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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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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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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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Stefan Wolfsberger, Ahmed Ba-Ssalamah, Katja Pinker, Vladimír Mlynárik, Thomas Czech, Engelbert Knosp and Siegfried Trattnig

Object

The aim of this study was to determine the value of high-field magnetic resonance (MR) imaging for diagnosis and surgery of sellar lesions.

Methods

High-field MR images were obtained using a 3-tesla unit with emphasis on sellar and parasellar structures in 21 patients preoperatively to delineate endo-, supra-, and parasellar anatomical structures. Special attention was given to the medial border of the cavernous sinus and possible invasion of a sellar tumor therein, and to assessing the application of high-resolution images during intraoperative neuronavigation. The 3-tesla MR images were compared with the standard MR images already obtained and with intraoperative findings.

Anatomical structures were studied in all 42 cavernous sinuses; in 32 of them comparisons with intraoperative findings were possible. The medial cavernous sinus border was rated intact in 53% on standard MR images, in 72% on 3-tesla MR images, and in 81% intraoperatively. With a positive correlation to surgical findings on 84% of 3-tesla MR images compared with 59% of standard MR images, a sensitivity of 83% compared with 67%, and a specificity of 84% compared with 58% (p = 0.016, McNemar test), 3-tesla MR imaging was superior for predicting tumor invasion through the medial cavernous sinus border. Although no difference was noted in delineation of the medial, superior, and inferior compartments, there was a better delineation of the lateral cavernous sinus compartment with 3-tesla MR imaging. This compartment was clearly visible on 40 sides (95%) on 3-tesla MR images compared with 34 sides (81%) on standard MR images. Identification of the cavernous sinus segments of the third, fourth, fifth (V1 and V2), and sixth cranial nerves was improved using high-resolution 3-tesla imaging compared with standard MR imaging. A mean of four cranial nerves was found as hypo-intense spots (range two–five spots) on 3-tesla MR imaging compared with a mean of three (range zero–four spots) on standard MR imaging. After addition of contrast agents, the anterior pituitary gland was found to be highly intense on 78% of T1-weighted three-dimensional magnetization-prepared rapid acquisition gradient-echo (MPRAGE) 3-tesla MR images compared with 73% of standard T1-weighted MR images. The optochiasmatic system displayed increased intensity on pre-contrast T1-weighted MPRAGE 3-tesla compared with standard T1-weighted MR images; it was hyperintense on 76% of 3-tesla compared with 15% of standard MR images, which was helpful for its delineation from suprasellar pituitary and tumor structures. Intraoperative navigation guided by fusion of 3-tesla MR images and computerized tomography (CT) scans was performed in seven patients. Whereas CT scanning was used during the transsphenoidal approach to depict the nasal bone structures, 3-tesla MR imaging was particularly useful for the visualization of parasellar tumor extension during microsurgical and/or endoscopic resection.

Conclusions

Due to its higher resolution, 3-tesla MR imaging was found to be superior to standard MR imaging for the delineation of parasellar anatomy and tumor infiltration of the cavernous sinus, and this modality provided improved imaging for intraoperative navigation.

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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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Walter F. Saringer, Brian Reddy, Iris Nöbauer-Huhmann, Rene Regatschnig, Marion Reddy, Manfred Tschabitscher and Engelbert Knosp

Object. Cervical radiculopathy is typically caused by posterolateral disc herniation or spondylotic foraminal stenosis, either of which may compress the ventral aspect of the nerve root. The authors undertook a study to establish the feasibility of performing an endoscopic approach for anterior cervical foraminotomy (ACFor) in a clinical setting.

Methods. Application of this method on cadavers was conducted to verify the practicability of this technique. The clinical study included 16 patients (eight men and eight women; mean age 46.6 years) all presenting with unilateral radicular symptoms (one at two adjacent ipsilateral levels), which were associated with various degrees of neck pain. Disc herniations and/or uncovertebral osteophytes were confirmed on magnetic resonance imaging and high-resolution computerized tomography scanning. A total of 17 endoscopic ACFors (one two-level procedure) were performed using a rigid glass endoscope (25° angled, 3-mm diameter, 10-mm length) mounted on a tubular retractor.

No major surgery-related complications were encountered. During a mean follow-up period of 13.8 months an average absolute improvement of 44% (p > 0.05) in the neck disability index score and of 96% (p > 0.05) in the visual analog scale score for radicular pain (compared with the preoperative score) was observed. During the follow-up period strength improved to normal in 84% and sensory deficit in 80% of the patients. The overall subjective patient satisfaction rate was 87.6%; the return-to-work rate after 4 weeks was 81.4%.

Conclusions. The advantages of endoscopic ACFor include minimial surgical exposure, improved intraoperative visualization, direct decompression of the nerve root, and the preservation of the intervertebral disc and the motion segment.

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Georg Widhalm, Wolfgang Dietrich, Leonhard Müllauer, Berthold Streubel, Werner Rabitsch, Mark R. Kotter, Engelbert Knosp and Karl Roessler

✓ The authors report the unusual case of a 35-year-old woman suffering from left leg numbness and radiculopathy due to multiple lesions in the central nervous system: one right parietal extracranial–intracranial lesion with invasion of the sensory cortex, and two intraspinal, intradural lesions compressing the spinal cord at T3–5 and S1–4. Biopsy sampling of the extracranial part of the parietal lesion led to a diagnosis of myeloid sarcoma. Further examination revealed no evidence of leukemic disease or myeloproliferative disorder. An aggressive multimodal approach to treatment in this patient with a combination of chemotherapy, whole-body radiotherapy, and allogeneic bone marrow transplantation was started immediately. The patient experienced full neurological recovery and complete disappearance of all lesions. At the 7-year follow-up examination, there was no evidence of disease. To the authors’ knowledge, this is the first report of a myeloid sarcoma with both intracranial and intraspinal manifestations in a patient without leukemia.

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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.