Intraosseous odontogenic, non-odontogenic, neoplastic, and non-neoplastic pathologies are common in the maxilla and mandible(1,2). Imaging data are required for diagnosis, treatment planning, and follow-up(1). Clinical examination is used first to diagnose intra- and extra-bone jaw lesions, followed by radiological evaluation(3,4). Traditional radiography modalities (orthopantomography, and occlusal and periapical radiography) are primarily used to evaluate maxillofacial lesions, but these methods have disadvantages including magnification errors, distortion, and structural misrepresentation(5). Although computed tomography (CT) and magnetic resonance imaging (MRI) are useful for assessment of jawbone lesions, they have several disadvantages. Low-dose cone-beam CT (CBCT) is particularly suited for evaluation of the maxillofacial region(6). However, both CT and CBCT expose patients to ionizing radiation and yield limited data on lesional contents. MRI does not employ ionizing radiation but is the best-suited modality for imaging of intracranial and soft-tissue lesions. In addition, the equipment is costly, and the screening time is long; moreover, this imaging technique is contraindicated in claustrophobic patients, and in those with certain types of surgical clips, pacemakers, and cochlear implants(7). Ultrasonography (US) is a new and promising diagnostic imaging modality for evaluation of head and neck lesions in lymph nodes and salivary glands, as well as facial bone fractures(8). US reveals the contents of intraosseous jaw lesions(1,2,8–11), and currently plays auxiliary and supportive roles. US enhances our understanding of lesional histology(12). Also, US is safe; no ionizing radiation is used. US is indicated for pregnant and pediatric patients, being simple, painless, repeatable, non-invasive, and economical. US provides useful information on intraosseous jaw lesions(1,2,8–11).
In our previous study on intraosseous US pathologies, we sometimes observed mobile hyperechoic particles in anechoic areas(9) which we termed “snowflakes appearance”, have not been discussed previously. The purpose of this study is to explain and discuss this incidental snowing-like appearance and describe the patient populations that exhibit them.
Preoperative US images of 120 intraosseous jaw lesions from 113 patients admitted to our clinic were reviewed retrospectively. The study group consisted of 43 (38.05%) males and 70 (61.9%) females, with a mean age of 34.9 ± 17.2 years (range: 6–72 years); all patients provided written informed consent. This retrospective study adhered to all relevant principles of the Declaration of Helsinki. The Clinical Research Ethics Committee of the Eskisehir Osmangazi University Faculty of Medicine approved the study (permit no. 13; October 8, 2019). Biopsy data were collected prior to surgery. Lesional diagnoses were histopathologically confirmed.
Two US devices were used to evaluate pathologies. Extra-oral sonograms were obtained in the transverse and longitudinal planes using both an Aplio 300 device (Toshiba Corporation, Tokyo, Japan) fitted with an 8-MHz linear array transducer and a Mindray DC N3 device (Shenzhen, China) fitted with a 4–10-MHz linear array transducer. To ensure standardization of all US examinations, patients sat upright with the sagittal plane perpendicular to the floor and the occlusal plane of the jaw with the localized lesion parallel to the floor.
Mobile hyperechoic particles like snowflakes in anechoic areas were encountered as incidentally in ultrasonographic images. This apperance resembles a snowfall. Because of this, this view was named the ‘‘Snowing-like appearance’’ inspired snowing.
The 120 pathologies included neoplastic, non-neoplastic, odontogenic, and non-odontogenic lesions. Five (4.1%) lesions exhibited snowflakes (Fig. 1 and Video 1): 2 (1.6% of total) (localized maxillar anterior region and histopathological examinations show that microscopically, cyst lined by ciliated pseudostratified columnar epithelium) of 3 incisive canal cysts, 2 (1.6% of total) (localized maxillar anterior region and histopathological examinations show that nonkeratinized, stratified squamous epithelium) of 7 dentigerous cysts, and 1 (localized maxillar anterior-canine-premolar region and histopathological examination shows that microscopically, cyst lined by mature squamous epithelium and parakeratotic keratinaceous debris) (0.8% of total) of 19 odontogenic keratocysts (Tab. 1). All these lesions had cystic content. Characteristics of the lesions with the appearance of snowing-like were summarized Tab. 2.
Intraosseous jaw pathologies | Incisive duct cyst | Dentigerous cyst | Odontogenic keratocyst |
---|---|---|---|
|
3 | 7 | 19 |
|
2 | 2 | 1 |
Lesion localization | Lesion size | Content of the lesion | |
---|---|---|---|
|
Maxilla-anterior | 25.2 × 23.2 × 24.6 mm | Cystic |
|
Maxilla-anterior | 29.8 × 27.6 × 32.4 mm | Cystic |
|
Maxilla-anterior | 32.5 × 23.1 × 23.8 mm | Cystic |
|
Maxilla-anterior | 26.7 × 23.2 × 25.3 mm | Cystic |
|
Maxilla-anterior-canine-premolar | 33.1 × 30.1 × 36.1 mm | Cystic |
Many studies have used US to evaluate intraosseous lesions, principally in terms of lesional contents, margins, and vascularity(1,2,8–11) Lauria
Ferreira
However, we studied only a few lesions; this is a limitation of our work that we will address in future studies. Besides, we used two different linear array transducers for imaging of jaw lesions. Frequency of both probes was relatively low when considering examinations of small parts, even if we get the chance to view of snowing-like appearance in imaging of the intraosseous jaw lesions. Future studies should be eliminated this limitation using high frequency transducers.
The interesting snowflakes incidentally noted on US may be specific for certain pathologies, indicative of epithelial, infective, or keratin remnants. Future studies correlating pathology and radiology findings should aim to clarify when and why snowflakes occur, and which lesions are involved.