Interdisciplinary Management of Skull Base Tumors. / Interdisziplinäre Behandlung von Schädelbasistumoren.

OBJECTIVE: Endoscopic endonasal skull base surgery has gained acceptance worldwide. Comparative analysis has demonstrated that endoscopic skull base surgery may have advantages for many pathologies of the anterior skull base, e. g., sinonasal malignant tumors; pathologies of the central skull base, e. g., pituitary adenomas, craniopharyngiomas; well-selected cases of planum sphenoidale and tuberculum sellae meningiomas; or for clival lesions, e. g., chordomas, chondrosarcomas, or selected meningiomas. Over the past three decades, interdisciplinary surgical teams, consisting of otolaryngologists and neurosurgeons, have provided detailed anatomical knowledge, suggested new approaches or modifications of established surgical techniques, and offered continued surgical education. METHOD: A review of pertinent literature was conducted with an emphasis on interdisciplinary endoscopic surgery of skull base lesions. RESULTS: Based on the authors̓ surgical experience in two different interdisciplinary endoscopic skull base centers, the authors classify approaches for endoscopic endonasal skull base surgery, describe indications, and key anatomic landmarks for common pathologies, and highlight surgical techniques to avoid complications. CONCLUSION: Interdisciplinary endonasal endoscopic surgery combines surgical expertise, improves resection rates for many pathologies, and minimizes morbidity by reducing the incidence of surgical complications.

Neurosurgical care for patients with high-grade gliomas during the coronavirus disease 2019 pandemic: Analysis of routine billing data of a German nationwide hospital network.

Background: Little is known about delivery of neurosurgical care, complication rate and outcome of patients with high-grade glioma (HGG) during the coronavirus disease 2019 (Covid-19) pandemic. Methods: This observational, retrospective cohort study analyzed routine administrative data of all patients admitted for neurosurgical treatment of an HGG within the Helios Hospital network in Germany. Data of the Covid-19 pandemic (March 1, 2020-May 31, 2022) were compared to the pre-pandemic period (January 1, 2016-February 29, 2020). Frequency of treatment and outcome (in-hospital mortality, length of hospital stay [LOHS], time in intensive care unit [TICU] and ventilation outside the operating room [OR]) were separately analyzed for patients with microsurgical resection (MR) or stereotactic biopsy (STBx). Results: A total of 1763 patients underwent MR of an HGG (648 patients during the Covid-19 pandemic; 1115 patients in the pre-pandemic period). 513 patients underwent STBx (182 [pandemic]; 331 patients [pre-pandemic]). No significant differences were found for treatment frequency (MR: 2.95 patients/week [Covid-19 pandemic] vs. 3.04 patients/week [pre-pandemic], IRR 0.98, 95% CI: 0.89-1.07; STBx (1.82 [Covid-19 pandemic] vs. 1.86 [pre-pandemic], IRR 0.96, 95% CI: 0.80-1.16, P > .05). Rates of in-hospital mortality, infection, postoperative hemorrhage, cerebral ischemia and ventilation outside the OR were similar in both periods. Overall LOHS was significantly shorter for patients with MR and STBx during the Covid-19 pandemic. Conclusions: The Covid-19 pandemic did not affect the frequency of neurosurgical treatment of patients with an HGG based on data of a large nationwide hospital network in Germany. LOHS was significantly shorter but quality of neurosurgical care and outcome was not altered during the Covid-19 pandemic.

Management and risk of postoperative bleeding in patients with low-dose antiplatelet aspirin medication during endoscopic endonasal surgery for pituitary adenomas.

BACKGROUND: To analyze the risk of postoperative bleeding following endoscopic endonasal transsphenoidal surgery (EETS) for treatment of pituitary adenomas (PA) in patients with short-term discontinuation of low-dose aspirin, if required for prevention of artherothrombotic disease (ATD). METHODS: Patients with preoperative aspirin medication were identified in this single-center retrospective analysis of consecutive patients with PA, who underwent EETS between December 2008 and June 2022. Aspirin was discontinued perioperatively less than 2 days, > 2 and < 4 days, and > 4 and < 7 days according to the assumed risk of perioperative ATD. For those patients, the rate of postoperative bleeding, which required surgery, was compared to patients without aspirin. RESULTS: Forty-five (14.8%) out of 304 patients underwent EETS with short-term perioperative aspirin discontinuation. Thirty-six (80%) patients discontinued aspirin < 2 days, 6 (13.3%) patients > 2 and < 4 days, and 3 patients (6.7%) > 4 but < 7 days. Postoperative bleeding rate was not increased in patients with short-term perioperative aspirin discontinuation. One patient (0.3%) without perioperative aspirin medication underwent revision surgery for treatment of postoperative hemorrhage with suprasellar extension. Eight patients (2.6%) had postoperative epistaxis (1 patient (0.3%) with short-term discontinuation and 7 patients (2.3%) without aspirin). Patients with perioperative aspirin were significantly older (68.3 ± 8.6 vs. 57.9 ± 14.1; p < 0.01) and had a significantly lower rate of hormonally active tumors (11.1% vs. 25.1%; p < 0.05) compared to patients without aspirin. No differences were found for tumor characteristics (tumor extension, tumor volume, largest diameter) between both groups. CONCLUSION: Short-term discontinuation of low-dose aspirin was not associated with increased rate of postoperative bleeding in patients, who underwent EETS for treatment of PA.

Two- and three-dimensional endoscopic endonasal surgery of large and giant pituitary adenomas-outcome analysis of a series of 62 patients from a single pituitary center.

To analyze the perioperative course and clinical outcome of patients with large (lPA) and giant (gPA) pituitary adenoma who underwent endoscopic endonasal transsphenoidal surgery (EETS) using either two-dimensional (2D-E) or three-dimensional (3D-E) endoscopic systems. Single-center retrospective study of consecutive patients with lPA and gPA who underwent EETS between November 2008 and January 2023. LPA were defined as ≥ 3 cm and < 4 cm in diameter in at least one dimension and a volume of ≥ 10ccm; gPA were defined as larger than 4 cm in diameter and with a greater volume than 10ccm. Patient data (age, sex, endocrinological and ophthalmological status) and tumor data (histology, tumor volume, size, shape, cavernous sinus invasion according to the Knosp classification) were analyzed. 62 patients underwent EETS. 43 patients were treated for lPA (69.4%) and 19 patients for gPA (30.6%). 46 patients (74.2%) underwent surgical resection using 3D-E and 16 patients 2D endoscopy (25.8%). Statistical results are referred to the comparison between 3D-E and 2D-E. Patients' age ranged from 23-88 years (median 57), 16 patients were female (25.8%), 46 male (74.2%). Complete tumor resection was possible in 43.5% (27/62), partial resection in 56.5% (35/62). Resection rates did not differ between 3D-E (27 patients [43.5%]) and 2D-E (7 patients [43.8%], (p = 0.985). Visual acuity improved in 30 of 46 patients with preoperative deficit (65.2%). In the 3D-E group 21 of 32 patients (65.7%) improved, compared to 9 of 14 patients in the 2D-E group (64.3%). Improvement of visual field was achieved in 31 of 50 patients (62.0%; 22 of 37 patients in the 3D-E group [59.4%] and 9 of 13 patients in the 2D-E group [69.2%]). CSF leak was the most frequent complication and occurred in 9 patients (14.5%, [8 patients 17.4% 3D-E]) without statistical significance. Other surgical complications like postoperative bleeding, infection (meningitis) and deterioration of visual acuity and field were detected without statistical difference. New pituitary anterior lobe dysfunction was observed in 30 of 62 patients (48.4%, 8 patients [50.0%] in the 2D-E group and 22 patients [47.8%] in the 3D-E group). A transient deficit of posterior lobe was detected in 22.6% (14/62). No patient died within 30 days of surgery. Although 3D-E may improve surgical dexterity, in this series of lPA and gPA it was not associated with higher resection rates compared to 2D-E. However, 3D-E visualization during resection of large and giant PA is safe and feasible and patient's clinical outcome is not different compared to 2D-E.

Prospective Multicenter Trial of Cervical Arthroplasty with the ROTAIO® Cervical Disc Prosthesis.

STUDY DESIGN: Clinical observational study. OBJECTIVE: The ROTAIO® cervical disc prosthesis is a novel unconstrained implant with a variable center of rotation aiming at physiological motion. The objective of this multicenter prospective trial was to evaluate clinical outcome and complications within 2 years. MATERIAL AND METHODS: 120 patients (72 females and 48 males with median age of 43.0 years [23-60 yrs] underwent ACDA (ROTAIO®, SIGNUS Medical, Alzenau, Germany) and were prospectively followed for 24 months. Preoperative complaints were mainly associated with radiculopathy (n = 104) or myelopathy (n=16). There were 108 monosegmental and 12 bisegmental procedures including 6 hybrid constructs. Clinical outcome was evaluated at 3, 12 and 24 months in 100%, 96% and 77% of the cohort by VAS, NDI, WL-26, Patient`s Satisfaction Index (PSI), SF-36, Nurick Score, mJOA, Composite Success Rate, complications, patient`s overall satisfaction and analgesics use. RESULTS: Highly significant clinical improvements were observed according to NDI and VAS (P < .0001 (arm); P < .001 (neck); P = .002 (head)) at all time points. Analgetic use could be reduced in 87.1 to 95.2%. Doctor`s visits have been reduced in 93.8% after 24 months. Patient`s overall satisfaction was high with 78.4 to 83.5% of patients. The composite success rate was 77.5% after 12 months and 76.9% after 24 months. There were no major complications in this series. Slight subsidence of the prosthesis was observed in 2 patients and 3 patients demonstrated fusion after 24 months. 2 patients developed symptomatic foraminal stenosis, so that implant removal and fusion was performed resulting in a revision rate of 1.7% in 2 years. CONCLUSION: The ROTAIO® cervical disc prosthesis is a safe and efficient treatment option for symptomatic degenerative disc disease demonstrating highly significant clinical improvement and high patient`s overall satisfaction with very low revision rates at 2 years.

Short-term fasting in glioma patients: analysis of diet diaries and metabolic parameters of the ERGO2 trial.

PURPOSE: The prospective, randomized ERGO2 trial investigated the effect of calorie-restricted ketogenic diet and intermittent fasting (KD-IF) on re-irradiation for recurrent brain tumors. The study did not meet its primary endpoint of improved progression-free survival in comparison to standard diet (SD). We here report the results of the quality of life/neurocognition and a detailed analysis of the diet diaries. METHODS: 50 patients were randomized 1:1 to re-irradiation combined with either SD or KD-IF. The KD-IF schedule included 3 days of ketogenic diet (KD: 21-23 kcal/kg/d, carbohydrate intake limited to 50 g/d), followed by 3 days of fasting and again 3 days of KD. Follow-up included examination of cognition, quality of life and serum samples. RESULTS: The 20 patients who completed KD-IF met the prespecified goals for calorie and carbohydrate restriction. Substantial decreases in leptin and insulin and an increase in uric acid were observed. The SD group, of note, had a lower calorie intake than expected (21 kcal/kg/d instead of 30 kcal/kg/d). Neither quality of life nor cognition were affected by the diet. Low glucose emerged as a significant prognostic parameter in a best responder analysis. CONCLUSION: The strict caloric goals of the ERGO2 trial were tolerated well by patients with recurrent brain cancer. The short diet schedule led to significant metabolic changes with low glucose emerging as a candidate marker of better prognosis. The unexpected lower calorie intake of the control group complicates the interpretation of the results. Clinicaltrials.gov number: NCT01754350; Registration: 21.12.2012.

ERGO2: A Prospective, Randomized Trial of Calorie-Restricted Ketogenic Diet and Fasting in Addition to Reirradiation for Malignant Glioma.

PURPOSE: ERGO2 is the first randomized clinical trial on a calorically restricted ketogenic diet (KD) and intermittent fasting (KD-IF) in addition to reirradiation for recurrent malignant gliomas. METHODS AND MATERIALS: Fifty patients were randomized 1:1 to reirradiation combined with either a calorically unrestricted diet or KD-IF. The KD-IF schedule included 3 days of KD (21-23 kcal/kg/d), followed by 3 days of fasting and again 3 days of KD. Primary endpoint was progression-free survival (PFS) at 6 months (PFS6). Secondary endpoints were PFS, local PFS, overall survival (OS), frequency of epileptic seizures, rate of ketosis and quality of life. RESULTS: Four patients quit the trial before treatment and 3 patients stopped KD-IF prematurely. Of the 20 patients who completed KD-IF, 17 patients developed ketosis at day 6 and glucose levels declined significantly. KD-IF was well-tolerated with a modest weight loss of -2.1 ± 1.8 kg. No severe adverse events attributable to the diet occurred. PFS6 was not significantly different between the 2 groups (KD-IF: 20%; calorically unrestricted diet: 16%). Similarly, no difference in PFS, local PFS6, or OS was observable. Explorative analysis revealed that patients in the KD-IF group who had a glucose level of less than the median (83.5 mg/dL) on day 6 had significantly longer PFS and OS compared with those above the median (P < .05). CONCLUSIONS: KD-IF is feasible and effective in inducing ketosis in heavily pretreated patients with recurrent glioma. However, the short schedule reported here failed to increase the efficacy of reirradiation. CLINICALTRIALS. GOV NUMBER: NCT01754350.

WHO grade of intracranial meningiomas differs with respect to patient's age, location, tumor size and peritumoral edema.

PURPOSE: To analyse whether the WHO grade of intracranial meningiomas differs itself depending on patients and meningioma characteristics at diagnosis. METHODS: Single center retrospective study of a series of consecutive patients with primary intracranial meningiomas who underwent surgery between January 2007 and March 2014. Patients (age, sex, outcome) and meningioma characteristics (histological diagnosis, tumor location, WHO grading, size, extend of peritumoral edema and tumor recurrence rate) were analysed. RESULTS: Of 240 included patients, 184 (76.7%) were female and 56 (23.3%) were male. 17 patients (7.1%) were in age group 20-40 years, 112 (46.7%) in group 41-60 years and 111 (46.3%) were in age group > 60 years. 189 patients (78.8%) were diagnosed with WHO grade I, 49 (20.4%) WHO grade II and 2 (0.8%) had a WHO grade III meningioma. WHO grade II meningiomas were significantly more frequent in the age group 20-40 years compared to age group 41-60 years (chi-square p < 0.05). Convexity meningiomas were significantly more frequent classified as WHO grade II meningiomas compared to all other locations (chi-square, p < 0.01). Mean calculated tumor volume and the tumor volume determined by volumetric measurement was significantly larger in grade II meningioma patients compared to grade I (46.3 ± 40.5 cc grade II versus 21.8 ± 27.8 cc grade I and 45.3 ± 38.2 cc versus 23.1 ± 30.0 cc respectively; t test < 0.01). Extend of the peritumoral edema was significantly larger in patients with grade II meningiomas (Wilcoxon test, p < 0.05). Short term outcome did not differ between different age groups nor was it associated with tumor size. During a mean follow up of 49 months (min 3, max 144 months) recurrence rate was significantly higher in WHO grade II (4 out of 49 [8.2]%) compared to WHO grade I patients (3 out if 186, [1.6%]; Chi-square, p < 0.05). CONCLUSION: In this series atypical meningioma was associated with younger age, location on the convexity, larger tumor size and more peritumoral edema.

Endoscopic Endonasal Surgery for Removal of Pituitary Adenomas: A Surgical Case Series of Treatment Results Using Different 2- and 3-Dimensional Visualization Systems.

BACKGROUND: Endoscopic endonasal transsphenoidal surgery (EETS) is a common treatment for patients with pituitary adenomas (PAs). A disadvantage of endoscopic surgery has been the lack of stereoscopic vision and depth perception. Recent developments offer high-definition 3-dimensional (3D-HD) visualization with a higher resolution and better image quality compared with 3D standard endoscopy (3D-SD). In this study, we compared treatment results of surgically treated patients with PAs using 3 different visualization systems: 2-dimensional (2D)-HD, 3D-SD, and 3D-HD. METHODS: Data from patients with primary PAs that were surgically treated between December 2008 and December 2017 were analyzed. Preoperative and postoperative tumor size and location, perioperative complications, and ophthalmologic, endocrine, and clinical outcomes were compared. RESULTS: A total of 170 patients underwent endoscopic resection of a primary PA (54 patients with 2D-HD, 75 with 3D-SD, and 41 with 3D-HD). Preoperatively, no statistical differences were found for tumor size, extension, and endocrine and ophthalmologic status. Tumor resection was not statistically different among the 3 groups. Complete resection was performed in 33 patients (80%) in the 3D-HD group, 54 patients (72%) in the 3D-SD group, and 39 patients (72%) in the 2D-HD group. The number of complications was not different across the groups (P = 0.436). Ophthalmologic outcomes did not differ based on EETS technique. The rate of new pituitary insufficiency was slightly lower in the 3D-HD group compared with 2D-HD and 3D-SD groups (4.8%, 16.6%, and 12%, respectively; P = 0.290). CONCLUSIONS: Although the resection rate was higher in the 3D-HD group, and subjective advantages of the 3D-HD endoscopes were noted, there were no significant differences in terms of gross total resection or new hormonal deficits among the 3 groups.

Implementation of the ultra low field intraoperative MRI PoleStar N20 during resection control of pituitary adenomas.

OBJECTIVE: To describe our experience with the application of an intraoperative ultra low field magnetic resonance imaging system (ioMRI) PoleStar N20, Medtronic Surgical Navigation Technologies, Louisville, USA during resection control of pituitary adenomas. METHODS: Forty-four patients were operated on a pituitary adenoma (1 microadenoma, 43 macroadenomas; mean size 26.0 ± 9.7 mm). The ioMRI system was used for navigation and resection control after transseptal, transsphenoidal microsurgical tumour removal using standard instruments and standard microscope. If any accessible tumour remnant was suspected surgery was continued for navigation guided re-exploration and if necessary continued resection. RESULTS: The applications of the scanner integrated navigation system, with a 3-planar reconstruction of the coronal scan, enabled the surgeon to safely approach and remove the tumour. The quality of preoperative tumour visualization with the ultra low field ioMRI in patients with macroadenomas is very good and has a good congruency with the preoperative 1.5 T MRI. For microadenomas the preoperative visualization is poor and very difficult to interpret. In seven patients ioMRI resection control showed residual tumours leading to further resection. After final tumour resection the ioMRI scan documented adequate decompression of the optic pathway in all patients. However, the intraoperative image interpretation was equivocal in four patients in whom it was difficult to distinguish between small intrasellar tumour remnants and perioperative changes. CONCLUSIONS: The PoleStar N20 is a safe, helpful and feasible tool for navigation guided pituitary tumour approach. Image interpretation is requires some experience, but decompression of the optic system can be reliable shown in cases with pituitary macroadenomas. This system is of limited value for resection control of pituitary microadenomas.

Hemostatic and hemorrhagic problems in neurosurgical patients.

BACKGROUND: Abnormalities of the hemostasis can lead to hemorrhage, and on the other hand to thrombosis. Intracranial neoplasms, complex surgical procedures, and head injury have a specific impact on coagulation and fibrinolysis. Moreover, the number of neurosurgical patients on medication (which interferes with platelet function and/or the coagulation systems) has increased over the past years. METHOD: The objective of this review is to recall common hemostatic disorders in neurosurgical patients on the basis of the "new concept of hemostasis". Therefore the pertinent literature was searched to provide a structured and up to date manuscript about hemostasis in Neurosurgery. FINDINGS: According to recent scientific publications abnormalities of the coagulation system are discussed. Pathophysiological background and the rational for specific (cost)-effective perioperative hemostatic therapy is provided. CONCLUSIONS: Perturbations of hemostasis can be multifactorial and maybe encountered in the daily practice of neurosurgery. Early diagnosis and specific treatment is the prerequisite for successful treatment and good patients outcome.

Traumatic epidural hematomas in children and adolescents: outcome analysis in 39 consecutive unselected cases.

OBJECTIVE: Despite early diagnosis of traumatic epidural hematomas (EDHs) in children, mortality remained quite high in recent series. The aims of this analysis were to review the cause and outcome of pediatric EDH nowadays and to discuss outcome-related variables in a large consecutive series of surgically treated EDH in children. METHODS: This is a retrospective case series of 39 patients (27 males, 69%) with surgically treated EDH between June 1997 and February 2007. Patients' medical records, computed tomographic scans, and, if performed, magnetic resonance imagings were reviewed to define variables associated with outcome. Variables included in the analysis were age, associated severe extracranial injury, abnormal pupillary response, hematoma thickness, severity of head injury (Glasgow Coma Scale score < or = 8), parenchymal brain injury, and diffuse axonal injury. Long-term follow-up (mean [SD], 51.3 [27] months) was available in 38 patients, and outcomes were classified as excellent (modified Rankin Scale score [mRS], 0; Glasgow Outcome Scale score, 5) and good (mRS scores, 1 and 2; Glasgow Outcome Scale score, 4). RESULTS: The mean (SD) age of the patients was 83.1 (59.9) months (range, 1-191 months). The mortality was zero, and the outcomes were excellent in 34 and good in 4 patients (one was lost to follow-up). Most of the injuries with EDH occurred in familial settings (23 cases), with falls being the most common mechanism of injury in 20 patients. Trauma was caused by traffic accidents in 14 cases (pedestrians hit by a motor vehicle, 7 cases; bicycle accidents, 5 cases; and motorbike and car accidents, 1 case each). One EDH occurred during delivery. The mean size of the EDH was 18.5 (12) mm (range, 5-40 mm). Three patients were referred with unilateral or bilateral dilated pupil(s). Except in 4 patients, all EDHs were associated with skull fracture(s) (90%). Computed tomography or magnetic resonance imaging revealed brain contusion in 13 patients, and 1 had diffuse axonal injury. None of the tested variables were found to have a prognostic relevance as tested by multivariate analysis (backward exclusion, Wald method). CONCLUSIONS: Regardless of the EDH size, the clinical status of the patients, the abnormal pupillary findings, or the cause of injury, the outcome and prognosis of the patients with EDH are excellent.

Thrombophilic risk factors in patients with cranial and spinal dural arteriovenous fistulae.

OBJECTIVE: Numerous studies have reported the technical aspects and results of surgical and/or endovascular treatment of cranial dural arteriovenous fistulae (cDAVF) and spinal dural arteriovenous fistulae (sDAVF). Only a few of them have addressed the question of thrombophilic conditions, which may be relevant as pathogenetic factors or can increase the risk for venous thromboembolic events. Therefore, the objective of this study is to compare thrombophilic risk factors in patients with cDAVF and sDAVF with no history of trauma. METHODS: A total of 43 patients (25 with cDAVF and 18 with sDAVF) were included in this study. Blood samples were analyzed for G20210A mutation of the prothrombin gene and factor V Leiden mutation. In all patients, prothrombin time, international normalized ratio, fibrinogen, antithrombin, protein C and S activity, von Willebrand factor antigen, ristocetin cofactor activity, D-dimer, coagulation factor VIII activity, and tissue factor pathway inhibitor were determined. Screening was performed for the occurrence of lupus antiphospholipid and cardiolipin antibodies. RESULTS: The prevalence of G20210A mutation of the prothrombin gene was significantly higher in patients with cDAVF (n = 6) compared with patients with sDAVF (n = 0; P < 0.05, Fisher's exact test). A factor V Leiden mutation was found in 3 patients with sDAVF and in 1 patient with cDAVF (P = 0.29, Fisher's exact test). No significant difference was found for other parameters, except for fibrinogen, but decreased protein C activity was more frequent in patients with cDAVF compared with patients with sDAVF (4 versus 1). Decreased protein S activity was encountered in 3 patients (2 with sDAVF and 1 with cDAVF). Cardiolipin antibodies were found in 2 patients with cDAVF but in none with sDAVF, whereas only 1 patient with sDAVF had lupus antiphospholipid antibodies. CONCLUSION: In both groups of patients with dural arteriovenous fistulae, genetic thrombophilic abnormalities occurred in a higher percentage than in the general population. The differences of the genetic abnormalities may be involved in different pathophysiological mechanism(s) in the development of these distinct neurovascular entities.

Feasibility of Polestar N20, an ultra-low-field intraoperative magnetic resonance imaging system in resection control of pituitary macroadenomas: lessons learned from the first 40 cases.

OBJECTIVE: To evaluate the feasibility of PoleStar N20 (Medtronic Surgical Navigation Technologies, Louisville, KY), an ultra-low-field intraoperative magnetic resonance imaging (iMRI) system during resection control of pituitary macroadenomas and to compare intraoperative images with postoperative 1.5-T MRI images obtained 3 months after the procedure. METHODS: Forty patients with a pituitary macroadenoma (mean size, 26.9 +/- 9.1 mm) underwent a surgical procedure to remove the tumor. The iMRI system was implemented in a standardized microsurgical procedure (endonasal, transseptal, transsphenoidal approach) using standard microsurgical instruments. Intraoperative imaging was performed for tumor visualization/navigation and resection control. If an accessible tumor remnant was suspected, surgery was continued for reexploration and, if necessary, continued resection. Total anesthesia time and operation time were compared with a historical cohort of 100 patients who underwent a surgical procedure on pituitary adenomas without iMRI. Sensitivity and specificity of the iMRI to detect residual tumor tissue was assessed in 33 patients (82.5%) after comparison with standard postoperative 1.5-T MRI 3 months after the procedure. RESULTS: Preoperative tumor visualization with the ultra-low-field iMRI showed a very good congruency with the preoperative 1.5-T MRI scans. A three-dimensional reconstruction of the coronal scan enabled the surgeon to safely approach the tumor using the integrated navigation system. In seven patients (17.5%), iMRI resection control showed accessible residual tumors leading to further resection. After tumor resection, the final iMRI scan documented adequate decompression of the optic pathway in all patients. Implementation of iMRI led to a significant increase of anesthesia time (246.0 +/- 50.7 versus 163.4 +/- 41.2 min) and operation time (116.9 +/- 43.9 versus 78.2 +/- 33.0 min; P < 0.05, t test). Sensitivity of the iMRI was 88.9, 85.7, 93.3, and 100% for the suprasellar, intrasellar, and right and left parasellar regions, respectively, and the specificity was 90.5% in the suprasellar and 100% in the intra- and parasellar regions on both sides. In four patients, the intraoperative interpretation of iMRI was equivocal; thus, it was difficult to distinguish between very small tumor remnants and perioperative changes. CONCLUSION: Ultra-low-field 0.15-T iMRI is a safe, helpful, and feasible tool for navigation and tumor resection control in patients with pituitary macroadenomas. Total anesthesia and operation times are prolonged, but iMRI adequately documents the extent of tumor resection. In this series, the PoleStar system increased the rate of resection without disrupting the neurosurgical workflow.