18.1 Benign Tumors of Maxillofacial Region

18.1.1 Epithelial Odontogenic Tumors

18.1.1.1 Ameloblastoma

Ameloblastomas are the most common epithelial odontogenic tumors which have the ability to grow progressively. It may cause huge expansions if not removed entirely and has a tendency for local recurrence. Initial clinical features are slow-growing painless expansions however bigger lesions can cause malocclusion, paresthesia, trismus, facial asymmetries, and even airway obstruction [1–6].

Ameloblastomas have four different subtypes as solid, unicystic, peripheral, and metastasizing ameloblastoma. Unicystic ameloblastomas occur as a single cavity while solid ameloblastomas are multilocular lesions. Peripheral ameloblastomas are extraosseous that occur in soft tissues and metastasizing ameloblastomas are benign odontogenic tumors which have the ability to metastasize [1–6].

Unless cortical destruction or thinning is present, intraosseous cystic lesions and tumors cannot be visualized, since the sonographic waves cannot penetrate the cortical plates. Similar to their radiological appearances in CBCT, MRI, and 2D Imaging techniques, solid ameloblastomas have multilocular appearances (Figs. 18.1, 18.2, and 18.3) at US images and unicystic ameloblastomas have unilocular appearances (Fig. 18.4).

18.1.1.2 Squamous Odontogenic Tumor

Squamous odontogenic tumors (SOT) are extremely rare cases with just <200 cases published. SOTs show terminal squamous differentiations and they have an asymptomatic, slow-growing nature. Most cases appear as unilocular radiolucencies however multilocular SOT cases were also reported. Unlike ameloblastoma, they may not have cortication in their margins. Their characteristic radiological appearance is triangular, with the base of the triangle located at the apical region, radiolucent area which causes root divergence [1, 7].

18.1.1.3 Calcifying Epithelial Odontogenic Tumor

Calcifying epithelial odontogenic tumor (CEOT), also known as Pindborg tumor is a benign epithelial odontogenic tumor which has a characteristic amyloid protein that has a tendency to calcify. They only represent less than 1% of the odontogenic tumors. CEOTs usually grow slowly and asymptomatically until they cause facial asymmetries. 3/4 of the CEOTs are unilocular and generally they have well-defined borders. More than half of the CEOTs are associated with unerupted teeth and 2/3 of CEOTs are mixed lesions with radiopaque focis [1–4, 8]

18.1.1.4 Adenomatoid Odontogenic Tumor

Adenomatoid odontogenic tumors (AOT) are epithelial benign tumors which show duct-like structures histopathologically. They account for less than 5% of odontogenic tumors and they are mostly seen in the first three decades. Less than 5% of the AOTs are extraosseous and 60% of all cases are associated with an unerupted canine (Figs. 18.5 and 18.6). Expansion may not be present since this tumor has a limited growth potential and is considered as a hamartoma by some authorities. Radiographically this lesion may have small foci of radiopacity which is present in 2/3 of cases. They tend to localize at the apically to cementoenamel junction which is a diagnostic feature to differentiate from dentigerous cysts [1–5, 9, 10]

Common sonographic features of adenomatoid odontogenic tumors are (Fig. 18.7):

• Internal Structure: Hypoechoic internal structure is seen with some hyperechoic calcified masses. Minimal or moderate vascularization is seen on Doppler examination. Since they are unilocular lesion a single hyperechoic lining will surround the lesion.

• Peripheral Structure: If no secondary infection is involved, cortical boundaries of the lesion usually appear as clear continuous hyperechoic linings. If destructions at cortical bones are present, disrupted hyperechoic linings can be seen. Acoustic enhancement is usually present.

18.1.2 Mixed Odontogenic Tumors

18.1.2.1 Ameloblastic Fibroma

Ameloblastic fibroma (AF) is a benign mixed tumor and constitute 1.5–6.5% of all odontogenic tumors. 80% of AFs occur in patients younger than 22 years. AFs locate at posteriors of the jaws (82%) and mandible (74%). They are usually painless slow-growing tumors and most of the time they will not cause facial deformity. 80% of AFs are associated with an impacted tooth (Figs. 18.8 and 18.9) [1–3, 11, 12]

18.1.2.2 Primordial Odontogenic Tumor

Primordial odontogenic tumor is a benign mixed tumor and only 7 cases (6 in mandible, 1 in maxilla) were reported. Age range is 3–19 years. All reported cases were well-defined, radiolucent intraosseous lesions which were associated with an unerupted tooth. They are usually asymptomatic until they cause expansion at the cortical plates [1, 2]

18.1.2.3 Odontoma

Odontomas are mixed tumor-like hamartomas composed of soft tissues and dental hard tissues. Odontomas have two variants as compound odontoma and complex odontoma. Odontomas are the most common odontogenic tumors. Complex odontomas are usually found in the mandibular posterior site whereas complex odontomas are usually found in maxillary anterior site. They are usually asymptomatic and generally associated with unerupted teeth. Unless they cause expansion, impaction, malocclusion, diastema, aplasia, and malformation they are generally asymptomatic and detected on routine radiographs. Radiographically, early odontomas appear as a radiolucent lesion with radiopaque calcification areas. As the lesion maturates a well-defined radiopacity which is surrounded by a thin soft tissue lining and corticated bone is observed. Complex odontomas consist of disorganized radiopaque calcified masses (Fig. 18.10) whereas compound odontomas consist of multiple tooth-like radiopaque structures (Fig. 18.11) [1–5, 13, 14].

• Internal Structure: The images are similar to calcified structures and osteomas. Since they are composed of hard tooth-like structures, their internal structure is mostly anechoic. Acoustic shadowing is prominent.

18.1.2.4 Dentinogenic Ghost Cell Tumor

Dentinogenic ghost cell tumor (DGCT) is a benign but locally infiltrating neoplasm of odontogenic epithelium. DGCT is the rarest of all ghost cell cases. Less than 50 cases have been reported. Both intraosseous and extraosseous variants are present and DGCTs are mostly localized at the posterior of the jaws. Extraosseous variants are usually located in the gingiva and alveolar mucosa. DGCTs are mostly unilocular and have a mixed internal structure with well-defined borders. DGCTs with ill-defined borders are also reported as 32%. Almost half of the cases are symptomatic. DGCTs associated with an odontoma is also reported [1, 2, 15]

18.1.3 Mesenchymal Odontogenic Tumors

18.1.3.1 Odontogenic Fibroma

Odontogenic fibroma (OF) is a rare neoplasm which has intraosseous and extraosseous variants. Extraosseous variant is more common. OF occurs almost equally in the mandible and maxilla. Small OFs are generally asymptomatic; however, the bigger OFs can cause facial asymmetries and loosening of teeth. While smaller intraosseous OFs are generally well-defined, unilocular, radiolucencies, it may be also multilocular. Well-defined corticated borders are often present in intraosseous OFs. Extraosseous odontogenic fibromas (EOF) usually develop slowly with an intact mucosal surface and locate at gingiva [1–5, 16, 17]

Common sonographic features of extraosseous odontogenic fibromas are (Fig. 18.12):

• Internal Structure: Hyperechoic internal structure is seen with indistinct calcified hyperechoic contents. No vascularization pattern is expected to be visualized with Doppler examination. They are mostly unilocular.

• Peripheral Structure: If no secondary infection is involved, EOFs generally have smooth borders.

18.1.3.2 Odontogenic Myxoma/Myxofibroma

Odontogenic myxoma is a benign odontogenic neoplasm characterized by stellate and spindle-shaped cells dispersed in an abundant myxoid extracellular matrix. When a greater amount of collagen is evident, the term “odontogenic myxofibroma” may be used. Odontogenic Myxomas (OM) are the third most frequent odontogenic tumors following odontomas and ameloblastomas. OMs are benign odontogenic tumors characterized by spindle-shaped and stellate cells scattered in a myxoid extracellular matrix. Odontogenic myxofibroma term is used when the amount of collagen is greater [1, 2, 18, 19]

OMs are usually located in mandibular molar regions. Maxillary sinus obliteration is common in OMs which is located in the maxilla. Extraosseous form is unique but there are reports especially located in the gingiva. Radiographically, OMs usually have characteristic tennis-racket trabeculations in multilocular lesions; however, they can be unilocular too (Figs. 18.13 and 18.14). Painless expansion is common and occasionally cortical plate perforation may develop. Margins of the OMs are usually a misleading feature in orthopantomographs since the actual borders of OMs are relatively diffuse and defined better in CT/MRI images [1, 3–5, 20]

18.1.3.3 Cementoblastoma

Cementoblastoma (CB) is a benign odontogenic tumor that is associated with the roots of teeth. It is characterized by the formation of cementum-like tissue on a tooth root. CB is a relatively rare tumor, accounting for less than 7% of all odontogenic tumors. Majority of the CBs locate at mandibular premolar-molar site. Pulpitis-like pain with expansion at buccal-lingual/palatal cortical plates are the most common clinical findings. A well-defined radiopaque calcified mass with a thin radiolucent surrounding zone appearance is almost pathognomonic. CBs relatively grow slowly and they can reach quite big sizes if they left untreated [1–5, 21]

18.1.3.4 Cemento-Ossifying Fibroma

See Sect. 18.1.5.1.

18.1.4 Benign Maxillofacial Bone and Cartilage Tumors

18.1.4.1 Chondroma

Chondromas are the benign mesenchymal tumor of hyaline cartilage which arise in the trabecular cavity of mandible/maxilla. If the tumor has malignant features “chondrosarcoma” is the term that should be used. They are very rare in the dentomaxillofacial region. MRI and CT are useful imaging modalities to visualize chondromas and MRI is superior in defining the extension of the tumor. Chondromas are seen as well-defined hypodense tumors with some internal calcifications [1–5]

18.1.4.2 Osteoma

Osteomas are benign tumors composed of mature bone. Their main localization is craniofacial bones. They are more common in mandible (especially mandibular condyle) than in the maxilla (Fig. 18.15). There are two variants of osteomas as surface osteomas and central osteomas. Surface osteomas are usually painless swellings which are located on the cortical surface of the bone (Fig. 18.16). Central osteomas are well-defined calcified hyperdense masses that are mostly smaller than 2 cm in size [1–5, 22, 23].

Common sonographic features of bone and cartilage tumors are (Fig. 18.17):

• Internal Structure: Since they are calcified structures their internal structure is mostly anechoic. Acoustic shadowing is prominent. No vascularization is expected in osteomas; thus, Doppler examination will not reveal any vascularization. They are mostly unilocular

• Peripheral Structure: If no secondary infection is involved, cortical boundaries of the lesion usually appear as well-defined.

18.1.4.3 Melanocytic Neuroectodermal Tumor of Infancy

Melanocytic neuroectodermal tumor of infancy (MNTI) is a rare tumor which is defined by WHO as “locally aggressive, rapidly growing tumour consisting of a biphasic population of small neuroblast-like and larger melanin-producing epithelioid cells.” The most common localization is maxilla which accounts for more than 50% of all MNTI. 90% of MNTIs were reported in infants. Clinically a sessile, black-blue colored lesion which grows rapidly is seen. Radiographically, an aggressive lesion which causes destruction at cortical and trabecular bone is seen [1].

18.1.4.4 Chondroblastoma

Chondroblastoma is a benign chondroid-producing tumor which is composed of chondroblasts. They are very unique at maxillofacial region. Chondroblastomas which are localized in maxillofacial region is mostly seen in temporomandibular joint [1].

18.1.4.5 Chondromyxoid Fibroma

Chondromyxoid fibroma is a rare benign cartilaginous tumor and around 5% of cases are associated with maxillofacial bones [1].

18.1.4.6 Osteoid Osteoma

Osteoid Osteoma is a very rare benign bone-forming tumor with limited growth potential. Most of the cases have diameters less than 2 cm and pain is common. Radiographically a mixed lesion with cortical radiopaque/hyperdense periphery and radiolucent/hypodense internal structure is seen [1, 24].

18.1.4.7 Osteoblastoma

Osteoblastoma is a rare benign bone-forming tumor which has local aggressive features. They are mostly seen in spinal column and around 10% of osteoblastomas are seen in craniofacial bones. Their differential diagnosis with osteoid osteomas is made with lesion’s diameter since osteoblastomas have diameters more than 2 cm while osteoid osteomas are relatively small and less aggressive. Radiographic features of osteoblastomas may resemble a malignant tumor and a predominantly radiolucent/hypodense lesion is seen [1, 25].

18.1.4.8 Desmoplastic Fibroma

Desmoplastic fibromas (DF) are locally aggressive myofibroblastic lesions of the bone. About 86% of the DFs occur in mandible and they are generally localized in the mandibular ramus and mandibular angulus region. Clinically DFs are generally painless slow-growing lesions. DFs are seen as well-defined hypodense lesions without any calcified structure at the internal structure. They may cause destruction at the mandibular angulus site which may have a malignant lesion appearance (Fig. 18.18) [1–5, 26, 27].

Sonographic features of desmoplastic fibromas are (Fig. 18.19):

• Internal Structure: DFs have heterogeneous internal structure, mostly hypoechoic to the surrounding soft tissue and muscles. Minimal or moderate vascularization is seen on Doppler examination.

• Peripheral Structure: DFs do not have corticated capsules; thus, no hyperechoic lining surrounds the lesion. Their periphery has smooth and occasionally lobulated margins.

18.1.5 Fibro-Osseous and Osteochondromatous Lesions

18.1.5.1 Ossifying Fibroma

Ossifying fibromas (OF) are benign fibro-osseous neoplasms affecting both the craniofacial skeleton and jawbones. There are three different variants of OFs as juvenile ossifying fibroma (JOF), juvenile psammomatoid ossifying fibroma (JPOF), and cemento-ossifying fibroma (COF) the ossifying fibroma of odontogenic origin. COF is usually seen in the third and fourth decades; whereas, JOF is usually seen in children and adolescents. JPOF has a relatively wide age range since there are cases which have been reported in 3-month-old patients and a 72-year-old patient. COF is generally seen in the tooth-bearing areas of the jawbones and predominantly in mandibular premolar/molar site (Figs. 18.20 and 18.21). Although OFs which were located outside of the jawbones were reported, they are extremely rare. COFs are generally painless intraosseous expansive lesions which may elevate the floor of the maxillary sinus and expand the basis mandibularis. Initial COF lesions are radiolucent/hypodense and as they progressively maturate they become radiopaque/hyperdense calcified structures [1–5, 28–31].

18.1.5.2 Familial Gigantiform Cementoma

Familial gigantiform cementoma (FGC) is a rare form of fibro-osseous lesion which is only seen in jawbones. They are characterized by the facial deformities caused by multifocal expansive lesions. Sporadic, familial, and autosomal dominant inheritance cases were reported. Radiographically, radiopaque calcifications in a radiolucent lesion with well-defined expansive borders are seen in CT images. Most of the time these lesions are bilateral and bimaxillar [1, 32].

18.1.5.3 Fibrous Dysplasia

Polyostotic and Monostotic FDs usually occur in femur and craniofacial bones but every single bone can have FDs. FDs are more common in maxilla than in the mandible [3–5].

FDs are characterized with painless expansive lesion of the jawbones which may lead to malocclusion. Clinical findings of the advanced and extensive lesions are visual loss, headache, nasal obstruction, and hearing loss. Radiographically, FDs appear radiolucent in early lesions and progressively they become sclerotic. “Ground-glass appearance” is a characteristic radiographical finding for FDs with ill-defined borders and radiopaque internal structure which is indistinct from the surrounding healthy trabecular bone [3–5, 35, 36] (Figs. 18.22 and 18.23).

18.1.5.4 Cemento-Osseous Dysplasia

Cemento-osseous dysplasia (COD) is the most common fibro-osseous lesions of the jaws which is mostly seen in middle-aged women. WHO defines this lesion as “a non-neoplastic fibro-osseous lesion of the tooth-bearing regions of the gnathic bones” [1].

Only florid CODs can cause expansive and pain but periapical CODs and focal CODs are generally asymptomatic and may only be detected on routine radiographic examinations (Figs. 18.24 and 18.25). Anterior teeth that are associated with periapical CODs are vital. Regardless of their location, they initiate as homogenous radiolucent lesions and as they maturate calcified areas in the central portion of the lesion occur. Advanced or maturated lesions can have a completely radiopaque internal structure with a thin radiolucent rim [3–5, 37–39].

18.1.5.5 Osteochondroma

Osteochondromas are rare benign neoplasms and less than 1% of the cases are located in the head and neck region. It is mostly found in the axial skeleton since it generally occurs where endochondral ossification exists. Skull base, zygomatic bone, mandibular coronoid process and mandibular condyle, and maxillary sinus are the most common reported sites in the head and neck region. Common clinical features are malocclusion, pain, asymmetry, and trismus for the lesions that are located in mandible. Radiographically a thin cartilaginous cap and a lobulated bone growth is seen within the cortical or trabecular area of the relevant bone [1, 3–5, 40, 41].

Common sonographic features of fibro-osseous and osteochondromatous lesions are (Fig. 18.26):

• Internal Structure: Since these lesions are known for their calcified features, maturated lesions will have a complete anechoic internal structure with extensive acoustic shadowing.

• Peripheral Structure: These lesions generally have smooth borders; however, no hyperechoic lining is visible surrounding the lesions periphery.

18.1.6 Giant Cell Lesions and Simple Bone Cyst

18.1.6.1 Central Giant Cell Granuloma

Central giant cell granulomas (CGCG) are occasionally aggressive benign osteolytic lesions of the jawbones that account for 10% of the benign tumors in mandible/maxilla. It was previously known as “reparative giant cell granuloma”; however, as the WHO stated, this synonym is obsolete. Majority of CGCG are found in patients younger than 20 years and in females. Most frequent localization of this lesion is mandibular anterior region. Syndromes such as Noonan syndrome and Neurofibromatosis Type I should be considered in cases with multiple CGCG [1, 3–5, 42, 43].

CGCGs are generally asymptomatic but less than half of the CGCG may present pain, cortical perforation, invasion of surrounding tissues, and tooth resorption. Radiographically, expansive, well-defined hypodense/radiolucent lesions can be seen in CBCT images and MRI-CT images can demonstrate the soft tissue involvement of the CGCGs. They are mostly unilocular. PET-CT images are helpful in detecting multicentric lesions [1, 3–5, 42, 43] (Fig. 18.27).

Common sonographic features of central giant cell granulomas are (Fig. 18.28):

• Internal Structure: Hypoechoic/anechoic internal structure is mostly seen. Moderate to advanced vascularization is seen on Doppler examination. They are mostly unilocular but advanced cases can be multilocular.

• Peripheral Structure: If no secondary infection is involved, well-defined cortical boundaries of the lesion usually appear as clear continuous hyperechoic linings. If destructions at cortical bones are present, disrupted hyperechoic linings can be seen. Acoustic enhancement is usually present.

18.1.6.2 Peripheral Giant Cell Granuloma

Peripheral giant cell granulomas (PGCG) are the most common giant cell lesion that affects the oral tissues. They are localized in alveolar mucosa or gingiva. Mechanism of the lesion is described by the WHO as “As a result of local irritation of the muco-periosteum or the coronal part of the periodontal ligament by dental calculus deposits or other types of chronic irritation.” PGCGs are frequently seen in the mandibular gingiva and mandibular edentulous alveolar ridges. Clinically, a purple-blue lesion with an ulcerated or papillomatous surface is seen. CBCT images may reveal a recess at the surface of the adjacent cortical plate (Fig. 18.29) [1, 44, 45]

Common sonographic features of peripheral giant cell granulomas are (Figs. 18.30 and 18.31):

• Internal Structure: Hypoechoic internal structure is mostly seen. An advanced vascularization is frequently seen in Doppler examination. They are mostly unilocular. Elastography will demonstrate a harder tissue than the surrounding soft tissues.

• Peripheral Structure: If no secondary infection is involved, the lesion has usually well-defined boundaries. If perforations on the surface are present, the well-defined periphery structure may disappear. Acoustic enhancement is usually present.

18.1.6.3 Aneurysmal Bone Cyst

WHO defines Aneurysmal Bone Cyst (ABC) as “cystic or multicystic expansile osteolytic neoplasm composed of blood-filled spaces separated by fibrous septa containing osteoclast-type giant cells.” ABCs account for 1.5% of all lesions in the mandible and maxilla; however, they can be seen in the craniofacial complex structures [1].

They are frequently seen in the mandibular posterior region since the ABCs in mandible account for more than 60% of all cases. Clinically, a painful swelling is present which may cause tooth displacement and root resorption. Mandibular ABCs are rather safer since ABCs in maxilla can affect the orbits, paranasal sinuses, and nasal fossa. Radiographically, CBCT reveals a well-defined, unilocular or multilocular hypodense lesion with an expansion or a perforation in the cortical plates. Extension of ABCs may not be visible with CBCT in cases with cortical perforation; thus, CT and MRI should be performed (Figs. 18.32 and 18.33) [1, 3–5, 46, 47].

MRI reveals the fluid-fluid level in ABCs; however, this imaging feature is not unique for the ABCs and can be found in the other giant cell tumors, chondroblastoma, and telangiectatic osteosarcomas.

Common sonographic features of aneurysmal bone cysts are (Fig. 18.34):

• Internal Structure: A heterogeneous hyperechoic internal structure with or without a fluid-fluid level is seen. Doppler imaging may reveal mild vascularity.

• Peripheral Structure: Cases without perforations or destruction reveal well-defined hyperechoic borders; however, cases with cortical destruction reveal ill-defined borders with an extension of the ABC to the adjacent soft tissue.

18.1.6.4 Simple Bone Cyst

Simple Bone Cyst (SBC), also known as traumatic bone cyst and hemorrhagic bone cyst, is an intraosseous cavity without any epithelial surroundings. SBCs may have hematic fluid inside their cavity and also they may represent empty cavities. SBCs are frequently seen in the metaphysis of long bones and the most common localization in the head and neck region is the mandibular body [1, 3–5, 48, 49].

Most of the SBCs are asymptomatic; however, some cases with a pathological fracture were also reported.

Radiographically, OPG and CBCT reveal well-defined, generally unilocular, radiolucent/hypodense lesions which extend between the roots at the relevant area. Root resorption or tooth displacement is not seen (Figs. 18.35 and 18.36) [1, 3–5, 48, 49].

Common sonographic features of simple bone cyst are (Fig. 18.37):

• Internal Structure: Homogeneous anechoic internal structure is generally seen without any hyperechoic focis.

• Peripheral Structure: Well-defined oval or round borders are seen. SBCs with hematic fluid may have an acoustic enhancement; however, SBCs with empty cavities may not have an acoustic enhancement.

18.1.6.5 Cherubism

Cherubism is an autosomal dominant inherited genetic condition that affects mandible and maxilla. They are usually seen before age of 6 years and followed by complete or partial regression after. Clinically, slow-growing, bilateral, symmetrical expansive lesions which are located at the posterior sites of the jaw is seen. These cyst-like giant cell lesions cause retraction of the facial skin, which causes the characteristic appearance which is falsely known as cherubs. The appearance is actually similar to the “putti” facial appearance [1, 3–5, 50, 51].

Radiographically, bilateral symmetrical expansive lesions are seen starting from the tuberosity of maxilla and first molar region of the mandible. These expansive lesions are multilocular radiolucent/hypodense lesions which may cause thinning at cortical plates, malocclusion, tooth displacement, and loosening of the teeth. As the giant cell lesions have regression, lytic cherubism lesions are replaced by sclerotic new bone [3–5, 50, 51]. (Figs. 18.38, 18.39, and 18.40).

18.1.7 Hematolymphoid Tumors

18.1.7.1 Solitary Plasmacytoma of Bone (SPB)

Solitary plasmacytoma of bone (SPB) is the only tumor that is classified under the “hematolymphoid tumors” section. WHO defines SPBs as “a localized proliferation of monoclonal plasma cells involving bone.” SPBs are rare and they only represent around 4% of plasma cell neoplasms. They are usually seen in the axial skeleton; however, rare cases are reported in the head and neck region. SPBs in the head and neck region are more common in the mandible than in the maxilla and they are usually located in the mandibular body, mandibular ramus, and mandibular angulus. Those areas were more affected since they are marrow rich areas in the head and neck region [1, 3, 52].

Clinically, hemorrhage and expansion of the jaw are seen with the pain in the jaws and teeth. Some cases with multiple teeth migration were also reported. Radiographically, a well-defined, multilocular hypodense/radiolucent lesion with or without septas is seen mostly in the mandible. The anteroposterior extension of the lesion may resemble an odontogenic keratocyst which should be included in the differential diagnosis [1].

Common sonographic features of the solitary plasmacytoma of bone are (Fig. 18.41):

• Internal Structure: A mix (Hypo and Hyperechoic internal structure) usually be seen. Moderate vascularization is seen on Doppler examination. The lesions may appear multilocular with septas. In the case of internal bony septas, hyperechoic linings can be present.

• Peripheral Structure: Cortical boundaries of the lesion usually appear as clear continuous hyperechoic linings. If destructions at cortical bones are present, a disrupted hyperechoic linings can be seen.

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