Pronounced reduction of acquisition of conditioned eyeblink responses in young adults with focal cerebellar lesions impedes conclusions on the role of the cerebellum in extinction and savings.

Human cerebellar lesion studies provide good evidence that the cerebellum contributes to the acquisition of classically conditioned eyeblink responses (CRs). As yet, only one study used more advanced methods of lesion-symptom (or lesion-behavior) mapping to investigate which cerebellar areas are involved in CR acquisition in humans. Likewise, comparatively few studies investigated the contribution of the human cerebellum to CR extinction and savings. In this present study, young adults with focal cerebellar disease were tested. A subset of participants was expected to acquire enough conditioned responses to allow the investigation of extinction and saving effects. 19 participants with chronic surgical lesions of the cerebellum and 19 matched control subjects were tested. In all cerebellar subjects benign tumors of the cerebellum had been surgically removed. Eyeblink conditioning was performed using a standard short delay protocol. An initial unpaired control phase was followed by an acquisition phase, an extinction phase and a subsequent reacquisition phase. Structural 3T magnetic resonance images of the brain were acquired on the day of testing. Cerebellar lesions were normalized using methods optimized for the cerebellum. Subtraction analysis and Liebermeister tests were used to perform lesion-symptom mapping. As expected, CR acquisition was significantly reduced in cerebellar subjects compared to controls. Reduced CR acquisition was significantly more likely in participants with lesions of lobule VI and Crus I extending into Crus II (p<0.05, Liebermeister test). Cerebellar subjects could be subdivided into two groups: a smaller group (n=5) which showed acquisition, extinction and savings within the normal range; and a larger group (n=14) which did not show acquisition. In the latter, no conclusions on extinction or savings could be drawn. Previous findings were confirmed that circumscribed areas in lobule VI and Crus I are of major importance in CR acquisition. In addition, the present data suggest that if the critical regions of the cerebellar cortex are lesioned, the ability to acquire CRs is not only reduced but abolished. Subjects with lesions outside these critical areas, on the other hand show preserved acquisition, extinction and saving effects. As a consequence, studies in human subjects with cerebellar lesions do not allow drawing conclusions on CR extinction and savings. In light of the present findings, previous reports of reduced extinction in humans with circumscribed cerebellar disease need to be critically reevaluated.

Occipital nerve stimulation for the treatment of chronic cluster headache - lessons learned from 18 months experience.

OBJECTIVE: Neuromodulation has been recognized as a valuable surgical treatment option for patients with refractory chronic cluster headache (CCH). Due to the small number of afflicted individuals, the knowledge about this specific therapy is limited. In this study, we present our experiences with bilateral occipital nerve stimulation (ONS) in patients with CCH focusing on patient selection, pre- and postoperative evaluation, surgical procedures, and outcome. PATIENTS AND METHODS: Since December 2008, 10 patients with CCH have been treated with ONS at our department. Patients were recruited and clinically followed by a neurologist and a neurosurgeon. Baseline data records on frequency, intensity, and duration of attacks as well as the use of medication were assessed with a 30-day diary. Standardized questionnaires were used pre- and postoperatively and during the follow-up on a regular basis. Surgical procedure and stimulation parameters were standardized for all patients. Lead implantation was followed by a test period of 30 days prior to implantation of the permanent generator. Mean follow-up time was 12 months (range 3-18). RESULTS: All patients responded to the stimulation treatment. Frequency, duration, and severity of the cluster attacks were reduced in 90% of the patients. One patient had a significant reduction of his concomitant tension headache. 70 % of the patients needed less medication during the attacks. All patients reported an improvement in their quality of life. The SF-36 showed a tendency toward objective improvement in the field of psychological comfort. As a major adverse event, one generator had to be exchanged due to a local infection. Another patient had to be reoperated due to a scar tissue formation around the thoracic connector. CONCLUSIONS: ONS is a valuable tool in the treatment of patients with refractory CCH. According to our data, the potential side effects and complication rates of the operation are small. With a meticulous selection of patients by an interdisciplinary team, CCH can bed improve in the majority of the patients. Yet, the optimal parameters for the stimulation regarding pulse width and frequency remain unclear. For this reason, we started a prospective single-center observational trial at our center in October 2009, including patients with ONS, to identify the best stimulation parameters.

Predictive value of intrathecal interleukin-6 for ventriculostomy-related Infection.

BACKGROUND AND STUDY AIM: Early diagnosis of ventriculostomy-related infection (VRI) is crucial for the early treatment and course of this disease. In neurosurgical patients the diagnostic criteria are equivocal, mostly because of bloodstained cerebrospinal fluid (CSF). The predictive value, sensitivity and specificity of intrathecal interleukin-6 (IL-6 (CSF)) has been proven for VRI compared with classical diagnostic CSF parameters, i.e. cell countCSF (CC (CSF)) and total protein (CSF). PATIENTS AND METHODS: We prospectively analyzed the daily clinical data and CSF samples of 75 neurosurgical patients with an external ventricular drainage (EVD), which had been inserted predominantly because of poor-grade subarachnoid hemorrhage (SAH). The intrathecal interleukin-6 concentrations (IL-6 (CSF)) were correlated with the clinical course and VRI incidence, as diagnosed by the classical VRI criteria (CC (CSF), total protein (CSF), clinical symptoms). RESULTS: Based on classical criteria, bacterial meningitis occurred in 26.7% of patients. Patients with VRI manifested significantly (p<0.001) higher median values of IL-6 (CSF) (up to 2,000-fold increase) the day before (day -1) infection was diagnosed by conventional parameters. Using a cut-off value of IL-6 (CSF)>or=2,700 pg/ml [4,050 pg/ml after WHO standardization] on day -1, the relative risk for VRI was 6.09 (95% CI: 2.62-14.18%). A predictive value of IL-6 (CSF)>or=2,700 pg/ml [4,050 pg/ml] for VRI was calculated of 89% (95% CI: 79.6-98.0%), a sensitivity of 73.7% and a specificity of 91.4%. The amount of intrathecal blood was an independent risk factor for VRI occurrence, whereas the mean duration of EVD in place showed no impact on the rate of infection. CONCLUSION: Our data indicate that IL-6 (CSF) is a reliable marker for predicting VRI prior to clinically manifest meningitis, one day earlier than the common diagnostic criteria of CSF infection (CC (CSF), total protein (CSF), clinical symptoms).

Electronics for a high temperature superconducting receiver system for magnetic resonance microimaging.

We describe an MRI (magnetic resonance imaging) receiver system that incorporates a high temperature superconducting (HTS) resonator as a surface coil. Techniques for measuring the Q of the HTS resonator in a 7 Tesla field are discussed. A method for coupling a room temperature copper resonant circuit to the HTS element is covered, and it is shown that such a coupling scheme preserves the signal-to-noise (SNR) gain afforded by the HTS coil. A preamplifier with a noise figure (NF) of < 0.15 dB at 300 MHz is described.

A high-temperature superconducting receiver for nuclear magnetic resonance microscopy.

A high-temperature superconducting-receiver system for use in nuclear magnetic resonance (NMR) microscopy is described. The scaling behavior of sources of sample and receiver-coil noise is analyzed, and it is demonstrated that Johnson, or thermal, noise in the receiver coil is the factor that limits resolution. The behavior of superconductors in the environment of an NMR experiment is examined, and a prototypical system for imaging biological specimens is discussed. Preliminary spin-echo images are shown, and the ultimate limits of the signal-to-noise ratio of the probe are investigated.

The NMR phased array.

We describe methods for simultaneously acquiring and subsequently combining data from a multitude of closely positioned NMR receiving coils. The approach is conceptually similar to phased array radar and ultrasound and hence we call our techniques the "NMR phased array." The NMR phased array offers the signal-to-noise ratio (SNR) and resolution of a small surface coil over fields-of-view (FOV) normally associated with body imaging with no increase in imaging time. The NMR phased array can be applied to both imaging and spectroscopy for all pulse sequences. The problematic interactions among nearby surface coils is eliminated (a) by overlapping adjacent coils to give zero mutual inductance, hence zero interaction, and (b) by attaching low input impedance preamplifiers to all coils, thus eliminating interference among next nearest and more distant neighbors. We derive an algorithm for combining the data from the phased array elements to yield an image with optimum SNR. Other techniques which are easier to implement at the cost of lower SNR are explored. Phased array imaging is demonstrated with high resolution (512 x 512, 48-cm FOV, and 32-cm FOV) spin-echo images of the thoracic and lumbar spine. Data were acquired from four-element linear spine arrays, the first made of 12-cm square coils and the second made of 8-cm square coils. When compared with images from a single 15 x 30-cm rectangular coil and identical imaging parameters, the phased array yields a 2X and 3X higher SNR at the depth of the spine (approximately 7 cm).

Proton-decoupled, Overhauser-enhanced, spatially localized carbon-13 spectroscopy in humans.

Spatially localized, natural abundance, carbon (13C) NMR spectroscopy has been combined with proton (1H) decoupling and nuclear Overhauser enhancement to improve 13C sensitivity up to five-fold in the human leg, liver, and heart. Broadhand-decoupled 13C spectra were acquired in 1 s to 17 min with a conventional 1.5-T imaging/spectroscopy system, an auxiliary 1H decoupler, an air-cooled dual-coil coplanar surface probe, and both depth-resolved surface coil spectroscopy (DRESS) and one-dimensional phase-encoding gradient NMR pulse sequences. The surface coil probe comprised circular and figure-eight-shaped coils to eliminate problems with mutual coupling of coils at high decoupling power levels applied during 13C reception. Peak decoupler RF power deposition in tissue was computed numerically from electromagnetic theory assuming a semi-infinite plane of uniform biological conductor. Peak values at the surface were calculated at 4 to 6 W/kg in any gram of tissue for each watt of decoupler power input excluding all coil and cable losses, warning of potential local RF heating problems in these and related experiments. The average power deposition was about 9 mW/kg per watt input, which should present no systemic hazard. At 3 W input, human 13C spectra were decoupled to a depth of about 5 cm while some Overhauser enhancement was sustained up to about 3 cm depth, without ill effect. The observation of glycogen in localized natural abundance 13C spectra of heart and muscle suggests that metabolites in the citric acid cycle should be observable noninvasively using 13C-labeled substrates.

Human in vivo phosphate metabolite imaging with 31P NMR.

Phosphorus (31P) spectroscopic images showing the distribution of high-energy phosphate metabolites in the human brain have been obtained at 1.5 T in scan times of 8.5 to 34 min at 27 and 64 cm3 spatial resolution using pulsed phase-encoding gradient magnetic fields and three-dimensional Fourier transform (3DFT) techniques. Data were acquired as free induction decays with a quadrature volume NMR detection coil of a truncated geometry designed to optimize the signal-to-noise ratio on the coil axis on the assumption that the sample noise represents the dominant noise source, and self-shielded magnetic field gradient coils to minimize eddy-current effects. The images permit comparison of metabolic data acquired simultaneously from different locations in the brain, as well as metabolite quantification by inclusion of a vial containing a standard of known 31P concentration in the image array. Values for the NMR visible adenosine triphosphate in three individuals were about 3 mM of tissue. The ratio of NMR detectable phosphocreatine to ATP in brain was 1.15 +/- 0.17 SD in these experiments. Potential sources of random and systematic error in these and other 31P measurements are identified.

Switched surface coil system for bilateral MR imaging.

A method is presented for acquiring magnetic resonance (MR) images in parallel from both members of a pair of organs, such as the temporomandibular joint (TMJ), with use of two surface coil receivers. Interleaved sagittal sections are broken into two groups, one on each side of the head, and the MR receiver is toggled between the two coils. The surface coil that is not receiving at a given time is decoupled from the other surface coil by the active gating of a diode blocking network located across the coil input. This method produces effective decoupling independent of coil loading and positioning and makes it possible to use the same surface coils already employed for single-coil MR reception. Clinical application in 95 patients (190 joints) with symptoms of internal derangement of the TMJ demonstrated a 24% average decrease in total patient examination time, even after the addition of coronal imaging to the procedure. In no case was there a sacrifice in diagnostic quality.

Surface-coil T1 images.

A method for producing calculated T1 images with high signal-to-noise ratio and good spatial resolution using surface coils is presented. Separate transmit and receive rf coils with electronic decoupling are employed to insure uniform B1 excitation. The sensitivity profile of the receiver coil is normalized out of the image by the T1 calculation. T1 values determined by this method show close agreement with previously reported values.

Anatomy and metabolism of the normal human brain studied by magnetic resonance at 1.5 Tesla.

Proton magnetic resonance (MR) images were obtained of the human head in magnetic fields as high as 1.5 Tesla (T) using slotted resonator high radio-frequency (RF) detection coils. The images showed no RF field penetration problems and exhibited an 11 (+/- 1)-fold improvement in signal-to-noise ratio over a .12-T imaging system. The first localized phosphorus 31, carbon 13, and proton MR chemical shift spectra recorded with surface coils from the head and body in the same instrument showed relative concentrations of phosphorus metabolites, triglycerides, and, when correlated with proton images, negligible lipid (-CH2-) signal from brain tissue on the time scale of the imaging experiment. Sugar phosphate and phosphodiester concentrations were significantly elevated in the head compared with muscle. This method should allow the combined assessment of anatomy, metabolism, and biochemistry in both the normal and diseased brain.