cells with the internal carotid artery and the optic nerve. DELaNo et al. (1996) classified the relationship with the optic nerve in four different types. In type 1, the nerve does not contact or impinge either the sphenoid or posterior ethmoid cells. In type 2, the nerve indents the sphenoid sinus, without contacting the posterior ethmoid cells. In type 3, the nerve runs through the sphenoid sinus, and it is surrounded by the pneumatized sinus for at least 50%. In type 4, the nerve courses close to both the sphenoid sinus and posterior ethmoid cells.
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