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  • Author or Editor: Rudolf Fahlbusch x
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Christian Strauss, Johann Romstöck, Christopher Nimsky and Rudolf Fahlbusch

✓ Intraoperative electrical identification of motor areas within the floor of the fourth ventricle was successfully carried out in a series of 10 patients with intrinsic pontine lesions and lesions infiltrating the brain stem. Direct electrical stimulation was used to identify the facial colliculus and the hypoglossal triangle before the brain stem was entered. Multichannel electromyographic recordings documented selective stimulation effects. The surgical approach to the brain stem was varied according to the electrical localization of these structures. During removal of the lesion, functional integrity was monitored by intermittent stimulation. In lesions infiltrating the floor of the fourth ventricle, stimulation facilitated complete removal. Permanent postoperative morbidity of facial or hypoglossal nerve dysfunction was not observed. Mapping of the floor of the fourth ventricle identifies important surface structures and offers a safe corridor through intact nervous structures during surgery of brain-stem lesions. Reliable identification is particularly important in mass lesions with displacement of normal topographical anatomy.

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Rudolf Fahlbusch, Oliver Ganslandt, Michael Buchfelder, Werner Schott and Christopher Nimsky

Object. The aim of this study was to evaluate whether intraoperative magnetic resonance (MR) imaging can increase the efficacy of transsphenoidal microsurgery, primarily in non—hormone-secreting intra- and suprasellar pituitary macroadenomas.

Methods. Intraoperative imaging was performed using a 0.2-tesla MR imager, which was located in a specially designed operating room. The patient was placed supine on the sliding table of the MR imager, with the head placed near the 5-gauss line. A standard flexible coil was placed around the patient's forehead. Microsurgery was performed using MR-compatible instruments. Image acquisition was started after the sliding table had been moved into the center of the magnet. Coronal and sagittal T1-weighted images each required over 8 minutes to acquire, and T2-weighted images were obtained optionally. To assess the reliability of intraoperative evaluation of tumor resection, the intraoperative findings were compared with those on conventional postoperative 1.5-tesla MR images, which were obtained 2 to 3 months after surgery.

Among 44 patients with large intra- and suprasellar pituitary adenomas that were mainly hormonally inactive, intraoperative MR imaging allowed an ultra-early evaluation of tumor resection in 73% of cases; such an evaluation is normally only possible 2 to 3 months after surgery. A second intraoperative examination of 24 patients for suspected tumor remnants led to additional resection in 15 patients (34%).

Conclusions. Intraoperative MR imaging undoubtedly offers the option of a second look within the same surgical procedure, if incomplete tumor resection is suspected. Thus, the rate of procedures during which complete tumor removal is achieved can be improved. Furthermore, additional treatments for those patients in whom tumor removal was incomplete can be planned at an early stage, namely just after surgery.

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Sven Berkmann, Sven Schlaffer, Christopher Nimsky, Rudolf Fahlbusch and Michael Buchfelder

Object

The loss of anatomical landmarks, frequently invasive tumor growth, and tissue changes make transsphenoidal reoperation of nonfunctioning pituitary adenomas (NFAs) challenging. The use of intraoperative MRI (iMRI) may lead to improved results. The goal of this retrospective study was to evaluate the impact of iMRI on transsphenoidal reoperations for NFA.

Methods

Between September 2002 and July 2012, 109 patients underwent reoperations in which 111 transsphenoidal procedures were performed and are represented in this study. A 1.5-T Magnetom Sonata Maestro Class scanner (Siemens) was used for iMRI. Follow-up iMRI scans were acquired if gross-total resection (GTR) was suspected or if no further removal seemed possible.

Results

Surgery was performed for tumor persistence and regrowth in 26 (23%) and 85 (77%) patients, respectively. On the initial iMRI scans, GTR was confirmed in 19 (17%) patients. Remnants were located as follows: 65 in the cavernous sinus (71%), 35 in the suprasellar space (38%), 9 in the retrosellar space (10%). Additional resection was possible in 62 (67%) patients, resulting in a significant volume reduction and increased GTR rate (49%). The GTR rates of invasive tumors on initial iMRI and postoperative MRI (poMRI) were 7% and 25%, respectively. Additional remnant resection was possible in 64% of the patients. Noninvasive tumors were shown to be totally resected on the initial iMRI in 31% of cases. After additional resection for 69% of the procedures, the GTR rate on poMRI was 75%. Transcranial surgery to resect tumor remnants was indicated in 5 (5%), and radiotherapy was performed in 29 (27%) patients. After GTR, no recurrence was detected during a mean follow-up of 2.2 ± 2.1 years.

Conclusions

The use of iMRI in transsphenoidal reoperations for NFA leads to significantly higher GTR rates. It thus prevents additional operations and reduces the number of tumor remnants. The complication rates do not exceed the incidences reported in the literature for primary transsphenoidal surgery. If complete tumor resection is not possible, iMRI guidance can facilitate tumor volume reduction.

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Andreas Stadlbauer, Ewald Moser, Stephan Gruber, Christopher Nimsky, Rudolf Fahlbusch and Oliver Ganslandt

Object. It is often difficult to delineate the extent of invasion of high- and low-grade gliomas into normal brain tissue by using conventional T1- and T2-weighted magnetic resonance (MR) imaging. Knowledge of the relationship between the tumor infiltration zone and normal brain, however, is one of the prerequisites for performing as radical a tumor resection as possible. Proton MR spectroscopy allows noninvasive measurements of the concentrations and spatial distributions of brain metabolites and, therefore, may provide biochemical information in vivo, that is useful in distinguishing pathological from normal areas of the brain.

The authors have developed a method to use the properties of MR spectroscopy to investigate intraoperatively pathological changes in the spatial distribution of choline (Cho)-containing compounds, total creatine, and N-acetylaspartate (NAA) in brain tumors with the aid of frameless stereotaxy.

Methods. Maps of the Cho/NAA ratio were calculated and automatic segmentation of the tumors was performed. Spectroscopic images of the segmented tumor were matched to an anatomical three-dimensional (3D) MR imaging set by applying a fully automated mutual-information algorithm. The resulting 3D MR image can be used subsequently for neurosurgical planning, transfer to a frameless stereotactic system, and display in the navigation microscope during surgery leading to 1H-MR spectroscopy-guided navigation.

Conclusions. This method may allow better intraoperative identification of tumor border zones based on metabolic changes due to tumor infiltration.

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Oliver Ganslandt, Rudolf Fahlbusch, Christopher Nimsky, Helmut Kober, Martin Möller, Ralf Steinmeier, Johann Romstöck and Jürgen Vieth

The authors conducted a study to evaluate the clinical outcome in 50 patients with lesions around the motor cortex who underwent surgery in which functional neuronavigation was performed.

The sensorimotor cortex was identified in all patients with the use of magnetoencephalography (MEG). The MEG-source localizations were superimposed onto a three-dimensional magnetic resonance image, and the image data set was then implemented into a neuronavigation system. Based on this setup, the surgeon chose the best surgical strategy. During surgery, the pre- and postcentral gyrus were identified by neuronavigation, and in addition, the central sulcus was localized using intraoperative recording of somatosensory evoked potentials. In all cases MEG localizations of the sensory or motor cortex were correct. In 30% of the patients preoperative paresis improved, in 66% no additional deficits occurred, and in only 4% (two patients) deterioration of neurological function occurred. In one of these patients the deterioration was not related to the method.

The method of incorporating functional data into neuronavigation systems is a promising tool that can be used in more radical surgery to cause less morbidity around eloquent brain areas.

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Oliver Ganslandt, Rudolf Fahlbusch, Christopher Nimsky, Helmut Kober, Martin Möller, Ralf Steinmeier, Johann Romstöck and Jürgen Vieth

Object. The authors conducted a study to evaluate the clinical outcome in 50 patients with lesions around the motor cortex who underwent surgery in which functional neuronavigation was performed.

Methods. The sensorimotor cortex was identified in all patients with the use of magnetoencephalography (MEG). The MEG-source localizations were superimposed onto a three-dimensional magnetic resonance image and the image data set was implemented into a neuronavigation system. Based on this setup, the surgeon chose the best surgical strategy. During surgery, the pre- and postcentral gyri were identified by neuronavigation and, in addition, the central sulcus was localized using intraoperative recording of somatosensory evoked potentials. In all cases MEG localizations of the sensory or motor cortex were correct. In 30% of the patients preoperative paresis improved, in 66% no additional deficits occurred, and in only 4% (two patients) deterioration of neurological function occurred. In one of these patients the deterioration was not related to the procedure.

Conclusions. The method of incorporating functional data into neuronavigation systems is a promising tool that can be used in more radical surgery to lessen morbidity around eloquent brain areas.