BACKGROUND: During endoscopic transsphenoidal pituitary surgery, identification and constant awareness of the midline is imperative to prevent injury to critical lateral structures, such as the internal carotid arteries.
OBJECTIVE: To describe the relevance of a midline filum of the sellar dura which, when present, can serve as a useful intraoperative anatomic marker.
METHODS: Intraoperative video recordings of twenty patients undergoing endoscopic transsphenoidal surgery were retrospectively reviewed to assess for the presence and location of a midline dural filum or apparent central dural vascular structure. Prospective intraoperative data were gathered on an additional 16 patients.
RESULTS: A midline dural filum was identified in 18 of 36 patients (50%) undergoing endoscopic transsphenoidal surgery. This structure was identified on the midline in all cases, as confirmed by intraoperative neuronavigation and comparison with the vomer. The midline dural filum was identified as a strand-like dural extension (13 patients) or as a small vascular dural structure usually exhibiting low pressure venous bleeding (5 patients). Samples of the midline dural filum were obtained from 2 patients for histopathological analysis, which demonstrated dense collagenous connective tissue without evidence of vessel wall or ductal epithelium.
CONCLUSION: In addition to anatomic structures such as the vomer and midline sphenoid sinus septations, a midline dural filum serves as a useful marker during the sellar phase of endoscopic transsphenoidal surgery. Along with intraoperative neuronavigation and Doppler ultrasonography of the cavernous carotid arteries, identification of this structure may further aid in safeguarding against injury to critical paramedian structures.