Interpreting CTs of the Nose and Sinuses
This tutorial is about how to read a CT scan of the nose and paranasal sinuses. It is for interest only as you will not be ordering a CT scan yourself. Some patients come to the clinic with a CT scan in their hands so it is useful to be able to interpret them a little.
There are some things that you need to know before you start.
1. 40% of people have abnormalities in the sinuses on CT scanning. This means that four out of ten people without any nasal symptoms or problems with their sinuses have an abnormality when scanned.
2. Rhinosinusitis is diagnosed clinically. This means that we use our knowledge of the disease and our physical examination skills to make the diagnosis. We do not use a CT scan.
3. A CT scan is used when we are planning surgery as it gives a good view of the anatomy of the sinuses and shows the surgeon where important structures such as the lamina papyracea and cribriform plate are.
4. Plain X-rays of the sinuses are no help in making a diagnosis in the majority of patients.
A good knowledge of the anatomy of the face, nose and sinuses is essential before trying to understand the CT anatomy. CT scans can be formatted in any plane: axial, coronal and parasagittal. In practice we use the coronal scans most but when we operate on the sinuses all views are useful. Review the tutorial on the physiology and anatomy of the nose before proceeding.
Normal Radiological Anatomy
The following sequence of slides shows normal anatomy in the axial plane and then the coronal plane. Once you understand the radiological appearances of the sinuses we will look at pathology.
Axial CT scan through the forehead
Axial CT scan through the root of the nose
Axial CT scan through the orbit
Axial CT scan through the cheek
Axial CT scan through the palate
Coronal CT through the nose
Coronal CT through frontal Sinuses
Coronal CT through the Cribriform Plate
Coronal CT through Posterior Nose
Coronal CT through the Orbital Apex
Coronal CT through Sphenoid Sinus
Cases with Pathology
Below are examples of CT scans with pathology. It is not usually possible to state what the exact pathology is by looking at a CT scan and clinical examination with histological study give a better understanding. Don’t be tempted to make a diagnosis on the scan alone, always correlate the scan with clinical findings.
The scan shows extensive opacity of the left maxillary sinus and left ethmoids sinus.
The right sided sinuses are not affected. The contents of the left orbit are normal.
The patient was suffering a left sided acute sinusitis.
Here we see opacification in both maxillary and both ethmoids sinuses. The patient had bilateral chronic rhinosinusitis.
The scan shows opacification of the right maxillary sinus and a polyp filling the right nasal cavity.
This was an antro-choanal polyp and the polyp extended backwards into the back of the nose. These polyps can sometimes be seen through the open mouth.
There is a small amount of mucosal swelling in the left maxilla.
The left side of this patient shows opacification throughout the maxilla and ethmoids sinuses. The density of the opacity is different in the maxilla from that in the ethmoids.
This patient had an inverting papilloma in the nose that had obstructed the maxillary drainage and caused a secondary maxillary sinusitis.
You can see that the papilloma is expanding and pushing the septum to the right.
Inverting papillomas have a slight tendency to become malignant. See tutorial 8.
Here we see opacification of the left sphenoid sinus and an adjacent posterior ethmoids cell.
The patient had a sphenoid sinusitis and headache. This case is unusual and we usually see sphenoid disease in cases where all of the sinuses are involved.
This scan shows a number of interesting features.
The right maxilla and ethmoids are full of a soft tissue which has variable opacification. The lamina papyracea is broken down in places and the septum also appear to be eroded.
This is an invasive fungal sinusitis – a rapidly fatal disease if left untreated.
It is commoner in immunocompromised patients.
Management is with aggressive medical and surgical treatment.
This is why we treat unilateral polyps with caution.
The scan shows opacification of the left maxilla and ethmoids and there is a polyp in the nasal cavity on the same side.
Histology found it to be a sinonasal adenocarcinoma.
If you see unilateral polyps always suspect a malignant cause and, especially if there are unilateral symptoms of visual change, numbness in the cheek, loss of upper teeth or palatal ulceration, refer to the ENT department.
Patients may come to see you with CT scans of their sinuses and ask you what is wrong with them. Remember that you cannot make a diagnosis without a full history and an examination.
Also remember that an abnormal scan does not mean an abnormal patient. Up to 40% of us have abnormal CTs of our sinuses yet most of us don’t have sinus disease. Treat the patient, not the scan!
CT is used for planning treatment or in cases where a malignancy is a possibility.
This site is for educational purposes only and as such does not replace clinical judgement. The site contains high-resolution images, although mobile compatible. For optimum viewing, please switch to a HD ready computer.