Head and Neck Imaging

Maxillary sinus

1. Anatomy

paranasal sinus in the maxilla, also called the antrum. At birth, it is usually present as a small slit-like cavity; during childhood, the pneumatization of the maxilla gradually increases, finally reaching the zygoma. The maxillary sinus is sometimes septated. See also face.

The volume of the maxillary sinuses is usually symmetrical. Uni- or bilateral hypoplasia may be seen; the nasal cavity and orbit are usually somewhat larger on the affected side. In maxillary hypoplasia, sinus pneumatization is incomplete, showing no penetration into the alveolar process and malar eminence (Fig.1). This condition needs to be differentiated from atelectasis of the maxillary sinus.

Other variations of the maxillary sinus include hyperplasia and the extension of a posterior ethmoid cell laterally into the maxilla; this latter condition is known as an ethmomaxillary sinus.

2. Pathology

  • inflammation

    Inflammatory changes are commonly seen in the maxillary sinus (see sinonasal cavities inflammation). In the inferior part of the maxillary sinus, reactive inflammatory changes secondary to dental pathology are common (see also oroantral fistula). Fungal sinusitis is sometimes seen, secondary to migration of dental filling material into the maxillary sinus (see aspergillosis, head and neck (VI:2), Fig. 1)

  • mucocele

    Rarely seen in the maxillary sinus.

  • antrochoanal polyp

  • trauma

    Direct fractures of the anterolateral maxillary wall are common; fractures of the inferior orbital rim are less common, and may be associated with a blow out fracture. Indirect fracture of the maxillary walls is seen, for example, in blow out fracture and Le Fort fractures.

    Tumoral pathology

    Maxillary neoplasms are uncommon, and patients usually present with locally advanced disease. The most frequent malignant tumour is squamous cell carcinoma. Imaging is of paramount importance in determining the extent of local tumour (see sinonasal cavities cancer; Ohngrens line, squamous cell carcinoma head and neck).

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    Fig.1

    Coronal CT image showing hypoplasia of the left maxillary sinus. Note low position of left orbital floor, and lack of pneumatization of the left alveolar process and malar eminence (inner and outer arrow, respectively).
    Maxillary sinus, Fig.1