated with acute temporal bonefracture,27 and surgical procedures of the temporalbone affected by PAT can be complicated.7,24,27–29

During any TMJ surgery in patients with PAT,perforation can occur owing to firm dissection orforceful flap retraction. The treatment of some TMJdysfunction requires fossa-eminence prostheses tocorrect the effects of the pathology. When these areplaced between the condyle and skull base, perforationmay occur because of the screws.5,30 Therefore, CTmust be performed to determine exact size and therelationship to adjacent tissue of PAT cases detected inthe panoramic radiographs before TMJ surgery.Treatment of PAT is unnecessary. If pneumatizationwithout any ipsilateral symptomatology is seen inthe articular eminence coincidentally, it should bekept under observation. The presence of PAT can bea contraindication for performing eminoplasty oreminectomy to treat recurrent chronic mandibulardislocation.4,5,7,14,17,19,21 Lindenmuth and Clark19 indicatedthat such surgical considerations dictate that an

awareness of pneumatization of the articular eminencebe part of our anatomical knowledge.

In conclusion, our results suggest that the prevalenceof PAT is higher than has been previously believed.Diagnosis of this anomaly has become incidental, since itdoes not present any clinical symptoms. Such prevalencestudies, particularly from developing countries, willprovide useful information to understand better the

nature and different clinical features of uncommonentities.AcknowledgmentsWe would like to express our sincere gratitude to Fatih Akcayfor his support in proofreading our article and to AssistantProfessor Hamit Acemoglu for his statistical evaluation.