What is the structured approach to interpreting a computed tomography (CT) scan of the paranasal sinuses (PNS)?

From the Guidelines

A structured approach to interpreting a CT scan of the paranasal sinuses involves systematic evaluation of all sinus groups and surrounding structures, as recommended by the most recent guidelines 1. This approach is crucial for accurate diagnosis and treatment planning, particularly in cases of suspected sinonasal disease or complications. The guidelines emphasize the importance of CT scans in evaluating sinonasal anatomy and detecting potential complications, such as orbital or intracranial involvement.

Key Steps in CT PNS Interpretation

• Begin by assessing the frontal sinuses, followed by the ethmoid air cells (anterior, middle, and posterior), maxillary sinuses, and sphenoid sinuses.
• Examine each sinus for mucosal thickening, air-fluid levels, complete opacification, or bone remodeling, as these findings can indicate sinusitis or other conditions 1.
• Evaluate the ostiomeatal complex, including the middle meatus, uncinate process, and middle turbinate, as this region is critical for sinus drainage and often the primary site of obstruction.
• Assess the nasal cavity for septal deviation, concha bullosa, or polyps, which can contribute to sinus disease or obstruction.
• Examine orbital structures for any extension of sinus disease, such as orbital complications or intracranial involvement, which can be detected with CT scans 1.

Importance of CT Scans in Sinus Disease Evaluation

CT scans are considered the gold standard for imaging evaluation of sinusitis, allowing for accurate depiction of sinus anatomy, soft-tissue changes, and potential associated complications 1. The use of multidetector CT volume isometric imaging enables reconstruction of images in the coronal and sagittal planes, providing a more comprehensive evaluation of the sinuses. Additionally, low-dose CT of the paranasal sinuses has a radiation dose similar to two radiographic views of the paranasal sinuses, making it a relatively safe and effective imaging modality 1.

Limitations and Considerations

While CT scans are highly effective in evaluating sinonasal disease, they may not be superior to clinical symptom score questionnaires in diagnosing chronic sinusitis 1. Furthermore, MRI may be more useful than CT for evaluating intracranial and intraorbital complications, although CT is often the first imaging study ordered 1. It is essential to consider these limitations and use CT scans in conjunction with clinical evaluation and other imaging modalities, as needed, to ensure accurate diagnosis and effective treatment planning.

From the Research

Structured Approach to CT PNS Interpretation

The structured approach to interpreting a computed tomography (CT) scan of the paranasal sinuses (PNS) involves a systematic evaluation of the regional anatomy and identification of anatomic variants and disease extent.

• The preferred radiographic modality for the evaluation of the nasal cavity and paranasal sinuses is computed tomography (CT) 2.
• Coronal CT imaging perpendicular to the bony palate affords the best display of the ostiomeatal channels and facilitates the surgeon's perception of this regional morphology 2.
• A structured approach to CT scans of the paranasal sinuses using a checklist, such as the CLOSE mnemonic, can improve identification of critical anatomic variants in CT scans of the paranasal sinuses 3.

Key Anatomic Structures and Variants

• The examiner must understand and systematically check 14 anatomic structures in the evaluation of the nasal cavity and paranasal sinuses 2.
• Anatomic variations, such as the presence of Onodi cells, can influence the patency of the ostiomeatal channels and must be identified on CT scans 2, 3.
• The relationship between the paranasal sinuses, the orbits, and the intracranial compartment must also be evaluated on CT scans 2.

Disease Evaluation

• CT is superior for detecting bony erosion and hyperdense fungal elements in fungal sinusitis 4.
• Magnetic resonance imaging (MRI) excels in evaluating soft tissue and mucosal involvement in fungal sinusitis 4.
• Chronic paranasal sinusitis can be evaluated on CT scans, which can show mucosal thickening, fluid levels, and total sinus opacification 5.
• Granulomatous and chronic invasive fungal sinusitis can be differentiated from allergic fungal sinusitis based on radiological features, such as homogenous opacity and lack of expansion of sinuses 6.