Paranasal Sinuses Week 10
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 Age 6-7 Maxillary sinuses 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 Can be single or paired Extends between dorsum sellae and post clinoid processes 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 Anterior, middle & posterior 2-8 cells Drains into middle nasal meatus Posterior 2-6 cells Drain into superior nasal meatus Copyright © 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 Radiograph Frontal & 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 ðmoid 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
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