Detection and Management of Skull Base Cerebrospinal Fluid Leaks Using HRCT-MRI Fusion Imaging

Background: Endoscopic repair of cerebrospinal fluid (CSF) leaks has been well described in the literature as an effective method for the treatment of sinonasal skull base defects. However, despite the ongoing evolution of the endoscopic techniques for repair, site localization is a diagnostic challenge. The limitations and morbidity associated with diagnostic imaging studies such as high-resolution computer tomography (HRCT), magnetic resonance imaging (MRI), and computed tomography (CT) cisternography in detecting CSF leaks has created a need for more accurate and less invasive radiographic imaging modalities. In our study, we evaluate a novel technique of fusing HRCT and MRI imaging for the detection of CSF leaks, as well as its ability to aid in intraoperative localization of skull base defects through computer-assisted image guidance.

Methods: We retrospectively reviewed 17 cases of patients who underwent HRCT-MRI fusion studies with intraoperative fluorescein localization for the evaluation and repair of CSF leaks during a 3-year period between 2008 and 2011 at the Mount Sinai Medical Center.

Results: Seventeen HRCT-MRI fusion studies were evaluated from 17 different patients suspected of having anterior skull base CSF leaks. The etiology of the CSF leaks was spontaneous in seven, postpartum in two, and iatrogenic in one. Ten out of the 17 subjects had a confirmed diagnosis of CSF leaks on intraoperative nasal endoscopy. HRCT-MRI fusion imaging accurately identified the CSF leak and its location in each of the 10 subjects, yielding a sensitivity of 100%. Six of the 17 patients were found to have no signs of active CSF leak or skull base defect on intraoperative nasal endoscopy; 4 of these correlated with negative findings on fusion imaging. One patient is currently awaiting surgical intervention.

Conclusion: HRCT-MRI fusion is an excellent imaging modality that not only provides accurate identification and localization of CSF leaks but also acts as a great adjunct for intraoperative localization and repair. HRCT-MRI fusion can be incorporated into the diagnostic algorithm in the management of CSF leaks.