This article aims to help the practitioner identify structures found in routine three-dimensional imaging studies of the head and neck region and understand their significance and possible need for intervention. The prevalence of advanced imaging in dental practice, especially cone beam computed tomography, highlights the need to recognize and identify various high-density structures that are, in fact, soft tissue calcifications or alterations of normal bony anatomy. The wide range of these findings includes both benign and malignant pathologic entities as well as age-related calcifications and remodeling of normal anatomic structures and dystrophic calcifications.
Key points
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A broader range of commonly calcified structures can be viewed in cone beam computed tomography (CBCT) examinations than in other diagnostic dental imaging studies. Head and neck calcifications are within the soft tissue and hence are better attenuated and visible on CBCT.
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Dental practitioners must recognize subtle alterations of normal bony anatomy and not mistake them as pathology.
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A wide range of calcifications includes mostly benign entities as well as age-related calcifications and remodeling of normal anatomic structures and dystrophic calcifications. Often, these changes are incidental findings on dental imaging studies.
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Occasionally, bony or soft tissue changes can alert the clinician to more sinister disease processes, such as a malignancy. Such changes always have other clinical findings before changes appear on radiographs.
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CBCT seldom is the primary method for detecting diseases affecting the soft tissues of the head and neck.
Introduction
The increased use of advanced imaging in dental practice, in particular, cone beam computed tomography (CBCT), has highlighted the need to recognize head and neck calcifications that are of importance to the dentist. Many of these calcifications are within a soft tissue and hence are better attenuated and visible on CBCT. Alterations of normal bony anatomy are subtle, but the dental practitioner must recognize them so as not to identify them mistakenly as pathology. A wide range of these findings includes mostly benign entities as well as age-related calcifications and remodeling of normal anatomic structures and dystrophic calcifications. These changes often are incidental findings on dental imaging studies. On occasion, there can be bony or soft tissue changes that can alert the clinician to a more sinister disease process, such as a malignancy, but they always have other clinical findings before a radiographic appearance. This article aims to help the practitioner identify the structures found on three-dimensional imaging studies of the head and neck region so that appropriate referral can be made for intervention.
CBCT examinations often include larger sections of the head and neck region than both intraoral radiographs and panoramic imaging. Furthermore, the multiplanar reconstructions permit viewing of small structures at good contrast resolution and adequate spatial resolution for small calcified areas to be viewed. A broader range of commonly calcified structures can be viewed in CBCT examinations than in other diagnostic dental imaging studies. Contrast resolution in CT imaging is defined as “the ability of an imaging system to distinguish minor differences in tissue attenuation and to display them with different gray levels.” A large majority of CBCT examinations are obtained for viewing teeth and alveolar bone, are well attenuated, and are recorded as high-contrast structures relative to other head and neck structures. Soft tissue calcifications tend to be incidental or serendipitous findings and not the main goal of any imaging study in dentistry.
A retrospective study by Yalcin and Ararat reported the prevalence of head and neck region soft tissue calcifications found in CBCT examinations. This study found tonsilloliths to be the most prevalent soft tissue calcification in their study population and concluded that the prevalence of soft tissue calcifications was high.
Khojastepour and colleagues also found a high prevalence of calcifications in their study of CBCT images of the mandibular region. They found the prevalence of calcifications to be higher in males and increasing with age. It also was noted that calcifications were more common in the “posterior region.”
It has been stated that both physiologic and pathologic or ectopic mineralization require the coordinated actions of mineralization inhibitors and propagators. Although some of the visualized calcifications are indicators of a disease process and require timely intervention, other calcified structures tend to be associated with normal aging and require merely identification and differentiation from more sinister entities. This article describes the various soft tissue calcifications, both physiologic and pathologic, and their significance.
Calcified carotid atheromas
Calcified carotid artery atheromas (CCAAs) are noted incidentally on CBCT studies of older patients where the neck was included. These calcifications typically occur at the level of the carotid bifurcation, in the region of cervical vertebrae C3-C4 in most adults. They may be unilateral or bilateral. The shape of the calcified atheromas depends on whether the calcification is atheromatous in origin or due to medial arterial calcinosis (MAC). Calcifications that are of MAC may be circular or arc-shaped in axial reconstructions ( Fig. 1 ). They also can be seen as vertical, linear, high-density structures in coronal reconstructions ( Fig. 2 ). The calcified atheromas are formed by calcification of cholesterol and fat along the intima of the carotid artery. Common risk factors for CCAA include, “diabetes mellitus, hypertension, hyperlipidemia, obesity, and smoking.” , They are considered risk factors and possibly markers for stroke risk. , Mupparapu and Kim conducted a systematic review and concluded that CCAA is not an independent risk factor although associated with risk estimates related to cerebrovascular events. Recently, a meta-analysis conducted by Mupparapu and Nath demonstrated that patients with Doppler ultrasound verification after a diagnosis of CCAA on panoramic radiographs showed slightly higher risk for broadened endpoints, such as stroke, cerebral vascular accident or transient ischemic attack, symptomatic plaque, stenosis greater than 70%, and endarterectomy, as demonstrated via a forest plot of random effects meta-analysis.
Calcified atheromas of the internal carotid arteries (ICAs) also are indicators of stroke risk, especially if they are atherosclerotic variety. These calcifications may be seen at the foramina of the carotid canal lateral to the sella turcica and extending superiorly and posteriorly over the sphenoid sinus ( Fig. 3 ). Often, the shape of the arteries is traced by the calcifications, simplifying their identification ( Fig. 4 ). There are seven arterial segments for ICA as follows: C1 (cervical), C2 (petrous), C3 (lacerum), C4 (cavernous), C5 (clinoid), C6 (ophthalmic), and C7 (communicating). Calcified atheromas are seen rarely in other arteries. Fig. 5 demonstrates a calcified atheroma in the vertebral artery as it passes through the transverse foramen of C3.
Calcifications stemming from bone remodeling
Chronic low-grade inflammatory processes and both normal function and parafunction eventually cause remodeling of bone in the area of the joints. These conditions are referred to as degenerative joint disease or osteoarthritis. Systemic diseases, such as rheumatoid arthritis (RA), ankylosing spondylitis, psoriatic arthritis, and gout, can affect the joint. The temporomandibular joint (TMJ) is a common site for this adaptive remodeling. Osteoarthritic changes to the TMJ include flattening of the anterior articulating surface of the condylar heads and posterior slopes of the articular eminences ( Fig. 6 ), subchondral cyst formation on the affected cortical surfaces, thinning of the cortical bone, osteosclerosis of the medullary bone, and osteophyte formation. Over time, as the articular disk (not seen in CBCT scans) is displaced or worn, the joint space diminishes. Osteophytes may break off and find their way into the joint space ( Fig. 7 ). These changes take place over decades and may be accelerated with parafunctional habits, such as bruxism, as well as the loss of vertical dimension and teeth. A 2019 systematic review found high levels of association of temporomandibular disorder with both RA and osteoarthritis. Tonsillar calcifications are noted on the panoramic radiographs usually in the region of the rami either unilaterally or bilaterally and should be identified as tonsilloliths ( Fig. 8 ).
Osteoarthritic changes also may be seen in the cervical spine. Osteophyte formation typically is seen at the articulation between the dens and the anterior arch of C1 ( Fig. 9 ), as well as on the anterior and posterior edges of the articulating surfaces of the vertebral bodies ( Fig. 10 ). Similar to the degenerative changes to the TMJ, osteosclerosis and subchondral cyst formation also are common indicators of osteoarthritic changes to the cervical spine.
Similar destruction and remodeling of bony structures may be seen in cases of RA. In RA, the changes to the bony structures occur over a much shorter time, may be more extreme, and may affect only one bone in the joint. Another sequela to RA (as well as trauma or other inflammatory process) in the TMJ may be fibrous union and ankylosis of the condylar head to the glenoid fossa , ( Fig. 11 ).
Limbus vertebrae
First described by Schmorl in 1927, limbus vertebra is thought to be formed due to intrabony herniation of disc material during childhood or adolescence, and, on plain radiographs, it appears as a triangular osseous fragment at the corner of the vertebral body mimicking a fracture or an infection. They were found to be disc material that were calcified upon their herniation. Anterior limbus vertebra is most common compared with posterior limbus vertebra. An association was found between α1 chain of type XI collagen (COL11A1) and sporting experience as risk factors for occurrence of limbus vertebrae ( Fig. 12 ).
Dystrophic calcification of soft tissue anatomic structures
Deposition of calcium salts in normal anatomic structures, such as the pineal gland, choroid plexus, anterior and posterior longitudinal ligaments, petroclinoid ligament, falx cerebri, and skin, commonly is seen as high-density areas on CBCT scans exposed for such purposes as implant planning, assessment of bony lesions, and other common diagnostic and treatment planning tasks. These almost always are incidental findings. Knowledge of the general location of these structures aids in the identification of these calcifications. Typically, they are associated with normal aging and often may be visualized at an early age in a percentage of the population. For example, as many as 33% of children may demonstrate pineal calcification ( Fig. 13 ) by 18 years of age. Although rare, pineal gland calcification in children has been associated with conditions, including brain tumors.
