M. Brock

Multimodal protocol for awake craniotomy in language cortex tumour surgery

SummaryBackground. Intra-operative neurophysiological language mapping has become an established procedure in patients operated on for tumours in the area of the language cortex. Awake cranial surgery has specific risks and patients are exposed to an increased physical and mental stress. The aim of the study was to establish an algorithm that enables tailoring the neurosurgical and anaesthetic techniques to the individual patient.n Method. A total of 25 patients underwent awake craniotomy for intra-operative language mapping between 1999 and 2004. Following craniotomy under analgesia and sedation without rigid pin fixation of the head, cortical language mapping was performed in the fully co-operative patient. The results of functional magnetic resonance imaging and of cortical language mapping were incorporated into the 3D dataset for neuronavigation. Depending on the functional data and the individual operative risk tumour resection then proceeded either under conscious sedation with the option of subcortical language monitoring or under general anaesthesia.n Findings. After cortical language mapping patients are assigned to one of four groups: BACC (Berlin awake craniotomy criteria) I–IV. BACC I (9 patients): adequate functional data + operative risk not increasedu2009⇒u2009tumour resection in the awake patient; BACC II (4 patients): limited functional data + operative risk not increasedu2009⇒u2009tumour resection in the awake patient with the option of language monitoring as needed; BACC III (9 patients): adequate functional data + increased operative risku2009⇒u2009tumour resection under general anaesthesia using functional navigation; BACC IV (3 patients): limited functional data + increased operative risku2009⇒u2009tumour resection in the awake patient with the option of language monitoring as needed. We observed less adverse events in group BACC III. No permanent deterioration of language function occurred in this series.n Conclusions. The multimodal protocol for awake craniotomy provides for tumour resection under general anaesthesia in selected patients using functional neuronavigation. Our experience with the algorithm suggests that it is a useful tool for preserving function in patients undergoing surgery of the language cortex while reducing the operative risk on an individual basis.

Novalis frameless image-guided noninvasive radiosurgery: initial experience.

OBJECTIVETo evaluate our initial experience with Novalis (BrainLAB, Heimstetten, Germany) frameless image-guided noninvasive radiosurgery. METHODSThe system combines the dedicated Novalis linear accelerator with ExacTrac X-Ray 6D, an infrared camera and a kilovolt stereoscopic x-ray imaging system, a noninvasive mask system, and ExacTrac robotics for patient positioning in six degrees of freedom. Reference cranial skeletal structures are radiographically imaged and automatically fused to digital reconstructed radiographs calculated from the treatment planning computed tomographic scan to find the target position and accomplish automatic real-time tracking before and during radiosurgery. We present the acceptance testing and initial experience in 15 patients with 19 intracranial lesions treated between December 2005 and June 2006 at the Charité by frameless image-guided radiosurgery with doses between 12 and 20 Gy prescribed to the target-encompassing isodose. RESULTSPhantom tests showed an overall system accuracy of 1.04 ± 0.47 mm, with an average in-plane deviation of 0.02 ± 0.96 mm for the x-axis and 0.02 ± 0.70 mm for the y-axis. After infrared-guided patient setup of all patients, the overall average translational deviation determined by stereoscopic x-ray verification was 1.5 ± 1.3 mm, and the overall average rotational deviation was 1.0 ± 0.8 degree. The data used for radiosurgery, after stereoscopic x-ray verification and correction, demonstrated an overall average setup error of 0.31 ± 0.26 mm for translation and 0.26 ± 0.23 degree for rotation. CONCLUSIONThis initial evaluation demonstrates the system accuracy and feasibility of Novalis image-guided noninvasive radiosurgery for intracranial benign and malignant lesions.

Intraoperative electrocortical stimulation of Brodman area 4: a 10-year analysis of 255 cases.

BackgroundBrain tumor surgery is limited by the risk of postoperative neurological deficits. Intraoperative neurophysiological examination techniques, which are based on the electrical excitability of the human brain cortex, are thus still indispensable for surgery in eloquent areas such as the primary motor cortex (Brodman Area 4).MethodsThis study analyzed the data obtained from a total of 255 cerebral interventions for lesions with direct contact to (121) or immediately adjacent to (134) Brodman Area 4 in order to optimize stimulation parameters and to search for direct correlation between intraoperative potential changes and specific surgical maneuvers when using monopolar cortex stimulation (MCS) for electrocortical mapping and continuous intraoperative neurophysiological monitoring.ResultsCompound muscle action potentials (CMAPs) were recorded from the thenar muscles and forearm flexors in accordance with the large representational area of the hand and forearm in Brodman Area 4. By optimizing the stimulation parameters in two steps (step 1: stimulation frequency and step 2: train sequence) MCS was successful in 91% (232/255) of the cases. Statistical analysis of the parameters latency, potential width and amplitude showed spontaneous latency prolongations and abrupt amplitude reductions as a reliable warning signal for direct involvement of the motor cortex or motor pathways.ConclusionMCS must be considered a stimulation technique that enables reliable qualitative analysis of the recorded potentials, which may thus be regarded as directly predictive. Nevertheless, like other intraoperative neurophysiological examination techniques, MCS has technical, anatomical and neurophysiological limitations. A variety of surgical and non-surgical influences can be reason for false positive or false negative measurements.

Injection therapy of lumbar facet syndrome: a prospective study

SummaryBackground. Chronic low back pain remains a major health problem. Facet joint injection therapy is an easy to perform therapeutic option. However, few prospective studies use a standardized protocol to investigate injection therapy. The aim of our study was to evaluate quantity and duration of clinical improvement after this protocol, and to identify the best time for additional repetitive injection therapy.Materials and Methods. Thirty-nine patients (21 men, 18 women; mean age 55.2 years [range, 29–87 years]) with lumbar facet syndrome were treated with injection using a standardized protocol (prednisolone acetate, lidocaine 1%, phenol 5%) under fluoroscopic control. Follow-up was based on a specially designed questionnaire. Analysis included MacNab criteria, visual analogue scale, and pain disability index.Results. Reduction of pain was found up to 6 months after treatment. The outcome was assessed excellent or good by 62% (24 patients) of the patients after 1 month, by 41% (16 patients) after 3 months, and by 36% (14 patients) after 6 months. There was no influence of age, body mass index, or previous lumbar spinal surgery on improvement after treatment. There were no severe side effects. Short-lasting self limiting mild side effects were found in 26% (increased back pain, numbness, heartburn, headache, allergy).Conclusion. Facet joint injection therapy using a standardized protocol is safe, effective, and easy to perform. The clinical effect is limited, and we recommend repetitive injection according to this protocol after 3 months.

Functional Magnetic Resonance Imaging and Cortical Mapping in Motor Cortex Tumor Surgery: Complementary Methods

Functional magnetic resonance imaging (fMRI) and direct electrocortical stimulation (DES) are the most commonly used means of analyzing the functional brain topography prior to surgery in the vicinity of Brodmann area 4. No consensus has been established in the literature about the significance of both procedures in reducing operative morbidity. The study presented here was conducted in 30 patients with tumors in the area of the primary motor cortex. Blood oxygen level dependent (BOLD) sequences were preoperatively established with a standardized paradigm. Intraoperatively motor mapping was performed with DES. The results of both methods were digitally matched with a frameless image-guidance system. Correlations between the results of fMRI and of DES were analyzed. Furthermore, the potential influences of the size, position, and histology of the lesions on the mapping results were analyzed and the motor outcome was evaluated. The mean deviation between the results of fMRI and of DES was 13.8 mm (range: 7-28 mm). This deviation was independent of the histology, size, or location of the corresponding lesion. The individual variability of the analysis threshold value for the evaluation of the BOLD sequences led to a considerable topographical inaccuracy. As complementary methods, fMRI contributes to estimating the operational risk, while DES is performed when the results of MRI and fMRI suggest an immediate proximity of the tumor to motor areas.

Neuronavigation without rigid pin fixation of the head in left frontotemporal tumor surgery with intraoperative speech mapping.

OBJECTIVE Intraoperative speech mapping has evolved into the “gold standard” for neurosurgical removal of lesions near the language cortex. The integration of neuronavigation into a multimodal protocol can improve the reliability of this type of operation, but most systems require rigid fixation of the patients head throughout the operation. This article describes and evaluates a new noninvasively attached sensor-based reference tool, which can replace rigid pin fixation of the patients head during awake craniotomies. METHODS The attachment technique and the resulting application accuracy were investigated under clinical conditions in 13 patients undergoing awake craniotomy with intraoperative mapping of cortical language sites. RESULTS Spatial information was used for updating the image guidance by continuously adjusting the image planes relative to the position of the patients head. The mean registration error achieved with this technique was 1.53 ± 0.51 mm (fiducial registration error ± standard deviation). The systems median application accuracy between dura opening and closure ranged from 0.83 to 1.85 mm (position error). CONCLUSION The use of a reference sensor can replace uncomfortable pin fixation of the patients head during navigation-supported awake craniotomies. Application accuracy is not affected by repositioning of the patient or by unavoidable head movements. Thus, this technique enables full exploitation of the benefits of navigation in a multimodal operative protocol without the need to rigidly fix the patients head.

Study on the clinical application of pulsed DC magnetic technology for tracking of intraoperative head motion during frameless stereotaxy

BackgroundTracking of post-registration head motion is one of the major problems in frameless stereotaxy. Various attempts in detecting and compensating for this phenomenon rely on a fixed reference device rigidly attached to the patients head. However, most of such reference tools are either based on an invasive fixation technique or have physical limitations which allow mobility of the head only in a restricted range of motion after completion of the registration procedure.MethodsA new sensor-based reference tool, the so-called Dynamic Reference Frame (DRF) which is designed to allow an unrestricted, 360° range of motion for the intraoperative use in pulsed DC magnetic navigation was tested in 40 patients. Different methods of non-invasive attachment dependent on the clinical need and type of procedure, as well as the resulting accuracies in the clinical application have been analyzed.ResultsApart from conventional, completely rigid immobilization of the head (type A), four additional modes of head fixation and attachment of the DRF were distinguished on clinical grounds: type B1 = pin fixation plus oral DRF attachment; type B2 = pin fixation plus retroauricular DRF attachment; type C1 = free head positioning with oral DRF; and type C2 = free head positioning with retroauricular DRF. Mean fiducial registration errors (FRE) were as follows: type A interventions = 1.51 mm, B1 = 1.56 mm, B2 = 1.54 mm, C1 = 1.73 mm, and C2 = 1.75 mm. The mean position errors determined at the end of the intervention as a measure of application accuracy were: 1.45 mm in type A interventions, 1.26 mm in type B1, 1.44 mm in type B2, 1.86 mm in type C1, and 1.68 mm in type C2.ConclusionRigid head immobilization guarantees most reliable accuracy in various types of frameless stereotaxy. The use of an additional DRF, however, increases the application scope of frameless stereotaxy to include e.g. procedures in which rigid pin fixation of the cranium is not required or desired. Thus, continuous tracking of head motion allows highly flexible variation of the surgical strategy including intraoperative repositioning of the patient without impairment of navigational accuracy as it ensures automatic correction of spatial distortion. With a dental cast for oral attachment and the alternative option of non-invasive retroauricular attachment, flexibility in the clinical use of the DRF is ensured.

Giant intracerebral choroid plexus calcification

SummaryWhile small calcifications of the choroid plexus are frequent, a large, single intracerebral calcification originating from the choroid plexus is rare. This report presents a 27-year-old woman who was admitted because of right temporal headache which had persisted for months. There was no neurological deficit. Computed tomography demonstrated a mass of calcium density measuring approximately 3u2009×u20093u2009×u20094u2009cm in the right temporal region, extending to the temporal skull base and to the rostral edge of the petrous bone. At surgery a very hard, poorly vascularised tumour originating from the choroid plexus of the temporal horn of the right lateral ventricle was completely removed. Histological workup yielded the diagnosis of a markedly calcified choroid plexus with no indication of neoplasia or inflammation.Physiological intracranial calcifications resulting from local tissue dystrophy are usually incidental. In the case presented here, a large intracerebral choroid plexus calcification was detected in a patient presenting with episodes of severe headache. The potential pathogenetic mechanism is discussed.

Persistent cerebrospinal fluid rhinorrhea by intrasphenoidal encephalocele.

The case of a 60-year-old man with a 6-month history of cerebrospinal fluid (CSF) rhinorrhea is presented. Computed tomography (CT) and magnetic resonance (MR) imaging revealed an intrasphenoidal mass extending through a bony defect of the roof of the left sphenoid sinus. Transnasal surgical repair was performed; intraoperatively the mass was identified as an intrasphenoidal encephalocele. The pathogenesis of this anomaly is analyzed, the clinical findings and the operative treatment are described, and the literature is reviewed.

Real-time tracking of vertebral body movement with implantable reference microsensors

Objective: In the spine, navigation techniques serve mainly to control and accurately target insertion of implants. The main source of error is that the spine is not a rigid organ, but rather a chain of semiflexible movement segments. Any intraoperative manipulation of the patient alters the geometry and volumetry as compared to the 3D volume model created from the image data. Thus, the objective of the study was to implement the theoretical principle of microsensor referencing in a model experiment and to clarify which anatomical structures are suitable for intermittent implantation of positional sensors, as illustrated with cervical vertebral bodies. Materials and Methods: Laboratory tests were conducted using 70 models of human cervical vertebral bodies. The first experiment investigated whether arbitrary movements of vertebral bodies can be tracked with the positional information from the implanted microsensors. The accuracy of this movement monitoring was determined quantitatively on the basis of positional error measurement. In the second experiment, different ventral and dorsal surgical operations were simulated on five models of the cervical spine. Quantifiable measurement values such as the spatial extension of the intervertebral space and the relative positions of the planes of the upper plates were determined. Results: With respect to the differing anatomy of the individual vertebral bodies of the cervical spine, the sensors could be placed securely with a 5u2009×u20092 mm drill. The registration error (RE) was determined as a root mean square error. The mean value was 0.9425 mm (range: 0.57–1.2 mm; median: 0.9400 mm; SD: 0.1903 mm). The precision of the movement monitoring of the vertebral body was investigated along its three main axes. The error tolerance between post-interventional 3D reconstruction and direct measurement on the model did not exceed 1.3 mm in the distance measurements or 2.5° in the angular measurements. The tomograms on the system monitor could be updated in close to real time on the basis of the positional information from the reference sensor. Conclusions: Motion sensors implanted into the vertebral bodies communicated any change in position to the navigation system in close to real time, thus enabling the preoperative image data set to be updated. The experiments described could ultimately show that continuous real-time visualization of individual vertebral body movements along the movement axes (flexion-extension, tilting and rotation) is possible with high accuracy using implantable microsensors. A future application of such microsensors might be the integration of robot systems into spinal microsurgery.