1. MedPix Medical Image Database COW - Case of the Week Case Contributor: Dr. Balasubramanian Thiagarajan Affiliation: Unlisted Institution

2. MedPix No: 10681 - History Pt Demographics: Age = 60 y.o. Gender = woman 60 year old woman with complaints of swelling over left forehead and protrusion of left eye ball of 10 years duration. Patient is a known diabetic on irregular treatment. Downloaded by (-1)

3. MedPix No: 10681 - EXAM & LABS Boggy swelling over left forehead. Doughy on palpation, anterior table of frontal bone eroded. Proptosis of left eye was seen. Ocular movements complete. Vision normal. Ears / Nose / Throat - No significant findings.

4. Frontal Sinus Mucocele CT scan of para nasal sinuses plain showing expansile lesion involving the left frontal sinus with erosion of the outer and inner tables of frontal sinus with intracranial extension and proptosis of left eye ball. Downloaded by (-1)

5. Frontal Sinus Mucocele This image shows thick mucoid secretion extruding from frontal sinus ostium which was widened endoscopically. Downloaded by (-1)

6. Frontal Sinus Mucocele This image shows the frontal lobe of brain visualised through frontal sinus ostium which was enlarged to drain the secretions from frontal sinus during endoscopic sinus surgery. The brain tissue can be identified by its pulsations in synchrony with the patient*s respiration. Downloaded by (-1)

7. FINDINGS CT scan Coronal section of para nasal sinuses showed expansile lesion involving the left frontal sinus with erosion of the inner and outer tables of frontal bone. Left eye showed proptosis with intact orbital walls.

8. DIFFERENTIAL DIAGNOSIS What is your Differential Diagnosis? Malignancy of the frontal sinus - Frontal mucocele - Fungal sinusitis

9. Diagnosis: Frontoethmoidal mucocele, intracranial extension Dx Confirmed by: Endoscopic sinus surgery. Thick mucoid discharge was seen coming through the frontal sinus ostium as soon as it was widened.

10. DISCUSSION Frontal mucocele is caused due to obstruction (long standing) of frontal sinus ostium. This obstruction leads to pent up secretions which expands the frontal sinus. It also led to erosion of the outer and inner tables of frontal sinus.