Diagnosing The Sinuses

Paranasal Sinus Diagnosis

Diagnosis of the Paranasal sinuses is the ability to appreciate clearly; the Sinuses, their features, and the pathology that affects them. It also enables the complete evaluation of the extent of these pathologies.

The modalities, X-ray, CT, and MRI vary in their diagnostic characteristics of the Paranasal sinuses.

X-RAY:

The Frontal and Sphenoid sinuses become visible on radiographs at age 6 or 7 of an individual, with the Ethmoid sinus being the last to develop. The Paranasal sinuses all become visible on radiographs by late teenage years.

In cases of pathology to the Paranasal sinuses, X-ray is carried out initially and it’s a form screening procedure.

Thus, the need for further diagnostic options for the Paranasal sinuses [in some cases of pathology] is dependent on the result from an X-ray diagnosis of the sinuses.

It demonstrates the bony [although lesser than the CT] and also shows a lesser detail of the soft tissue feature of the sinuses. It does not provide appreciative detail on the extent of soft tissue tumour in the sinuses.

The X-ray also demonstrates air-fluid levels in the Paranasal sinuses, thus the examinations are carried out in an erect position of the patient.

X-ray projections for the Paranasal sinuses includes; Basic skull projections (Occipito-frontal and Lateral), Facial Waters Projections (Occipito-mental [open mouth]), Sub-mento vertical (SMV) projection, Caldwell (PA Axial).

PATHOLOGY TO THE SINUSES

COMPUTED TOMOGRAPHY:

CT scan of the paranasal sinuses is mandatory. It should be performed to diagnose and provide a roadmap for sinus surgery.

It has the advantage over X-ray in the aspect of detailed diagnostic information. It shows good bone detail and soft tissue.

 A CT scan may differentiate inflammatory disease from neoplasm, and bacteria from fungal infections with the different characteristics of muscular and bony appearance of each disease.

CT requires the use very high ionizing radiation (X-ray) in diagnosis of the Paranasal sinuses. Therefore, technical factors are optimized with scanning in the prone position in the coronal plane with thin sections obtained through the anterior paranasal sinuses.

This allows optimal visualization of the osteomeatal unit. The remaining posterior portions of the sinuses are adequately imaged with thicker slices.

MAGNETIC RESONANCE IMAGING:

MRI is not always necessary as it is only required when intracranial or orbital extension is suspected to delineate the interphase with neighbouring structures and to rule out any associated intracranial pathology.

MRI presents with better appreciation of the extent of soft tissue.It may be useful in differentiating among mucoceles, benign tumours, encephaloceles, and internal carotid artery aneurysm.

A contrast called Gadolinium better shows, in the anterior fossa discrimination between cerebral oedema and tumour invasion. It also clearly evaluate sinuses tumour from retained secretion and inflamed mucosa.

Thus, this contrast (Gadolinium) is the most often used contrast in the MRI diagnosis of the Paranasal sinuses.