X-ray Diagnosis of the Paranasal Sinuses

X-ray diagnosis of the paranasal sinuses (NNH) is an imaging technique commonly used in otolaryngology. It is used for primary routine diagnosis as an overview X-ray of the NNH. As a procedure with comparatively low radiation exposure, conventional radiography is suitable for imaging the entire pneumatized (ventilated) system of the NNH in one image. Statements can be made about inflammatory or expansive processes of the mucosa or the facial skull bones as well as about the extension of the NNH. X-ray diagnosis is particularly suitable as a method of excluding manifest affections of the NNH in the absence of clinical symptoms or before planned invasive procedures such as punctures, endoscopies or operations. However, the information gain from radiography is considered low compared to cross-sectional imaging (CT or MRI). Reductions in radiation patency or shadowing are signs of pathologies (pathological changes), but no conclusions can be drawn about their quality. The less detailed information does not allow diagnosis of the fine and internal structures of the NNH. For example, 1/3 of rhinosinusitis (inflammation of the NNH) is missed on a conventional radiograph compared with a computed tomography scan.

Indications (areas of application)

The diagnostic value of conventional radiography lies in the speed of the procedure resulting in a clear visualization of the NNH with only low radiation exposure. Thus, useful applications are:

  • Exclusion of space-occupying (expansive) processes.
  • Exclusion of fractures (breaks) after trauma.
  • Overview presentation before invasive procedures such as surgery, endoscopies, punctures.
  • Presentation of congenital (congenital) variations and malformations.
  • Detection and follow-up of sinusitis/sinusitis (nowadays more background).

For better detailed imaging and especially when malignant processes are specifically suspected, computed tomography (CT) (bone and mucosa imaging) and magnetic resonance imaging (MRI) (soft tissue imaging) are widely used today. The following are differential diagnoses that can be visualized by conventional radiography of the NNH but are not necessarily indications for radiographic diagnosis:

  1. Inflammatory diseases:
    • Acute sinusitis
    • Chronic sinusitis
    • Mucocele (accumulation of mucus due to drainage obstruction, usually associated with inflammatory swollen mucosa).
    • Pyocele (accumulation of pus)
    • Specific inflammations: Syphilis (lues), tuberculosis, sarcoidosis (systemic disease of connective tissue).
  2. Traumatological changes:
    • Midface fractures (bone fractures of the midface).
    • Frontobasal fractures (form of skull base fracture resulting from force on the forehead and midface).
  3. Benign (benign) tumors
    • Osteoma (benign bone tumor): the NNH represent a very common localization
    • Polyp (protrusions of the mucosa).
    • Juvenile angiofibroma (vascular benign tumor): primarily benign tumor, but locally aggressive growth with origin in the nasopharynx (nasopharynx) and in about 1/3 of cases with intracranial (within the skull) involvement.
    • Retention cyst (encapsulated accumulation of secretions in a gland).
  4. Malignant (malignant) tumors
    • Carcinomas: squamous cell carcinomas (malignant tumor originating from the epithelium of the skin or mucosa), adenoid-cystic carcinomas (malignant tumor originating from glandular tissue and forming an encapsulated structure), adenocarcinomas (malignant tumor originating from glandular tissue) Malignant lymphomas (malignant tumors of the lymphatic tissue).
    • Sarcomas: osteosarcomas (malignant bone tumor), chondrosarcomas (malignant bone tumor that forms cartilage).
    • Metastases (daughter tumors).
    • Other: Basal cell carcinoma (BZK; basal cell carcinoma; semi-malignant/semi-malignant skin tumor (does not form metastases/daughter tumors), secondary in NNH / orbita), eosinophilic granuloma (is the localized course form of histiocytosis X; a disease from the group of histiocytoses), melanoma (malignant skin tumor), salivary gland tumor etc.
  5. Congenital malformations
    • Choanal atresia: occlusion of the choanae (posterior nasal opening), bony (90%) or membranous (10%), often unilateral
    • Choanal stenosis: narrowing of the choans.
    • Dermoid cysts: cyst lined with epidermis and may be mixed with sebum, hair, cartilage, teeth, etc., malignant degeneration possible.
    • Meningocele / encephalocele: Protrusion of the meninges (meningocele) with possibly protrusion of the brain (encephalocele).
    • Cleft lip, jaw and palate (LKG).
    • Kartagener syndrome: triad of situs inversus viscerum (mirror-image arrangement of organs), bronchiectasis (synonym: bronchiectasis; dilatation of bronchi), and aplasia (nonformation) of the NNH
  6. Iatrogenic (physician-induced) changes such as postoperative defects.

Contraindications

X-ray diagnosis of the NNH is a radiation-exposing procedure and should not be used in pregnant women and children whenever possible. It is contraindicated in infants younger than 1 year of age because the NNH are not fully formed and no pathologic significance can be attributed to the shadowing. Transparency reductions can be classified as definitely pathologic only after 3 years of age.

The procedure

A radiographic overview image is a projection radiographic image on which all radiopaque structures are displayed on one plane and superimposed on each other. For better assessment, superimpositions should be avoided whenever possible, which is complicated in the case of the NNH because of its anatomic location. Therefore, special imaging techniques have been developed to direct the central X-ray beam through different planes of the head and oriented to the localization of the different NNH:

Occipitofrontal (o. f.) beam path (according to Caldwell): the patient lies with nose and forehead against the X-ray plate so that the central beam passes through the orbit. The frontal sinus and ethmoidal sinus can be better assessed in this way. Occipitomental (o. m.) beam path (according to Waters): The patient has the mouth wide open and lies with nose and chin against the X-ray plate. The center beam is directed 30° opposite the German horizontal (synonyms: Frankfurt horizontal, Frankfurt horizontal plane; imaginary horizontal line through the lowest point of the orbit and highest point of the external auditory canal). Good visualization of the sinus maxillares (maxillary sinuses) as well as the sinus sphenoidales (sphenoid sinuses) is possible, which project into the open mouth. The os zygomaticum (zygomatic bone), the temporomandibular joints and the nasal pyramid are also well visible. The frontal sinus is noted by obliquity and the ethmoidal sinus is superimposed by the nasal bone. Lateral x-ray: A lateral x-ray can also be taken and provides information about the depth of the maxillary sinus and the frontal sinus. It is also taken in cases of suspected involvement of the sphenoid sinus if the evaluation in the occipitomental beam is limited. As a general rule, superimpositions limit the informative value of NNH overview images. Previous surgery may also lead to additional misinterpretations, as scarring is imaged as nonspecific shadowing. Furthermore, knowledge of age-related development of the NNH is essential for adequate assessment. Pneumatization (ventilation) of the different NNH occurs at different ages in childhood:

  • Sinus ethmoidal: at birth.
  • Frontal sinus: at 3 years of age.
  • Sphenoid sinus: 2. to 4. year of life.
  • Sinus maxillaris: from 4 years of age.

Not infrequently, unilateral or bilateral aplasia (non-formation) of the frontal sinus is observed.