Paranasal Sinuses Flashcards
2 purposes of imaging the maxillary sinuses
- To verify the integrity of the sinus walls
- To identify the presence of disease
2 ways sinus walls may be compromised
- Cysts and benign tumors –> displace walls
- Malignant tumors –> destroy walls
9 functions of the maxillary sinus
- Air conditioning (heating and humidification)
- Acting as an air reservoir
- Ventilation
- Aiding in olfaction
- Reductoin in weight of the cranium
- Addition of resonance to the voice
- Protection
- Insulation of the cerebrum and orbits
- Participation in formation of the cranium
How to distinguish a cyst in the posterior maxilla from a normal maxillary sinus
Presence of nutrient canals in the walls of the maxillary sinus (radiolucencies)
When does pneumatization mostly occur?
Following extractions
2 problems with pneumatization
Often limits implant placement
Often combined with resorption
Define pneumatization
The presence or development of air-filled cavities in a bone
Radiographic appearance of hypoplasia of the sinus
The hypoplastic sinus appears more radiopque because there is more bone and less air in the maxilla
Describe sinus septa
Radiopaque lines within the sinus, usually indicating incomplete divisions
Describe hyperostosis (exostosis)
Bony projection attached to the wall of the sinus, appearing as radiopacities within the sinus. Can have the appearance of retained root tips but have no ligament space and no lamina dura
6 types of projections to image the paranasal sinuses
- Periapical radiograph
- Maxillary lateral occlusal
- Panoramic
- Plain films
- CT
- MRI
4 types of plain films to visualize the sinuses
- Waters
- Posteroanterior - Caldwell
- Lateral
- Submentovertex
4 observations when imaging the maxillary sinus using Waters technique in plain film
- Lateral wall
- Medial wall
- Posteroinferior aspect obscured by the teeth
- Roof appears as 2 lines
- Superior = inferior orbital rim
- Inferior = floor of the orbit
Describe what can be seen on plain film with a posteroanterior view
- Midline and posterior facial structures displayed well
- Frontal sinus
- Ethmoid sinus
- Nasal cavity
- Lower half not seen well due to superimposition of the petrous ridge
Describe what can be seen on plain film with a submentovertex view
- Maxillary sinus
- Lateral wall
- Medial wall
- Sphenoid sinus
Describe what can be seen in axial CT images
Anterior wall
Posterior wall
Describe what can be seen in a coronal CT
Roof
Floor
Best use of CT in imaging the paranasal sinuses
Best to demonstrate the bony walls (i.e. bony sclerotic reaction to sinus disease)
Evaluation of the extent of disease
4 uses of MRI in imaging
- Best for imaging soft tissues
- Demonstrates well infiltration of adjacent soft tissues by a malignant tumor
- Differentiates neoplastic tissue from inflammatory tissue
- Differentiates fluids from soft tissue
2 limitations of MRI
- Unable to image bone (no signal)
- Air produces no signal
5 inflammatory changes that may occur in the paranasal sinuses
- Thickened mucosa
- Sinusitis
- Fluid levels
- Polyps
- Mucous retention pseudocyst
3 characteristics of normal sinus mucosa
- 1 mm thick
- Not visible on radiographs
- Bony walls of sinus distinct and clear
When is the sinus mucosa considered abnormally thick?
Greater than 3 mm (can thicken 10 - 15 times)
4 possible causes of thickened mucosa mucositis
- Allergy
- Infectious process
- Periapical disease
- Periodontal disease
Radiographic appearance of thickened mucosa mucositis
Radiopaque band parallel to the floor of the sinus. Usually incidental finding.
4 characteristics of acute sinusitis
- Inflammation
- Often complciated an upper respiratory tract infection
- Blockage of drainage from the ostio-meatal complex
- Lasts more than 7 days
4 symptoms of acute sinusitis
- Pain over the involved sinus, pain referred to the teeth
- Stuffiness
- Purulent discharge
- Fever, chills, malaise
4 radiographic characteristics of acute sinusitis
- Air-fluid level
- Uniform thickening of the mucosa or polyposis all the way to complete sinus opacification
- Accumulation of secretions
- Reduction of the air content producing an increased density of the sinus
Define chronic sinusitis
Sinusitis following several episodes of acute sinusitis
When inflammation persists more than 3 months
4 radiographic characteristics of chronic sinusitis
- Non-specific
- Opacification of the sinus
- Uniform thickening of the mucosa or polyposis all the way to complete sinus opacification
- Sclerosis and thickening of the sinus walls due to chronic inflammation in adjacent mucosa
Define maxillary sinus retension pseudocyst
Obstruction of a duct of a seromucinous gland in the sinus lining
At all ages but more in males in the 3rd decade. Asymptomatic
6 radiographic characteristics of maxillary sinus retention pseudocyst
- Smooth
- Dome shaped
- Homogenous in density, density > to air
- Uncorticated
- Broad base usually
- Rest of sinus is normal
What physiologic structure of the face is often misinterpreted as a lesion when prominent on a panoramic radiograph
Inferior nasal concha
3 characteristics of an anthrolith
- Calcified masses in the sinus
- Could be mucous, bony fragment, foreign body, retained root
- Usually asymptomatic
- Incidental finding
6 radiographic characteristics of anthroliths
- Density: homogenous or heterogenous
- Radiolucent center in some cases
- Periphery smooth or lobulated
- Variation in size
- Variation in shape: round, elliptical
2 radiographic characteristics of retained roots
- A root pushed into the sinus has no ligamen and no lamina dura
- An associated thickened sinus mucosa can be present
Difference between human bone and artificial bone radoigraphically
Artifical bone tends to be more granular
4 benign sinus lesions
- Mucous retention pseudocyst
- Mucocele: destructive, blocked ostium
- Inverted papilloma: from respiratory epithelium
- Osteoma
2 malignant sinus lesions
Squamous cell carcinoma
Lymphoma
6 types of benign alveolar bone lesions encroaching upon the maxillary sinus
- Cysts affecting the maxillary sinus
- Radicular cyst
- Dentigerous cyst
- KCOT
- Benign tumors
- Ameloblastoma
- Myxoma
- Fibrous dysplasia
