Sinus Cases 21-30

Case I: Large Type 1 Frontal Infundibular Cell

CaseCase 21: II:What are the labeled structures?

Large Type 3 Frontal Infundibular Cell A Type 1 frontal infundibular cell (red arrow) is a single air cell immediately above the agger nasi cell (A). A Type 3 frontal infundibular cell (blue arrow) extends from just above the agger nasi cell into the inferior most aspect of the frontal sinus. For completeness sake, type II infundibular cells are two air cells immediately above the agger nasi cell. These infundibular cells have the same significance as enlarged agger nasi cells in that they can obstruct the frontal recess but may be invisible to the sinus surgeon.

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Case 22: What are the labeled structures?

Onodi Cells Onodi cells are pneumatized projections from the posterior ethmoid sinuses that extend into the optic struts.

Similar cells may arise from the sphenoid sinus, itself. They are located in close relationship to the optic nerve and may partially surround the nerve. Onodi cells are found in 8 to 14% of the population. The presence of Onodi cells increase the chance that the optic nerve injury will be injured from FESS or trauma. In endoscopic surgery, it’s identification is of paramount importance because it complicates surgical approaches to the sphenoid and posterior ethmoid sinuses.

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Case 23: What is the labeled structure?

Uncinate Bulla Pneumatization of the uncinate process may produce an accessory air cell that can cause ostiomeatal complex obstruction.

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Mesiodens

Case 24: What is the most likely diagnosis?

The presence of an extra or supernumerary tooth in the central portion of the maxilla. These teeth can be a part of a syndrome or can be found as an isolated finding. Mesiodens is the most frequently found extra tooth, with a prevalence of up to 2% of the population with a higher frequency in males compared to females. Usually the shape is conical and the mesiodens is smaller than the neighboring incisor. One or two mesiodens may be present. Their name refers to their similar appearance to the C2 vertebral dens on AP radiographs.

DDx: Mesiodens 1.

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Solitary Central Median Maxillary Incisor May be seen in Holoprosencephaly, Hypomelanosis of Ito, Ectodermal Dysplasia, and other syndromes.

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DDx

Case 25: What is the most likely diagnosis?

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DDx: Dentigerous Cyst

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Case 25: What is the most likely diagnosis?

Keratocystic Odontogenic Tumor (KCOT) (Odontogenic Keratocyst) Adenomatoid Odontogenic Tumor Cystic Ameloblastoma Other Odontogenic Tumor (e.g. radicular cyst, primordial cyst)

Dentigerous Cyst A follicular cyst thought to be of developmental origin. The cyst forms around the crown of an unerupted tooth and therefore appears as a pericoronal radiolucency that extends to the cementoenamel junction (red arrows).

The size of the cyst is variable and they are most common in young or middle-aged adults. The third molars and maxillary cuspids are most commonly involved. The accumulation of fluid between the unerupted tooth and the surrounding dental follicle may begin to virtually hollow out the mandible or completely fill the entire maxillary sinus. Dentigerous cysts are epithelial-lined structures and are more defined by their location than by any histological characteristics. Adenomatoid odontogenic tumors are also associated with an unerupted tooth in 75% of cases but in the later case the pericoronal lucency will extend beyond the beyond the cementoenamel junction. One should also be aware that 17% of ameloblastomas arise within a dentigerous cyst.

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DDx

Case 26: What is the most likely diagnosis?

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DDx: Mandibular Mass- Probable Dentigerous Cyst

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Case 26: What is the most likely diagnosis?

Keratocystic Odontogenic Tumor (KCOT) (Odontogenic Keratocyst) Adenomatoid Odontogenic Tumor Cystic Ameloblastoma Other Odontogenic Tumor (e.g. radicular cyst, primordial cyst)

Mandibular Dentigerous Cyst Although the mandible is the most common site for development of dentigerous cyst they are less commonly seen by the radiologist. These lesions are often detected by the local dentist early in life and treated without any imaging. The cyst forms around the crown of an unerupted tooth and therefore appears as a pericoronal radiolucency that extends to the cementoenamel junction (red arrows). The third molars and maxillary cuspids (canines) are most commonly involved. The accumulation of fluid between the unerupted tooth and the surrounding dental follicle may virtually hollow out the mandible so that it predisposes for fractures.

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DDx

Case 27: What is the most likely diagnosis?

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Case 27: What is the most likely diagnosis?

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DDx: Keratocystic Odontogenic Tumor (KCOT) (Odontogenic Keratocyst) 1.

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Case 27: What is the most likely diagnosis?

Dentigerous Cyst Adenomatoid Odontogenic Tumor Cystic Ameloblastoma Other Odontogenic Tumor (e.g. radicular cyst, primordial cyst)

Keratocystic Odontogenic Tumor Keratocystic odontogenic tumors (KCOT) are believed to arise from the dental lamina and associated with impacted teeth. This lesion was previously called odontogenic keratocyst (OKC). The change in nomenclature better reflects the neoplastic potential of this lesion. A small percent of these lesions can undergo malignant transformation to SCCA. Multiple KCOTs are a feature of the basal cell nevus syndrome. The most common maxillary location for OKC is the canine region where they may be mistaken for an periapical inflammatory lesion. KCOTs have a high recurrence rate and are more aggressive than most other jaw cysts. Most commonly seen in patients in their 20s and 30s. KCOTs appear as well-defined radiolucencies, which can be either unilocular or multilocular. Large unilocular KCOTs can be indistinguishable from cystic ameloblastomas.

They may extend into the maxillary sinus (red arrows) and mimic dentigerous cysts. KCOTs are associated with mutations in the autosomal dominant PTCH gene which is part of the Hedgehog signaling pathway.

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DDx

Case 28: What is the most likely diagnosis?

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Case 28: What is the most likely diagnosis?

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Periapical Abscess - Osteomyelitis

Case 28: What is the most likely diagnosis?

A periapical abscess is a complication of tooth decay and carious teeth. Prior surgery or trauma may also be causative. Caries allow bacteria to infect the center (pulp) of the tooth. The infection then spreads through the aperture of the tooth root into the bone at the periapical region. Infection results in a collection of pus which leads to bone demineralization at the tooth apex. A periapical abscess results from endodontal inflammatory disease and is treated by an endodontis who performs a root canal procedure. Left untreated more extensive osteomyelitis may develop in the maxillary or mandibular alveolus. The periodontal abscess, on the other hand, is caused by inflammation and abscess formation between the periodontal ligament and the tooth. These abscesses can be traced downward from the gum line and usually stop short of the apex of the tooth.

Periodontal abscesses are not treated with a root canal but therapy directed at better gum hygiene and intraoral drainage of the abscess along the periodontal ligament.

DDx: Periapical Abscess - Osteomyelitis 1.

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Periodontal Abscess Periapical Granuloma Periodontal Cyst Dentigerous Cyst

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DDx

Case 29: What is the most likely diagnosis?

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Subperiosteal Abscess of the Mandible

Case 29: What is the most likely diagnosis?

A periapical abscess and, less commonly, a periodontal abscess may erode the bony cortex of the alveolus and extend between the cortical bone and the overlying periosteum producing a subperiosteal abscess. They may be initially contained but often fistulalize to the gum line and drain spontaneously. They can be differentiated from other inflammatory lesions by a lack of overlying bone.

DDx: Subperiosteal Abscess of the Mandible 1.

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Periapical Abscess Periodontal Abscess Periodontal Cyst Dentigerous Cyst

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DDx

Bilateral Palatine Sinuses

Case 30: What are the structures indicated?

Palatine sinuses (red arrows) occur when there is pneumatization of the vertical plate of the palatine bone.

These sinuses are posterior to the maxillary sinus and usually have a direct opening into the nasal cavity.

Palatine sinuses are particularly large in ruminants (see ox skeleton below).

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