ANATOMY OF PARANASAL SINUSES

Introduction

Air-containing spaces 4 on each side Clinically:

a. Anterior : Maxillary, frontal, anterior ethmoidal (middle meatus)

b. Posterior: Posterior ethmoidal (superior meatus) and sphenoidal (sphenoethmoidal recess)

Function: Makes skull lighter; Adds resonance

Rudimentary /absent at birth

Enlarges 6-7 years

Development: outpouchings from mucous membrane of lateral wall of nose.

Frontal Sinus

Loc: Btw inner and outer tables of frontal bone; above and deep to supraorbital margin

Asymmetric Bony septum thin & oblique 32x24x16mm Better developed in males.

Opens into Middle meatus

Relations: Ant : Skin over forehead Posterior: Meninges + frontal lobe of

brain Inf: Orbit + contents

Drains into Frontal recess Arterial supply: Supraorbital artery Venous Drainage: Supraorbital and superior

ophthalmic veins Lymphatic: Submandibular nodes Nerve: Supraorbital nerve

Maxillary Sinus

Lies in body of maxilla Largest; first to develop Pyramidal; Base : med towards lat wall of nose;

apex: lat in zygomatic process of maxilla Opens into middle meatus (lower part of hiatus

semilunaris) Relations: Ant. Wall- Formed by facial surface of

maxilla, related to soft tissues of cheek Post. Wall- infratemporal and pterygopalatine

fossa

Medial wall- middle and inferior meatuses. At places uncinate process, ant and post fontanelle and inferior turbinate

Floor-Alveolar and palatine processes of maxilla Roof- Floor of orbit 3.4x2.5x3.5cm Arterial: Facial, infraorbital, greater palatine

arteries Venous: facial vein, pterygoid plexus Lymphatic: Submandibular nodes Nerve: Infraorbital, ant, middle, post alveolar

nerves

Ethmoidal Sinus

Numerous (3-18) Lie within labyrinth of ethmoid bone Relations:

Above: orbital plate of frontal bone Behind: Sphenoidal conchae+ orbital

process of palatine Ant: lacrimal bone

Divided into anterior, middle and posterior groups.

Anterior: 1-11; opens to ant part of hiatus semilunaris; Ant ethmoidal nerve + vessels; lymph – submandibular nodes

Middle: 1-7; opens to middle meatus; Post ethmoidal nerve+ vessels+ orbital branches of pterygopalatine ganglion; SM nodes

Posterior: 1-7; opens to sup meatus; Post ethmoidal nerve + vessels; orbital branches of pterygopalatine ganglion; Retropharyngeal nodes.

Important cells in anterior group- Agger nasi cells, ethmoidal bulla, supraorbital cells, frontoethmoid cells, Haller cells

Important cell in posterior group- Sphenoethmoid or Onodi cell

Sphenoidal Sinus

Within body of sphenoid bone Separated from each by thin bony

septum Asymmetric Opens to shpenoethmoidal recess Relations:

Sup: Optic chiasma+ hypophysis cerebri Lat: int carotid artery+ cavernous sinus

Arterial supply: Post ethmoidal + int carotid

Venous: Pterygoid venous plexus + cavernous sinus

Lymph: Retropharyngeal nodes Nerve: Post ethmoidal nerve+

pterygopalatine ganglion branches.

Development and growth of PNS

Sinus Status at birth

Growth First radiologic evidence

Maxillary At birth; Vol:6-8mL

Rapid growth from birth-3years; from 7-12years.

4-6months after birth.

Ethmoid At birth;Ant grp:5x2x2mmPost grp:5x4x2

Reaches adult size by 12 years.

1 year

Frontal Not present Invades frontal bone at 4 years. Increases until teens. Till 20y.

6 years.

Sphenoid Not present. Reach sella turcica 7years, dorsum sellae late teens, basisphenoid adult

4 years.

Clinical Aspects

Acute Sinusitis acute inflammation of sinus mucosa. Most common:

Maxillary>ethmoid>frontal>sphenoid Can be open/closed type- drainage of the

inflammatory products into nasal cavity. Aetiology:

Exciting causes: Nasal infections, swimming and diving(bacteria, chlorine), trauma, dental infection(Max Sinus; molar/pre-molar tooth extraction)

Predisposing causes: Local: obstruction to sinus ventilation and

drainage (DNS, nasal packing, hypertrophic turbinates, nasal polypi, structural abnormalities of ethmoidal air cells, neoplasm)

Stasis of secretions in nasal cavity: adenoids, choanal atresia, cystic fibrosis

Previous attacks of sinusitis

General Environment:pollution, smoke, dust Poor general health: exanthematous fever,

nutritional deficiency, systemic disorder

Chronic Sinusitis Sinus infection lasting for months/years

Complications of sinusitis Local:Mucocele, mucous retention cyst,

osteomyelitis Orbital: Preseptal inflm edema of lids,

subperiosteak abscess, orbital cellulitis, orbital abscess, superior orbital fissure syndrome

Intra-cranial: Meningitis, extradural abscess, subdural abscess, brain abscess, cavernous sinus thrombosis

Descending infections Focal infection.

Neoplasms of PNS

Benign: Osteomas, fibrous dysplasia, ossifying fibroma, ameloblastoma

Malignant:CommonMostly Maxillary>ethmoid>frontal>sphenoid.80% squamous cell type. Rest

adenocarcinoma, adenoid cystic carcinoma, melanoma, sarcoma.

Thank you