A detailed analysis of the largest series to date of patients treated with the transglabellar/subcranial approach for anterior skull base lesions yields an encouraging 0% mortality rate and an overall complication rate of 28.7% in the perioperative period. The variables shown to be independent predictors of perioperative complication were dural invasion, surgical margins, and routine use of perioperative lumbar drain. Despite inclusion of a significant number of tumors demonstrating aggressive histology, high rates of invasion of nearby anatomic subsites, and a significant number of patient comorbidities, we were able to achieve negative margins in 78% patients and no mortalities. This data compare favorably with recent landmark articles on perioperative complications following anterior skull base surgery with the standard anterior craniofacial resection as the surgical approach of choice.3,4,5,6,7,8,9,10
An international collaborative study with 17 participating institutions performed an analysis of complications of craniofacial resection employed for malignancies of the skull base.5
With a database containing over 1300 patients, this study serves as a benchmark for anterior skull base surgery outcomes. Multivariate analysis of the data revealed that the presence of medical comorbidity was the only independent predictor of perioperative mortality. Independent predictors of postoperative complications were medical comorbidity, prior radiotherapy, and extent of intracranial involvement. In comparison, similar analysis of our data series also showed extent of intracranial involvement to be an important predictor of complication. By contrast, prior radiotherapy did not predispose to higher risk of complication, which may argue for the utility of the subcranial approach in the setting of prior radio- or chemotherapy.
One notable distinction is that the present study, as opposed to the aforementioned multi-institutional study, classified complications into major versus minor subcategories, in addition to listing individual complications by category. Our classification of major versus minor complication draws upon analogous outcomes research in reconstructive surgery in our discipline.18
The rate of major perioperative complication in this analysis was 18.0%. The benchmark study did not break down complications in major versus minor subtype. We believe that this distinction is important, however, in terms of interpreting complication results and in addition how we counsel patients prior to surgery.
The multi-institutional study calculated the mortality rate among patients undergoing anterior craniofacial resection for malignant tumors of the anterior skull base as 4.7%.5
The perioperative complication rate was 36.3%. For comparison purposes, the calculated complication rate among our malignant tumor group (n
104) was 31.7%. Gil et al recently published a large series of patients treated with traditional craniofacial resection for malignant disease over a period of ~30 years. The overall complication rate was 42.7%, and the perioperative mortality rate was 3.9%.8
They separated their results into historical versus recent cohorts; over the last decade, the complication rate has significantly decreased from 52 to 33%.8
The authors have attributed this improvement to a more broad-spectrum antibiotic regimen that was developed from wound culture data from the historic cohort.19
Specifically, the authors employed a standardized, broad-spectrum regimen that consisted of ceftazidime, metronidazole, and vancomycin.
It is therefore notable that the present study demonstrated at least comparable perioperative outcomes and employed a perioperative antibiotic regimen of cefuroxime only. In any approach to the anterior cranial base, the presumed nidus of infection was the contaminated sinonasal cavity that was exposed to the neuraxis during exposure and tumor resection.20
It is possible that the subcranial approach offered more direct access to the tumor, thus minimizing the time of exposure intraoperatively and facilitating closure.
It is also worth noting that the most common individual major complication in this series was CSF leak, occurring in 19 patients (11.6%). This is a relatively consistent finding across other large series that employ anterior craniofacial resection as the surgical approach.3,4,7,9,10
However, studies focusing on the subcranial approach have not noted similar rates of postoperative CSF leak.13,21
Some authors argue that CSF leak is a key predisposing factor to the development of postoperative meningitis.9
Despite an appreciable rate of postoperative CSF leak in our study (11.6%), the incidence of meningitis was very low (1.3%). This may provide indirect validation of the standard perioperative antibiotic regimen utilized (cefuroxime) or perhaps provide evidence against a direct causal relationship between CSF leak and meningitis in these patients.
Our algorithm for management of postoperative CSF rhinorrhea begins with a head computed tomography (CT) to assess for significant pneumocephalus. In addition to conservative measures that include stool softeners, head of bead elevation, and avoidance of Valsalva, a lumbar drain is inserted under sterile conditions at bedside. We employ a closed continuous lumbar drainage system that is connected to a mechanical pump that maintains drainage at a constant rate. We begin drainage at a conservative rate, usually 6 mL per hour, and titrate this based on clinical response. Intermittent head CT scans are obtained to assess for increasing pneumocephalus. If the patient fails to respond over the next 48 to 72 hours, we consider surgical repair. We have increasingly moved toward endoscopic repair of these persistent CSF leaks as our primary means of surgical management.
A post hoc review of the 19 patients who had delayed CSF leak was performed to better characterize our management strategy of this complication. Of the 19 patients with evidence of delayed CSF fistula following subcranial surgery, six had postoperative CSF leak despite having a lumbar drain inserted prior to tumor resection. Twelve patients did not have lumbar drains inserted at the time of surgery, and therefore underwent delayed lumbar drain placement. As noted above, one patient in this series with postoperative CSF leak underwent ventriculostomy placement instead of lumbar drain. This patient had evidence of cerebral edema on postoperative CT scan, and therefore the neurosurgery team decided to insert a ventriculostomy to closely monitor the intracerebral pressure. In total, five patients in this series eventually required revision surgery to definitively close the CSF fistula. Surgical techniques included free tissue transfer, temporoparietal fascia flap, and abdominal fat graft placement with bovine xenograph reinforcement.
An interesting finding of the multivariate analysis was that prophylactic placement of a lumbar drain at the time of surgery was an independent predictor of complication. The decision to place a lumbar drain was based on neurosurgeon preference, and therefore this analysis is prone to selection bias. Lumbar drain placement has been associated with a 12.5% rate of major complication following skull base surgery.22
Kryzanski et al maintain that judicious use of perioperative CSF drains in skull base surgery is warranted in light of these data.23
In contrast, routine CSF drain has been shown to decrease rates of postoperative CSF leak after posterior fossa sugery.24
The neurosurgical members of our multidisciplinary team currently feel that the benefits of routine CSF drainage are outweighed by possible risks, and these data seem to confirm their suspicion. It is possible that the more inferiorly placed craniotomy associated with the subcranial approach requires less retraction of parenchyma and thereby reduces the need for routine CSF drainage at the time of surgery.10
We routinely place nasopharyngeal airways to divert the flow of air from the site of surgical repair. In accordance with current principles of airway management in skull base surgery, the routine placement of a tracheostomy for airway diversion is felt to be unnecessary.25,26
Overall, we observed five episodes of tension pneumocephalus in this review. Nasopharyngeal stents are associated with lower rates of tension pneumocephalus17
and may underlie the relatively low rate of this complication over the period reviewed (3.0%).
Limitations of this study include its retrospective nature and the inherent difficulty in making even indirect comparisons to other studies that employed standard anterior craniofacial resection. Given the rare and heterogeneous nature of anterior skull base lesions, head-to-head comparisons are exceedingly rare. As with any single institution study of this type, key determinants of outcome and variability include tumor histology, extent of disease, as well as operative techniques and perioperative protocols. Despite these limitations, it is worthwhile to analyze large series of patients that feature a unique surgical approach to achieve a full grasp of the efficacy of these treatments.
As a whole, data presented in this study affirm the transglabellar/subcranial approach as having a favorable risk profile in the treatment of a wide variety of anterior skull base lesions. This issue is of utmost relevance given the recent surge in interest in endoscopic approaches to the anterior cranial base.27
Indeed, the advent of advanced endoscopic approaches has brought the issue of perioperative morbidity and mortality into sharp focus. There are an increasing number of studies that compare endoscopic resection against open resection through anterior craniofacial resection28,29
As such, it is critical to obtain an accurate gauge of the perioperative complication rates associated with all varieties of open procedures, with the understanding that not all “open” procedures necessarily pose the same perioperative risk to the patient.14
In particular, procedures that spare facial incisions and brain retraction yet offer excellent surgical access, such as the subcranial approach, will continue to have a high level of utility and can be used as an appropriate reference for open procedures when scrutinizing operative morbidity.