Ethnic variation in medial orbital wall anatomy and its implications for decompression surgery

Background To describe the inter-ethnic variation in medial orbital wall anatomy between Chinese, Malay, Indian and Caucasian subjects. Methods Single-centre, retrospective, Computed Tomography (CT)-based observational study. 20 subjects of each ethnicity, were matched for gender and laterality. We excluded subjects younger than 16 years and those with orbital pathology. OsiriX version 8.5.1 (Pixmeo., Switzerland) and DICOM image viewing software CARESTREAM Vue PACS (Carestream Health Inc., USA) were used to measure the ethmoidal sinus length, width and volume, medial orbital wall and floor angle and the relative position of the posterior ethmoid sinus to the posterior maxillary wall. Statistical analyses were performed using Statistical Package for Social Sciences version 25.0 (IBM, USA). Results There were 12 males (60 %) in each group, with no significant difference in age (p = 0.334–0.994). The mean ethmoid sinus length in Chinese, Malay, Indian and Caucasian subjects, using the Chinese as reference, were 37.2, 36.9, 38.0 and 37.4mm, the mean width was 11.6, 10.5, 11.4 and 10.0mm (p = 0.020) and the mean ethmoid sinus volume were 3362, 3652, 3349 and 3898mm3 respectively. The mean medial orbital wall and floor angle was 135.0, 131.4, 131.0 and 136.8 degrees and the mean relative position of posterior ethmoid sinus to posterior maxillary wall were − 2.0, -0.2, -1.5 and 1.6mm (p = 0.003) respectively. Conclusions No inter-ethnic variation was found in decompressible ethmoid sinus volume. Caucasians had their posterior maxillary sinus wall anterior to their posterior ethmoidal walls unlike the Chinese, Malay and Indians. Awareness of ethnic variation is essential for safe orbital decompression.

Superiorly based subperiosteal orbital abscess: an uncommon presentation

A 32-year-old female patient presented with severe facial pain, right eye proptosis and diplopia. Endoscopy revealed ipsilateral crusting, purulent discharge and bilateral nasal polyps. Imaging demonstrated a subperiosteal abscess on the roof of the right orbit. Due to patient’s significant ocular manifestations, surgical management was decided. The abscess was drained using combined endoscopic and external approach, via a Lynch-Howarth incision. Following rapid postoperative improvement, patient’s regular follow-up remains uneventful. A subperiosteal orbital abscess is a severe complication of rhinosinusitis that can ultimately endanger a patient’s vision. It is most commonly located on the medial orbital wall, resulting from direct spread of infection from the ethmoid cells. The rather uncommon superiorly based subperiosteal abscess occurs superiorly to the frontoethmoidal suture line, with frontal sinusitis being its main cause. Treating it solely endoscopically is more challenging than in medial wall abscesses, and a combined approach is often necessary.