Vidian canal

The pterygoid canal (also vidian canal) is a passage in the skull leading from just anterior to the foramen lacerum in the middle cranial fossa to the pterygopalatine fossa.

The vidian canal (VC), a bony tunnel in which the vidian artery and vidian nerve pass, has been widely known as an important landmark to identify the anterior genu of the petrous segment of the internal carotid artery (AGPCA) especially during lateral extended endoscopic endonasal approachs (LEEEAs).

Adin et al., from the Department of Radiology, Tatvan Can Hospital, Bitlis, Department of Radiology, Dicle University, Diyarbakır, Turkey and Division of Neuroradiology, Russel H. Morgan Department of Radiology, Johns Hopkins Hospital, reviewed skull base computed tomographic images of 640 consecutive subjects. Studies were analyzed in axialcoronal and sagittal planes.

The mean (±SD) length of the vidian canal was 15.4 ± 2.0 mm in female subjects and 16.6 ± 1.7 mm in male subjects, and the difference between genders was statistically significant (P < 0.001). The most common rostral-caudal course of the vidian canal was medial to lateral and was followed by the straight course, tortuous course, and lateral-to-medial course. The frequency of pneumatization pattern from most common to least common was types 0, III, II and I. Of 342 evaluated sides, the vidian canal was located below the level of the anterior genu of petrous ICA in 303 (89%) sides, at same level with the anterior genu of petrous ICA in twenty-five(7%) sides, and above the level of the anterior genu of petrous ICA in fourteen(4.1%) sides.

A variety of previously undefined features of the vidian canal that can alter the course of surgical procedure were defined. The position of the vidian canal with respect to the petrous internal carotid artery (ICA) was extensively described. From a surgical standpoint, a working room inferior and medial to the vidian canal might not always be a safe approach, because the vidian canal could be located superior to the level of the anterior genu of petrous ICA according to the findings in this study 1)

The objectives of a study in the Japanese population are to describe the radiological anatomic features and relationships between VC and its surrounding structures, and discuss the clinical implications.

Mato et al studied 231 high-resolution computed tomography (CT) scans with a slice thickness of 0.5 mm. All the patients had known sellar or parasellar pathologies but without any involvement of VC. The following VC-related parameters were examined: its length, relationship to AGPCA, course from the pterygopalatine fossa to the carotid canal, its position relative to the medial pterygoid plate and pneumatization pattern of the sphenoid sinus. Mean length of VC is 14.6 mm. There is more tendency of straight-running VC compared to other populations. VC locates infero-lateral to AGPCA in all the cases. The protrusion of VC and the paraclival carotid artery to the sphenoid sinus, as well as well-pneumatization of the sinus is also observed more frequently in almost a half of the population. Surgeons who perform LEEEAs in Japanese patients must know these anatomical features. The characteristics particular to Japanese populations may facilitate better identification of VC and exposure to AGPCA intraoperatively 2).



Adin ME, Ozmen CA, Aygun N. Utility of the Vidian Canal in Endoscopic Skull Base Surgery: Detailed Anatomy and Relationship to the Internal Carotid Artery. World Neurosurg. 2019 Jan;121:e140-e146. doi: 10.1016/j.wneu.2018.09.048. Epub 2018 Sep 18. PubMed PMID: 30240854.

Mato D, Yokota H, Hirono S, Martino J, Saeki N. The vidian canal: radiological features in Japanese population and clinical implications. Neurol Med Chir (Tokyo). 2015;55(1):71-6. doi: 10.2176/nmc.oa.2014-0173. Epub 2014 Dec 20. PubMed PMID: 25744352; PubMed Central PMCID: PMC4533395.

Extent of resection in glioblastoma

The value of incomplete resection in Glioblastoma surgery remains questionable. If gross total resection (GTR) cannot be safely achieved, biopsy only might be used as an alternative surgical strategy 1).

see Wounded glioma syndrome.

The impact of extent of resection (EOR) on survival in glioblastoma multiforme treatment (GBM) continues to be a point of debate despite multiple studies demonstrating that increasing EOR likely extends survival for these patients. In addition, contrast-enhancing residual tumor volume (CE-RTV) alone has rarely been analyzed quantitatively to determine if it is a predictor of outcome.

CE-RTV and EOR were found to be significant predictors of survival after GBM resection. CERTV was the more significant predictor of survival compared with EOR, suggesting that the volume of residual contrast-enhancing tumor may be a more accurate and meaningful reflection of the pathobiology of GBM 2).


It is difficult to reproducibly judge EOR in studies due to the lack of reliable tumor segmentation methods, especially for postoperative magnetic resonance imaging (MRI) scans. Therefore, a reliable, easily distributable segmentation method is needed to permit valid comparison, especially across multiple sites.

Cordova et al. report a segmentation method that combines versatile region-of-interest blob generation with automated clustering methods. Applied this to glioblastoma cases undergoing FGS and matched controls to illustrate the method’s reliability and accuracy. Agreement and interrater variability between segmentations were assessed using the concordance correlation coefficient, and spatial accuracy was determined using the Dice similarity index and mean Euclidean distance. Fuzzy C-means clustering with three classes was the best performing method, generating volumes with high agreement with manual contouring and high interrater agreement preoperatively and postoperatively. The proposed segmentation method allows tumor volume measurements of contrast-enhanced T 1-weighted images in the unbiased, reproducible fashion necessary for quantifying EOR in multicenter trials 3).

Maximal safe resection

Safely performed maximal surgical resection is shown to significantly increase progression free survival and overall survival while maximizing quality of life. Upon invariable tumor recurrence, re-resection also is shown to impact survival in a select group of patients. As adjuvant therapy continues to improve survival, the role of surgical resection in the treatment of glioblastoma looks to be further defined.

During surgery, identifying margins of brain tumors, particularly glioblastomas (GBMs) and highly invasive neoplasms, remains a technical challenge. Thus, for both benign and malignant brain tumors, the most common cause of relapse is local recurrence at the resection margins. At the time of the operation, surgeons typically use visual inspection and tactile discrimination to differentiate tumor margins from surrounding normal brain parenchyma. In addition, imaging adjuncts such as navigation and intraoperative ultrasound can provide value. However, this method has many limitations, which accounts for the high rate of local failure.

Intraoperative adjunctive technologies, such as imaging-based navigational systems, have been useful in allowing the surgeon to estimate areas of contrast enhancement, which likely represent tumor. Although ultrasound-based re-registration can be used to account for brain shift, navigation alone is hampered by the inaccuracies attributable to brain shift and poor resolution when performing surgery in vivo. For the past 2 decades, intraoperative fluorescent contrast agents have been proposed to aid the neurosurgeon in identifying tumor tissue during surgery. The most popular approach has been fluorescent-guided intraoperative imaging with 5 aminolevulinic acid fluorescence guided resection. This method has been studied since the 1990s 4) 5)

It is difficult to reproducibly judge extent of resection (EOR in these studies due to the lack of reliable tumor segmentation methods, especially for postoperative magnetic resonance imaging (MRI) scans. Therefore, a reliable, easily distributable segmentation method is needed to permit valid comparison, especially across multiple sites 6).

Treatment advances will depend on identifying agents that target mechanistic vulnerabilities that are relevant to specific subgroups of patients; increasing patient enrollment into clinical trials is essential to accelerate the development of patient-tailored treatments 7).

Most studies that examine the notion of gross total resection (GTR) in glioblastoma treatment are conducted with the assumption that extended survival is universally desirable 8).

There are limited data in terms of how such survival benefits should be weighed against the risk of the surgery and the impact of surgical morbidity on the patient’s quality of life 9).

To study this issue, Chen et al., designed a survey entitled Putting yourself in your patient’s shoes: a pilot study of physician personal preferences for treatment of glioblastoma (U.C.S.D. institutional review board protocol no. 151821), where they survey physician members who have cared for glioblastoma patients. These physicians are well-acquainted with the consequences of surgery performed for glioblastoma located in different regions.

They pose the question of whether the respondent would elect for GTR if s/he were afflicted with glioblastoma located in the right frontal lobe, right hemisphere, left hemisphere, or the posterior corpus callosum.

Information on physician age, marital status, medical specialty (neurosurgery, neuro-oncology, medical oncology, neuroradiology, neuropathology or radiation oncology), years of practice, and personal values will be collected.

They would like to make neurosurgeons in Europe aware of this study, and to invite them to take part in it. They hope this study will give us more insight into our own preferences as physicans, when faced with the decision we council our patients on how to make on a daily basis.

To participate in the study please go to the following webpage by 31 October 2016: 10).

Case series

Data from Extent of resection in glioblastoma patients who underwent gross total resection (GTR), subtotal resection (STR), or open biopsybetween 2005 and 2014 were retrieved from the Surveillance, Epidemiology, and End Results database in the Seoul National University College of Medicine.

Univariate and multivariate analyses for overall survival (OS) were performed. Between 2005-2009 and 2010-2014, the proportion of GTR and STR performed increased from 41.4 to 42.3% and 33.0 to 37.1%, respectively. EOR only affected OS in the 3 years after diagnosis. Median survival in the GTR (n = 4155), STR (n = 3498), and open biopsy (n = 2258) groups was 17, 13, and 13 months, respectively (p < .001). STR showed no significant difference in OS from open biopsy (p = .33). GTR increased OS for midline-crossing tumors. Although STR was more frequently performed than GTR for tumors ≥ 6 cm in size, GTR significantly increased the OS rate relative to STR for tumors 6-8 cm in size (p = .001). For tumors ≥ 8 cm, STR was comparable to GTR (p = .61) and superior to open biopsy (p = .05). GTR needs to be performed more frequently for glioblastoma measuring ≥ 6 cm or that have crossed the midline to increase OS. STR was marginally superior to open biopsy when the tumor was ≥ 8 cm 11).


Esquenazi et al. retrospectively evaluated 86 consecutive patients with primary GBM, managed by the senior author, using a subpial resection technique with or without carmustine wafer implantation. Multivariate Cox proportional hazards regression was used to analyze clinical, radiological, and outcome variables. Overall impacts of extent of resection (EOR) and BCNU wafer placement were compared using Kaplan-Meier survival analysis.

Mean patient age was 56 years. The median OS for the group was 18.1 months. Median OS for patients undergoing gross total, near-total, and subtotal resection were 54, 16.5, and 13.2 months, respectively. Patients undergoing near-total resection ( P = .05) or gross total resection ( P < .01) experienced statistically significant longer survival time than patients undergoing subtotal resection as well as patients undergoing ≥95% EOR ( P < .01) when compared to <95% EOR. The addition of BCNU wafers had no survival advantage.

The subpial technique extends the resection beyond the contrast enhancement and is associated with an overall survival beyond that seen in similar series where resection of the enhancement portion is performed. The effect of supratotal resection on survival exceeded the effects of age, Karnofsky performance score, and tumor volume. A prospective study would help to quantify the impact of the subpial technique on quality of life and survival as compared to a traditional resection limited to the enhancing tumor 12).


Coburger et al. prospectively enrolled 33 patients with GBMs eligible for gross-total-resection(GTR) and performed a combined approach using 5-ALA and iMRI. As a control group, we performed a retrospective matched pair assessment, based on 144 patients with iMRI-assisted surgery. Matching criteria were, MGMT promotor methylation, recurrent surgery, eloquent location, tumor size and age. Only patients with an intended GTR and primary GBMs were included. We calculated Kaplan Mayer estimates to compare OS and PFS using the Log-Rank-Test. We used the T-test to compare volumetric results of EoR and the Chi-Square-Test to compare new permanent neurological deficits (nPND) and general complications between the two groups.

Median follow up was 31 months. No significant differences between both groups were found concerning the matching criteria. GTR was achieved significantly more often (p <0.010) using 5-ALA&iMRI (100%) compared to iMRI alone (82%). Mean EoR was significantly (p<0.004) higher in 5-ALA&iMRI-group (99.7%) than in iMRI-alone-group (97.4%) Rate of complications did not differ significantly between groups (21% iMRI-group, 27%5-ALA&iMRI-group, p<0.518). nPND were found in 6% in both groups. Median PFS (6 mo resp.; p<0.309) and median OS (iMRI:17 mo; 5-ALA&iMRI-group: 18 mo; p<0.708)) were not significantly different between both groups.

We found a significant increase of EoR when combining 5-ALA&iMRI compared to use of iMRI alone. Maximizing EoR did not lead to an increase of complications or neurological deficits if used with neurophysiological monitoring in eloquent lesions. No final conclusion can be drawn whether a further increase of EoR benefits patient’s progression free survival and overall survival 13).


retrospective review of 128 patients who underwent primary resection of supratentorial GBM followed by standard radiation/chemotherapy was undertaken utilizing quantitative, volumetric analysis of pre- and postoperative MR images. The results were compared with clinical data obtained from the patients’ medical records.

At analysis, 8% of patients were alive, and no patients were lost to follow-up. The overall median survival was 13.8 months, with a median Karnofsky Performance Scale (KPS) score of 90 at presentation. The median contrast-enhancing preoperative tumor volume (CE-PTV) was 29.0 cm3, and CE-RTV was 1.2 cm3, equating to a 95.8% median EOR. The median T2/F-RV was 36.8 cm3. CE-PTV, CE-RTV, T2/F-RV, and EOR were all statistically significant predictors of survival when controlling for age and KPS score. A statistically significant benefit in survival was seen with a CE-RTV less than 2 cm3 or an EOR greater than 98%. Evaluation of the volumetric analysis methodology was performed by observers of varying degrees of experience-an attending neurosurgeon, a fellow, and a medical student. Both the medical student and fellow recorded correlation coefficients of 0.98 when compared with the attending surgeon’s measured volumes of CE-PTV, while for CE-RTV, correlation coefficients of 0.67 and 0.71 (medical student and fellow, respectively) were obtained.

CE-RTV and EOR were found to be significant predictors of survival after GBM resection. CERTV was the more significant predictor of survival compared with EOR, suggesting that the volume of residual contrast-enhancing tumor may be a more accurate and meaningful reflection of the pathobiology of GBM 14).


Of 345 patients, 273 underwent open tumor resection and 72 biopsies; 125 patients had gross total resections (GTRs) and 148, incomplete resections. Surgery-related morbidity was lower after biopsy (1.4% versus 12.1%, P = 0.007). 64.3% of patients received radiotherapy and chemotherapy (RT plus CT), 20.0% RT alone, 4.3% CT alone, and 11.3% best supportive care as an initial treatment. Patients ≤60 years with a Karnofsky performance score (KPS) of ≥90 were more likely to receive RT plus CT (P < 0.01). Median overall survival (OS) (progression free survival; PFS) ranged from 33.2 months (15 months) for patients with MGMT-methylated tumors after GTR and RT plus CT to 3.0 months (2.4 months) for biopsied patients receiving supportive care only. Favorable prognostic factors in multivariate analyses for OS were age ≤60 years [hazard ratio (HR) = 0.52; P < 0.001], preoperative KPS of ≥80 (HR = 0.55; P < 0.001), GTR (HR = 0.60; P = 0.003), MGMT promoter methylation (HR = 0.44; P < 0.001), and RT plus CT (HR = 0.18, P < 0.001); patients undergoing incomplete resection did not better than those receiving biopsy only (HR = 0.85; P = 0.31).

The value of incomplete resection remains questionable. If GTR cannot be safely achieved, biopsy only might be used as an alternative surgical strategy 15).


retrospectively analyzed preoperative and postoperative radiographic tumor volumes in 92 patients who underwent hemispheric glioblastoma multiforme operations (107) to determine the factors that affect time to tumor progression (TTP) and overall survival.

METHODS: Quantification of tumor volumes was based on a previously described method involving computerized image analysis of contrast enhancing tumor on computerized tomography or magnetic resonance imaging scans.

RESULTS: Among the variables analyzed, preoperative Karnofsky Performance Status (KPS) (p < 0.05), chemotherapy (p < 0.05), percent of resection (POR) (p < 0.001), and volume of residual disease (VRD) (p < 0.001) had a significant effect on TTP. Factors that affected survival were age (p < 0.05), preoperative KPS (p = 0.05), postoperative KPS (p < 0.005), POR (p < 0.0005), and VRD (p < 0.0001). Greater resections did not compromise the quality of life, and patients without any residual disease had a better postoperative KPS than those patients who received less than total resections.

CONCLUSIONS: The extent of tumor removal and the amount of residual tumor volume, documented on postoperative imaging studies, are highly significant factors affecting the median time to tumor progression and median survival for patients with glioblastoma multiforme of the cerebral hemisphere 16).

1) , 15)

Kreth FW, Thon N, Simon M, Westphal M, Schackert G, Nikkhah G, Hentschel B, Reifenberger G, Pietsch T, Weller M, Tonn JC; German Glioma Network.. Gross total but not incomplete resection of glioblastoma prolongs survival in the era of radiochemotherapy. Ann Oncol. 2013 Dec;24(12):3117-23. doi: 10.1093/annonc/mdt388. PubMed PMID: 24130262.

Grabowski MM, Recinos PF, Nowacki AS, Schroeder JL, Angelov L, Barnett GH, Vogelbaum MA. Residual tumor volume versus extent of resection: predictors of survival after surgery for glioblastoma. J Neurosurg. 2014 Nov;121(5):1115-23. doi: 10.3171/2014.7.JNS132449. Epub 2014 Sep 5. PubMed PMID: 25192475.

Cordova JS, Schreibmann E, Hadjipanayis CG, Guo Y, Shu HK, Shim H, Holder CA. Quantitative tumor segmentation for evaluation of extent of glioblastoma resection to facilitate multisite clinical trials. Transl Oncol. 2014 Feb 1;7(1):40-7. eCollection 2014 Feb. PubMed PMID: 24772206; PubMed Central PMCID: PMC3998691.

Zhao S, Wu J, Wang C, et al. Intraoperative fluorescence-guided resection of high-grade malignant gliomas using 5-Aminolevulinic acid-induced porphyrins: a systematic review and meta-analysis of prospective studies. PLoS One. 2013:8(5):e63682.

Stummer W, Pichlmeier U, Meinel T, Wiestler OD, Zanella F, Reulen HJ. Fluorescence-guided surgery with 5-aminolevulinic acid for resection of malignant glioma: a randomised controlled multicentre phase III trial. Lancet Oncol. 2006;7(5):392–401.) ((Stummer W, Novotny A, Stepp H, Goetz C, Bise K, Reulen HJ. Fluorescence-guided resection of glioblastoma multiforme by using 5-aminolevulinic acid-induced porphyrins: a prospective study in 52 consecutive patients. J Neurosurg. 2000;93(6):1003–1013.

Cordova JS, Schreibmann E, Hadjipanayis CG, Guo Y, Shu HK, Shim H, Holder CA. Quantitative tumor segmentation for evaluation of extent of glioblastoma resection to facilitate multisite clinical trials. Transl Oncol. 2014 Feb 1;7(1):40-7. eCollection 2014 Feb. PubMed PMID: 24772206.

Thomas AA, Brennan CW, DeAngelis LM, Omuro AM. Emerging Therapies for Glioblastoma. JAMA Neurol. 2014 Sep 22. doi: 10.1001/jamaneurol.2014.1701. [Epub ahead of print] PubMed PMID: 25244650.

Kramm CM, Wagner S, Van Gool S, Schmid H, Strater R, Gnekow A, Rutkowski S, Wolff JE (2006) Improved survival after gross total resection of malignant gliomas in pediatric patients from the HITGBM studies. Anticancer Res 26:3773–3779

Ausman JI (2014) Gross total resection: do we want survival statistics or quality of life measurements. Surg Neurol Int 5:77

Chen CC, Depp C, Wilson B, Bartek J Jr, Carter B. A pilot study of physician personal preferences for treatment of glioblastoma. Acta Neurochir (Wien). 2016 Oct;158(10):1933. doi: 10.1007/s00701-016-2913-2. Epub 2016 Aug 19. PubMed PMID: 27541491.

Kim YJ, Lee DJ, Park CK, Kim IA. Optimal extent of resection for glioblastoma according to site, extension, and size: a population-based study in the temozolomide era. Neurosurg Rev. 2019 Jan 5. doi: 10.1007/s10143-018-01071-3. [Epub ahead of print] PubMed PMID: 30612289.

Esquenazi Y, Friedman E, Liu Z, Zhu JJ, Hsu S, Tandon N. The Survival Advantage of “Supratotal” Resection of Glioblastoma Using Selective Cortical Mapping and the Subpial technique. Neurosurgery. 2017 Mar 23. doi: 10.1093/neuros/nyw174. [Epub ahead of print] PubMed PMID: 28368547.

Coburger J, Hagel V, Wirtz CR, König R. Surgery for Glioblastoma: Impact of the Combined Use of 5-Aminolevulinic Acid and Intraoperative MRI on Extent of Resection and Survival. PLoS One. 2015 Jun 26;10(6):e0131872. doi: 10.1371/journal.pone.0131872. eCollection 2015. PubMed PMID: 26115409; PubMed Central PMCID: PMC4482740.

Grabowski MM, Recinos PF, Nowacki AS, Schroeder JL, Angelov L, Barnett GH, Vogelbaum MA. Residual tumor volume versus extent of resection: predictors of survival after surgery for glioblastoma. J Neurosurg. 2014 Sep 5:1-9. [Epub ahead of print] PubMed PMID: 25192475.

Keles GE, Anderson B, Berger MS. The effect of extent of resection on time to tumor progression and survival in patients with glioblastoma multiforme of the cerebral hemisphere. Surg Neurol. 1999 Oct;52(4):371-9. PubMed PMID: 10555843.
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