Purpose: Considering the rapidly increasing number of clinical high-field MR imagers and the lack of data regarding interference with magnetically adjustable cerebrospinal fluid (CSF) shunt valves, valve safety was assessed with regard to magnetic field interactions: imaging artifacts, heating, magnetic forces, and functional changes in a phantom study at 3.0 Tesla using explanted devices as a realistic model for in vivo conditions.Materials and Methods: Sixteen explanted Codman-Medos and Sophy-SU8 shunt valves, all in perfect working order, were selected and exposed to a 3.0 Tstatic magnetic field. Valve-induced imaging artifacts and signal drop-outs and the heating experiments were evaluated using standard diagnostic MR sequences with different SAR values. Translational attraction for the adjustable valves was assessed using the deflection angle method. To test adjustability and function, the spherical phantom containing the valve was placed in the isocenter of the MR scanner and exposed to a static magnetic field of 3.0 T for 0.25 to 12 hours (repeated exposure 1 - 12 times), including typical entrance and move-out procedures.Results: The diameters of imaging artifacts ranged from 10 - 70 mm and were most prominent on T2*w sequences. There was no relevant MR-imaging-related heating. Magnetic forces were not critical. Reproducible adjustment failures occurred in 6 valves.Conclusion: Until suggestions can be made concerning the exposure of hydrocephalic patients to 3.0T-MRI, further testing is necessary.

Chiari II-malformation is a complex congenital deformity of the brain which is frequently associated with hydrocephalus. Abnormalities of the corpus callosum are known to occur in the majority of patients. The objective of the present study was to study the microstructure of the corpus callosum (CC) and the anterior commissure (AC) to differentiate between different mechanisms of damage to these structures. We investigated 6 patients with Chiari II-malformation and 6 well-matched healthy volunteers employing T1-weighted 3D imaging and diffusion tensor imaging (DTI) to determine the fractional anisotropy (FA) and cross-sectional area of the CC and AC, as well as with neuropsychological testing. Four patients showed hydrocephalus, two patients had callosal dysplasia and four had a hypoplastic CC. The callosal FA in the patients was significantly reduced which was less pronounced for the genu alone. The area of CC was also reduced in Chiari II-patients. There was a strong correlation between the size and FA of the CC in the patients. In contrast, the thickness of the AC was significantly increased and was associated with higher FA in the patients. In psychological tests all patients showed reduced verbal memory; all but one patient showed reduced IQ as well as impaired visuo-spatial performance, indicating deficits in tasks requiring parieto-occipital integration. The existence of callosal dysplasia in two patients, the diminished FA reduction in the genu and the correlation of the cross-sectional area and FA in the patients point to a developmental white matter damage beside that exerted by hydrocephalus alone.

Preoperative fMRI is one of the best established clinical fMRI applications. Due to the difficulties in recording and coregistration of functional image data, we present methods to standardize and automate these procedures. We used a self-made interactive software package (AFI - Automated Functional Imaging) to automate the time consuming and complex analysis of fMRI data. AFI controls the BrainVoyager program, a postprocessing software package, and furthermore facilitates data management, anonymization of patient data, storage, documentation, data export to neuronavigation systems and the opportunity of spatial transformation of image data for use in group studies. By the end of 2006 we have used this method on 123 patients with brain tumors and 47 patients with trigeminal neuralgia. The fundamental basis of multimodal neuronavigation is precise coregistration. EPI images contain spatial distortions of 5-15 mm. We were able to reduce the misregistration of EPI and FLASH images in a selectable region of interest to 1-2 mm. Furthermore AFI reduces the average evaluation time for a standard clinical fMRI study (four functional measurements, one anatomical data set) by approx. 50% from 140 minutes to about 70 minutes in comparison to manual evaluation by an expert. More importantly, the personal attendance time required for the evaluation decreases by 84% to 23 minutes as the remainder of the program runs automatically. In comparison to currently available online postprocessing software tools which are more limited in use, BrainVoyager can be used for coregistration, data export to neuronavigation systems and spatial transformation.

Ziele: Chronischer Schmerz ist ein belastender Krankheitszustand, der sich auf eine Vielzahl neuronaler Systeme von der taktilen bis hin zur komplexen emotionalen Wahrnehmung auswirkt. Der somatosensorische Kortex ist an der Verarbeitung von sensorischen Schmerzaspekten maßgeblich beteiligt, ist aber auch gleichzeitig die erste kortikale Instanz für die Verarbeitung nicht schmerzhafter sensorischer Information. Da also die Verarbeitung von schmerzhaften und nicht schmerzhaften Reizen in überlappenden Strukturen stattfindet, stellt sich die Frage, ob chronische Schmerzzustände mit Veränderungen der somatosensorischen Funktion an sich assoziiert sind, was in dieser Studie am Beispiel der idiopathischen Trigeminusneuralgie (ITN) untersucht wurde. Methode: 19 Patienten mit ITN und 13 gesunde Probanden wurden bei nicht schmerzhafter taktiler Stimulation der Lippen und der Finger mit der funktionellen MRT untersucht und spezifische Hirnaktivierungen im somatosensorischen System gemessen. 10 langfristig schmerzfreie Patienten nach erfolgreicher neurochirurgischer Intervention (Jannetta-OP) wurden im Verlauf untersucht. Ergebnis: Bei Stimulation der Lippen war die Aktivierung des primären somatosensorischen Kortex in beiden Patientengruppen im Vergleich zu der Probandengruppe signifikant reduziert (p<0,05). Aktivierung im sekundären somatosensorischen Kortex war nicht abgeschwächt, was im Umkehrschluss einer relativen Mehrbeteiligung dieser Region an der Reizverarbeitung bei Patienten mit ITN entspricht. Bei Stimulation der Finger war sowohl die Aktivierung im primären, als auch im sekundären somatosensorischen Kortex signifikant reduziert (p<0,01), was auf eine generelle Verminderung der somatosensorischen Reizverarbeitung bei Patienten mit ITN hindeutet. Die gemessenen Veränderungen waren unabhängig von der betroffenen Seite der ITN und nicht mit einer Abnahme des thalamischen Signals korreliert. Schlussfolgerung: Chronische Schmerzpatienten mit ITN zeigen signifikante funktionelle Veränderungen im somatosensorischen Kortex bei der Verarbeitung nicht schmerzhafter taktiler Reize. Die Veränderungen sind unabhängig von der durch die Krankheit betroffenen Gesichtsseite, erfassen auch Reize aus nicht betroffenen Körperregionen (Finger) und persistieren überdies nach längerer Schmerzfreiheit. Dieses weist auf eine globale und langfristige Modulation somatosensorischer kortikaler Funktion bei chronischen Schmerzpatienten hin, die dem Schutz vor übermäßiger Reizexposition dienen könnte.

Ziele: Untersuchung der funktionelle Organisation des primären Motorkortex bei Patienten mit angeborener Paraplegie. Methode: 11 Patienten mit angeborener Paraplegie durch thorakale spinale Läsionen und 14 rechtshändige Versuchspersonen (VP) wurden standardisiert mit der BOLD-FMRT bei 1,5 oder 3 Tesla untersucht, bei ausgeführten (EM) und imaginierten (IM) Zungen, Finger- und Zehenbewegungen. Die Aktivierung wurde jeweils für die kontralateralen primär motorischen Körperrepräsentationen gemessen. Auswertung: BrainVoyager®, Parameter: anatomische Korrelate und euklidische und Talairach Koordinaten der Aktivierungsschwerpunkte, BOLD-Signalintensität (DS) und Korrelation zur hämodynamischen Referenzfunktion (r). Ergebnis: Die somatotope Organisation des primären Motorkortex war bei 10/11 Patienten erhalten (91%, rechte Hemisphäre), bzw. bei 6/7 Patienten (86%, linke Hemisphäre). Bei 4 Patienten konnten die Daten der linken Seite wegen Metallartefakten durch Shunt-Ventile nicht ausgewertet werden. Die Lokalisation und Intensität der funktionellen Aktivierungen war signifikant variabler als bei VP's (p<0,05). 5 MMC-Patienten (45%) wiesen bilaterale Aktivierung bei einseitiger imaginierter Zehenbewegung auf. Schlussfolgerung: Bei Patienten mit kongenitaler Paraplegie scheint sich der primäre Motorkortex funktionell „normal“ zu entwickeln – mit weitgehend erhaltener Somatotopie. Die größere anatomische Streuung der funktionellen Lokalisationen kann zumindest teilweise auf die Fehlbildungen des Gehirns zurückgeführt werden. Ob die bilaterale Aktivierung der kortikalen Fussrepräsentationen bei einseitig imaginierten Bewegungen tatsächlich eine fehlende Differenzierung im motorischen System oder lediglich eine falsche Ausführung der „Bewegungsaufgabe“ widerspiegelt kann nicht abschließend beurteilt werden.

Objective: The mechanisms of chronic pain and its influence on pain processing structures are poorly understood. Since pain and somatosensory processing take place in overlapping cortical structures, we examined chronic pain patients with idiopathic trigeminal neuralgia (TN) and healthy volunteers using fMRI during somatosensory stimulation. In a second study we re-examined TN patients relieved from pain by successful surgical treatment (microvascular decompression using Jannetta-technique).

Objective: Standardized tactile stimulation of fingers and lips in order to localize the primary (SI) and secondary (SII) somatosensory cortex can be used for various purposes, such as presurgical identification of these important brain areas in patients with cerebral tumors as well as in clinical studies with patients with different diseases and healthy volunteers. Standardized and reproducible stimulation and an optimized block design paradigm are important prerequisites for robust localization of SI and SII in clinical context.

Object: Simultaneous mapping of functional and anatomical MRI data can be useful for different fields of neuroradiology and neurosurgery. Due to the difficulties in recording and coregistration of functional image data, we present methods to standardize and automate these procedures.

Standardized, robust and time-efficient localization of the human secondary somatosensory cortex (S2) is a challenge in clinical blood oxygen level dependent (BOLD) functional magnetic resonance imaging (fMRI). A fully automated tactile stimulation was optimized in seven right-handed volunteers at 1.5T for minimum scan time, high BOLD signals and robust localization of S2 by systematically varying the applied block-design. All volunteers had six different fMRI measurements of five stimulation-baseline-cycles (sbc) each with equal block duration that was changed between the measurements from 6s to 30s. Additional data sets of 4, 3 and 2 cycles were generated post hoc resulting in a total of 168 data sets that were evaluated individually for BOLD-signal intensity (dS%), correlation to the hemodynamic reference function (r) and Euclidean coordinates (x, y, z). Using different block-designs the S2 activation was highly variable regarding the localization rate (lr), the hemispheric symmetry and the BOLD-signals. The protocol with 3 cycles, a block duration (dp) of 15s and a total scan time (dt) of 105s most robustly localized S2 (contralateral: lr=71.4%, r=0.65, dS=1.01%; ipsilateral: lr=100%, r=0.6, dS=1.14%) whereas the most time-efficient protocol to localize SI (sbc=5, dp=6s, dt=66s) provided no robust localization of S2. Compared to other published fMRI protocols a scan time reduction up to 86% was achieved.

BACKGROUND:Spinal cord stimulation (SCS) is an effective alternative treatment in patients with chronic neuropathic pain and mainly radicular distribution. The aim of this prospective study was to investigate changes in BOLD signal with fMRI during active SCS and to correlate the results with the clinical pain intensity, measured with a visual analogue scale (VAS).PATIENTS AND METHODS:Three patients with failed back surgery syndrome were tested during the clinical trial of SCS. A first fMRI was performed with marked pain and a high VAS score. Before the second fMRI a therapeutic stimulation phase with pain reduction was carried out.RESULTS:With high pain levels SCS activated the cingulate gyrus, thalamus, prefrontal cortex, supplementary motor area and postcentral gyrus. After pain reduction, SCS did not elicit these activations in the second fMRI, using the same stimulation parameters.CONCLUSIONS:In patients with chronic neuropathic pain and high VAS levels, SCS elicited BOLD activation in the cingulate gyrus, thalamus, prefrontal cortex, and primary and secondary somatosensory area. Pain reduction by SCS resulted in a reduction of functional activity in these areas as revealed by follow-up fMRI.

PURPOSE:Functional magnetic resonance imaging (fMRI) localizes Broca's area (B) and Wernicke's area (W) and the hemisphere dominant for language. In clinical fMRI, adapting the stimulation paradigms to each patient's individual cognitive capacity is crucial for diagnostic success. To interpret clinical fMRI findings correctly, we studied the effect of varying frequency and number of stimuli on functional localization, determination of language dominance and BOLD signals.MATERIALS AND METHODS:Ten volunteers (VP) were investigated at 1.5 Tesla during visually triggered sentence generation using a standardized block design. In four different measurements, the stimuli were presented to each VP with frequencies of 1/1 s, (1/2) s, (1/3) s and (1/6) s.RESULTS:The functional localizations and the correlations of the measured BOLD signals to the applied hemodynamic reference function (r) were almost independent from frequency and number of the stimuli in both hemispheres, whereas the relative BOLD signal changes (DeltaS) in B and W increased with the stimulation rate, which also changed the lateralization indices. The strongest BOLD activations were achieved with the highest stimulation rate or with the maximum language production task, respectively.CONCLUSION:The adaptation of language paradigms necessary in clinical fMRI does not alter the functional localizations but changes the BOLD signals and language lateralization which should not be attributed to the underlying brain pathology.

A clinical functional magnetic resonance imaging (fMRI) protocol based on a fully automated tactile stimulation was optimized in 10 right-handed volunteers at 1.5T for minimum scan time, high BOLD-signals and robust localization of the primary somatosensory cortex (S1) by systematically varying the applied block design. All volunteers had six different fMRI measurements of 5 stimulation/baseline cycles each with equal block duration that was changed between the measurements from 6 to 30s. Data sets of 4, 3 and 2 cycles were generated post hoc resulting in a total of 240 data sets that were evaluated individually for BOLD-signal intensity (dS%), correlation to the hemodynamic reference function (r) and Euclidean coordinates (x, y, z). The protocol with 5 cycles, a block duration of 6s and a total scan time of 66s provided the best BOLD-signal characteristics (dS%=1.15, r=0.78). Compared to the mean scan time of other clinical fMRI protocols (174s) a reduction of 62% was achieved.