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Anatomy of Paranasal Sinuses

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Meghna Rai

The paranasal sinuses are air spaces that develop within the bones of the skull. There are four pairs - maxillary, frontal, ethmoid, and sphenoid. They are rudimentary at birth and enlarge throughout childhood. The maxillary sinus is the largest and the first to develop. Acute sinusitis is usually caused by bacterial infections spreading from the nose. Chronic sinusitis lasts for months or years. Complications can include infections of nearby structures like the orbit or brain. Neoplasms of the sinuses can also occur but are usually benign growths like osteomas.

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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
Anatomy of Paranasal Sinuses
Anatomy of Paranasal Sinuses
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
Anatomy of Paranasal Sinuses
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.
Anatomy of Paranasal Sinuses
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.
Anatomy of Paranasal Sinuses
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:5x2x2mm Post 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 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:Common Mostly Maxillary>ethmoid>frontal>sphenoid. 80% squamous cell type. Rest adenocarcinoma, adenoid cystic carcinoma, melanoma, sarcoma.
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Anatomy of Paranasal Sinuses

  • 2. 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
  • 5. Rudimentary /absent at birth Enlarges 6-7 years Development: outpouchings from mucous membrane of lateral wall of nose.
  • 6. 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.
  • 7. 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
  • 9. 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
  • 10. 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
  • 11. 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.
  • 12. 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.
  • 14. 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
  • 15. 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
  • 16. Arterial supply: Post ethmoidal + int carotid Venous: Pterygoid venous plexus + cavernous sinus Lymph: Retropharyngeal nodes Nerve: Post ethmoidal nerve+ pterygopalatine ganglion branches.
  • 18. 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:5x2x2mm Post 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 4 years.
  • 19. 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)
  • 20. 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
  • 21. 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.
  • 22. Neoplasms of PNS Benign: Osteomas, fibrous dysplasia, ossifying fibroma, ameloblastoma Malignant:Common Mostly Maxillary>ethmoid>frontal>sphenoid. 80% squamous cell type. Rest adenocarcinoma, adenoid cystic carcinoma, melanoma, sarcoma.