Paranasal Sinuses: Anatomy, Arterial Supply, and Nerve Supply - PDF

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Okay, here is the conversion of the document into a structured markdown format: ### FEATURES OF THE PARANASAL SINUSES | Sinus | Location | Comment | Artery | Nerve | | :-------- | :--------------------------- | :--------------------------------- | :------------------------ | :------------------------------------------ | | Frontal | Within frontal bone | Flattened triangular shape Manifests as a small outpouching at birth | Ophthalmic branches | Ophthalmic division of the trigeminal n. | | Maxillary | Within maxillary bone | Pyramidal shape Small sinus is present at birth | Maxillary branches | Maxillary division of the trigeminal n. | | Ethmoid | Within ethmoid bone | 3 to 18 irregularly shaped cells Small sinus is present at birth | Ophthalmic and maxillary branches | Ophthalmic and maxillary divisions of the trigeminal n. | | Sphenoid | Within sphenoid bone | Cuboid shape No pneumatization at birth | | | ### OVERVIEW AND TOPOGRAPHIC ANATOMY General Information * The paranasal sinuses are invaginations from the nasal cavity that drain into spaces associated with the lateral nasal wall * There are 4 paranasal sinuses: * Frontal * Maxillary * Ethmoid * Sphenoid * Each paranasal sinus is named after the bone in which it is located * Each is lined by a respiratory epithelium (pseudostratified columnar epithelium with cilia) * Morphology of the sinuses is highly variable ### OVERVIEW AND TOPOGRAPHIC ANATOMY Drainage of the Paranasal Sinuses and Associated Structures * All paranasal sinuses drain into the nasal cavity * Different sinuses serve as drainage conduits for different regions ### SUMMARY OF PARANASAL SINUS DRAINAGE | Region Drained | Location | Structure(s) Drained | | :-------------------- | :---------------------------------- | :-------------------------- | | Sphenoethmoidal recess | Superior to the superior concha | Sphenoid sinus | | Superior meatus | Inferior to the superior concha | Posterior ethmoid sinus | | Middle meatus | Inferior to the middle concha | Anterior ethmoid sinus Middle ethmoid sinus Maxillary sinus Frontal sinus | | Inferior meatus | Inferior to the inferior concha | Nasolacrimal duct | ### FRONTAL SINUS General Information * The 2 frontal sinuses typically are asymmetric * Usually not present at birth, or there is a small outpouching * The most common of the paranasal sinuses to undergo aplasia * Is the last paranasal sinus to begin to pneumatize beginning around the 2nd year * Usually well developed by the age of 7 or 8 years * A prime expansion in size occurs when the 1st deciduous molars erupt and another when the permanent molars begin to appear at about age 6 * The adult frontal sinus has 2 extensions: * Frontal which extends superiorly into the frontal bone in the region of the forehead * Orbital which extends posteriorly into the frontal bone over the medial part of the orbit * Drainage varies; may drain in front of, above, or into the ethmoidal infundibulum * Primary lymphatic drainage is to the submandibular lymph nodes * The frontal sinus receives its nerve supply from branches of the ophthalmic division of the trigeminal nerve ### RELATIONS OF SINUS * Superior: anterior cranial fossa and contents * Inferior: orbit, anterior ethmoidal sinuses, nasal cavity * Anterior. forehead, superciliary arches * Posterior. anterior cranial fossa and contents * Medial: other frontal sinus ### LOCATION OF OSTIUM * Middle meatus ### FRONTAL SINUS Arterial Supply | Artery | Source | Course | | :---------------- | :--------------------------------------- | :------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | | Anterior ethmoid | Ophthalmic a. (from the internal carotid a.) | Enters the anterior ethmoid foramen with the nerve to pass through the canal At this location, it supplies the anterior and middle ethmoid air cells and the frontal sinus | | Supraorbital | | Branches from the ophthalmic a. when crossing the optic n. Ascends medial to both the levator palpebrae superioris and the superior rectus mm. At this location, it runs with the supraorbital n. and is | | | | found between the levator palpebrae superioris m. and the periosteum of the orbit Travels to the supraorbital foramen (notch) At the level of the supraorbital margin, it supplies the frontal sinus | ### FRONTAL SINUS Nerve Supply | Nerve | Source | Course | | :----------- | :------------------------------------ | :---------------------------------------------------------------------------------------------------------------------------------- | | Supraorbital | Ophthalmic division of the trigeminal n. | Passes between the levator palpebrae superioris m. and periosteum of the orbit Continues anteriorly to the supraorbital foramen (notch) At the level of the supraorbital margin, it sends nerve supply to the frontal sinus | ### ETHMOID SINUS General Information * Ethmoid sinuses form within the ethmoid as many individual air cells * Anatomically they are located between the superior portion of the nasal cavity and the orbit, and the surrounding bone is very thin * From 3 to 18 total ethmoid air cells may be present on each side * Divided into an anterior and a posterior group, or into anterior, middle, and posterior groups, by different authors * The most anterior ethmoid sinus is called the agger nasi * The ethmoidal bulla, which protrudes from the lateral wall of the nasal cavity, represents the largest group of ethmoidal air cells * The most posterior group of ethmoidal air cells is closely related to the orbit * Ethmoid air cells may invade any of the other 3 sinuses * The middle ethmoid air cells produce the swelling on the lateral wall of the middle meatus called the ethmoid bulla * Primary lymphatic drainage is to the submandibular lymph nodes for the anterior and middle ethmoid sinuses, and the retropharyngeal lymph nodes for the posterior ethmoid sinus ### RELATIONS OF SINUS * Superior: anterior cranial fossa and contents, frontal bone with sinus * Medail: nasal cavity * Lateral: orbit ### LOCATION OF OSTIUM * Anterior: middle meatus (frontonasal duct or ethmoidal infundibulum) * Middle: middle meatus (on or above ethmoid bulla) * Posterior. superior meatus ### ETHMOID SINUS Arterial Supply | Artery | Source | Course | | :----------------------- | :------------------------------------------- | :-------------------------------------------------------------------------------------------------------------------------- | | Anterior ethmoid | Ophthalmic a. (from the internal carotid) | Enters the anterior ethmoid foramen with the nerve to pass though the canal There it supplies the anterior and middle ethmoid air cells and sometimes the frontal sinus | | Posterior ethmoid | | Passes through the posterior ethmoid foramen to enter the canal There it supplies the posterior ethmoid air cells and sphenoid sinus | | Posterior lateral nasal branches | Sphenopalatine a. (from the maxillary a. from the external carotid a.)| Anastomose with the ethmoidal arteries to help supply the ethmoid air cells and sphenoid sinus | ### ETHMOID SINUS Nerve Supply | Nerve | Source | Course | | :------------------------- | :------------------------------------------------------------------------------- | :---------------------- | | Anterior ethmoid | Nasociliary n. on the medial wall of the orbit (from the ophthalmic division | Enters the anterior ethmoid foramen and travels through the canal to enter the anterior cranial fossa | | | of the trigeminal n.) | Descending toward the nasal cavity, it provides innervation to the anterior and middle ethmoid air cells | | Posterior ethmoid | | Enters the posterior ethmoid foramen to supply the posterior ethmoid air cells Also innervates the sphenoid sinus at this location | | Posterior lateral superior nasal| Pterygopalatine ganglion, from the maxillary artery | Travels laterally through the pterygomaxillary fissure to enter the infra temporal fossa | | | | Descending to form dental plexus, it innervates part of the maxillary sinus | ### MAXILLARY SINUS General Information * The maxillary sinus (also referred to as the antrum of Highmore) is a large pyramidal cavity that is present at birth * Pneumatization occurs rapidly during the early years, with the floor of the sinus being superior to the unerupted permanent teeth * As the permanent teeth erupt into the oral cavity, the maxillary sinus pneumatizes into the alveolar bone * The epithelium of the maxillary sinus is often called the Schneiderian membrane in clinical texts * Because the floor of the adult maxillary sinus typically is in close proximity to the roots of the maxillary molars and premolars, it is not uncommon for a maxillary sinus infection to manifest as tooth pain (via referred pain) * The maxillary sinus tends to be more prone to sinus infections because the ostium is located at the superior part of the sinus * The maxillary sinus is thin-walled and may be divided by septa * Primary lymphatic drainage is to the submandibular lymph nodes ### RELATIONS OF SINUS * Superior. orbit, infraorbital nerve and vessels * Inferior. roots of molars and premolars * Medial: nasal cavity * Anterior and Lateral: cheek * Posterior. infratemporal fossa, pterygopalatine fossa and contents ### LOCATION OF OSTIUM * Middle meatus ### MAXILLARY SINUS Arterial Supply | Artery | Source | Course | | :-------------------------- | :----------------------------------- | :------------------------------------------------------------------------------------------------------------------------ | | Anterior superior alveolar | Maxillary a. from the external carotid a. | Arises from the infraorbital a. of the maxillary a. after it passes through the inferior orbital fissure and into the infraorbital canal | | | | Descends via the alveolar canals to supply the sinus | | Middle superior alveolar | | When present, it arises from the infraorbital a. of the maxillary a. after passing through the inferior orbital fissure and into the infraorbital canal Descends via the alveolar canals to supply the sinus | | Posterior superior alveolar | | Arises from the 3rd part of the maxillary a. before the maxillary a. enters the pterygopalatine fossa Enters the infratemporal surface of the maxilla to supply the sinus | ### MAXILLARY SINUS Nerve Supply | Nerve | Source | Course | |----------------------|-------------|------------------------------------------------------------------------------------------------------------| | Anterior superior alveolar | Infraorbital nerve, which is | Branches from the infraorbital nerve as it travels to the infraorbital canal | | | the continuation branch Maxillary division of the trigeminal | As it forms descending superior dental, it innervates part of the maxillary sinus | | Middle superior alveolar | Infraorbital nerve | As it travels in the infraorbital canal it branches, Then Descends | | Posterior superior alveolar | Maxillary division of the trigeminal n.| Ascends in the Pterygoid Palatine Fossa, through infra temporal, enervating some maxillary sinuses | ### SPHENOID SINUS General Information * The sphenoid sinus consists of 2 large, irregularly shaped cavities * Separated by an irregular septum * Pneumatization begins around 7 to 8 months after birth * Sphenoid sinus anatomy is important in transsphenoidal approaches to the pituitary gland * Primary lymphatic drainage is to the retropharyngeal lymph nodes ### RELATIONS OF SINUS * Superior. hypophyseal fossa, pituitary gland, optic chiasm * Inferior. nasopharynx, pterygoid canal * Medial: other sphenoid bone * Lateral: cavernous sinus, internal carotid artery, cranial nerves III, IV, V1, V2, and VI * Anterior. nasal cavity ### LOCATION OF OSTIUM * Sphenoethmoidal recess | Artery | Source | Course | | ----------- | ----------- | ----------- | | Posterior ethmoid | Ophthalmic a. (from the internal carotid a.) | Passes through the posterior ethmoid foramen to enter the canal There it supplies the sphenoid sinus and the posterior ethmoid air cells | | Posterior lateral nasal branches | Sphenopalatine a (from the maxillary) | These branches Anastomose to help arterial ethmoid supply to cell air | ### CLINICAL CORRELATES Sinusitis * Sinusitis, an inflammation of the membrane of the sinus cavities caused by infections (by bacteria or viruses) or non infectious means (such as allergy) * 2 types of sinusitis: acute and chronic * Common clinical manifestations include sinus congestion, discharge, pressure, face pain, headaches ### ACUTE SINUSITIS * The most common form of sinusitis * Typically caused by a cold that results in inflammation of the sinus membranes * Normally resolves in 1 to 2 weeks * Sometimes a secondary bacterial infection may settle in the passageways after a cold; bacteria normally located in the area (*Streptococcus pneumoniae* and *Haemophilus influenzae*) may then begin to increase, producing an acute bacterial sinusitis ### CHRONIC SINUSITIS * An infection of the sinuses that is present for longer than 1 month and requires longer-duration medical therapy * Typically either chronic bacterial sinusitis or chronic non infectious sinusitis * Chronic bacterial sinusitis is treated with antibiotics * Chronic noninfectious sinusitis often is treated with steroids (topical or oral) and nasal washes ### LOCATIONS * Maxillary: the most common location for sinusitis; associated with all of the common signs and symptoms but also results in tooth pain, usually in the molar region * Sphenoid: rare, but in this location can result in problems with the pituitary gland, cavernous sinus syndrome, and meningitis * Frontal: usually associated with pain over the forehead and possibly fever; rare complications include osteomyelitis * Ethmoid: potential complications include meningitis and orbital cellulitis Let me know if you need anything else!