Background: Vascular perfusion of the flap is an important means of assessing flap viability. Classically, imaging using the fluorescent dye indocyanine green (ICG) was used to measure blood flow, determining cardiac output and hepatic function, and monitor blood flow in free flap reconstruction. Here, we present the use of intraoperative near-infrared (NIR) imaging using ICG dye to assess the viability of nasoseptal flaps during reconstruction of skull base defects following resection of anterior skull base lesions.
Methods: Three patients at our institution who underwent oncologic resection of skull base lesions (2 pituitary adenomas and 1 sarcoma) were included in this pilot study. Following resection of the tumor and elevation of a nasoseptal flap, a 4-mm endoscope with both visible and NIR light capabilities and real time superimposition was used to visualize the pedicle of the nasoseptal flap during surgery. Each patient was injected intravenously with 5mg intravenous bolus of ICG within minutes of visualization. Intraoperative fluorescence was compared with enhancement of the nasoseptal flap on MRI imaging obtained on post-operative day one.
Results: In 2 patients, video angiography demonstrated bright fluorescence of the nasoseptal flap pedicle but minimal flap perfusion was identified. One patient demonstrated brisk flow into both the pedicle and the flap. In contrast, all three patients demonstrated MRI enhancement of the nasoseptal flap on post-operative day one imaging, suggesting flap viability. There was no evidence of cerebrospinal fluid leak in each of the three cases in short term follow-up.
Conclusion: NIR video angiography using ICG dye can be considered for intraoperative assessment of viability of nasoseptal flap for repair of skull base defects following tumor resection. This technique does not seem to correlate with gadolinium enhancement of the flap at the postoperative day one MRI scan, and thus vascular perfusion and gadolinium enhancement may represent different phenomena.