Incidental findings on cone beam computed tomography

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Original Article

Incidental findings on cone beam computed tomography: Relate and relay Suhas P Pande, Subhash P Kumbhare, Amit R Parate Department of Oral Medicine and Radiology, Government Dental College and Hospital, Nagpur, Maharashtra, India

ABSTRACT Objective: To evaluate the presence of incidental findings on cone beam computed tomography (CBCT) images and to recognize their clinical importance. Materials and Methods: A total of 700 CBCT scans between January 2013 to August 2014 at Government Dental College and Hospital were evaluated retrospectively. Results: 459 incidental findings (65.57%) were observed in 700 patients. Most common individual incidental finding was mucosal thickening (119) followed by pineal/habenula calcification (99) and choroid plexus (77). Conclusion: The oral and maxillofacial radiologist should carefully interpret all scans and should not ignore the incidental findings and hence avoid untoward snowballing effects.

Key words: Cone beam CT, incidental finding, referral

Introduction

C

one beam computed tomography (CBCT) has experienced comprehensive growth as a diagnostic modality in the maxillofacial region. CBCT is an advancement in CT imaging that has begun to emerge as a potentially low-dose tomographic technique for visualizing bony structures in the head and neck.[1] CBCT was first adapted for clinical use in 1982 at the Mayo Clinic Biodynamic Research Laboratory.[2] With increase in field of view, the incidental findings (IFs), i.e. the findings visualized other than the findings for which the purpose of scan was meant, have increased considerably. The frequency of IFs varies from one study to another depending on the age group and the geography of the population studied. Caglayan and Tozoglu found as high as 92.8% of IFs in their study population, whereas Cha Access this article online Quick Response Code: Website: www.jiaomr.in

et al. found a frequency of 24.5%.[3,4] Many IFs are of limited clinical significance. They are benign or age related, while other findings represent manifestations of the primary lesion/systemic disorder or clinically significant pathologic processes. Hence, not all IFs require further diagnostic investigations or treatment. The dentist/oral radiologist should know how to deal with an IF to avoid unnecessary consequences. This can be accomplished by having a profound knowledge of all findings of head and neck region and knowing their clinical importance and severity. This article provides a brief review of common IFs on CBCT and gives an insight into their clinical significance and basis wherever possible, which may help the oral health care professionals to decide on further diagnostic tests and treatment. This is an open access article distributed under the terms of the Creative Commons Attribution-NonCommercial-ShareAlike 3.0 License, which allows others to remix, tweak, and build upon the work non-commercially, as long as the author is credited and the new creations are licensed under the identical terms. For reprints contact: [email protected]

DOI: 10.4103/0972-1363.167080

How to cite this article: Pande SP, Kumbhare SP, Parate AR. Incidental findings on cone beam computed tomography: Relate and relay. J Indian Acad Oral Med Radiol 2015;27:48-54.

Address for correspondence: Dr. Suhas P Pande, Room No 25, Department of Oral Medicine and Radiology, Government Dental College and Hospital, GMC Campus, Medical Square, Nagpur, Maharashtra, India. E-mail: [email protected] Received: 27-11-2014 Accepted: 14-07-2015 Published: 12-10-2015 48

© 2015 Journal of Indian Academy of Oral Medicine and Radiology | Published by Wolters Kluwer - Medknow

[Downloaded free from http://www.jiaomr.in on Wednesday, September 28, 2016, IP: 83.161.156.248] Pande SP et al.: Incidental findings in CBCT

Materials and Methods The images were acquired using PLANMECA 3D MID (Planmeca, Helsinki, Finland) CBCT machine with Romexis software version 3.2.0 (Planmeca®, Helsinki, Finland). The parameters ranged 60-90 kVp and 5-15 mA depending upon the field of volume (FOV) selected and the built of patient. The FOV ranged from 4 × 4 to 8 × 8 inch. The total scan time ranged from 18 to 26 s and the voxel size from 200 to 400 μm. A total of 700 CBCT scans taken between January 2013 and August 2014 at Government Dental College and Hospital, India were retrospectively evaluated for any IF. The sample consisted of 277 implant patients, 125 obstructive sleep apnea (OSA) patients, 115 trauma patients, 59 tumor/malignancy patients, 21 sinusitis patients, 64 cyst/granuloma patients, and 39 temporomandibular joint (TMJ) disorder patients. For the purpose of this study, IF was defined as any abnormal finding that is not related to the original purpose of imaging. The IFs were classified as sinus findings, cervical vertebrae findings, calcifications, TMJ findings, cystic/ tooth related findings, and others. Findings such as missing tooth, caries, restoration, and periodontal bone loss were not recorded. Findings related to the primary purpose of scan were also excluded. All scans were independently viewed by two radiologists (SP, SK) in all three planes for IFs. Any conflicts in the reviews were solved by consensus.

Results In the sample of 700 patients, 459 IFs were seen (65.57%). For convenience purpose, the IFs were grouped into sinus findings, cervical vertebrae findings, calcifications, TMJ findings, cystic/tooth related findings, and others. The most common IF was seen in the calcification group which accounted for 187 IFs out of 459 (40.74%), followed by sinus region which accounted for 137 (29.85%) findings and then by 66 cervical spine findings (14.32%). The most common individual IF was mucosal thickening (119), followed by pineal/habenula calcification (99) and then by choroid plexus calcification (77). Partial unilateral type of ponticulus posticus (PP) was the most common (22) subtype of PP, which was followed by complete unilateral type (15). Complete bilateral type was seen in 4 cases, partial bilateral type in 6 cases, whereas a combination of both was seen in 10 cases. All IFs were classified as no referral, routine referral, and urgent referral required depending upon the severity of the finding.

The IFs were grouped as sinus findings, cervical findings, calcifications, TMJ disorder, cystic/tooth related findings, and others. These findings varied from age-related physiologic, benign lesions to pathologic findings. The age of patients ranged from 5 to 78 years with 381 of them being males and 319 females. Incidental findings of the sinus region comprised 29.85% of total IFs. Mucosal thickening [Figure 1] was the most common sinus finding seen in 119 subjects (17%), followed by mucous retention cyst [Figure 2] in 12 (1.71%) and sinusitis (complete opacification) in 6 (0.85%) subjects [Figure 3]. Cha et al. reported sinus findings in 18.8% of subjects, of which sinusitis was seen in 7.5% and retention cyst in 3.5% cases.[4] A study by Fatma Caglayan et al. reported mucosal thickening in 31.3% cases and retention cyst in 2.9% cases.[3] This difference in the frequency of sinus findings may be because of the different sample sizes and geographic differences. We considered 3 mm as a reference measure and anything higher than 3 mm was considered as mucosal thickening.[4-6] Mucosal thickening was the most commonly observed abnormality. It may be associated with odontogenic infection, trauma, or irritation from the environmental pollutants.[5] These findings should be given importance when planning for implant placement in the maxillary posterior region or during paranasal sinus surgery. Whenever a graft placement is considered, the patency of the osteomeatal complex should be checked; otherwise, it may result in blockage of the complex and, thus, accumulation of inflammatory products within the sinus.[7] Therefore, this factor should be kept in mind before planning for surgery. Sandham (1986) divided IF of cervical column into two categories: Posterior arch deficiency and fusion anomalies.[8] Fusion was seen in three subjects (0.42%) between C3 and C4 vertebrae [Figure 4]. Associations between malformed cervical vertebra and head posture

Discussion In the present study, 700 CBCT scans were examined for the frequency of IFs, which was found to be 65.57%.

Figure 1: Sagittal section showing mucosal thickening of the maxillary sinus

Journal of Indian Academy of Oral Medicine & Radiology | Jan-Mar 2015 | Vol 27 | Issue 1

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and craniofacial aberrations have been shown.[9] Fusion of cervical vertebrae is associated with change in head posture.[10] Obstructive sleep apnea is a complex syndrome wherein craniofacial abnormalities, elongated soft palate, extended head posture, and hyoid position are considered as predisposing factors.[11] Change in head posture may indicate some deep pathology like OSA in which the patient assumes extended neck position. Recently, associations between malformations of upper cervical vertebrae and those of maxilla and condyle have come up.[9] This indicates that malformations of cervical vertebra are associated with craniofacial and jaw malformation. Thus, any change in the morphology of cervical vertebra (fusion, head posture) should be referred properly to the physician for a detailed examination. Apart from fusion, three more findings were seen with the cervical vertebrae — Dehiscence, ossification of anterior longitudinal ligament (OALL), and PP. Dehiscence [Figure 5] is a mild variation in the anatomy of cervical vertebrae. Dehiscence, which means incomplete development of a part of vertebrae, was seen in three cases (0.42%) in the present study.[12] Farman et al. found

this variation in 3.6% of cases, and this difference might be because of the different imaging technique used and the geographic variation.[13] Oral radiologist/dentist should be familiar with this variation, as it may be mistaken for fracture or any other pathology. Two ligaments, anterior and posterior, run longitudinally along the vertebral body from the cervical spine to sacrum. Ossification of these ligaments is a part of an entity termed diffuse idiopathic skeletal hyperostosis. In this, ossification is seen on the anterior or anterolateral aspect of four adjacent vertebrae, with no loss of intervertebral disc space. Three types of OALL are seen: Segmental type, continuous type, and mixed type. In segmental type, ossification is seen over the vertebral body without involving the disc space. The continuous type shows ossification over disc space and many vertebral bodies. In mixed type, a combination of both is seen.[14] In our study, only first, second, third, and fourth cervical vertebrae were seen. Therefore, it is difficult to classify them into the above groups. Further radiographs are required to classify them. This type of ossification [Figure 6] was seen in three cases (0.42%) in this study. OALL is mostly asymptomatic, but it may cause compression of trachea and esophagus. Dysphagia and suffocation have been described in about 10% of cases.[15] These patients should be referred for further investigations, as a complete view of the entire cervical spine is not obtained with CBCT scan.

Figure 2: Axial section showing retention cyst in both maxillary sinuses with septa seen in the right sinus

Figure 3: Coronal section showing complete opacification of the left maxillary sinus suggesting sinusitis

Figure 4: Sagittal section showing fusion of C3 and C4

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Figure 5: Sagittal section showing dehiscence



The other anomaly we found was with atlas vertebra: PP. It is a malformed bony bridge connecting the posterior portion of the superior articular process and the posterolateral portion of the superior margin of the posterior arch of the atlas, thus forming foramina through which the vertebral artery and the first cervical nerve pass. This variation is associated with various types of headache, hearing loss, and vertebro-basilar insufficiency. [16] Ponticulus posticus is classified as unilateral and bilateral. In bilateral type, it is subgrouped as complete, partial, or a combination of both. In unilateral type, it is classified as complete or partial. Out of 700 scans, PP was seen in 8.14% cases [Figure 7]. Our finding was in accordance with that of Takaaki et al. wherein PP was found in 9.1% cases.[17] However, Kim et al. found PP in higher number of subjects (26%). This difference might be because the subjects in the study of Kim et al. were having cervical spine problems. During spinal surgery, fixation of atlas is performed by insertion of lateral mass screws at a higher level than the classic entry point at the junction of posterior arch and lateral mass, which causes bleeding from the epidural plexus. This modified placement is best achieved when a broad posterior arch is present. Sometimes PP may be mistaken for broad posterior arch and may lead to damage to the vertebral artery and C1 nerve. [18] Thus, patients complaining of cervical pain, headache, or posted for spine surgery should be informed of such anomaly and appropriate consultation should be sought. Carotid atheroma [Figure 8] was seen in three subjects in this study. Calcified carotid atheroma was first described in 1981 on panoramic X-ray. This occurs secondary to mature atheromatous plaque and represents an increased risk for stroke known as cerebrovascular accident. Atheromatous plaques are fatty deposits within the tunica intima of arteries. These plaques produce ischemia by occluding the artery thus reducing the blood flow or by emboli which occlude the cerebral end artery.[19] The patient should be informed about this IF and also about the relation of internal carotid artery with carotid atheroma. Age, medical history, and current cardiovascular status should be considered before referring or initializing any medical treatment for the same. Intracranial calcifications are hardening of organic tissues (cortices, glands, blood vessels) within the cranium by deposit of calcium salts and sometimes iron within its substance. They can be classified mainly into six groups based on their etiopathogenesis as: Age related/physiologic, congenital, infectious, endocrine and metabolic, vascular, and neoplastic.[20] Intracranial physiologic calcifications are more common than other types of calcification. Pineal gland is a small endocrine gland located posterodorsal to superior colliculus

Figure 6: Ossification of anterior longitudinal ligament is seen in sagittal section

Figure 7: Showing complete type of PP

Figure 8: Carotid atheroma seen in sagittal section in front of C2-C3

and between the laterally positioned thalamic bodies. Habenula is present anterior to the pineal gland and has a central role in regulation of the limbic system. Choroid plexus is a structure in the ventricles of brain where CSF is produced.[21] On CBCT, it is very difficult to distinguish between pineal and habenula calcifications, hence they are considered as one group. In the present study, pineal/habenula calcifications [Figure 9] were seen in 99 subjects (14.14%) and choroid plexus [Figure 9] calcifications in 77 subjects (11%). These calcifications are physiologic and their identification is important to rule out any pathologic calcification.


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Pineal/habenula calcifications appeared as single, welldemarcated, radiopaque mass in the center. In choroid plexus, they appeared as symmetric, faint punctuate or a coarse, conglomerated calcification pattern, which was bilateral in all cases. Any calcification occurring at any other site in the brain region should be investigated properly. Pineal calcification over 1 cm in diameter or occurring under 9 years of age may be suggestive of neoplasm.[20] The reason for physiologic calcification is that some areas in brain like choroid plexus, petroclinoid ligament, falx cerebri, and predominantly pineal gland contain calcified structures called as corpora arenacea or brain sand, whose concentration increases with age.[22] They are mostly composed of calcium carbonate, calcium phosphate, magnesium phosphate, and calcite.[23] Tonsilolith [Figure 10] was seen in seven cases. If large enough, it may cause pain and foul breath. When asymptomatic, no further referral is required. Sialolith [Figure 11] was seen in one case. It may go unnoticed by the patient when small, but the patient may complain

of decreased salivation, pain while eating, swelling, and sometimes pus discharge from the orifice of salivary duct. Sialolith was seen in the submandibular salivary duct. Bifid condyle [Figure 12] was seen in one case in the present study. It is an uncommon finding and may be mistaken for fracture or tumor. The etiology is not completely understood, but it is suggested that trauma to condylar growth center may result in bifurcation. It is mostly asymptomatic requiring no referral, but sometimes may be associated with pain or ankylosis.[24] Subcondylar Ely’s cyst [Figure 13] was also seen in one case and may suggest osteoarthritic changes. Such patients should be kept on regular follow-up. Cyst/granuloma [Figure 14] was seen in 22 subjects (3.14%). Trauma, pulpal necrosis, periodontal infection, or residual infection may result in development of a cystic lesion. Such subjects should be referred to either an oral surgeon or endodontist. Impacted teeth were seen in 39 subjects (5.57%), with mandibular 3 rd molar being the most common impacted tooth. Impacted tooth may cause pain, drifting, or resorption of adjacent teeth. Deficient arch lengths, trauma during development, and cyst around tooth are some of the most common causes for impaction of teeth. Pulp stones were seen in four subjects (0.57%). The etiology for pulp calcification is not known yet, but it is suggested that long-standing irritation like caries, erosion, attrition, and orthodontic treatment may be a causative factor.

Figure 9: Bilateral choroid plexus calcification and single midline pineal/ habenula calcification seen in the axial section

Figure 10: Bilateral tonsilolith seen in coronal section

Figure 11: Radiopacity seen on lingual aspect of mandible suggestive of sialolith

Figure 12: Axial section showing bifid condyle on the right side

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Figure 13: Small radiolucency seen with corticated borders over condyle, suggestive of subchondral cyst

has been revealed.[25] Edds et al. have suggested that presence or absence of pulp stones can be used for screening of cardiovascular diseases.[26] Thus, patients with presence of pulp stones should be referred to medical care physician for complete evaluation of renal and cardiovascular systems. In one case, multiple radiopaque foreign bodies [Figure 15] were seen in the neck region, which were suggestive of either brachytherapy needles, acupuncture needles, or suture needles. An interesting case of hair artifact was seen in one case. Scheifele et al. illustrated three cases of hair artifacts, in which they stated that with soft radiation technique, the thickness of hair can be seen which may resemble microcalcifications or intracranial neoplasms. Anything that is positioned in between central beam and detector will be seen.[27] Thus, radiologist should be familiar with the possibility of hair artifact in head and neck imaging.

Conclusion With increasing use of CBCT and various oral manifestations of systemic disorders, the detection of IFs has been increasing. The radiologist should interpret the entire image, be familiar with the anatomy, its variations and abnormalities which affect the maxillofacial area, and its clinical importance and should refer the patient on time to avoid any consequence. This may also avoid any overzealous referral and unnecessary diagnostic tests and treatment to the patient, in turn benefitting the patient. Figure 14: Well-defined radiolucency with corticated borders seen with apex of 22 suggestive of cyst

Acknowledgment The authors would like to thank Dr. Vinay Hazarey, Dean, Government Dental College and Hospital, Nagpur for providing them the latest technology.

Financial support and sponsorship Nil. Conflicts of interest There are no conflicts of interest.

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Figure 15: 3D reconstructed image showing multiple foreign bodies suggestive of radon seeds for brachytherapy or acupuncture needles or suture needles

Also, aging and dentinogenesis imperfecta have been suggested as the etiology for calcifications in pulp. Pulp stones are a common finding in patients with renal disease and in transplanted renal patients. Association between pulp stones and chronicity of renal diseases

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