Experimental testing of a prototype cantilevered liquid-nitrogen-cooled silicon mirror.

This report presents testing of a prototype cantilevered liquid-nitrogen-cooled silicon mirror. This mirror was designed to be the first mirror for the new soft X-ray beamlines to be built as part of the Advanced Light Source Upgrade. Test activities focused on fracture, heat transfer, modal response and distortion, and indicated that the mirror functions as intended.

[Cognitive Function in Patients Before and After Micro-neurosurgical Resection of Frontal Brain Tumors]. / Kognitive Funktion bei Patienten vor und nach mikrochirurgischer Resektion von frontalen Hirntumoren.

Patients with lesions of the prefrontal cortex as a result of frontal brain tumors (intra- and extra-axial) can show impairments of executive functions 1 2 3 4. Although there are a large number of psychological tests, the detection of impairments of relevant everyday executive functions in these patients is still extremely difficult. In 30 patients with lesions of the prefrontal cortex, the executive functions were tested with the Behavioral Assessment of Dysexecutive Syndrome (BADS) and 21 patients were also followed up postoperatively. Additionally, if possible, the Wisconsin Card Sorting Test (WCST), a widely used executive function test, and the Wechsler Adult Intelligence Scale (WAIS) for general cognitive performance were conducted. Pre- and postoperatively, a total of 16 patients were followed up with all three tests. The aim was to investigate the neuropsychological assessment pre- and postoperatively, to evaluate it in terms of deficits and changes in performance and to ensure that no new relevant everyday cognitive deficits arose. Preoperatively, only one patient, who could not be tested post-surgery, showed a reduced overall profile value in the BADS.  In all tested patients, there was no evidence of deterioration of cognitive status 8 - 12 weeks postoperatively. Further investigations using fMRI should be used to clarify whether the results obtained should be interpreted as neuroplastic adaptations of prefrontal cognitive functions or as a failure to detect deficits due to a lack of sensitivity of the tests used.

Normative data for arm swing asymmetry: how (a)symmetrical are we?

Arm swing asymmetry during gait may be a sensitive sign for early Parkinson's disease. There is only very limited information about how much asymmetry can be considered to be physiological. To assess the normal range of arm swing asymmetry, we investigated 60 healthy subjects. The influence of age, gender, and additional mental tasks (dual-tasking) on arm swing asymmetry was assessed. Limb kinematics of 60 healthy persons in three age groups (between 40 and 75 years) were measured with an ultrasound motion capture system while subjects walked on a treadmill. Treadmill velocity was varied (3 steps) and mental loads (2 different tasks) were applied in different trials. Additionally, a group of 7 patients with early Parkinson's disease was investigated. Arm swing amplitude as well as arm swing asymmetry varied considerably in the healthy subjects. Elderly subjects swung their arms more than younger participants. Only the more demanding mental load caused a significant asymmetry, i.e., arm swing was reduced on the right side. In the patient group, asymmetry was considerably higher and even more enhanced by mental loads. Our data indicate that an asymmetry index above 50 (i.e., one side has twice the amplitude of the other) may be considered abnormal. Evaluation of arm swing asymmetry may be used as part of a test battery for early Parkinson's disease. Such testing may become even more important when disease-modifying drugs become available for Parkinson's disease.

WITHDRAWN: Treatment outcome of visual feedback training in an adult patient with habitual toe walking.

Ahead of Print article withdrawn by publisher.

Validation of functional motor and language MRI with direct cortical stimulation.

BACKGROUND: Functional magnetic resonance imaging (fMRI) is a widely available method and is therefore progressively utilized in neurosurgical practice. This study was carried out to determine fMRI sensitivity and specificity and to emphasize the threshold dependence of fMRI data. METHODS: A total of 17 consecutive patients, scheduled for surgery on intracerebral lesions near eloquent brain areas, underwent preoperative motor (N = 12) and language (N = 5) fMRI. Functional data were analyzed with SPM software and displayed on a neuronavigation system for intraoperative guidance. High-risk maps for motor and language deficits obtained from direct electric cortical stimulation (DECS) were used for validation of functional activated areas. In a first analysis step, sensitivity and specificity were calculated in terms of a side-by-side correlation. The next step, the threshold dependence of fMRI data sensitivity and specificity, was estimated according to four statistical thresholds (p1 < 0.05, p2 < 0.0005, p3 < 0.00001, p4 < 0.0000001). RESULTS: Both functional imaging and DECS revealed definite results for the investigated areas in all patients. Calculation of sensitivity and specificity resulted in 100 % and 68 % for the motor group and a sensitivity of 75 % and specificity of 68 % for the language group at the fixed threshold analysis. Threshold-dependent analysis of the obtained data revealed a sensitivity/specificity relationship from 100 %/0 % at threshold (p1), 100 %/5 % at (p2), 74 %/9 % at (p3), and 37 %/36 % at (p4) for the motor group. Evaluation of threshold-dependent sensitivity and specificity for the language group resulted in 78 %/51 % at threshold (p1), 67 %/75 % at (p2), 50 %/78 % at (p3), and 33 %/89 % at (p4). CONCLUSIONS: The present findings on the threshold dependence of fMRI data demonstrate why individualized thresholds should be obtained in case of fMRI evaluation. Although the results are satisfying in most cases, fMRI is apparently not sufficient for critical intraoperative decision-making.

Differential effects of absent visual feedback control on gait variability during different locomotion speeds.

Healthy persons exhibit relatively small temporal and spatial gait variability when walking unimpeded. In contrast, patients with a sensory deficit (e.g., polyneuropathy) show an increased gait variability that depends on speed and is associated with an increased fall risk. The purpose of this study was to investigate the role of vision in gait stabilization by determining the effects of withdrawing visual information (eyes closed) on gait variability at different locomotion speeds. Ten healthy subjects (32.2 ± 7.9 years, 5 women) walked on a treadmill for 5-min periods at their preferred walking speed and at 20, 40, 70, and 80 % of maximal walking speed during the conditions of walking with eyes open (EO) and with eyes closed (EC). The coefficient of variation (CV) and fractal dimension (α) of the fluctuations in stride time, stride length, and base width were computed and analyzed. Withdrawing visual information increased the base width CV for all walking velocities (p < 0.001). The effects of absent visual information on CV and α of stride time and stride length were most pronounced during slow locomotion (p < 0.001) and declined during fast walking speeds. The results indicate that visual feedback control is used to stabilize the medio-lateral (i.e., base width) gait parameters at all speed sections. In contrast, sensory feedback control in the fore-aft direction (i.e., stride time and stride length) depends on speed. Sensory feedback contributes most to fore-aft gait stabilization during slow locomotion, whereas passive biomechanical mechanisms and an automated central pattern generation appear to control fast locomotion.

Speed-dependent temporospatial gait variability and long-range correlations in cerebellar ataxia.

OBJECTIVE: This study investigated the influence of impaired cerebellar locomotion function on the magnitude and structure of stride-to-stride fluctuations in the walking pattern. On the basis of studies reporting a dependency of variability magnitude and structure on the walking speed, we hypothesized that patients with cerebellar ataxia (CA) would show alterations of gait variability in a speed-dependent manner. METHODS: 11 patients with CA [7 idiopathic sporadic ataxia, 4 inherited spinocerebellar ataxia] and 11 healthy subjects (HS) walked on a treadmill for 5-min periods at their preferred walking speed and at 20%, 40%, 70%, and 80% of maximal walking speed. The variability magnitude of stride time, stride length and base width was calculated, and long-range correlations were detected by a detrended fluctuation analysis. RESULTS: Both temporal and spatial gait variability were impaired in CA. Variability magnitude and structure of all examined parameters depended on the walking speed. The preferred walking speed of patients was linked to minimal levels of stride time and stride length variability magnitude and to the strongest correlations within the fluctuations of these parameters. Long-range correlations were present for all examined gait parameters in patients and HS. Compared to HS, patients showed alterations in the speed dependency of stride time and stride length variability, with increased variability occurring at slow and maximal pace, whereas base width variability remained unaffected. CONCLUSIONS: Gait variability and therefore walking stability is critically dependent on the walking speed in patients with CA. At preferred walking speed, however, variability is minimal and similar to HS.

Is the center of mass (COM) a reliable parameter for the localization of brain function in fMRI?

The center of mass (COM) in functional MRI studies is defined as the center of a cerebral activation cluster. Although the COM is a well-accepted parameter for exactly localizing brain function, the reliability of COMs has not received much attention until now. Our goal was to investigate COM reliability as a function of the thresholding technique, the threshold level, and the type of COM calculation. Therefore 15 subjects were examined repeatedly using simple hand and tongue movement paradigms. Postprocessing was performed with uncorrected, corrected, and proportional thresholding as well as different threshold levels. Geometric and T-weighted COMs of left-hemispheric primary hand and tongue motor clusters were calculated. The COM variation was evaluated within and between repeated sessions depending on the different postprocessing setups. Mean COM variations over three repeated sessions varied between 1.6 mm and 9.8 mm for the hand paradigm and between 7.0 mm and 14.4 mm for the tongue task. Stringent thresholding techniques and high threshold levels were required to assess reliable results, whereas the kind of COM calculation was of lesser relevance. Thus, COM reliability cannot be presupposed; it depends strongly on the individual postprocessing techniques. This should be considered when using COMs for localizing brain function.

Reproducibility of activations in Broca area with two language tasks: a functional MR imaging study.

BACKGROUND AND PURPOSE: Functional MR imaging (fMRI) is rapidly evolving and claims to complement or even substitute intraoperative mapping (IOM) of language functions. However, little is known about the reproducibility of imaging data in the language domain. The aim of our study was to assess the reproducibility of activations for 2 widely used paradigms: naming and word generation. Individual analysis was focused on the Broca area and the left insula. MATERIALS AND METHODS: We examined 13 healthy right-handed subjects in 3 sessions with fMRI. Two conditions were assessed: overt naming and overt naming plus noun generation. The same stimuli were used in all of the sessions. A random-effects analysis was performed to analyze whole-brain activation on a group level. For the regions of interest, the number of voxels classified as active were counted for each subject, and individual reproducibility coefficients were calculated over sessions. RESULTS: For the naming condition, the random-effects analysis did not reveal significant activations in the specified regions; small individual activations were not reproducible. For the combined task, all of the subjects showed activations in the Broca area that were more extensive and reproducible than in the naming task. Activations in the insula were only poorly reproducible. CONCLUSION: Naming is an approved task in IOM but does not identify the Broca area with fMRI in a reproducible way. Priming may have affected our results, but the use of a combined task, in which naming is paired with noun generation, improves the reproducibility of activations and is also suitable for IOM.

Surgical resection of gliomas WHO grade II and III located in the opercular region.

BACKGROUND: Surgery in the opercular region especially in the dominant hemisphere impose a major challenge for the neurosurgeon due to the close vicinity to functional important motor and speech areas. The purpose of the present study is to analyse on a homogenous patient group pre- and postoperative functional deficits with regard to different speech qualities (e.g. aphasia, apraxia), and to correlate these data with MR and intraoperative monitoring results. METHOD: Fourteen patients with suspected low grade astrocytomas in the opercular region consecutively treated by surgery were eligible for this study (histology revealed 3 WHO grade III tumours). Degree and duration of postoperative deficits were retrospectively evaluated according to tumour location and boundaries on MR, intraoperative neuromonitoring results and extent of tumour resection. FINDINGS: Postoperatively, 8 patients showed speech or language disturbances, in 4 patients combined with motor deficits mainly of the contralateral upper extremity. Fifty percent of the neuropsychologically tested patients exhibited speech apraxia while the other 50% had a true aphasic syndrome. Recovery of the latter deficits was in general faster and more complete. The severity and duration of postoperative deficits was in good correlation with the distance of the resection margin to the next positive stimulation point(s), and a distance of more than 0.5 cm proved to avoid major impairments. The distribution of functional important stimulation points in relation to the tumour extension was not predictable, and -- unexpectedly -- up to 50% of these sites were found overlaying the tumour. INTERPRETATION: Surgery for WHO grade II and III gliomas in the opercular region can result in speech apraxia or an aphasic syndrome with or without concomitant motor deficits. Intraoperative cortical electrical stimulation is essential in resecting tumours in the opercular region to avoid permanent morbidity.

[Comparison of the Aachen Aphasia Test, clinical study and Aachen Aphasia Beside Test in brain tumor patients]. / Vergleich von Aachener Aphasie-Test, klinischer Untersuchung und Aachener Aphasie-Bedside-Test bei Hirntumorpatienten.

In the clinical routine examination of patients with brain tumors, aphasic symptoms are often not recognized. In order to document the incidence of such symptoms, three diagnostic methods of testing for aphasia were compared: the Aachen aphasia test (AAT), which is the German standard aphasia test, clinical examination, and the Aachen aphasia bedside test (AABT), which was designed to test patients in the acute phases of illness. In the AAT, 50% of patients with left-sided tumors and 36% of those with right-sided tumors showed aphasic disturbances. The AAT results were defined as the gold standard. Clinical examination showed only low sensitivity; less than half of the aphasic patients were diagnosed as such. The AABT also detected only about half of the patients with aphasic disturbances. The low sensitivity is caused mainly by the results of the patients with right-hemisphere tumors, in which the mental set of the examiner during clinical examination (aphasic symptoms are not expected in patients with right-hemisphere lesions) and the pattern of disturbances in the AABT (deficits may be less severe and different in nature) may prevent detection of aphasic symptoms. Both clinical examination and AABT are thus not suitable for aphasia diagnostics in brain tumor patients. As the AAT is very time-consuming in everyday clinical routine, however, the development of an aphasia screening test seems desirable.

Functional magnetic resonance imaging of human olfaction.

Olfaction is our basic sense phylogenetically and embryologically. Little is known, however, about how the human brain encodes the quality of odors, odor-associated memories, and emotions. Olfactory information is projected from the olfactory bulb to the primary olfactory cortex, which is composed of the anterior olfactory nucleus, the olfactory tubercle, the piriform cortex, the amygdala, the periamygdaloid region, and the entorhinal cortex. From there, the primary olfactory cortex projects to secondary olfactory regions including the hippocampus, ventral striatum and pallidum, hypothalamus, thalamus, orbitofrontal cortex, agranular insular cortex, and cingulate gyrus. Functional MR studies using olfactory stimuli as paradigms show activation of many of these areas and can advance our understanding of odor perception in humans.

The influence of essential oils on human attention. I: alertness.

Scientific research on the effects of essential oils on human behavior lags behind the promises made by popular aromatherapy. Nearly all aspects of human behavior are closely linked to processes of attention, the basic level being that of alertness, which ranges from sleep to wakefulness. In our study we measured the influence of essential oils and components of essential oils [peppermint, jasmine, ylang-ylang, 1,8-cineole (in two different dosages) and menthol] on this core attentional function, which can be experimentally defined as speed of information processing. Substances were administered by inhalation; levels of alertness were assessed by measuring motor and reaction times in a reaction time paradigm. The performances of the six experimental groups receiving substances (n = 20 in four groups, n = 30 in two groups) were compared with those of corresponding control groups receiving water. Between-group analysis, i.e. comparisons between experimental groups and their respective control groups, mainly did not reach statistical significance. However, within-group analysis showed complex correlations between subjective evaluations of substances and objective performance, indicating that effects of essentials oils or their components on basic forms of attentional behavior are mainly psychological.

Performance in picture naming and word comprehension: evidence for common neuronal substrates from intraoperative language mapping.

Correlations of naming ability and performance in the Token Test are known from aphasia; however, the mechanisms underlying these correlations are unclear. Naming tasks are commonly used in intraoperative mapping for identification of cortical areas involved in language processing. In the present study, we measured performance in an elementary Token Test task, i.e., single word comprehension, during electrical stimulation of cortical sites at which this stimulation previously had disturbed the naming process. It was found that at about half of the sites at which naming could be disturbed electrical stimulation also led to disturbances in Token Test performance, indicating that there are common neural structures critical for performance in both tasks. These findings are discussed in terms of a multilayered semantic network in which the level of the simultaneous binding of features into concepts and the level of units that are organized with respect to semantic relations may be disturbed separately.

Transcallosal interforniceal-transforaminal approach for removing lesions occupying the third ventricular space: clinical and neuropsychological results.

OBJECTIVE: The present study was undertaken to describe the clinical and prospective neuropsychological results for our group of 30 patients who were treated using a transcallosal interforniceal-transforaminal microsurgical approach. METHODS: The transcallosal interforniceal and transcallosal-transforaminal approaches were used to treat 30 patients with space-occupying lesions located in the anterior part of the third ventricle. We used a modified anterior transcallosal microsurgical approach, as described recently. The patients underwent extensive, pre- and postoperative, prospective neuropsychological testing, using a specially designed test battery. RESULTS: Twenty-three of 30 patients (77%) experienced excellent clinical outcomes (Glasgow Outcome Scale Grade V). The surgical procedures described in this report did not themselves impair attentional function. In both the early and late postoperative neuropsychological testing sessions, deficits in verbal memory were only rarely observed and were not noted to be correlated with the surgical procedures. The most relevant neuropsychological results for individual patients are reported in detail. CONCLUSION: The approach described here can be successfully used for the resection of various space-occupying lesions in the anterior part of the third ventricle. The anatomic landmarks we recently defined and described (for example, the midline vessel on the trunk of the corpus callosum, to direct the callosotomy) guide the surgical path. Furthermore, we recommend the use of neuropsychological test batteries for both scientific and rehabilitative purposes.

[Noninvasive protocol for surgical treatment of focal epilepsies]. / Nichtinvasives Protokoll für die epilepsiechirurgische Behandlung fokaler Epilepsien.

We present a non-invasive epilepsy surgery protocol, which includes EEG-video-monitoring, magnetic resonance imaging (MRI), interictal positron emission tomography (PET) and ictal single photon emission computerized tomography (SPECT). According to this non-invasive protocol 50 of 173 patients with medically intractable focal epilepsy underwent resective surgery. The localization of the epileptogenic zone was based on the congruence of the localizing results of EEG-video-monitoring, MRI, interictal PET and ictal SPECT. 46 (92%) of the patients had temporal and 4 (8%) had extratemporal epilepsies. 78% (n = 39) of all patients operated according to our non-invasive protocol were postoperatively completely or almost seizure free. Extramesiotemporal resections could be carried out without invasive EEG-recording if the epileptogenic zone was not adjacent to the eloquent cortex. We conclude from our results that in a considerable number of patients with medically intractable particularly temporal focal epilepsies, resective epilepsy surgery can be based on non-invasive EEG-evaluations and the risk of invasive recordings can be avoided.

Preoperative activation and intraoperative stimulation of language-related areas in patients with glioma.

OBJECTIVE: Evaluation of the accuracy of preoperative localization of language-related cortex by magnetic resonance imaging-guided positron emission tomography. METHODS: Patients with gliomas in the left dominant hemisphere were examined preoperatively with magnetic resonance imaging-guided positron emission tomography and intraoperatively by electrical stimulation of cortex. RESULTS: A verb generation task yielded more intense and better lateralized local increases of cerebral blood flow in the positron emission tomographic examination than did a naming task. Significant correspondence of preoperative and intraoperative findings was observed for the verb generation task. Cortical sites with aphasic disturbance during electrical stimulation had a significantly higher cerebral blood flow increase during preoperative activation than did sites without intraoperative language impairment. Areas with cerebral blood flow increases above an optimum threshold had 73% sensitivity and 81% specificity to predict aphasic disturbance during intraoperative stimulation. CONCLUSION: The data suggest that with further technical improvements, imaging of language function may become a preoperative diagnostic tool for patients with tumors close to language-related brain structures.

[Tumor surgery of the speech cortex in local anesthesia. Neuropsychological and neurophysiological monitoring during operations in the dominant hemisphere]. / Tumorchirurgie im Sprachkortex in Lokalanästhesie. Neuropsychologisches und neurophysiologisches Monitoring während Operationen in der dominanten Hirnhälfte.

We report on 30 cases where we have used cortical stimulation mapping to define the areas representing sensorimotor, language and speech functions under local anesthesia to facilitate resection of space-occupying lesions near these areas. Under the simplistic concept that Broca's area lies in the frontal operculum (inferior frontal gyrus) and that Wernicke's area is located in the posterior perisylvian area (superior temporal, angular and supramarginal gyri), we found language and speech function to be represented outside these areas in up to 4 stimulation sites of 15 patients. The results of cortical stimulation mapping were therefore essential to decide on the optimal access route to the lesions that were located subcortically and on the optimal resection plane in gliomas. After the limits of these areas and of the lesions had been established with stimulation mapping and with intrasurgical microscopic smear preparations, respectively, lesions were safely removed under continuous monitoring of sensorimotor, language and speech function. Immediately after surgery we encountered language and speech deficits in 9 patients (30%), which resolved completely in 5 and incompletely in 4 instances. Thus, language functions were normal in 26 patients (87%) at the end of the follow-up period. It is concluded that use of this technique allows safe and extensive resection of lesions that would otherwise have been considered hazardous to remove or inexcisable.

Keeping in mind the mind: mental functions, networks and neurosurgery.

The object of the neurosurgeons daily endeavour, the human brain, is less well understood in its overall organization than any other organ. This puts the neurosurgeon in a very difficult position. However, a substantial body of knowledge has been accumulated during recent years, and scientists from a variety of different disciplines have worked out theoretical frameworks to accomodate the available data. Here we present some of the evolving concepts on the organization of the substrate of the mind. Review of the literature shows that application of mathematical neural network models to the nervous system is very successful in explaining function. An implicit aspect of neural network models is that information storage is not localized in certain neurons but that the information is stored as the global pattern of activity in the network. Because networks of the brain involve often millions of neurons, exact identification and comparison with the theoretical models is not possible today.