How To Read CT Sinus Scans Like An Expert





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Published on Sep 20, 2007


Dr Kevin Soh explains the nose and sinus anatomy using slices from a CT sinus scan.

3 Mount Elizabeth, #07-02, Mount Elizabeth Medical Centre, Singapore 228510


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0:27 – Cut number 1: CT scans are read the same way you would look at someone’s face.

1:11 – Cut number 2: The frontal bone. The nasal bone and pyriform aperture.

1:33 – Cut number 3: The right and left frontal sinuses, separated by the inter-sinus septum. The frontal sinuses are air spaces within the frontal bone. The nasal septum is cartilaginous in front, but bony behind. In this cut, we see a little bit of the bony nasal septum. In this cut, most of the nasal septum is still made up of cartilage. In later cuts, we will see more of the bony nasal septum. We also see the front end of the inferior turbinates.

2:26 – Cut number 4: Notice that the frontal sinus becomes smaller with this cut. The maxillary sinus is an air space within the maxillary bone. The front part of the anterior ethmoid sinus. The lacrimal sac which drains tears from the eye into the nose. The inferior turbinate. The inferior turbinate is made up of bone and erectile tissue that can expand and contract. The nasal septum is now more bony. The upper bony segment of the nasal septum is called the perpendicular plate of ethmoid (or PPE). The lower bony segment is the vomerine crest. Later, both the perpendicular plate of ethmoid and vomerine crest will meet and join together.

3:13 – Cut number 5: The frontal sinus is no longer visible. We now see the frontal lobe of the brain. We start to see the front end of the middle turbinate. The anterior ethmoid sinus. The maxillary sinus. The middle and inferior turbinates.

3:38 – Cut number 7: The olfactory area (which is important for smell and taste) comes into view. Because this area is narrow, it is also called the olfactory cleft. Nerves from the olfactory cleft pass upwards to enter the brain. The bone here is very thin. The bone is perforated by small branches of the olfactory nerve. Since it has a perforated and sieve-like appearance, it is called the cribriform plate. The roof of the ethmoid sinus is very thin. Care must be taken during sinus surgery not to damage this thin bone. The bone between the eye and ethmoid sinus is also very thin. It is called the lamina papyracea which means “paper thin layer”. The middle turbinate is attached to the roof of the nose, and therefore, to very thin bone. It is very easy to fracture this thin roof during middle turbinate surgery. The surgeon must avoid pulling on the middle turbinate too hard! The maxillary sinus opening (ostium) is very narrow. This narrowing is caused by the proximity between the ethmoid sinus and the uncinate process. Uncinate means “hook shape”. The ostium often becomes blocked, resulting in poor drainage and sinusitis. Sinus surgery widens this opening by removing the anterior ethmoid sinus and uncinate process. Infra-orbital nerve which receives sensory information from the skin of the cheek. Care must be taken to avoid injury to this nerve during maxillary sinus surgery. The anterior ethmoid sinus is compartmentalized into many cavities by thin partitions or septae. The ethmoid sinus is so named because it looks like a sieve. Ethmoid means “sieve”. For this reason, the ethmoid sinus is also called the ethmoid labyrinth.

5:21 – Cut number 9: This is where the anterior ethmoid sinus ends, and the posterior ethmoid sinus begins. The middle turbinate no longer attaches to the roof of the nose. Instead, it is now attached to the side wall of the nasal cavity. This marks the separation between the anterior and posterior ethmoid sinuses. The upper teeth is separated from the maxillary sinus by a thin plate of bone. If this bone is breached or dehiscent, there is risk of sinusitis of dental origin.

6:02 – Cut number 10: In this cut, the sphenoid sinus is seen. Pituitary fossa and pituitary gland. The sphenoid sinus is an air space within the sphenoid bone. The sphenoid sinus is so named because it has the shape of a butterfly. The optic nerve. The lateral and medial pterygoid plate. The ramus, coronoid process, and angle of mandible. No more turbinates are seen. The last remaining bit of nasal septum is seen.

6:46 – Cut number 12: We leave the nasal cavity, and enter the postnasal space (or nasopharynx). “Nose cancer”, or more appropriately called nasopharyngeal carcinoma (NPC), originates from the nasopharynx. Since there is no separation by the nasal septum, there is only one common chamber. The Eustachian tube opening.

7:04 - Quiz


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