Noninvasive diagnosis and treatment tactics in patients with CT-negative cerebrospinal fluid fistulas of the skull base

Introduction. Currently diagnosis of cerebrospinal fluid (CSF) leak involves the use of instrumental and laboratory techniques. Computed tomography of the brain (CT brain) is the preferred instrumental method. However, it is not always effective for visualization of skull base defects less than 2 mm in size. Aim. To confirm nasal CSF leak primarily using laboratory diagnostic methods, rather than instrumental diagnostic methods. Materials and methods. Instrumental diagnosis of nasal CSF leak (outpatient): high-resolution CT brain with subsequent image analysis in multiplanar projections. Laboratory diagnosis: quantitative test of glucose in nasal fluid using test strips (Russia) and quantitative test using hexokinase method and biochemical analyzers (Japan, USA). Results. Diagnostic tactics and types of surgical treatment for 34 patients are presented. CT brain was performed in all patients, and no bone defect was found in 5 (14.7 %) cases. However, thinning of the bone tissue in the area of the cribriform plate of the ethmoid bone with the presence of a soft tissue inclusion (meningoencephalocele), as well as a low position of the olfactory fossa (8.16 ± 0.14 mm) was observed. Through laboratory diagnostics, admixture of CSF in nasal fluid was verified in 5 (14.7 %) patients. Reconstruction of CSF fistulas was performed in all patients through endoscopic endonasal access using multilayer closure technique with allo- and autografts. In the postoperative period, no recurrence of CSF leak was observed. Follow-up period ranged from 6 months to 3 years. Discussion. In verification of CSF in nasal fluid, CSF fistula diagnosis requires CT brain; in the absence of obvious defects of the skull base according to CT results, endoscopic examination of the nasal cavity and cribriform plate of the ethmoid bone should be performed without the use of invasive diagnostic methods. Conclusion . In the context of negative CT and positive laboratory results, the area of the cribriform plate of the ethmoid bone should be regarded as the most likely source of CFS.