R. Fahlbusch

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Claire Sergent

Inserm

Oleg Yu Vorobyev

Siberian Federal University

Amir Manbachi

Johns Hopkins University

Linnaea Stockall

Queen Mary, University of London

john van der kamp

Vrije Universiteit Amsterdam

Hakan Gurvit

Istanbul University

Sule Tinaz

Yale University School of Medicine

Jürgen Konczak

University of Minnesota

Yoshikazu Ugawa

FMU

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UBC

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Papers by R. Fahlbusch

Application accuracy of automatic registration in frameless stereotaxy

Stereotactic and functional neurosurgery, 2006

We compared the application accuracy of an infrared-based neuronavigation system when used with a... more We compared the application accuracy of an infrared-based neuronavigation system when used with a novel automatic registration with its application accuracy when standard fiducial-based registration is performed. The automatic referencing tool is based on markers that are integrated in the headrest holder we routinely use in our intraoperative magnetic resonance imaging (MRI) setting and can be detected by the navigation software automatically. For navigation targeting we used a Plexiglas phantom with 32 notched rods of different heights. The phantom was fixed in the head holder and multiple optimized gradient echo slices containing the clamp-integrated markers were acquired. After that we measured a T1 MPRAGE sequence with a slice thickness of 1.0 mm for navigation. The deepest points of the surface of the rods were defined as target points in image space. In three measurement series we referenced the phantom once with 4, once with 7 fiducials and twice automatically. In one series...

Visualization of the pyramidal tract in glioma surgery by integrating diffusion tensor imaging in functional neuronavigation

Zentralblatt für Neurochirurgie, 2005

The aim of this study was to investigate whether diffusion tensor imaging (DTI) can be integrated... more The aim of this study was to investigate whether diffusion tensor imaging (DTI) can be integrated into functional navigation for the intraoperative visualization of the pyramidal tract. A single-shot spin-echo diffusion-weighted echo planar imaging sequence on a 1.5 T magnetic resonance (MR) scanner was used for DTI. One null image and six diffusion-weighted images (high B value 1 000 mm/s (2)) were obtained. Color-encoded fractional anisotropy maps of the principal eigenvector rendered as a boxoid within each voxel were used for segmentation of the pyramidal tract. The segmented images were rigidly registered with a T(1)-weighted gradient echo 3D dataset for navigation in 16 patients with gliomas. In tumors adjacent to the motor cortex (n = 6) data from functional MR imaging were co-registered. The whole DTI processing lasted about 25-30 minutes in each case. In all cases DTI could be integrated into the navigational dataset resulting in an intraoperative visualization of the pyram...

Frameless stereotactic surgery using intraoperative high-field magnetic resonance imaging

by R. Fahlbusch and Eiji Kohmura

Neurologia medico-chirurgica, 2004

This study evaluated the clinical validity of frameless stereotaxy using high-field intraoperativ... more This study evaluated the clinical validity of frameless stereotaxy using high-field intraoperative magnetic resonance (iMR) imaging combined with an in-room neuronavigation system. A 1.5 Tesla MR scanner in conjunction with a ceiling-mounted neuronavigation system was used during 32 frameless stereotaxy procedures consisting of 19 brain biopsies and 13 catheter placements between April 2002 and mid-October 2003. Evaluation of the procedure was based on either the rate of histological diagnostic yield or the ability to accurately position the catheter in the target region. This technique allowed successful registration with a mean error of 1.2 +/- 0.8 mm and resulted in successful placement of the instrument within the target tissue. Intraoperatively, frozen section analysis showed all biopsy samples contained pathological tissue and locations of sampling points were confirmed by iMR imaging. Specific final diagnosis was made in all 19 brain biopsies. The tip of the catheter was succ...

Intraoperative MRI developments

Neurosurgery clinics of North America, 2005

Co-registration of function and anatomy in frameless stereotaxy by contour fitting

Stereotactic and functional neurosurgery, 2002

We investigated a co-registration algorithm using a contour-fitting procedure to integrate functi... more We investigated a co-registration algorithm using a contour-fitting procedure to integrate functional data from magnetoencephalography (MEG) and functional magnetic resonance imaging (fMRI) for frameless stereotaxy. In fMRI the shape of the head was reconstructed from anatomical images, in MEG it was scanned using an electromagnetic sensor position indicator. Functional information was transferred to the 3D-MR image set used for frameless stereotaxy by fitting the digitized (MEG) and reconstructed head shape (fMRI) to the 3D-MR images. The mean residual error of the contour fit was 2.3 mm for the MEG and 1.3 mm for the fMRI registration. According to computer simulations, the achievable transformation error is 0.75 and 0.5 mm, respectively. This method enables independent recording of functional and anatomical measurements with a co-registration accuracy better than 2 mm.

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Low-field magnetic resonance imaging for intraoperative use in neurosurgery: a 5-year experience

European radiology, 2002

The aim of this study was to evaluate the feasibility and point out the indications of intraopera... more The aim of this study was to evaluate the feasibility and point out the indications of intraoperative MR imaging in neurosurgical procedures. The MR imaging was performed using a 0.2-T scanner which was located in a radiofrequency-shielded operating theater. Three major setups for intraoperative imaging were possible: inside the scanner; at the 5-Gauss line; or in an adjacent operating theater. Additionally, in lesions adjacent to eloquent brain areas microscope- and pointer-based neuronavigation with integrated functional data was applied. Three hundred ten patients were investigated in the previous 5 years, among them gliomas ( n=95), pituitary tumors ( n=81), and 39 non-lesional cases in whom resective or disconnective epilepsy surgery was carried out. We did not observe any adverse effects due to intraoperative MR imaging. Image quality was sufficient to evaluate the extent of the tumor resection in the majority of cases. The main indications for intraoperative MR imaging were t...

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Factors influencing the application accuracy of neuronavigation systems

by R. Fahlbusch and Ralf Steinmeier

Stereotactic and functional neurosurgery, 2000

The overall accuracy of neuronavigation systems may be influenced by (1) the technical accuracy, ... more The overall accuracy of neuronavigation systems may be influenced by (1) the technical accuracy, (2) the registration process, (3) voxel size and/or distortion of image data and (4) intraoperative events. The aim of this study was to test the influence of the registration and imaging modality on the accuracy. A plexiglas phantom with 32 rods was taken for navigation targeting. Sixteen fiducials were attached to the surface of the phantom forming two different attachment patterns (clustered vs. diffusely scattered). This model was scanned by MRI and CT (1-mm slices). Registration was performed using different numbers and attachment patterns of the fiducials. Using CT or MRI, the localization error was measured in image space as the Euclidean distance between targets defined in image space and those detected in the physical space. Accuracy was measured with two commercial systems, the Zeiss MKM and the StealthStation. The mean localization error varied between 1.59 +/- 0.29 mm (MKM, 8...

Intraoperative compensation for brain shift

Surgical neurology, 2001

Tumor removal, brain swelling, the use of brain retractors, and cerebrospinal-fluid drainage all ... more Tumor removal, brain swelling, the use of brain retractors, and cerebrospinal-fluid drainage all result in an intraoperative brain deformation that is known as brain shift. Thus, neuronavigation systems relying on preoperative image data have a decreasing accuracy during the surgical procedure. Intraoperative image data represent the correct anatomic situation, so their use may compensate for the effects of brain shift. In a series of 16 brain tumor patients, we used intraoperative magnetic resonance (MR) imaging to obtain 3-D data, which were then transferred to the microscope-based neuronavigation system. With the help of bone fiducial markers these images were registered intraoperatively, updating the neuronavigation system. In all patients the updating of the neuronavigation system with the intraoperative MR data was successful. It led to reliable neuronavigation with high accuracy; the mean registration error of the update procedure in all patients was 1.1 mm. The updating proc...

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Prolactin-producing pituitary adenoma and carcinoma with neuronal components--a metaplastic lesion

Pituitary, 1999

Recent studies indicate that cells of various epithelial tumors are capable of transformation to ... more Recent studies indicate that cells of various epithelial tumors are capable of transformation to neurons. Observing both neurons and neuropil in two prolactin-producing adenohypophyseal tumors, one benign and one malignant, we sought to assess their cellular differentiation, the presence of nerve growth factor receptor, and expression of the dopamine receptor gene using immunocytochemistry, electron microscopy, and in situ hybridization. Light and electron microscopy clearly revealed cells morphologically transitional between adenoma/carcinoma cells and neurons. Large neurons lacked proliferative activity. Neurons in varying number showed immunoreactivity for pituitary hormones including prolactin, growth hormone and alpha subunit in the adenoma and prolactin alone in the carcinoma. The distribution of nerve growth factor receptor staining was similar. In both tumors, in situ hybridization showed mRNAs for prolactin and dopamine receptor within adenohypophyseal cells and neurons. Ou...

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Clinical correlates in acromegalic patients with pituitary tumors expressing GSP oncogenes

Pituitary, 1999

We herein review published findings on the clinical characteristics of acromegalic patients harbo... more We herein review published findings on the clinical characteristics of acromegalic patients harboring pituitary somatotrophinomas expressing adenylyl cyclase activating gsp mutations and present an update of our own data on a large series of 176 patients with and without these oncogenes. Gsp oncogenes are the result of point mutations in either codon 201 or 227 of the Gs-alpha subunit of the Gs-protein which controls adenylyl cyclase. They result ultimately in increased intracellular cAMP levels and thus in excessive growth hormone (GH) secretion. Our large series has allowed us to characterise patients with mutations in codon 201 and the far rarer group possessing codon 227 defects. Both groups were compared with patients without gsp oncogenes. In accordance with previous findings, there was no statistically significant difference in age of the patients belonging to each group, the overall average tumor diameter nor in pre-operative serum GH levels, although the latter showed a ten...

Relationship between GHRP-6 and TPA in the regulation of growth hormone secretion by human pituitary somatotrophinomas

Journal of Tongji Medical University = Tong ji yi ke da xue xue bao, 1997

Growth hormone releasing peptide (GHRP-6) is a synthetic hexapeptide which specifically stimulate... more Growth hormone releasing peptide (GHRP-6) is a synthetic hexapeptide which specifically stimulates secretion of growth hormone (GH) by pituitary somatotrophs. Phorbel ester, 1, 2 tetradecanoylphorbol 13 acetate (TPA) can also stimulate releasing of GH. The precise intracellular mechanism has not been entirely deciphered. We used cell cultures of human pituitary somatotrophinomas to investigate the relation between GHRP-6 and TPA on membrane phosphatidylinositol (PI) turnover and GH secretion. The results showed that the working mechanisms of GHRP-6 and TPA are not identical, although they all can stimulate GH secretion in human pituitary somatotrophinomas. This indicates that PI-PKC signal transduction system may play a crucial role in the regulation of GH secretion.

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Factors that limit the use of flash visual evoked potentials for surgical monitoring

Electroencephalography and clinical neurophysiology

A study was conducted comparing the incidence with which the N2/P2/N3 was obtained after flash VE... more A study was conducted comparing the incidence with which the N2/P2/N3 was obtained after flash VEP in 3 groups: anterior visual pathway lesions, non-tumor craniotomies and non-cranial surgery. These groups allowed evaluation of the effects of anesthesia, visual pathway lesions and craniotomy on the stability of the flash VEP. It was found that the latency was not significantly affected in the 3 groups, whereas the incidence of obtainable peaks and the amplitudes were adversely affected by anesthesia, cranial surgical manipulation and especially by the presence of a visual pathway lesion. These adverse effects were so marked that the application of flash VEP for intraoperative monitoring seems of little use.

Modeling of retraction and resection for intraoperative updating of images-Comments

Number 1—Decmber 2004

Alveolar rhabdomyosarcoma of the clivus with intrasellar expansion: Case report

Zentralblatt für Neurochirurgie, 2006

Rhabdomyosarcomas are common tumors of the head and neck region in children. However, a primarily... more Rhabdomyosarcomas are common tumors of the head and neck region in children. However, a primarily intracranial localization of this tumor entity is rare. We report on a 3-year-old boy presenting with double vision due to left VI (th) nerve palsy. No other neurological deficits were recognized by clinical inspection. MRI scans visualized an enhancing mass lesion in the upper clivus compressing the cavernous sinus and the pituitary gland. Transsphenoidal biopsy was performed and histopathological examination as well as molecular diagnostics confirmed the diagnosis of an alveolar rhabdomyosarcoma (ARMS). Staging identified a metastatic lesion in the fourth thoracic vertebra resulting in the diagnosis of stage IV disease. Treatment modality included stereotactic radio- and chemotherapy.

Intraoperative functional MRI: Implementation and preliminary experience

by R. Fahlbusch and Erol Sandalcioglu

NeuroImage, 2005

For a non-invasive identification of eloquent brain areas in neurosurgical procedures up to now o... more For a non-invasive identification of eloquent brain areas in neurosurgical procedures up to now only preoperative functional brain mapping techniques are available. These are based, e.g., on preoperative functional magnetic resonance imaging (fMRI) investigations in awake patients. The aim of this study was to investigate the feasibility to perform fMRI during neurosurgical procedures in anesthetized patients. For that purpose, a passive stimulation paradigm with peripheral nerve stimulation was applied. A 1.5-T MR scanner placed in a radiofrequency-shielded operating room with an adapted operating table was used for intraoperative fMRI. The fMRI data were analyzed during acquisition by an online statistical evaluation package installed on the MR scanner console. In addition, phase reversal of somatosensory evoked potentials was used for verification of intraoperative fMRI. In four anesthetized patients with lesions in the vicinity of the central region a total of 11 fMRI measurements were successfully acquired and analyzed online. Activation was found in the somatosensory cortex, which could be confirmed by intraoperative phase reversal for each measurement. Furthermore, statistical parametric mapping (SPM) was employed for an extensive offline data analysis. We did not observe any neurological deterioration or complications due to the stimulation technique. Intraoperative fMRI is technically feasible allowing a real-time identification of eloquent brain areas despite brain shift.

Delayed hearing loss after surgery for acoustic neurinomas: clinical and electrophysiological observations

by R. Fahlbusch and Johannes Schramm

Neurosurgery, 1991

In a series of 26 patients with medium-sized and large acoustic neurinomas and documented hearing... more In a series of 26 patients with medium-sized and large acoustic neurinomas and documented hearing before surgery, 7 patients had preservation of hearing initially after the procedure but then developed delayed hearing loss. The most prominent intraoperative electrophysiological finding in these cases was a gradual deterioration of brain stem auditory evoked potentials (BAEP), especially of Wave V. Four additional patients with a similar gradual intraoperative loss of BAEP and severe postoperative hearing deterioration received vasoactive treatment after surgery (low-molecular weight dextran). In all 4 patients, including 1 patient with documented total deafness after surgery, hearing was preserved. Initial preservation of cochlear nerve function after the removal of an acoustic neurinoma does not guarantee postoperative hearing. Intraoperative BAEP help to identify patients at risk for delayed postoperative hearing loss. The pathophysiological mechanism can be attributed to disturbances of the microcirculation in endoneurial vasa nervorum caused by the mechanical manipulation of the cochlear nerve.

Effect of dopamine agonist medication on prolactin producing pituitary adenomas

Virchows Archiv A Pathological Anatomy and Histopathology, 1991

Conventional light microscopy, immunocytochemistry, electron microscopy and in situ hybridization... more Conventional light microscopy, immunocytochemistry, electron microscopy and in situ hybridization were used to evaluate the effect of dopamine agonists (bromocriptine-LAR and bromocriptine) on the morphology of surgically removed prolactin (PRL)-producing pituitary adenomas. Dopamine agonist therapy resulted in decrease of serum PRL, clinical improvement and tumour shrinkage. Using light and electron microscopy cellular atrophy, interstitial and perivascular fibrosis were noted; in several tumours connective tissue accumulation was pronounced. The cellular response was not uniform. In some adenomas populations of large cells and small cells were distinguished. The large cells contained immunoreactive PRL and expressed the PRL gene indicating resistance to dopamine agonists. It appears that these cells retained the potential to secrete PRL and proliferate despite exposure to dopamine agonists. In the small cells, PRL immunoreactivity and PRL gene expression decreased providing evidence that both PRL release and synthesis were blocked. Small cells can persist in tumours after discontinuation of dopamine agonist medication suggesting these small cells are irreversibly suppressed and are not capable of regaining their endocrine function and proliferative capability. The formation of irreversibly suppressed PRL cells may explain why some PRL-producing adenomas do not recur after withdrawal of dopamine agonists.

Repeatedly reversible alteration of acoustic-evoked brainstem responses with a cystic craniopharyngioma

Surgical Neurology, 1985

The case of a cystic craniopharyngioma in a young patient, in which the tumor extended in the par... more The case of a cystic craniopharyngioma in a young patient, in which the tumor extended in the parasellar and retrosellar region down to the left cerebellopontine angle, is described. The postoperative reversibility of alterations in the acoustic-evoked brainstem responses after repeated surgical intervention and refilling of the cyst is described. The correlations between clinical and CT findings and the repeated alterations in the evoked responses are presented. The evoked responses were instrumental in following the postoperative course and timing CT controls. It is stressed that alterations in evoked responses were used as a reliable indication to evacuate cyst fluid via a Rickham-reservoir, although hearing was still intact, thus keeping the number of repeated CT scans lower.

Quantification of, Visualization of, and Compensation for Brain Shift Using Intraoperative Magnetic Resonance Imaging

Neurosurgery, 2000

Modern neuronavigation systems lack spatial accuracy during ongoing surgical procedures because o... more Modern neuronavigation systems lack spatial accuracy during ongoing surgical procedures because of increasing brain deformation, known as brain shift. Intraoperative magnetic resonance imaging was used for quantitative analysis and visualization of this phenomenon. For a total of 64 patients, we used a 0.2-T, open-configuration, magnetic resonance imaging scanner, located in an operating theater, for pre- and intraoperative imaging. The three-dimensional imaging data were aligned using rigid registration methods. The maximal displacements of the brain surface, deep tumor margin, and midline structures were measured. Brain shift was observed in two-dimensional image planes using split-screen or overlay techniques, and three-dimensional, color-coded, deformable surface-based data were computed. In selected cases, intraoperative images were transferred to the neuronavigation system to compensate for the effects of brain shift. The results demonstrated that there was great variability in brain shift, ranging up to 24 mm for cortical displacement and exceeding 3 mm for the deep tumor margin in 66% of all cases. Brain shift was influenced by tissue characteristics, intraoperative patient positioning, opening of the ventricular system, craniotomy size, and resected volume. Intraoperative neuronavigation updating (n = 14) compensated for brain shift, resulting in reliable navigation with high accuracy. Without brain shift compensation, neuronavigation systems cannot be trusted at critical steps of the surgical procedure, e.g., identification of the deep tumor margin. Intraoperative imaging allows not only evaluation of and compensation for brain shift but also assessment of the quality of mathematical models that attempt to describe and compensate for brain shift.

Application accuracy of automatic registration in frameless stereotaxy

Stereotactic and functional neurosurgery, 2006