ClinicalRadiology (1991) 43, 252-254

Incidental Paranasal Sinus Abnormalities on M R I of the Brain F. G. MOSER, D. P A N U S H , J. S. RUBIN*, R. M. H O N I G S B E R G * , S. S P R A Y R E G E N and S. B. E I S I G t

Departments of Radiology *Otolaryngology and ~fOral and Maxillofacial Surgery, Montefiore Medical Center, Albert Einstein College of Medicine, Bronx, New York, USA T2-weighted magnetic resonance imaging (MRI) presents paranasal sinus pathology with remarkable clarity. However, it has yet to be demonstrated that all MRI findings represent true pathology and not minor or incidental findings of no consequence. In an effort to resolve this question, we have analysed retrospectively 263 consecutive T2weighted M R I examinations of the head performed for indications not associated with possible sinus pathology. We examined these studies for abnormally increased signal in the paranasal sinuses and the sites of involvement. Mucoperiosteal thickening, mucus retention cysts, air-fluid levels or total sinus opacification were recorded. Of the 263 studies examined, 65 (24.7%) demonstrated abnormalities in the paranasal sinuses. We conclude that because of its great sensitivity M R I will often detect abnormafities in the paranasal sinuses which are unrelated to the patients' presenting problems. Moser, F.G., Panush, D., Rubin, J_S., Honigsberg, R.M., Sprayregen, S_ & Eisig, S.B. (1991). Clinical Radiology 43, 252-254. Incidental Paranasal Sinus Abnormalities on M R I of the Brain

Traditionally, plain films have been used to examine the paranasal sinuses radiographically and are still considered to be very accurate (Kuhn, 1986). The newer modalities of CT and M R I are more sensitive and yield more detailed information than plain films (Mafee et al., 1986; Moore et al., 1986; Lloyd et al., 1987; Weber and Mikulis, 1987). M R I clearly demonstrates pathology in the paranasal sinuses_ On T2-weighted M R I most abnormalities within the paranasal sinuses show high signal intensity (Kuhn, 1986). The question remains as to whether the high signal seen commonly within the paranasal sinuses on T2weighted M R I ifidicates an abnormality. This study was performed to evaluate paranasal sinus M R I findings in patients without known sinus disease and to assess the possible significance of those findings. SUBJECT AND METHOD Two hundred and sixty-three consecutive magnetic resonance brain examinations performed for symptoms and diseases not related to the paranasal sinuses were reviewed retrospectively. For each patient the heavily T2weighted pulse sequence was examined. These were performed either as a single echo heavily T2-weighted study (TE = 80, T R = 3000) or as the second echo of a double echo acquisition ( T E = 4 5 - 9 0 , TR--2500). The studies were performed on a 0.6 Tesla super-conducting M R I unit (Technicare, USA). All studies were performed in the standard axial plane. When coronal or sagittal studies were available, they were also examined. The findings were sorted according to the anatomic location of the abnormality, and the characteristic of the abnormality. The abnormalities recorded were mucoperiosteal thickening, retention cysts or polyps, air-fluid Correspondence to: Dr F. G. Moser, Chief of Neuroradiology, Department of Radiology, Lenox Hill Hospital, 100 East 77th Street New York, New York 10021, USA. Presented at the XI International Congress of Head and Neck Radiology in Uppsala, Sweden, June 1988.

levels and total sinus opacification (Fig. 1). Inflammatory nasal abnormalities were not considered. Unilateral or bilateral involvement was noted. No attempt was made to correlate symptoms with M R I findings. The age distribution of the patients examined is presented in Fig. 2.

RESULTS N o r m a l sinuses with no evidence of high signal within them were seen in 75.3% of the 263 studies examined. Areas of high signal classified as abnormal were detected in 65 (24.7%) of the patients. The results are summarized in Table 1. Of the 65 patients with areas of high signal within their sinuses, 31 had abnormalities in more than one sinus. O f the abnormal cases 23.7% showed bilateral involvement. Mucoperiosteal thickening was the most c o m m o n finding and was demonstrated in 40 patients (89 sinuses). This was seen as an isolated finding in only seven patients. Retention cysts were seen in 33 patients (12.5% of the total number of the patients examined)_ All but three of the retention cysts were in the maxillary sinus. Air-fluid levels were seen in seven patients and total sinus opacification was seen in three patients.

DISCUSSION Using CT, the incidence of abnormalities of the paranasal sinuses has been shown to be 18% in an asymptomatic paediatric population (Diament et al., 1987) and 14.9% in asymptomatic patients over the age of 12 years (Glasier et al., 1986). A review of more than 2000 panoramic dental radiograph~ demonstrated that 2.6% of patients have incidental maxillary sinus retention cysts (Ruprecht et aI., 1986). A recent study of primarily symptomatic patients performed for the specific purpose of examining the paranasal sinuses with CT scans showed sinus abnormalities in 42.5% of patients (Havas et al., 1988). CT and M R I are very sensitive in detecting paranasal sinus disease. CT scans of the brain are usually performed

INCIDENTAL PARANASAL SINUS ABNORMALITIES ON MRI OF THE BRAIN

(a)

(c)

253

(b)

(d)

Fig. I - Examples of incidental abnormalities in the paranasal sinuses. (a) Total opacification of the maxillary sinuses. (b) Air-fluid level in the left maxillary sinus. (c) Retention cyst of the left maxillary sinus. (d) Mucoperiosteal thickening of the sphenoid and ethmoid sinuses.

254

CLINICAL RADIOLOGY

Table 1 - Tabulation of abnormal findings

Right maxillary Left maxillary Bilateral maxillary Right ethmoid Left ethmoid Bilateral ethmoid

Total opacification

Air-fluid level

Retention cyst

Mucoperiosteal thickening

2 2 1

4 5 1

19 14 4

14 14 10 23 27 18

1 3 1 1

1 2

l I 1 5 5 2

Right sphenoid Left sphenoid Bilateral sphenoid Right frontal Left frontal Bilateral frontal

1

Incidence of findings

1.1%

2,7%

12.5%

15_2%

Number of patients with abnormal sinuses = 65. Total number of patients = 263.

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REFERENCES

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is exceedingly sensitive in the detection of these findings. Had dedicated paranasal sinus examinations been performed using thin sections and different planes, we believe more abnormalities would have been seen. We recommend that MRI should not be used to screen for paranasal sinus disease in view of its high sensitivity and cost. CT and MRI should be reserved for specific clinical indications in patients with known or suspected paranasal sinus disease.

41-51

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Age

Fig. 2 - Age distribution•

in a superior orbito-meatal plane which does not demonstrate the paranasal sinuses. M R I of the brain is frequently performed in an imaging plane perpendicular to the long axis of the magnet resulting in the inclusion of the paranasal sinuses in the images. The extreme sensitivity of MRI in evaluating the paranasal sinuses is due to a combination of the perpendicular plane used for imaging, the high signal intensity on T2-weighted images of almost all sinus abnormalities, and the absence of signal from the cortical bone surrounding the paranasal sinuses and from air within the sinuses. It becomes important to distinguish 'normal changes' such as an asymptomatic retention cyst or slightly thickened sinus mucosa from true pathology. Of the patients in our survey 24.7% demonstrated changes which would often be interpreted as abnormalities in symptomatic patients. For the reasons stated above, MRI

Diament, M, Senac, M, Gilsanz, V, Baker, S, Gillespie, T & Larsson, S (1987). Prevalence of incidental paranasal sinuses opacification in pediatric patients: a CT study. Journal of Computer Assisted Tomography, 11,426-431. Glasier, C, Ascher, D & Williams, K (1986). Incidental paranasal sinus abnormalities on CT of children: clinical corrrelation. American Journal of Neuroradiology, 7, 861 864. Havas, T, Motbey, J & Gullane, P, (1988). Prevalence of incidental abnormalities on computed tomographic scans of the paranasal sinuses. Archives of Otolarygnology and Head and Neck Surgery, 114, 856-859_ Kuhn, J (1986). Imaging of the paranasal sinuses: current status. Journal of Allergy and Clinical Immunology, 77, 6 9. Lloyd, G, Lund, V, Phelps, P & Howard, D (1987). Magnetic resonance imaging in the evaluation of nose and paranasal sinus disease. The British Journal of Radiology, 60, 957-968. Mafee, M, Rasouli, F, Spigos, F, Valvassori, G, Friedman, M & Capek V (1986). Magnetic resonance imaging in nonsquamous tumors of the head and neck. Otolaryngologie Clinics of North America, 19, 523-536. Moore, J, Potchen, M, Waldenmaier, M, Sierra A & Potchen, E (1986). High-field magnetic resonance imaging of sinus inflamatory disease, Laryngoscope, 96, 267-271. Ruprecht, A, Batniji, S & el-Newiehi, E (1986). Mucous retention cyst of the maxillary sinus. Oral Surgery, Oral Medicine Oral Pathology, 62, 728-731. Weber, A & Mikulis, C. (1987). Inflammatory disorders of the paraorbital sinuses and their complications. Imaging in Ophthalmology, Radiology Clinics of North America, 25, 615-630.