gms | German Medical Science

Skull base dura lesions and cerebrospinal fluid (CSF) fistulas could cause life threatening complications if they are not properly diagnosed and treated. The most common complication, ascending meningitis, may well trigger devastating consequences regardless of continuously enhancing therapeutic agents. Once the dura lesion occurs, the healing process may build only a scar tissue or just a layer of nasal mucosa over the defect, which could stop the CSF leak in some instances but do not provide an adequate barrier for protection. Therefore, surgical repair and watertight closure of these defects should be assured [Ref. 1], [Ref. 2], [Ref. 3]. To reach this aim, a number of different approaches could be applied including intracranial and/or external procedures. Nevertheless, even the most recently favored endonasal endoscopic closure could not achieve a watertight sealing in all cases. The failure rate varies from about 10% by endonasal up to 27% by intracranial approaches [Ref. 4], [Ref. 5]. These failure cases also require further management, which could only be provided after reliable detection of CSF. Otherwise those cases would still face the same risks as they did before surgery. On the other hand, quality assessment after dura repairs remains to be an unsolved problem, as there is no worldwide accepted standard-of-care for postoperative screening. Various centers use mainly subjective diverse methods for this purpose, only some using objective reliable tools such as Beta-2-Transferrin (ß₂-Tr) or Sodium Fluorescein tests. Recently, a new, noninvasive, fast and sensitive diagnostic tool, Beta-Trace Protein (ßTP) test, is being used routinely as a marker for CSF in nasal secretions. It is an easily available, simple and cheap method that could without difficulty be applied for screening purposes [Ref. 6]. [Ref. 7], [Ref. 8]. In this study our aim is to demonstrate the significance of reliable postoperative screening and to assess the novel application of Beta-Trace-Protein test for dura repair success confirmation.

Between July 2001 and July 2004, 36 consecutive patients have undergone duraplasty for various dura lesions caused by different etiologies in a tertiary hospital setting. In all of them, intraoperative localization has been provided by preoperative intrathecal lumbar applied 0.5 ml fresh prepared %5 Sodium Fluorescein. According to the etiology, site and size of the defect, different approaches, techniques and graft material have been used. Nasal packing have been removed at day 10. In a prospective manner their postoperative nasal secretion has been collected at day 3 and 7 after the removal of surgical packing. Nasal secretion samples have been collected with PVA foam nasal pledges, which have been introduced into the nasal cavity and left for at least 4 to 6 hours. Together with patient’s serum, samples were analyzed for CSF marker ßTP, to detect or rule out postoperative CSF leakage. Test results were evaluated according to sensitive interpretation guidelines by Arrer et al [Ref. 8]. In case of test specific limitations, either ß₂-Tr or invasive sodium fluorescein tests have been used for reliable and objective controlling.

In our case material, the most common etiologic factor for dura lesions to occur was head traumas (56%). According to the localization as well as the requirements of the primary disease and etiologic factors, different approaches have been used to expose the primary disease and dural lesion. Endonasal endoscopic approach (59%) was the most common used followed by transfacial approaches (19%). ßTP test results of all but four patients revealed a negative test result, indicating no CSF leakage on both samples. On the other hand, three patients had a positive finding on first sample, showing an active postoperative CSF fistula. These patients required additional surgery, in which CSF leaks were verified intraoperatively. Two of them initially had anterior skull base tumors with large dural involvement resulting in substantial dura defects and the other had a skull base fracture after head trauma. After revision surgeries, further ßTP-testing was negative, revealing successful dura repair. Only in one case the ßTP test result was in between the test specific limits, thus the ßTP test had “no statement” for his samples. Therefore further controlling has been done by sodium fluorescein test 6 weeks after surgery, which was also negative. As a whole, our results have demonstrated that in 33 patients no CSF was detectable in the nasal secretion, indicating 91.7% dura repair success after first step. Different techniques and grafts used seem to be similarly efficient and look as if they do not alter the outcome.

Regardless of the etiology, all patients with a suspicion of dural lesion and CSF fistula require a reliable state-of-the-art detection or exclusion. In order to avoid related complications, it is imperative to detect, localize and repair dural defects and seal CSF fistulas for prevention [Ref. 1]. In our opinion, this is not only an issue of initial preoperative management, but also a requirement of postoperative quality control. Consequently, also after dura repair, persistent dural openings should be further diagnosed and treated, as they carry the same risks for complications as before the attempt for dura repair. Furthermore, in the literature it has been many times reported that dura repairs have an average success rate about 90% and worse, in accordance with the approach chosen [Ref. 1], [Ref. 2], [Ref. 3], [Ref. 9], [Ref. 4], [Ref. 5]. In our series, overall success rate was 91% after one surgery. Therefore, not only our results but also the reports of others indicate clearly that, there is about 10% chance of inadequate closure postoperatively. Hence, it would be a failure not to control the integrity of the dura repair with adequate, objective and reliable diagnostic tools, as routinely done prior to surgery for indication purposes. Otherwise this would lead to assumption of successful outcome in every case either without controlling or by examining only with insufficient, (mainly patient or even physician dependent) subjective methods, which could put the patients under the risk of recurrent meningitis episodes. On the other hand, if the current status is investigated, it could be easily observed that for dura repair efficacy control there is no worldwide accepted standard protocol [Ref. 10]. Commonly, operative success is primarily determined by clinical follow-up and examination, instead of an objective method. However, concerning objective methods, ß₂-transferrin and ßTP tests are the most suitable tools for postoperative screening. It is not only because they are noninvasive tests that are highly sensitive and specific for CSF diagnosis, but also they involve no complications and could be repeated easily anytime. Furthermore, easy sample collection also from unconscious patients, wide area of application and possibility of sample mailing makes them important and powerful tools [Ref. 6]. However, nearby having all advantages of ß₂-transferrin test, for this purpose in this study proposed quantitative ßTP test provides improvements on sensitivity, cost and turnaround time [Ref. 6], [Ref. 7], [Ref. 8]. It has a high analytical sensitivity, high specificity, is not expensive and the result is available within some minutes. More importantly, the distinctive advantages such as high-speed and low-cost of ßTP test on ß₂-transferrin test makes this reliable, objective and noninvasive test a good option for postoperative screening of dura repair success. Our preliminary results reveal that, ßTP test has various advantages for being the optimal objective screening test for postoperative CSF fistula confirmation or exclusion. Establishing an objective measure such as ßTP test for quality control after dura repair would enhance our therapeutic management by early and reliable detection of failure cases. Moreover, this would facilitate better and objective documentation of success rates.

Regardless of the selected approach, duraplasty do not always assure watertight sealing in all cases. Hence, dura repairs should be controlled for the presence or absence of postoperative CSF leakage. In our hands, the sensitive, fast and inexpensive ßTP test has shown its value as an effective postoperative screening tool for dura repair success confirmation. Hence, we consider this test as novel “standard-of-care” for screening after dura repairs and reserve invasive, more expensive or time-consuming methods as second choice.