Question

Discuss the imaging anatomy of nose and paranasal sinuses on NCCT with well-labelled diagrams. Also discuss the common anatomical variations that may be seen on NCCT PNS.

Hint:

NCCT is often preferred over MRI in evaluating the sinuses because it is more effective in visualizing bone structures and detecting calcifications.
Awareness of anatomical variations such as DNS and concha bullosa is essential for accurate interpretation of NCCT PNS scans, especially in pre-surgical assessments.

Answer 1

Step 1: Understanding NCCT Imaging of Nose and Paranasal Sinuses. 
Non-contrast computed tomography (NCCT) of the paranasal sinuses (PNS) is a key imaging technique used to evaluate the anatomical structures of the nose and sinuses. NCCT provides high-resolution images and is especially useful for detecting diseases and abnormalities of the nasal cavity and surrounding paranasal sinuses. This imaging modality is commonly used to assess conditions such as sinusitis, nasal polyps, and other sinus pathologies. NCCT is also essential for evaluating anatomical variations and pre-surgical planning. 
 

Step 2: Anatomical Structures on NCCT PNS. 
The following key anatomical structures can be clearly visualized on NCCT of the PNS: 
1. Nasal Cavity: The nasal cavity appears as a midline structure and is bordered by the nasal septum and the lateral nasal walls. The mucosal lining of the nasal cavity is thin and homogenous. The nasal turbinates, which include the inferior, middle, and superior turbinates, are seen clearly. 
2. Paranasal Sinuses: The paranasal sinuses, including the maxillary, frontal, ethmoidal, and sphenoidal sinuses, are well-delineated. The maxillary sinuses are typically the largest and are located lateral to the nasal cavity. The frontal sinuses are located above the eyes and are seen as air-filled cavities. The ethmoidal sinuses are situated between the eyes and are divided into anterior and posterior groups. The sphenoidal sinuses are located behind the ethmoid sinuses, near the central portion of the skull base. 
3. Nasal Septum and Bony Structures: The nasal septum, composed of cartilage and bone, divides the nasal cavity into two halves. The bony structures of the nasal cavity, such as the maxillary bones, frontal bones, and ethmoidal bony plates, are also clearly visible. 
 

Step 3: Diagram Description. 
A well-labeled diagram should show the nasal cavity, the paranasal sinuses, and the surrounding bony structures. Label the nasal septum, turbinates, and each sinus (maxillary, frontal, ethmoid, and sphenoid). The diagram should highlight key features like the sinus cavities, nasal passages, and mucosal lining. 

Common Anatomical Variations on NCCT PNS. 
 

Step 1: Understanding Common Variations. 
While the NCCT scan provides detailed images of normal anatomical structures, it also helps identify common anatomical variations in the nose and paranasal sinuses. These variations may not be pathological but can have clinical significance, particularly in surgical planning. 
 

Step 2: Common Anatomical Variations. 
The following are common anatomical variations seen on NCCT PNS: 
1. Deviated Nasal Septum (DNS): A deviation of the nasal septum is a frequent variation, where the septum is shifted to one side. This can cause airflow obstruction or contribute to conditions like sinusitis. The deviation is typically visible on NCCT as a shift in the midline of the nasal cavity. 
2. Concha Bullosa: This refers to the pneumatization (air-filled cavity) of the middle turbinate. It appears as an air-filled structure within the middle turbinate on NCCT and can sometimes cause obstruction of the sinus drainage pathways. 
3. Haller's Cell: Haller's cells are ethmoidal air cells located beneath the orbit. They may cause obstruction of the maxillary sinus ostium and contribute to sinusitis. On NCCT, they are seen as small, rounded air pockets near the lower part of the orbit. 
4. Agger Nasi Cell: This is an anterior ethmoidal cell located near the frontal sinus. It can sometimes extend into the frontal sinus or cause obstruction of the sinus drainage pathways. These cells appear as small, well-defined air pockets on NCCT. 
 

Step 3: Conclusion. 
Common anatomical variations on NCCT PNS do not always require treatment but should be taken into account when diagnosing conditions or planning surgical procedures. Understanding these variations helps avoid misinterpretations of the scan.