Presentation of the sinuses by MRI

introduction

The paranasal sinuses are cavities within the facial bones of the skull, which are filled with air, arranged around the nasopharynx and lined with nasal mucosa.

They are divided into the so-called

  • maxillary sinuses
  • sinuses
  • Sphenoid sinus
    and
  • ethmoid sinuses,

where they communicate with each other and with the nasal passages of the nasal cavity.

They serve primarily as resonance chambers when speaking as well as for moistening, cleaning and warming the air.

MRI or CT scan of the paranasal sinuses?

The magnetic resonance imaging (MRI) as an imaging method that works not with harmful X-rays, but with magnetic fields, is particularly well suited for soft tissue imaging and thus also for the imaging of pathological processes (eg sinusitis, tumor formation) of the paranasal sinuses, which among others comes to mucosal involvement.

Computed tomography (CT), as a further method for the representation of the paranasal sinuses can also serve the evaluation of the mucous membranes, but is also particularly suitable for bony imaging (eg to clarify the anatomical conditions in the paranasal sinus system). It works, however, unlike MRI, with X-rays.

Both methods can be applied equally, depending on where the focus is on the question and what indication behind the investigation stands.

You can also find much more information under our topic: MRI or CT - what's the difference?

indications

MRI (and also the CT) is used in the routine diagnostic survey of the paranasal sinuses in the craniofacial skull. In particular, it is possible to assess the inflammatory processes and masses of the nasal mucosa, craniofacial bone changes and the anatomical events of the sinus system.

The most common indications for MRI of the paranasal sinuses is the sinusitis (med sinusitis). Especially in the case of chronic sinusitis, MRI can provide information about the cause of the chronicity, eg by demonstrating drainage prevention, etc.

In addition, the MRI image also serves for imaging prior to planned invasive surgery on the sinuses, such as punctures or endoscopies.

In general, common indications for paranasal sinus MRI are the exclusion of inflammatory or space-occupying processes as well as follow-up in this respect, representations of congenital anatomical variants and malformations, overview shots before surgical procedures and the exclusion of fractures after trauma.

In particular, various differential diagnoses may be an indication for an MRI:

  • this includes inflammation, such as acute or chronic sinusitis (sinusitis)
  • Mucus or pus accumulation in the caves
  • Fractures in the midface or frontobasal (skull base fracture, frontal bone fracture) after trauma
  • benign tumors (eg osteomas, polyps, angiofibromas, retention cysts)
  • malignant tumors (eg carcinomas, sarcomas, metastases)
  • congenital malformations, such as narrowing or occlusion of the posterior nasal opening ( choanal stenosis, atresia), a cleft lip and palate or the Kartagener syndrome

MRI for sinusitis

As part of the diagnosis of a suspected sinusitis, MRI as a follow-up imaging diagnosis usually followed by a physical examination, a smear withdrawal from the nasal secretions and a rhinoscopy (nasal mirror), however, usually only when it comes to the occurrence of complications, an operative Intervention for therapy is planned or there is a chronic course of sinusitis.
Read more on this topic under: sinusitis

Simple, acute, complication-free courses usually do not require further diagnostics by means of an MRI.

Course of the head MRI examination

A special preparation for the MRI examination is usually not necessary, it should only be ensured that about 4 hours before the start of the study no more food and fluid intake takes place.

On the day of the examination, it is advisable to wear loose-fitting clothing without metal parts (eg buttons, zipper, underwired bra, etc.), which can usually be left on during the examination.
The patient is also encouraged to remove all metal objects from the body (eg jewelry, watches, dentures, piercings, hair clips, etc.).

The patient then lies supine on the examination couch, which is then pushed head-first into the MRI unit. If a patient suffers from claustrophobia, a sedative may be administered in advance.
For this purpose, and also for any necessary administration of a contrast agent before or during the examination, an indwelling cannula can be placed in advance in the elbow flexion vein.

During the examination, there are loud knocking sounds that cause the MRI. If this is perceived as unpleasant or disturbing, the patient can be given headphones, played over the music and the staff can also connect with the patient.
In addition, each patient receives an emergency ring in his hand, which can be pressed at any time during the exam, should problems arise.

The MRI scan lasts about 20 minutes in total, in which magnetic field images are used to make cross-sectional images of the head and paranasal sinuses, while keeping the patient as calm as possible.

MRI examination with contrast agent

The administration of a contrast agent allows a more accurate and better presentation and image quality, so it can be used before or during the examination.

The contrast agent, which is added via the vein into the bloodstream, becomes particularly important where the blood circulation is increased, for example also in sinusitis or tumors.

The contrast media for an MRI scan contain no iodine and are usually well tolerated without side effects.


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