Prevalence of the types of the petrotympanic fissure in the temporomandibular joint dysfunction

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1 Original article Prevalence of the types of the petrotympanic fissure in the temporomandibular joint dysfunction Binali Çakur, Muhammed Akif Sümbüllü, Doğan Durna and Hayati Murat Akgül Department of Oral Diagnosis and Oral Radiology, Faculty of Dentistry, Ataturk University, Erzurum, Turkey Correspondence to: Binali Çakur. Abstract Background: Petrotympanic fissure (PTF) is a fissure in the temporal bone that runs from the temporomandibular joint (TMJ) to the tympanic cavity (TC). In PTF, the discomallear ligament (DML) connects the malleus in the tympanic cavity and the articular disc and capsule of the temporomandibular joint. PTF with the DML is a possible cause of aural symptoms related to temporomandibular joint dysfunction (TMD). Purpose: To investigate the prevalence of different types of PTF in TMD using dental volumetric tomography (DVT) and determine whether PTF type correlates with age. Material and Methods: DVT scans in the sagittal planes of PTFs of 134 patients with TMD were examined for the types of PTF present. Three main PTF types were described: wide, tunnel-shaped structure (type 1); tunnel-shaped structure that is wide open in the PTF entrance to the mandibular fossa and gradually thins out in the tympanic cavity (type 2), tunnel-shaped structure that is wide open in the entrance of the mandibular fossa, with a middle region with a flat-shaped tunnel structure and a narrow exit in the tympanic cavity (type 3). Results: In DVT scans, PTF types 1, 2 and 3 were seen in 67.2%, 1.5%, and 31.3% of cases, respectively. We found no significant relationship between age or gender and PTF type. Conclusion: The low percentage of type 2 PTF and high percentage of type 1 PTF must be taken into consideration during pre-surgical planning related to TMD. However, future well-designed clinical studies involving larger numbers of subjects will be necessary to confirm the findings of this study. Keywords: Discomallear ligament, dental volumetric tomography, petrotympanic fissure, temporomandibular joint Submitted September 27, 2010; accepted for publication January 24, 2011 The temporomandibular joint (TMJ), the most complicated synovial joint, is closely related to the middle ear. Petrotympanic fissure (PTF) is a fissure in the temporal bone that runs from the TMJ to the tympanic cavity (TC) (1). The discomallear ligament (DML) is the structure connecting the TMJ and capsule with the malleus of the middle ear (2, 3). In 1962, Pinto originally described the DML as a tiny ligament (4). The ligament runs through a narrow space of the bony petrotympanic fissure. After passing through the PTF, the DML attaches to the disc or fibers of the posterosuperior part of the capsule of the TMJ (4 6). Although the ligament is not described in classical anatomy textbooks (3, 7 9), it has been established as an anatomical link in anatomical dissections of adults and fetuses (1). It has been suggested that the DML is a possible cause of aural symptoms such as otalgia, hearing loss, tinnitus and vertigo related to temporomandibular joint dysfunction (TMD) due to the structure of the PTF (3, 10). It was also suggested that TMJ inflammatory or functional disorders produce otitis media (1). Therefore, the PTF with the DML is an important factor in hearing function (3). PTF structure is classified as type 1 (wide, tunnel-shaped structure), type 2 (tunnel-shaped structure that is wide open in the entrance of the PTF to the mandibular fossa and gradually thins out in the tympanic cavity) and type 3 (tunnel-shaped structure that is widely open in the entrance of the mandibular fossa, with a middle region having a flat-shaped tunnel structure and a narrow exit into the tympanic cavity) (10). The type of PTF with the DML has an influence on the malleus, which is pulled by Acta Radiologica 2011; 00: 1 4. DOI: /ar

2 BÇakur et al. the TMJ disc. Movement of the malleus in the middle ear by traction of the DML depends on the structure of the petrotympanic fissure (10).

aim of this study was to investigate the prevalence of different petrotympanic fissure types and to determine whether PTF type correlates with age using dental volumetric tomography (DVT) in

2 2 BÇakur et al. the TMJ disc. Movement of the malleus in the middle ear by traction of the DML depends on the structure of the petrotympanic fissure (10). To our knowledge, there has been no study that has used dental volumetric tomography (DVT) to evaluate the prevalence of different PTF types in TMD and the relationship between PTF type and age The aim of this study was to investigate the prevalence of different petrotympanic fissure types and to determine whether PTF type correlates with age using dental volumetric tomography (DVT) in temporomandibular joint dysfunction. Materials and Methods We designed a retrospective study consisting of images of 134 patients with TMD (24 men, 110 women; aged years; mean age 34 years) who presented at our clinic between June 2008 and September Dental volumetric tomography (NewTom-FP; Quantitative Radiology, Verona, Italy) scanning was performed on patients who were resting in supine positions. Positioning of the patients heads was performed using two light-beam markers. The vertical positioning light was aligned with the patients mid-sagittal lines, which helped to keep the head centered with respect to the rotational axis. The lateral positioning light was centered at the level of the condyles, indicating the optimized center of the reconstruction area. In addition, the head position was adjusted in such a way that the hard palate was parallel to the floor, while the sagittal plane was perpendicular to the floor. DVT scans with 0.5-mm slices in the axial and sagittal planes were obtained. Imaging parameters were kv ¼ 110, ma ¼ 10, and FOV ¼ 140 mm. The output was automatically adjusted during 3608 rotation according to tissue density (automatic exposure control system). Three dental radiologists in this study evaluated the DVT images with respect to PTF structure on sagittal images according to a classification proposed by Sato et al. (10). Images were viewed in a darkened room on three computers with 17-inch LCD monitors and the same screen resolution. In this classification, Sato et al. (10) has described three main types of PTF: wide, tunnel-shaped structure (type 1), tunnel-shaped structure that is wide open in the entrance of the PTF to the mandibular fossa and gradually thins out in the tympanic cavity (type 2), tunnel-shaped structure that is wide open in the entrance of the mandibular fossa, with a middle region having a flat-shaped tunnel structure and a narrow exit into the tympanic cavity (type 3). The types of PTF obtained from sagittal images of the left and right middle regions were recorded. To determine the reliability of the method, a weighted kappa test was performed. Intra- and inter-observer agreement was analyzed using the weighted kappa test. Fig. 1 On a sagittal image, tunnel of type 1 PTF; wide, tunnel-shaped structure (white arrows). TC ¼ tympanic cavity, MF ¼ mandibular fossa Pearson s correlation coefficient with the level of significance set at p, A Student s t test was used to compare means for women and men. Results In the DVT scans, PTF types 1 3 (Figs. 1 3) were observed in 67.2%, 1.5%, and 31.3% of cases, respectively. In female patients, the same types were seen in 68.2%, 1.8%, and 30% of cases, respectively. In male patients, types 1 and 3 were seen in 62.5% and 37.5% of cases, respectively, but type 2 was not seen. The results of the Student s t test showed that there was no statistically significant difference Statistics Descriptive statistics (frequencies, means + SD) and correlation were calculated using the SPSS w statistics program (SPSS w v11.0; SPSS Inc., Chicago, IL, USA). The correlation between the types of PTF and age was established using Fig. 2 On a sagittal image, tunnel of type 2 PTF; tunnel-shaped structure that is wide open in the entrance of the PTF to the mandibular fossa (inferior white arrow) and gradually thins out in the tympanic cavity (superior white arrow). TC ¼ tympanic cavity, MF ¼ mandibular fossa

3 Prevalence of the types of the petrotympanic fissure in the temporomandibular joint dysfunction 3 Fig. 3 On a sagittal image, tunnel of type 3 PTF; tunnel-shaped structure that is wide open in the entrance of the mandibular fossa (inferior white arrow), with a middle region with a flat-shaped tunnel structure and a narrow exit in the tympanic cavity (superior white arrow). TC ¼ tympanic cavity, MF ¼ mandibular fossa between genders with respect to PTF. No correlation was observed between age and PTF type (r ¼ 0.041, p ¼ 0.503). The weighted kappa values for intra-observer reliability were calculated to be 0.86, 0.80, and 0.92 for the first, second and third observer, respectively. The weighted kappa values for interobserver reliability between observers 1 and 2, observers 2 and 3 and observers 1 and 3 were calculated to be 0.84, 0.81 and 0.87, respectively. Discussion The present study was conducted to investigate the prevalence of PTF types and, using DVT, determine whether PTF type in TMD is correlated with age. Type 1 was the most prevalent type, while type 2 was the least prevalent type in TMD. No significant relationship was found between age or gender and PTF type. The ossicular chain and middle ear muscles, which serve the hearing system, ontogenically belong to the masticatory system (1, 11) and are closely related to each other (2). Some studies have indicated possible clinical implications of DML and its relationship to craniomandibular dysfunction syndrome (2, 12, 13). It has been reported that otological symptoms could occur in anterior disc displacements with reduction because of DML tension and malleus movement (6, 12 14) and could also occur during TMJ surgery as a result of excessive inferior movement of the condyle or extreme stretching of the ramus during distraction osteogenesis (6, 13). However, it has also been reported that the DML is not linked to malleus movement (2, 5, 15, 16). Under anatomical observation, Rodriquez-Vazquez et al. (2) stated that the possible movement of bones in the middle ear depended on the degree of closure of the PTF. Hence, the points of adhesion between the DML and the edges of the PTF are important (2); these points of adhesion may vary among different types of PTF. Sato et al. (10) suggested that the DML is a possible cause of aural symptoms related to TMD because of the different PTF types (types 1 3). They stated that types 2 and 3 indicate limited movement of the malleus of the TMJ, and type 1 can cause TMJ pain and dysfunction. They also stated that the malleus with the DML in the wide structure of PTF type 1 is more easily affected by movement of the TMJ (10). This idea was also described by Rodriguez-Vazquez et al. (2). It was reported that the soft tissue within the PTF usually does not allow the transfer of force from the TMJ to the middle ear (16). However, a short, wide PTF might allow transmission of force from the TMJ to the middle ear (16). In addition, the ossification process of the tympanic bone and an abnormal foramen tympanicum can cause TMJ pain and dysfunction (17, 18). Schickinder et al. reported a variant PTF. In their case, the PTF opened medially into the hypotympanon at the height of the orifice of the Eustachian tube, and they suggested that the variant fissure was the possible cause of a tympanic membrane perforation during TMJ arthroscopy (19). In this study, we investigated the prevalence of PTF types and whether PTF type correlates with age in TMD. We found no significant relationship between age or gender and PTF type. However, in our study, type 2 PTF was not observed in male patients. Type 1 had the highest prevalence (67.2%), both in total and between genders. Sato et al. (10) examined the structures of PTFs collected from human cadavers with a mean age of 80.4 years (range years) and found that the prevalence of PTF types 1 3 were 29.1%, 20.8%, and 41.7%, respectively. The discrepancy between our findings and those of Sato et al. (10) may be due to the number of patients examined, race or experimental techniques. In addition, Sato et al. (10) examined the DML after anatomical dissection of Japanese cadavers. In our study, we examined PTFs using DVT only. PTF is a narrow, bony structure, and for this reason, radiological interpretation of PTF is difficult. It is easier to diagnose type 3thantypes1and2onsagittalimagesofDVT;therefore,it is likely that the prevalence of type 3 will be higher than those of other types. In addition, it would be difficult to diagnose type 2 because of gradually thins out. In conclusion, the low percentage of type 2 PTF and high percentage of type 1 PTF must be taken into consideration during pre-surgical planning related to TMD to prevent damage of the middle ear. However, future well-defined clinical studies using larger numbers of patients will be necessary to confirm our findings. REFERENCES 1 Ramírez LM, Ballesteros ALE, Sandoval OGP. A direct anatomical study of the morphology and functionality of disco-malleolar and anterior malleolar ligaments. Int J Morphol 2009;27: Rodriguez-Vazquez JF, Merida-Velasco JR, Merida-Velasco JA, et al. Anatomical considerations on the discomalleolar ligament. J Anat 1998;192: Rowicki T, Zakrzewska J. A study of the discomalleolar ligament in the adult human. Folia Morphol (Warsz) 2006;65: Pinto OF. A new structure related to the temporomandibular joint and middle ear. J Prosthet Dent 1962;12:95 103

4 4 BÇakur et al. 5 Coleman RD. Temporomandibular joint: relation of the retrodiskal zone to Meckel s cartilage and lateral pterygoid muscle. J Dent Res 1970;49: Sencimen M, Yalcin B, Dogan N, et al. Anatomical and functional aspects of ligaments between the malleus and the temporomandibular joint. Int J Oral Maxillofac Surg 2008;37: Bochenek A, Reicher M. Anatomia człowieka. 11th edn. Warszawa: Wydawnictwo Lekarskie PZWL, Morgan DH, House LR, Hall WP, et al. Diseases of the temporomandibular apparatus. A multidisciplinary approach. St Louis, MO: Mosby Company, Standring S. Gray s anatomy. The anatomical basis of clinical practice. 39th edn. Edinburgh: Elsevier, Sato I, Arai H, Asaumi R, et al. Classifications of tunnel-like structure of human petrotympanic fissure by cone beam CT. Surg Radiol Anat 2008;30: Myrhaug H. The incidence of ear symptoms in cases of malocclusion and temporo-mandibular joint disturbances. Br J Oral Surg 1964;2: Ioannides CA, Hoogland GA. The disco-malleolar ligament: a possible cause of subjective hearing loss in patients with temporomandibular joint dysfunction. J Maxillofac Surg 1983;11: Loughner BA, Larkin LH, Mahan PE. Discomalleolar and anterior malleolar ligaments: possible causes of middle ear damage during temporomandibular joint surgery. Oral Surg Oral Med Oral Pathol 1989;68: Ogutcen-Toller M, Juniper RP. The embryologic development of the human lateral pterygoid muscle and its relationships with the temporomandibular joint disc and Meckel s cartilage. J Oral Maxillofac Surg 1993;51: Komori E, Sugisaki M, Tanabe H, et al. Discomalleolar ligament in the adult human. Cranio 1986;4: Eckerdal O. The petrotympanic fissure: a link connecting the tympanic cavity and the temporomandibular joint. Cranio 1991;9: Lacout A, Marsot-Dupuch K, Smoker WR, et al. Foramen tympanicum, or foramen of Huschke: pathologic cases and anatomic CT study. Am J Neuroradiol 2005;26: Sperber GH. Craniofacial development. Ontario: BC Decker Inc., Schickinger B, Gstoettner W, Cerny C, et al. Variant petrotympanic fissure as possible cause of an otologic complication during TMJ arthroscopy. A case report. Int J Oral Maxillofac Surg 1998;27:17 9

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A study of the discomalleolar ligament in the adult human

O R I G I N A L A R T I C L E Folia Morphol. Vol. 65, No. 2, pp. 121 125 Copyright 2006 Via Medica ISSN 0015 5659 www.fm.viamedica.pl A study of the discomalleolar ligament in the adult human T. Rowicki