Microsurgical anatomy of the sphenoid ostia

We aimed to determine the position, number and variability of the sphenoid sinus ostia. A total of 32 dry skulls were examined under x6 magnification. The septum and nasal turbinates were removed to expose the anterior wall of the sphenoid sinus. A caliper was used for measurements. We found 2 ostia per skull, except for one (3%), in which the left ostium was absent. The inferior edges of both ostia were found at the same height in only four skulls (12.5%), and the superior edges of both ostia were found at the same height in only one skull (3%). Thus, in 27 skulls (84%) the lower and upper margins of both ostia were at different levels. The distance from the internal edge of the right ostium to the midline was 2.04 mm on average (range: 0.3-5.3 mm). The distance from the internal edge of the left ostium to the midline was 2.18 mm on average (range: 0.2 to 5.1 mm). In most skulls, the sphenoid ostia are located at different heights on each side; also a great variability in the distance from the internal border of the ostia to the midline was found. We found this anatomical knowledge useful when performing a transsphenoidal approach to the sella turcica. (C) 2010 Elsevier Ltd. All rights reserved.