Paranasal sinus MRI

The role of imaging modalities in diagnosis

Due to the high natural contrast between bone tissue and air, the primary imaging method for the sinonasal cavity is low-dose CT or cone-beam computed tomography (CBCT). These methods are indicated for functional endoscopic sinus surgery (FESS) planning, medical treatment failure, and acute conditions (orbital cellulitis, mucocele).

MRI acts as a problem-solving tool. The radiologist uses MRI for staging the tumor process (determining its borders, soft tissue infiltration) and ruling out pathologies unrelated to the sinuses themselves. For instance, if a patient develops loss of smell (anosmia) several months after a traumatic brain injury, MRI may reveal a bilateral hyperintense signal on T2-weighted images (T2-WI) in the gyrus rectus.

MRI findings in inflammatory processes

Rhinosinusitis is an extremely common pathology that can be allergic, vasomotor, infectious, iatrogenic, or associated with ciliary disorders.

On MRI (especially on T2-WI), acute sinusitis is clearly visualized due to a hyperintense signal. Characteristic features include fluid levels in the affected sinus (e.g., maxillary) and surrounding hyperintense mucosal thickening.

Nasal polyposis arising against the background of chronic rhinosinusitis causes bilateral sinus opacification and blocks drainage pathways. Contrast-enhanced (gadolinium) T1-weighted images allow assessment of the degree of anterior osteomeatal complex involvement. Important: when polyposis is detected in children, cystic fibrosis must be ruled out, and solitary polyps require special attention to exclude neoplasia.

Differential diagnosis of tumors

Nasal cavity tumors are often diagnosed late because they grow in hollow spaces and mimic chronic sinusitis for a long time. The radiologist's role is to assess the extent of the process.

• Inverted papilloma: causes unilateral obstruction (osteomeatal pattern). On MRI, the tumor has a characteristic "cerebriform" pattern. MRI is also the primary modality for diagnosing recurrences of this tumor post-surgery.
• Mucocele: most commonly occurs in the frontal and ethmoid sinuses. When localized in the sphenoid sinus, coronal T2-WI show an expanded sinus with hyperintense contents. The method confirms the close proximity of the lesion to the maxillary (V2) and optic nerves.
• Complications and infiltration: contrast-enhanced MRI (e.g., fat-suppressed T1-WI) excellently demonstrates the replacement of normal fatty tissue with pathological soft tissue, which is characteristic of orbital apex syndrome (in the context of IgG4-related disease).

Red flags and symptoms of malignancy

Patients with unilateral symptoms require increased clinical alertness. Imaging (MRI and CT) is mandatory in the presence of the following signs:

1. Early symptoms: unilateral facial pain, nasal obstruction, discharge from one half of the nose, recurrent epistaxis.
2. Late symptoms: sensory disturbance in the innervation zone of the second branch of the trigeminal nerve, exophthalmos (proptosis), decreased visual acuity, trismus, and epiphora due to nasolacrimal duct obstruction.
3. Solitary polyp in the upper nasal compartments: requires careful evaluation of the anterior skull base to exclude meningocele or encephalocele.

Class and exam questions

What else to study on this topic

• Anatomical variants of the nasal cavity structure (concha bullosa, paradoxical concha curvature)
• Computed tomography of the osteomeatal complex and mucociliary pathways
• Juvenile angiofibroma: routes of spread and skull base destruction
• Paranasal sinus osteoma: CT findings and indications for surgery
• Intracranial complications of severe fungal sinusitis

Other topics in the Neuroimaging section

Prepared by WhiteCoat Pro faculty in accordance with the medical school curriculum. For educational purposes only.