Sinuses - anatomy and routine projections

Paranasal sinuses

Air-filled spaces within the skull and facial bones

Four groups of paranasal sinuses

Frontal, ethmoid, sphenoid, and maxillary

Main functions of the paranasal sinuses

Help resonate the voice, decrease skull weight, warm and moisten inhaled air, absorb shock, and support respiratory defense

Frontal and sphenoid sinus development

Become distinguishable around 6–7 years of age

Paranasal sinus development by adolescence

All four sinus groups are generally distinguishable by the teenage years

Maxillary sinuses

Largest paranasal sinuses, located in the maxilla or cheek region

Maxillary sinus drainage

Communicates with the middle nasal meatus

Maxillary sinus memory clue

MAXillary = MAX-sized sinus

Frontal sinuses

Located posterior to the glabella in the frontal bone

Frontal sinus symmetry

Usually not perfectly symmetrical

Frontal sinus size pattern

Tend to be larger in adult males

Ethmoid sinuses

Air cells located between the orbits

Ethmoid air cell groups

Anterior, middle, and posterior

Sphenoid sinuses

Deep sinuses located inferior to the sella turcica

Sphenoid sinus memory clue

Deep and central at the skull base

Ostiomeatal complex

Drainage pathway connecting several paranasal sinuses with the nasal cavity

Routine sinus projections

Lateral, PA axial Caldwell, and parietoacanthial Waters

Lateral sinus projection

Demonstrates all four sinus groups in profile

PA axial Caldwell for sinuses

Best associated with the frontal and anterior ethmoid sinuses

Caldwell image clue

Petrous ridges are projected into the lower one-third of the orbits

Parietoacanthial Waters method

Best associated with the maxillary sinuses

Waters memory clue

Waters = maxillary sinuses

Open-mouth Waters

Demonstrates the sphenoid sinus through the open mouth

Why sinus radiographs are performed erect

To demonstrate air-fluid levels

Sinus projection shortcut

Caldwell = frontal + ethmoid; Waters = maxillary; open-mouth Waters = sphenoid; lateral = all four groups