paranasal

• Paranasal sinuses are invaginations from the nasal cavity, draining into spaces associated with the lateral nasal wall
• Four paranasal sinuses exist: frontal, maxillary, ethmoid, and sphenoid
• Paranasal sinuses are named after the bone in which they are located
• Paranasal sinuses are lined by a respiratory epithelium (pseudostratified columnar epithelium with cilia)
• Morphology of the sinuses is highly variable
• All paranasal sinuses drain into the nasal cavity
• Different sinuses serve as drainage conduits for different regions

Paranasal Sinus Features

• Frontal sinus is within the frontal bone
• Frontal sinuses are a flattened triangular shape, manifesting as a small outpouching at birth
• Frontal sinus receives blood from ophthalmic branches
• Frontal sinus receives nerve supply Opthalmic division of the trigeminal n
• Maxillary sinus is within the maxillary bone
• Maxillary sinuses are pyramidal shape
• Small maxillary sinuses are present at birth
• Maxillary sinus receives blood from maxillary branches.
• Maxillary sinus receives nerve supply Maxillary division of the trigeminal n
• Ethmoid sinus is within the ethmoid bone
• Ethmoid sinuses have 3 to 18 irregularly shaped cells
• Small ethmoid sinuses arepresent at birth
• Ethmoid sinus receives blood from Opthalmic and maxillary branches
• Ethmoid sinus receives nerve supply Opthalmic and maxillary divisions of the trigeminal n
• Sphenoid sinus is within the sphenoid bone
• Sphenoid sinus Cuboid shape
• Sphenoid sinus has no pneumatization at birth

Paranasal Sinus Drainage Summary

• Sphenoethmoidal recess drains sphenoid sinus
• Sphenoethmoidal recess is superior to the superior concha
• Superior meatus drains the posterior ethmoid sinus
• Superior meatus is inferior to the superior concha
• Middle meatus drains anterior ethmoid sinus, middle ethmoid sinus, maxillary sinus, and frontal sinus
• Middle meatus is inferior to the middle concha
• Inferior meatus drains the nasolacrimal duct
• Inferior meatus inferior to the inferior concha
• The 2 frontal sinuses typically are asymmetric
• Frontal sinuses are usually not present at birth, or there is a small outpouching
• Frontal sinus aplasia is common
• Frontal sinuses begin to pneumatize around the 2nd year
• Frontal sinuses are usually well developed by the age of 7 or 8 years
• A prime expansion in size occurs when the 1st deciduous molars erupt and when the permanent molars appear at about age 6
• Adult frontal sinus has Frontal and Orbital extensions
• Frontal extends superiorly into the frontal bone
• Orbital 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 goes to the submandibular lymph nodes
• Nerve supply comes from branches of the ophthalmic division of the trigeminal nerve
• Superior relation to anterior cranial fossa and contents
• Inferior relation to orbit, anterior ethmoidal sinuses, nasal cavity
• Anterior relation to forehead, superciliary arches
• Posterior relation to anterior cranial fossa and contents
• Medial relation to other frontal sinus
• Ostium is in the middle meatus

Frontal Sinus Arterial Supply

• Anterior ethmoid artery originates from the ophthalmic artery
• Anterior ethmoid artery enters the anterior ethmoid foramen with the nerve
• The anterior ethmoid artery supplies the anterior and middle ethmoid air cells and frontal sinus
• Supraorbital artery branches from the ophthalmic artery when crossing the optic nerve
• Supraorbital artery ascends medial to the levator palpebrae superioris and the superior rectus mm.
• Supraorbital artery runs with the supraorbital nerve and is found between the levator palpebrae superioris and the periosteum of the orbit
• Supraorbital artery travels to the supraorbital foramen (notch) and supplies the frontal sinus

Frontal Sinus Nerve Supply

• Supraorbital nerve originates from the ophthalmic division of the trigeminal nerve
• Supraorbital nerve passes between the levator palpebrae superioris and periosteum of the orbit
• Supraorbital nerve continues anteriorly to the supraorbital foramen (notch)
• At the level of the supraorbital margin, it sends nerve supply to the frontal sinus

Ethmoid Sinus Information

• Form within the ethmoid as many individual air cells
• Located between the superior portion of the nasal cavity and the orbit
• Surrounding bone is very thin
• 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
• Most anterior ethmoid sinus is called the agger nasi
• Ethmoidal bulla, which protrudes from the lateral wall of the nasal cavity, represents the largest group of ethmoidal air cells
• Most posterior group of ethmoidal air cells is closely related to the orbit
• Ethmoid air cells may invade any of the other 3 sinuses
• 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
• Superior relation to the anterior cranial fossa and contents, frontal bone with sinus
• Medial relation to nasal cavity
• Lateral relation to the orbit
• Anterior ostium is in the middle meatus (frontonasal duct or ethmoidal infundibulum)
• Middle ostium is in the middle meatus (on or above ethmoid bulla)
• Posterior ostium is in the superior meatus

Ethmoid Sinus Arterial Supply

• Anterior ethmoid artery originates from the ophthalmic artery
• Anterior ethmoid artery enters the anterior ethmoid foramen with the nerve
• Anterior ethmoid artery supplies the anterior and middle ethmoid air cells and sometimes the frontal sinus
• Posterior ethmoid artery passes through the posterior ethmoid foramen to enter the canal
• Posterior ethmoid artery supplies the posterior ethmoid air cells and sphenoid sinus
• Posterior lateral nasal branches originate from the sphenopalatine artery
• Posterior lateral nasal branches anastomose with the ethmoidal arteries to help supply the ethmoid air cells and sphenoid sinus

Ethmoid Sinus Nerve Supply

• Anterior ethmoid nerve originates from the nasociliary nerve
• Anterior ethmoid nerve enters the anterior ethmoid foramen and travels through the canal to enter the anterior cranial fossa
• Anterior ethmoid nerve provides innervation to the anterior and middle ethmoid air cells
• Posterior ethmoid nerve enters the posterior ethmoid foramen to supply the posterior ethmoid air cells
• The sphenoid sinus is also innervated at this location
• Posterior lateral superior nasal nerve originates from the pterygopalatine ganglion
• Posterior lateral superior nasal nerve passes through the sphenopalatine foramen to enter the nasal cavity
• Posterior lateral superior nasal nerve branches supply the posterior ethmoid air cells

Maxillary Sinus Information

• Also referred to as the antrum of Highmore
• Large pyramidal cavity
• Present at birth
• Pneumatization occurs rapidly during the early years
• 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
• Epithelium is often called the Schneiderian membrane in clinical texts
• Floor is close proximity roots of the maxillary molars and premolars
• Not uncommon for a maxillary sinus infection to manifest as tooth pain
• Tends to be more prone to sinus infections because the ostium is located at the superior part of the sinus
• Thin-walled and may be divided by septa
• Primary lymphatic drainage is to the submandibular lymph nodes
• Superior relation orbit, infraorbital nerve and vessels
• Inferior relation to roots of molars and premolars
• Medial relation to nasal cavity
• Lateral and anterior relation to cheek
• Posterior relation to infratemporal fossa, pterygopalatine fossa and contents
• Ostium is in the middle meatus

Maxillary Sinus Arterial Supply

• Anterior superior alveolar artery originates from the maxillary artery
• Arises from the infraorbital artery 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 artery arises from the infraorbital artery after passing through the inferior orbital fissure and into the infraorbital canal
• Descends via the alveolar canals to supply the sinus
• Posterior superior alveolar artery arises from the 3rd part of the maxillary artery before the maxillary Artery enters the pterygopalatine fossa
• Enters the infratemporal surface of the maxilla to supply the sinus

Maxillary Sinus Nerve Supply

• Anterior superior alveolar nerve branches from the infraorbital as it travels in the infraorbital canal
• As it descends to form the superior dental plexus, it innervates part of the maxillary sinus
• Middle superior alveolar nerve branches from the infraorbital as it travels in the infraorbital canal
• As it descends to form the superior dental plexus, it innervates part of the maxillary sinus
• Posterior superior alveolar nerve arises in the pterygopalatine fossa
• Travels laterally through the pterygomaxillary fissure to enter the infratemporal fossa
• Enters the infratemporal surface of the maxilla
• As it descends to form the superior dental plexus, it innervates part of the maxillary sinus

Sphenoid Sinus Information

• Consists of 2 large, irregularly shaped cavities
• Separated by an irregular septum
• Pneumatization begins around 7 to 8 months after birth
• Important in transsphenoidal approaches to the pituitary gland
• Primary lymphatic drainage is to the retropharyngeal lymph nodes
• Superior relation to hypophyseal fossa, pituitary gland, optic chiasm
• Inferior relation to nasopharynx, pterygoid canal
• Medial relation to the other sphenoid bone
• Lateral relation to cavernous sinus, internal carotid artery, cranial nerves III, IV, V1, V2, and VI
• Anterior relation to nasal cavity
• Ostium is in the sphenoethmoidal recess

Sphenoid Sinus Arterial Supply

• Posterior ethmoid artery originates from the ophthalmic artery from the internal carotid A
• Posterior ethmoid artery passes through the posterior ethmoid foramen to enter the canal and supplies the sphenoid sinus and the posterior ethmoid air cells
• Posterior lateral nasal branches originate from the sphenopalatine Artery
• Posterior lateral nasal branches anastomose with the ethmoidal arteries to help supply the sphenoid sinus and the ethmoid air cells

Clinical Correlations Sinusitis

• An inflammation of the membrane of the sinus cavities caused by infections or noninfectious means
• Two types of sinusitis: acute and chronic
• Common clinical manifestations include sinus congestion, discharge, pressure, face pain, headaches

Acute Sinusitis

• Most common form of sinusitis
• Typically caused by a cold
• 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 and Haemophilus 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
• Requires longer-duration medical therapy
• Typically either chronic bacterial sinusitis or chronic noninfectious sinusitis
• Chronic bacterial sinusitis is treated with antibiotics
• Chronic noninfectious sinusitis often is treated with steroids and nasal washes

Sinusitis Locations

• Maxillary: most common location for sinusitis
• Associated with all of the common signs and symptoms
• Also results in tooth pain
• Sphenoid is rare, but in this location can result in problems with the pituitary gland, cavernous sinus syndrome, and meningitis
• Frontal: pain over the forehead and possibly fever
• Rare complications include osteomyelitis
• Ethmoid: potential complications include meningitis and orbital cellulitis