June 1999
CHICAGO - The role of radiological imaging in acute sinusitis is controversial because it is usually a clinical diagnosis. The decision to treat patients is often based on symptoms alone rather than radiographic findings, according to William E. Shiels II, DO, chief of radiology and Brian D. Coley, MD, chief of ultrasound, Children's Hospital at Columbus, Ohio.
"In general," said Coley, "there is probably little role for imaging in acute sinus disease," and that is usually the recommendation. Imaging is useful for complications, he said. "Computed tomography (CT) is generally adequate, and magnetic resonance imaging (MRI) can be used for fungal disease or for intracranial extension."
If the clinician decides to image, the question, said Coley, becomes when should imaging be performed. According to the American College of Radiology Appropriateness Criteria, said Coley, there is no role for plain films in children with sinusitis if symptoms are present for less than 10 days or for patients with a headache. "Not everyone is going to agree with this, but this is what is being promoted." The reason for this, he said, is that plain films are insensitive.
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Plain films are not very good for imaging the sinuses, and they generate large false-positive and false-negative rates. When clinically normal children are getting plain films for a reason other than sinusitis and the sinuses happen to be seen, said Coley, a lot of abnormalities are present. Whereas, findings are not often present in children who have chronic or classic symptoms of sinusitis. This is especially true in younger children, in whom upper respiratory infections cause mucoperiosteal thickening, he said.
Crying can thicken sinus linings. The only diagnostic finding on plain films for acute sinusitis is an air-fluid level. A fluid level or mucosal thickening greater than 4 mm, according to Coley, is said by some physicians to have reasonably good sensitivity and specificity for sinusitis (Figure 1).
What is done with a patient who has a little bit of maxillary thickening on the left side and not the right? "This is seen all of the time," Coley said. A patient presenting with this may have some congestion and fever, but not necessarily sinusitis, he said.
CT, according to Coley and Shiels, is the modality of choice for imaging the paranasal sinuses. Preoperative planning for functional endoscopic sinus surgery, and patients refractory to medical therapy, with recurrent sinus symptoms, or with suspected complications of sinusitis are all indications for CT.
---Coronal CT scan of a 2-year-old with
normal sinuses.
A lot of institutions are using limited sinus CT. Clinicians who do not need the information from a full CT for presurgical planning, but want something with more diagnostic power than just a plain film are using these.
"We have a coronal CT that is priced within $50 of plain films," said Coley, and a lot of institutions are starting to offer these. It is a study that is quick, gets patients in and out, and provides the clinician with more information than would a plain film (Figure 2).
"In children we are trying to limit the radiation exposure," said Coley, and we just do coronal CT scans. When determining radiation exposure as part of the decision making process for imaging, consider that the amount of a full sinus CT "is probably only that of two or three sets of plain films."
The preferred method in children, according to Coley is direct coronal scanning, which can be difficult for less cooperative patients. Patients have to lie on their stomach or their head has to be tilted back. "You really have to bend them pretty severely," said Coley. If a patient cannot be sedated, axial imaging is used and then reconstructed coronally.
CT is needed in patients with impaired visual acuity because a surgical emergency may be involved, said Coley. If, however, the patient presented with only orbital cellulitis, proptosis, or alteration of extra ocular movement, "it is probably reasonable to give a trial of IV antibiotics" (Figure 3).
If the patient is no better after 24 hours of antibiotics, said Coley, "get a CT scan and see if there is something that needs to be intervened upon. Otherwise you can probably wait and just treat them."
If imaging a patient early is going to be a factor in the decision to send the child home for therapy, which, said Coley would be more economical, "then go ahead with the CT."
MRI, according to Coley, is occasionally used in sinus imaging, typically in the investigation of complications such as epidural abscess or cavernous sinus thrombosis. It is also useful in investigating suspected fungal disease. Fungus is generally dark on T2-weighted images, as opposed to the usual bright signal of routine sinusitis or trapped secretions.
For more information:
- Shiels WE II, Coley BD. Effective radiological techniques in infectious diseases. Session S235. Presented at the American Academy of Pediatrics. Spring Session. April 17-20. Chicago.
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