Faculty Bibliography

BACKGROUND:Subdural empyema (SDE) is a well-known entity in pediatric populations and is associated with a high rate of morbidity and mortality. Large scale evacuation of empyema, although effective, places the bone flap at risk of failure when replaced. CASE DESCRIPTION/METHODS:We report the case of a 19-year-old man with a history of a shunted left middle fossa cyst presenting with a panhemispheric SDE after removal of his cystoperitoneal shunt by an outside facility. Extensive evacuation was performed via the patients prior parietal shunt incision after expansion of the preexisting burr hole. Cultures grew methicillin-sensitive Staphylococcus aureus and Propionibacterium acnes, and he was treated with long-term antibiotics. The patient had a complete recovery with persistent empyema resolution on 6-month follow-up. CONCLUSIONS:Endoscopic-assisted burr hole evacuation of large panhemispheric and loculated SDE is feasible, effective, and safe. The primary advantage over conventional open evacuations is that it negates the need for a bone flap and its potential complications related to a secondary infection.

OBJECTIVE:Diffusion imaging tractography has allowed the in vivo description of brain white matter. One of its applications is preoperative planning for brain tumor resection. Due to a limited spatial and angular resolution, it is difficult for fiber tracking to delineate fiber crossing areas and small-scale structures, in particular brainstem tracts and cranial nerves. New methods are being developed but these involve extensive multistep tractography pipelines including the patient-specific design of multiple regions of interest (ROIs). The authors propose a new practical full tractography method that could be implemented in routine presurgical planning for skull base surgery. METHODS:A Philips MRI machine provided diffusion-weighted and anatomical sequences for 2 healthy volunteers and 2 skull base tumor patients. Tractography of the full brainstem, the cerebellum, and cranial nerves was performed using the software DSI Studio, generalized-q-sampling reconstruction, orientation distribution function (ODF) of fibers, and a quantitative anisotropy-based generalized deterministic algorithm. No ROI or extensive manual filtering of spurious fibers was used. Tractography rendering was displayed in a tridimensional space with directional color code. This approach was also tested on diffusion data from the Human Connectome Project (HCP) database. RESULTS:The brainstem, the cerebellum, and the cisternal segments of most cranial nerves were depicted in all participants. In cases of skull base tumors, the tridimensional rendering permitted the visualization of the whole anatomical environment and cranial nerve displacement, thus helping the surgical strategy. CONCLUSIONS:As opposed to classical ROI-based methods, this novel full tractography approach could enable routine enhanced surgical planning or brain imaging for skull base tumors.

BACKGROUND:The influence of the surgeon's preoperative goal regarding the extent of tumor resection on patient outcomes has not been carefully studied among patients with nonfunctioning pituitary adenomas. OBJECTIVE:To analyze the relationship between surgical tumor removal goal and patient outcomes in a prospective multicenter study. METHODS:Centrally adjudicated extent of tumor resection (gross total resection [GTR] and subtotal resection [STR]) data were analyzed using standard univariate and multivariable analyses. RESULTS:GTR was accomplished in 148 of 171 (86.5%) patients with planned GTR and 32 of 50 (64.0%) patients with planned STR (P = .001). Sensitivity, specificity, positive predictive value, and negative predictive value of GTR goal were 82.2, 43.9, 86.5, and 36.0%, respectively. Knosp grade 0-2, first surgery, and being an experienced surgeon were associated with surgeons choosing GTR as the goal (P < .01). There was no association between surgical goal and presence of pituitary deficiency at 6 mo (P = .31). Tumor Knosp grade (P = .004) and size (P = .001) were stronger predictors of GTR than was surgical goal (P = .014). The most common site of residual tumor was the cavernous sinus (29 of 41 patients; 70.1%). CONCLUSION:This is the first pituitary surgery study to examine surgical goal regarding extent of tumor resection and associated patient outcomes. Surgical goal is a poor predictor of actual tumor resection. A more aggressive surgical goal does not correlate with pituitary gland dysfunction. A better understanding of the ability of surgeons to meet their expectations and of the factors associated with surgical result should improve prognostication and preoperative counseling.

BACKGROUND:A simple, reliable grading scale to better characterize nonfunctioning pituitary adenomas (NFPAs) preoperatively has potential for research and clinical applications. OBJECTIVE:To develop a grading scale from a prospective multicenter cohort of patients that accurately and reliably predicts the likelihood of gross total resection (GTR) after transsphenoidal NFPA surgery. METHODS:Extent-of-resection (EOR) data from a prospective multicenter study in transsphenoidal NFPA surgery were analyzed (TRANSSPHER study; ClinicalTrials.gov NCT02357498). Sixteen preoperative radiographic magnetic resonance imaging (MRI) tumor characteristics (eg, tumor size, invasion measures, tumor signal characteristics, and parameters impacting surgical access) were evaluated to determine EOR predictors, to calculate receiver-operating characteristic curves, and to develop a grading scale. A separate validation cohort (n = 165) was examined to assess the scale's performance and inter-rater reliability. RESULTS:Data for 222 patients from 7 centers treated by 15 surgeons were analyzed. Approximately one-fifth of patients (18.5%; 41 of 222) underwent subtotal resection (STR). Maximum tumor diameter > 40 mm; nodular tumor extension through the diaphragma into the frontal lobe, temporal lobe, posterior fossa, or ventricle; and Knosp grades 3 to 4 were identified as independent STR predictors. A grading scale (TRANSSPHER grade) based on a combination of these 3 features outperformed individual variables in predicting GTR (AUC, 0.732). In a validation cohort, the scale exhibited high sensitivity and specificity (AUC, 0.779) and strong inter-rater reliability (kappa coefficient, 0.617). CONCLUSION:This simple, reliable grading scale based on preoperative MRI characteristics can be used to better characterize NFPAs for clinical and research purposes and to predict the likelihood of achieving GTR.

This 25-year-old woman presented after a second hemorrhage from a mesencephalic cavernous malformation. High-definition fiber tracking demonstrated lateral displacement of the corticospinal tracts, making a midline approach ideal. The lesion appeared to present to the third ventricle, but a transcallosal approach was abandoned due to the posterior third ventricular location and after FIESTA imaging revealed a superior and medial rim of normal parenchyma that would have to be transgressed to access the malformation. An endoscopic endonasal approach with interdural pituitary hemitransposition was performed. The interpeduncular cistern was accessed and the thalamoperforating arteries dissected to access the cavernous malformation that was completely removed in a piecemeal fashion. The patient's preexisting internuclear ocular palsies and hemiparesis were slightly worsened after surgery as predicted by a drop in anterior tibialis motor evoked potentials. Postoperative MRI showed no infarct, and the hemiparesis was back to baseline at 1-month follow-up. The video can be found here: https://youtu.be/e6203R9HHmk.

BACKGROUND:Vascularized intranasal flaps are the primary reconstructive option for endoscopic skull base defects. Flap vascularity may be compromised by injury to the pedicle or prior endonasal surgery. There is currently no validated technique for intraoperative evaluation of intranasal flap viability. OBJECTIVE:To evaluate the efficacy of indocyanine green (ICG) near-infrared angiography in predicting the viability of pedicled intranasal flaps during endoscopic skull base surgery through a pilot study. METHODS:ICG near-infrared fluorescence endoscopy was performed during endoscopic endonasal surgery for skull base tumors. Intraoperative and postoperative data were collected regarding enhancement of the flap body and pedicle. Fluorescence was rated qualitatively. Postoperatively, flap perfusion was evaluated via MRI-contrast enhancement in addition to clinical outcomes (cerebrospinal fluid leak and endoscopic flap appearance). RESULTS:Thirty-eight patients underwent ICG fluorescence angiography. Both the body and pedicle enhanced in 20 patients (53%), while the pedicle only enhanced for 12 patients (32%), the body only for 3 (8%), and neither for 3 (8%). When both the pedicle and body enhanced with ICG, the rate of postoperative MRI contrast enhancement was 100% and the rate of flap necrosis was 0%. The sensitivity and specificity of flap pedicle ICG enhancement for predicting postoperative flap MRI enhancement were 97% and 67%, respectively. Two of 3 patients without enhancement developed flap necrosis. CONCLUSION:ICG fluorescence angiography of intraoperative flap perfusion is feasible and correlates well with outcomes of postoperative MRI flap enhancement and flap necrosis. Additional study is needed to further refine the imaging technique and optimally characterize the clinical utility.

OBJECTIVE The aim in this paper was to determine risk factors for the development of a postoperative CSF leak after an endoscopic endonasal approach (EEA) for resection of skull base tumors. METHODS A retrospective review of patients who underwent EEA for the resection of intradural pathology between January 1997 and June 2012 was performed. Basic demographic data were collected, along with patient body mass index (BMI), tumor pathology, reconstruction technique, lumbar drainage, and outcomes. RESULTS Of the 615 patients studied, 103 developed a postoperative CSF leak (16.7%). Sex and perioperative lumbar drainage did not affect CSF leakage rates. Posterior fossa tumors had the highest rate of CSF leakage (32.6%), followed by anterior skull base lesions (21.0%) and sellar/suprasellar lesions (9.9%) (p < 0.0001). There was a higher leakage rate for overweight and obese patients (BMI > 25 kg/m²) than for those with a healthy-weight BMI (18.7% vs 11.5%; p = 0.04). Patients in whom a pedicled vascularized flap was used for reconstruction had a lower leakage rate than those in whom a free graft was used (13.5% vs 27.8%; p = 0.0015). In patients with a BMI > 25 kg/m², the use of a pedicled flap reduced the rate of CSF leakage from 29.5% to 15.0% (p = 0.001); in patients of normal weight, this reduction did not reach statistical significance (21.9% [pedicled flap] vs 9.2% [free graft]; p = 0.09). CONCLUSIONS Preoperative BMI > 25 kg/m² and tumor location in the posterior fossa were associated with higher rates of postoperative CSF leak. Use of a pedicled vascularized flap may be associated with reduced risk of a CSF leak, particularly in overweight patients.

OBJECTIVE Treatment of odontoid disease from a ventral corridor has consisted of a transoral approach. More recently, the endoscopic endonasal approach (EEA) has been used to access odontoid pathology. METHODS A retrospective review was conducted of patients who underwent an EEA for odontoid pathology from 2004 to 2013. During our analysis, the mean follow-up duration was 42.6 months (range 1-80 months). Patient outcomes, complications, and postoperative swallowing function were assessed either by clinic visit or phone contact. RESULTS Thirty-four patients underwent an EEA for symptomatic odontoid pathology. The most common pathology treated was basilar invagination (n = 17). Other pathologies included odontoid fractures, os odontoideum, and metastatic carcinoma. The mean patient age was 71.5 years. Thirty-one patients underwent a posterior fusion. All 34 patients experienced stability or improvement in symptoms and all had successful radiographic decompression. The overall complication rate was 76%. Nearly all of these complications were transient (86%) and the overall complication rate excluding mild transient dysphagia was only 44%. Twenty-one patients (62%) suffered from transient postoperative dysphagia: 15 cases were mild, transient subjective dysphagia (6 of whom had documented preoperative dysphagia), whereas 6 other patients required tube feedings for decreased oral intake, malnutrition, and dysphagia in the perioperative setting (5 of these patients had documented preoperative dysphagia). Sixteen patients had documented preoperative dysphagia and 6 of these had lower cranial nerve dysfunction. Postoperatively, 6 (37.5%) of 16 patients with preoperative dysphagia and 4 (67%) of 6 with lower cranial nerve dysfunction had significant dysphagia/respiratory complications. Eighteen patients had no documented preoperative dysphagia and only 2 had significant postoperative dysphagia/respiratory complications (11%). The rates of these complications in patients without preoperative dysphagia were lower than in those with any preoperative dysphagia (p = 0.07) and especially those with preexisting lower cranial neuropathies (p = 0.007). Dysphagia was also significantly more common in patients who underwent occipitocervical fixation (19/26, 73%) than in patients who underwent cervical fusion alone or no fusion (2/8, 25%; p = 0.02). All patients with perioperative dysphagia had improved at follow-up and all patients were tolerating oral diets. No patient suffered from velopalatal insufficiency. Two patients had intraoperative CSF leaks. One of these patients underwent a negative exploratory surgery for a questionable postoperative CSF leak. One patient developed infection in the resection bed requiring debridement and antibiotics. One patient died 8 days following surgery from an unknown cause. The 90-day perioperative mortality rate was 2.9%. CONCLUSIONS A completely EEA can be performed for compressive odontoid disease in all cases of neoplastic, degenerative, or invaginative atlantoaxial disease with satisfactory outcomes and low morbidity. Transient perioperative dysphagia and respiratory complications are common, usually as an exacerbation and reflection of underlying disease or occipitocervical fusion rather than the EEA, emphasizing the importance of avoiding transoral surgery.

BACKGROUND:Temporary arterial occlusion (TAO) is valuable for minimizing intraoperative rupture risk during intracranial aneurysm microsurgery; however, it may be associated with ischemic injury. This study aims to identify surgical and intraoperative neurophysiologic monitoring factors that predict perioperative stroke risk after TAO. METHODS:We performed a retrospective chart review of 177 intracranial aneurysm surgeries at our institution in which TAO was performed before placement of a permanent clip under monitoring with somatosensory evoked potentials (SSEPs) and electroencephalography. Perioperative stroke was defined as a new-onset neurologic deficit that developed within 24 hours postoperatively that was correlated with hypodensity on postoperative computed tomography. RESULTS:Ten (6%) patients developed perioperative stroke in the vascular territory of TAO. SSEP changes were observed in 50% (5/10) of patients with perioperative stroke and in 14% (24/167) of patients without stroke (P = 0.003). Mean maximum single-episode TAO duration for patients who developed perioperative stroke was 12.6 minutes (95% confidence interval 8.1-17.1) and TAO duration for patients without stroke was 8.0 minutes (95% confidence interval 7.3-8.7; P = 0.026). In patients with SSEP changes, risk of stroke was particularly elevated with unruptured aneurysms (P = 0.013) compared with patients with ruptured aneurysms. Temporary clip location, number of occlusive episodes, onset and duration of intraoperative neurophysiologic monitoring changes, and rupture status were not predictive of perioperative stroke. CONCLUSIONS:SSEP changes and increased single-episode TAO duration are independently associated with increased perioperative stroke risk. SSEP changes are most predictive for perioperative stroke in unruptured cases.