Paranasal Sinuses

Week 10

Anterior Sinus Anatomy Purpose of sinuses

Resonating chamber for voice

Decrease weight of skull

Warm & moisten air

Shock absorbers

Immune system

Lateral Sinus Anatomy

Aerated at birth Maxillary sinuses

Age 6-7 Frontal

/sphenoidal sinuses

Puberty- approx 17-18 yrs Ethmoid

Maxillary Sinuses

Largest sinuses 3.5 cm high 2.5 – 3 cm wide

Within maxilla Above upper teeth

Paired & symmetric

Communicates with middle nasal meatus

Copyright © 2005, Mosby, Inc.

Frontal Sinuses Second largest sinuses

2 – 2.5 cm

Normally: Between tables of

vertical plate in frontal bone

Can extend beyond frontal bone inot the orbital plates

Rarely symmetrical

Number varies (occassionally absent)

Drain into middle nasal meatus Copyright © 2005, Mosby, Inc.

Sphenoid Sinuses

Below sella turcica Extends between

dorsum sellae and post clinoid processes

Can be single or paired Usually no more than

two

Drains into sphenoethmoidal recess of nasal cavity

Copyright © 2005, Mosby, Inc

Ethmoid Sinuses

Within lateral masses of ethmoid bone

Three groups: Anterior, middle &

posterior

Anterior & middle 2-8 cells Drains into middle

nasal meatus

Posterior 2-6 cells Drain into superior

nasal meatusCopyright © 2005, Mosby, Inc

Osteomeatal complex – coronal view

Pathways of communication Frontal, ethmoid

and maxillary

2 key passageways Infundibulum Middle nasal

meatus

Osteomeatal Complex

Paranasal Sinuses Protocols Lateral

PA (Caldwell)

Parietoacanthial (Waters)

Parietoacanthial (Open mouth Waters)

SMV

Technical Considerations Radiographic density is critical

Overpenetration diminishes or obliterates patholgy

Underpenetration can simulate pathology Small focal spot

Clean screens

Perfect film/screen contact

No high contrast

Air Fluid Levels

Pathologic Indications Inflammatory conditions:

Sinusitis• Acute• Chronic

Secondary Osteomyelitis

Sinus Polyps

Trauma

Lateral Projection

Upright or cross table

IPL perp to IR

MSP and IOML parallel to IR

CR horizontal entering ½ - 1” post to outer canthus

Suspend respiration

Lateral Sinuses

Lateral Radiograph

All 4 sinuses Sphenoid of primary

interest

No rotation

SI orbital roofs, mandibular rami

Close beam restriction

Clear air-fluid levels

Caldwell Seated upright

Angled grid 15 degrees: OML & MSP perp Nose & forehead

Vertical grid: Tip of nose on grid

and use sponge OML 15 from CR

CR horizontal to exit nasion

Suspend respiration

Caldwell RadiographFrontal & Anterior ethmoid

No rotation

Petrous ridges symmetric

Petrous ridge in lower 1/3 of orbits

Frontal sinus above frontonasal suture

Anterior ethmoid cells above petrous ridges

Frontal &ethmoid air cells

Air fluid levels

Close beam restriction

Waters for Maxillary sinuses Upright

Chin on IR

MSP &MML perp

OML 37 degrees

Suspend respiration

CR horizontal and exiting acanthion

Waters

Waters Radiograph Petrose just below

maxillary sinuses

No rotation

Orbits & maxillary sinuses symmetric

Close beam restriction

Clear air-fluid levels

Open Mouth Waters for Maxillary / sphenoid sinuses

Upright

Chin on grid

OML 37 degrees

Open mouth

Suspend respiration

CR horizontal and exiting acanthion

Open mouth Waters Radiograph

Petrous ridges below maxillary sinuses

No rotation

Maxillary sinuses

Close beam restriction

Clear air-fluid levels

Sphenoid sinuses through open mouth

SMV for ethmoidal and sphenoidal sinuses

Seated upright

IOML parallel to IR

Backed strip of adhesive tape

Suspend respiration

CR horizontal and perp to IOML through the sella turcica

CR enters MSP ¾” anterior to level of EAM

SMV Sinuses

SMV Radiograph No tilt or rotation

Anterior frontal bone SI over mental protuberance

Mandibular condyles anterior to petrous pyramids

Clear air-fluid levels

Acute Sinusitis

Acute Sinusitis

Mucous Retention Cysts

Tripod Fracture

Chronic Sinusitis

MMT: mucous membrane thickening

OFS: opacified frontal sinus

OES: opacified ethmoid sinus

OMS: opacified maxillary sinus

M: mucocoele