Abstract
The aim of this study was to observe the relationship of the sphenoid sinus and posterior ethmoid cells with the optic nerve. 34 CT scans (68 sides) of paranasal sinuses of patients older than 18 years were retrospectively reviewed. Images were assessed in two planes--axial and coronal. We observed the position and relationship of the optic nerve to the posterior ethmoid and sphenoid sinuses, bony dehiscence and protrusion of the optic nerve into sinuses, and pneumatization of the anterior clinoid process. The most frequent position of optic nerve (ON) was a location close to the posterior ethmoid and sphenoid sinuses without contacting or indentation of the wall--55.9% (38 nerves). The bulging of ON to sphenoid sinus was found in 14.7% (10 nerves) and the course of the nerve through sinus in 16 nerves (23.5%). The position of ON intimately to both sinuses was observed in 5.9% (4 nerves). Protrusion of ON, dehiscence of the bony wall and pneumatization of anterior clinoid process (ACP) was seen in 12 (35.3%), 4 (11.8%) and 9 (26.5%) patients, respectively. Both the protrusion of ON and ACP pneumatization were present in 8 (23.5%) patients on the right side and in 5 (14.7%) patients on the left side. Variations of posterior ethmoid and sphenoid sinuses are numerous and may entail potential risk of injury of the ON during sinus surgery. Knowledge of individual differences and configurations in the operation area may help the surgeon to prevent complications. Computed tomography is the preferred radiographic modality for evaluation of bony variations and the pathology of this region.
Highlights
MATERIAL AND METHODSThe optic nerve (ON) has an intimate relationship to the posterior ethmoid cells and sphenoid sinus
Position of the optic nerve to ethmoid and sphenoid sinuses was divided into four categories according to Number of ON
Inadvertent injury to these structures can result in uncontrollable bleeding, retrobulbar hematoma with acute proptosis, diplopia caused by extraocular muscle injury and stretching of the optic nerve resulting in blindness, violation of the subarachnoid space with resultant pneumocephalus or cerebrospinal fluid rhinorrhea[2,5]
Summary
The optic nerve (ON) has an intimate relationship to the posterior ethmoid cells and sphenoid sinus. Pneumatization of the sphenoid sinus (SS) can be so extensive that it can even surround the anterior clinoid process (ACP), ON, foramen rotundum, vidian canal, pterygoid process, or maxilloethmoid process[1]. A surgically dangerous area is pneumatization of posterior ethmoid cells behind the annulus tendineus communis where the optic nerve is unprotected by surrounding extraocular muscles, fatty tissue and periorbita[2]. Detailed knowledge of paranasal sinuses and adjacent anatomical structures notably their variations are essential for clinicians performing sinus surgery. This is important to know preoperatively, so that unintentional damage to these structures can be avoided
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