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Manfred Mühlbauer, Wolfgang Pfisterer, Richard Eyb, and Engelbert Knosp

Anterior decompressive surgery with spinal fusion is considered an effective treatment for thoracolumbar fractures and tumors. However, it is also known to be associated with considerable surgical approach–related trauma. The purpose of this study was to show that lumbar corpectomy and spinal reconstruction can be performed via a minimally invasive retroperitoneal (MIR) approach and therefore, the surgical approach–related trauma can be reduced.

The hospital records and radiological studies obtained in five patients (mean age 67.4 years, range 59-76 years) who underwent lumbar corpectomy and spinal fusion via an MIR approach were studied retrospectively. Four patients presented with osteoporotic compression fractures at L-2 and L-3 and one patient with metastatic disease at L-4 from prostate cancer. In all patients neurological deficits due to cauda equina compression were demonstrated.

The MIR approach provided excellent exposure to facilitate complete spinal decompression and reconstruction in all patients, as verified on follow-up x-ray studies. All patients improved clinically. A 1-year follow-up record, available for four patients, showed evidence of continuing clinical improvement and, radiographically, a solid fusion or a stable compound union and anatomically correct reconstruction.

The MIR approach allows anterior lumbar spine surgery to be performed less invasively. The efficacy and safety of this technique compared with the conventional retroperitoneal approach to lumbar spine surgery should be further investigated in a larger series.

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Manfred Mühlbauer, Wolfgang Pfisterer, Richard Eyb, and Engelbert Knosp

✓ The anterior decompressive procedure in which spinal fusion is performed is considered an effective treatment for thoracolumbar fractures and tumors. However, it is also known to be associated with considerable surgery-related trauma. The purpose of this study was to show that lumbar corpectomy and anterior reconstruction can be performed via a minimally invasive retroperitoneal approach (MIRA) and therefore the surgical approach—related trauma can be reduced.

The authors studied retrospectively the hospital records and radiological studies obtained in five patients (mean age 67.4 years, range 59–76 years) who underwent lumbar corpectomy and spinal fusion via an MIRA followed by posterior fixation. Four patients presented with osteoporotic compression fractures at L-2 and L-3, and one patient presented with metastatic disease in L-4 from prostate cancer. Neurological deficits due to cauda equina compression were demonstrated in all patients.

The MIRA provided excellent exposure to facilitate complete decompression and anterior reconstruction in all patients, as verified on follow-up radiographic studies. All patients improved clinically. A 1-year follow-up record is available for four patients and a 6-month follow-up record for the fifth patient; continuing clinical improvement has been observed in all. Radiography demonstrated anatomically correct reconstruction in all patients, as well as a solid fusion or a stable compound union in the four patients for whom 1-year follow-up records were available.

The MIRA allows the surgeon to perform anterior lumbar spine surgery via a less invasive approach. The efficacy and safety of this technique and its potential to reduce perioperative morbidity compared with conventional retroperitoneal lumbar spine surgery should be further investigated in a larger series.

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Alexander S. G. Micko, Adelheid Wöhrer, Stefan Wolfsberger, and Engelbert Knosp

OBJECT

An important prognostic factor for the surgical outcome and recurrence of a pituitary adenoma is its invasiveness into parasellar tissue, particularly into the space of the cavernous sinus (CS). The aims of this study were to reevaluate the existing parasellar classifications using an endoscopic technique and to evaluate the clinical and radiological outcomes associated with each grade.

METHODS

The authors investigated 137 pituitary macroadenomas classified radiologically at least on one side as Grade 1 or higher (parasellar extension) and correlated the surgical findings using an endoscopic technique, with special reference to the invasiveness of the tumor into the CS. In each case, postoperative MRI was performed to evaluate the gross-total resection (GTR) rate and the rate of endocrinological remission (ER) in functioning adenomas.

RESULTS

The authors found a 16% rate of CS invasion during surgery for these macroadenomas. Adenomas radiologically classified as Grade 1 were found to be invasive in 1.5%, and the GTR/ER rate was 83%/88%. For Grade 2 adenomas, the rate of invasion was 9.9%, and the GTR/ER rate was 71%/60%. For Grade 3 adenomas, the rate of invasion was 37.9%, and the GTR/ER rate was 75%/33%. When the superior compartment of the CS (Grade 3A) was involved, the authors found a rate of invasion that was lower (p < 0.001) than that when the inferior compartment was involved (Grade 3B). The rate of invasion in Grade 3A adenomas was 26.5% with a GTR/ER rate of 85%/67%, whereas for Grade 3B adenomas, the rate of surgically observed invasion was 70.6% with a GTR/ER rate of 64%/0%. All of the Grade 4 adenomas were invasive, and the GTR/ER rate was 0%.

A comparison of microscopic and endoscopic techniques revealed no difference in adenomas with Grade 1 or 4 parasellar extension. In Grade 2 adenomas, however, the CS was found by the endoscopic technique to be invaded in 9.9% and by microscopic evaluation to be invaded in 88% (p < 0.001); in Grade 3 adenomas, the difference was 37.9% versus 86%, respectively (p = 0.002). Grade 4 adenomas had a statistically significant lower rate of GTR than those of all the other grades. In case of ER only, Grade 1 adenomas had a statistically significant higher rate of remission than did Grade 3B and Grade 4 adenomas.

CONCLUSIONS

The proposed classification proved that with increasing grades, the likelihood of surgically observed invasion rises and the chance of GTR and ER decreases. The direct endoscopic view confirmed the low rate of invasion of Grade 1 adenomas but showed significantly lower rates of invasion in Grade 2 and 3 adenomas than those previously found using the microscopic technique. In cases in which the intracavernous internal carotid artery was encased (Grade 4), all the adenomas were invasive and the GTR/ER rate was 0%/0%. The authors suggest the addition of Grades 3A and 3B to distinguish the strikingly different outcomes of adenomas invading the superior CS compartments and those invading the inferior CS compartments.

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Matthias Millesi, Engelbert Knosp, Georg Mach, Johannes A. Hainfellner, Gerda Ricken, Siegfried Trattnig, and Andreas Gruber

OBJECTIVE

In the last several decades, various factors have been studied for a better evaluation of the risk of rupture in incidentally discovered intracranial aneurysms (IAs). With advanced MRI, attempts were made to delineate the wall of IAs to identify weak areas prone to rupture. However, the field strength of the MRI investigations was insufficient for reasonable image resolution in many of these studies. Therefore, the aim of this study was to analyze findings of IAs in ultra–high field MRI at 7 Tesla (7 T).

METHODS

Patients with incidentally found IAs of at least 5 mm in diameter were included in this study and underwent MRI investigations at 7 T. At this field strength a hyperintense intravascular signal can be observed on nonenhanced images with a brighter “rim effect” along the vessel wall. Properties of this rim effect were evaluated and compared with computational fluid dynamics (CFD) analyses.

RESULTS

Overall, 23 aneurysms showed sufficient image quality for further evaluation. In 22 aneurysms focal irregularities were identified within this rim effect. Areas of such irregularities showed significantly higher values in wall shear stress and vorticity compared to areas with a clearly visible rim effect (p = 0.043 in both).

CONCLUSIONS

A hyperintense rim effect along the vessel wall was observed in most cases. Focal irregularities within this rim effect showed higher values of the mean wall shear stress and vorticity when compared by CFD analyses. Therefore, these findings indicate alterations in blood flow in IAs within these areas.

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Alexander Micko, Thomas Rötzer, Romana Hoftberger, Greisa Vila, Johannes Oberndorfer, Josa M. Frischer, Engelbert Knosp, and Stefan Wolfsberger

OBJECTIVE

According to the latest WHO classification of tumors of endocrine organs in 2017, plurihormonal adenomas are subclassified by their transcription factor (TF) expression. In the group of plurihormonal adenomas with unusual immunohistochemical combinations (PAWUC), the authors identified a large fraction of adenomas expressing TFs for gonadotroph adenoma (TFGA) cells in addition to other TFs. The aim of this study was to compare clinicopathological parameters of PAWUC with TFGA expression to gonadotroph adenomas that only express TFGA.

METHODS

This retrospective single-center series comprises 73 patients with TFGA-positive pituitary adenomas (SF1, GATA3, estrogen receptor α): 22 PAWUC with TFGA (TFGA-plus group) and 51 with TFGA expression only (TFGA-only group). Patient characteristics, outcome parameters, rate of invasiveness (assessed by direct endoscopic inspection), and MIB1 and MGMT status were compared between groups.

RESULTS

Patients in the TFGA-plus group were significantly younger than patients in the TFGA-only group (age 46 vs 56 years, respectively; p = 0.007). In the TFGA-only group, pituitary adenomas were significantly larger (diameter 25 vs 18.3 mm, p = 0.002). Intraoperatively, signs of invasiveness were significantly more common in the TFGA-plus group than in the TFGA-only group (50% vs 16%, p = 0.002). Gross-total resection was significantly lower in the nonfunctioning TFGA-plus group than in the TFGA-only group (44% vs 86%, p = 0.004). MIB1 and MGMT status showed no significant difference between groups.

CONCLUSIONS

These data suggest a more aggressive behavior of TFGA-positive adenomas if an additional TF is expressed within the tumor cells. Shorter radiographic surveillance and earlier consideration for retreatment should be recommended in these adenoma types.

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Klaus Novak, Georg Widhalm, Adauri Bueno de Camargo, Noel Perin, George Jallo, Engelbert Knosp, and Vedran Deletis

Object

Thoracic idiopathic spinal cord herniation (TISCH) is a rare neurological disorder characterized by an incarceration of the spinal cord at the site of a ventral dural defect. The disorder is associated with clinical signs of progressive thoracic myelopathy. Surgery can withhold the natural clinical course, but surgical repair of the dural defect bears a significant risk of additional postoperative motor deficits, including permanent paraplegia. Intraoperative online information about the functional integrity of the spinal cord and warning signs about acute functional impairment of motor pathways could contribute to a lower risk of permanent postoperative motor deficit. Motor evoked potential (MEP) monitoring can instantly and reliably detect dysfunction of motor pathways in the spinal cord. The authors have applied MEPs during intraoperative neurophysiological monitoring (IOM) for surgical repair of TISCH and have correlated the results of IOM with its influence on the surgical procedure and with the functional postoperative outcome.

Methods

The authors retrospectively reviewed the intraoperative neurophysiological data and clinical records of 4 patients who underwent surgical treatment for TISCH in 3 institutions where IOM, including somatosensory evoked potentials and MEPs, is routinely used for spinal cord surgery. In all 4 patients the spinal cord was reduced from a posterior approach and the dural defect was repaired using a dural graft.

Results

Motor evoked potential monitoring was feasible in all patients. Significant intraoperative changes of MEPs were observed in 2 patients. The changes were detected within seconds after manipulation of the spinal cord. Monitoring of MEPs led to immediate revision of the placement of the dural graft in one case and to temporary cessation of the release of the incarcerated spinal cord in the other. Changes occurred selectively in MEPs and were reversible. In both patients, transient changes in intraoperative MEPs correlated with a reversible postoperative motor deficit. Patients without significant changes in somatosensory evoked potentials and MEPs demonstrated no additional neurological deficit postoperatively and showed improvement of motor function during follow-up.

Conclusions

Surgical repair of the dural defect is effected by release and reduction of the spinal cord and insertion of dural substitute over the dural defect. Careful monitoring of the functional integrity of spinal cord long tracts during surgical manipulation of the cord can detect surgically induced impairment. The authors' documentation of acute loss of MEPs that correlated with reversible postoperative motor deficit substantiates the necessity of IOM including continuous monitoring of MEPs for the surgical treatment of TISCH.

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Aygül Mert, Barbara Kiesel, Adelheid Wöhrer, Mauricio Martínez-Moreno, Georgi Minchev, Julia Furtner, Engelbert Knosp, Stefan Wolfsberger, and Georg Widhalm

OBJECT

Surgery of suspected low-grade gliomas (LGGs) poses a special challenge for neurosurgeons due to their diffusely infiltrative growth and histopathological heterogeneity. Consequently, neuronavigation with multimodality imaging data, such as structural and metabolic data, fiber tracking, and 3D brain visualization, has been proposed to optimize surgery. However, currently no standardized protocol has been established for multimodality imaging data in modern glioma surgery. The aim of this study was therefore to define a specific protocol for multimodality imaging and navigation for suspected LGG.

METHODS

Fifty-one patients who underwent surgery for a diffusely infiltrating glioma with nonsignificant contrast enhancement on MRI and available multimodality imaging data were included. In the first 40 patients with glioma, the authors retrospectively reviewed the imaging data, including structural MRI (contrast-enhanced T1-weighted, T2-weighted, and FLAIR sequences), metabolic images derived from PET, or MR spectroscopy chemical shift imaging, fiber tracking, and 3D brain surface/vessel visualization, to define standardized image settings and specific indications for each imaging modality. The feasibility and surgical relevance of this new protocol was subsequently prospectively investigated during surgery with the assistance of an advanced electromagnetic navigation system in the remaining 11 patients. Furthermore, specific surgical outcome parameters, including the extent of resection, histological analysis of the metabolic hotspot, presence of a new postoperative neurological deficit, and intraoperative accuracy of 3D brain visualization models, were assessed in each of these patients.

RESULTS

After reviewing these first 40 cases of glioma, the authors defined a specific protocol with standardized image settings and specific indications that allows for optimal and simultaneous visualization of structural and metabolic data, fiber tracking, and 3D brain visualization. This new protocol was feasible and was estimated to be surgically relevant during navigation-guided surgery in all 11 patients. According to the authors' predefined surgical outcome parameters, they observed a complete resection in all resectable gliomas (n = 5) by using contour visualization with T2-weighted or FLAIR images. Additionally, tumor tissue derived from the metabolic hotspot showed the presence of malignant tissue in all WHO Grade III or IV gliomas (n = 5). Moreover, no permanent postoperative neurological deficits occurred in any of these patients, and fiber tracking and/or intraoperative monitoring were applied during surgery in the vast majority of cases (n = 10). Furthermore, the authors found a significant intraoperative topographical correlation of 3D brain surface and vessel models with gyral anatomy and superficial vessels. Finally, real-time navigation with multimodality imaging data using the advanced electromagnetic navigation system was found to be useful for precise guidance to surgical targets, such as the tumor margin or the metabolic hotspot.

CONCLUSIONS

In this study, the authors defined a specific protocol for multimodality imaging data in suspected LGGs, and they propose the application of this new protocol for advanced navigation-guided procedures optimally in conjunction with continuous electromagnetic instrument tracking to optimize glioma surgery.

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Alexander Micko, Arthur Hosmann, Aygül Wurzer, Svenja Maschke, Wolfgang Marik, Engelbert Knosp, and Stefan Wolfsberger

OBJECTIVE

The transsphenoidal route to pituitary adenomas challenges surgeons because of the highly variable sinunasal anatomy. Orientation may be improved if the appropriate information is provided intraoperatively by image guidance. The authors developed an advanced image guidance protocol dedicated to sinunasal surgery that extracts information from multiple modalities and forms it into a single image that includes fine sinunasal structures and arteries.

The aim of this study was to compare the advantages of this novel image guidance protocol with the authors’ previous series, with emphasis on anatomical structures visualized and complication rate.

METHODS

This retrospective analysis comprised 200 patients who underwent surgery for pituitary adenoma via a transnasal transsphenoidal endoscopic approach. The authors’ standard image guidance protocol consisting of CT for solid bone, T1CEMRI for soft tissues, and MRA for the carotid artery was applied in 100 consecutive cases. The advanced image guidance protocol added a first-hit ray casting of the CT scan for visualization of fine sinunasal structures, and adjustments to the MRA to visualize the sphenopalatine artery (SPA) were applied in a subsequent 100 consecutive cases.

RESULTS

A patent sphenoid ostium—i.e., an ostium not covered by a mucosal layer—was visualized significantly more often by the advanced protocol than the standard protocol (89% vs 40%, p < 0.001) in primary surgeries. The SPA and its branches were only visualized by the advanced protocol (87% and 91% of cases in primary surgeries and reoperations, respectively) and not once by the standard protocol. The number of visualized complete and incomplete sphenoid septations matched significantly more commonly with the surgical view when using the advanced protocol than the standard protocol at primary operation (mean 1.9 vs 1.6, p < 0.001). However, in 25% of all cases a complex and not a simple sinus anatomy was present. In comparison with the intraoperative results, a complex sphenoid sinus anatomy was always detected by the advanced but not by the standard protocol (25% vs 8.5%, p = 0.001).

Furthermore, application of the advanced protocol reduced the cumulative rate of complications (25% vs 18% [standard vs advanced group]). Although an overall significant difference could not be determined (p = 0.228), a subgroup analysis of reoperations (35/200) revealed a significantly lower rate of complications in the advanced group (5% vs 30%, p = 0.028).

CONCLUSIONS

The data show that the advanced image guidance protocol could intraoperatively visualize the fine sinunasal sinus structures and small arteries with a high degree of detail. By improving intraoperative orientation, this may help to reduce the rate of complications in endoscopic transsphenoidal surgery, especially in reoperations.