R. Santhana Lakshmi1, T. S. Gugapriya2, N. Vinay Kumar3, Arun T. Guru4
OBJECTIVE: The posterior most among the paranasal sinuses, the sphenoid sinuses exhibit high variability in their structure, pneumatisation and relation to surrounding neurovascular structures. The protrusion of optic nerve (ON) into the superolateral wall of the sinus has been reported in literature with varied incidence. The pneumatisation of sphenoid sinus and its extension to anterior clinoid process (ACP) is also been mentioned in few studies. The variability in the incidence and the inconsistency in the association between optic nerve protrusion and degree of pneumatisation seen in studies done in different ethnicity and with paucity of Indian studies necessitated this study on positional variation of optic nerve in relation to sphenoid sinuses and its association with pneumatisation of anterior clinoid process in South Indian ethnicity.
THE METHODS: CT scan images in coronal section collected from 114 patients with sinusitis with in the age group of 16-64 years belonging to both sexes were studied. The CT images were evaluated for the position of ON with sphenoid sinuses, protrusion of it into the sinus walls, bony dehiscence, pneumatisation of ACP. The position of ON was classified into Delano’s four types and their incidence noted.
RESULTS: Type 1 position of ON was observed predominantly in 65.8% sides while Type 2, 3, 4 were seen in 29.8%, 1.8% and 2.6% sides respectively out of 228 sides studied. Associated bony dehiscence was noted in only 5 out of 228sides (2.1%) studied. The pneumatisation of ACP was observed in 23.6% of the CT scans studied. The association between ON protrusion and ACP pneumatisation was found to be statistically significant with P= 0.008.
CONCLUSION: The varying position of ON, its protrusion with or without dehiscence in to the sphenoid sinus wall with statistically significant association with ACP pneumatisation in south Indian ethnicity warrants a systematic CT evaluation pre operatively to ensure efficient surgery with minimal complications.
