Bidirectional Neuronal Control of Epileptiform Activity by Repetitive Transcranial Focused Ultrasound Stimulations.

Repetitive stimulation procedures are used in neuromodulation techniques to induce persistent excitatory or inhibitory brain activity. The directivity of modulation is empirically regulated by modifying the stimulation length, interval, and strength. However, bidirectional neuronal modulations using ultrasound stimulations are rarely reported. This study presents bidirectional control of epileptiform activities with repetitive transcranial-focused ultrasound stimulations in a rat model of drug-induced acute epilepsy. It is found that repeated transmission of elongated (40 s), ultra-low pressure (0.25 MPa) ultrasound can fully suppress epileptic activities in electro-encephalography and cerebral blood volume measurements, while the change in bursting intervals from 40 to 20 s worsens epileptic activities even with the same burst length. Furthermore, the suppression induced by 40 s long bursts is transformed to excitatory states by a subsequent transmission. Bidirectional modulation of epileptic seizures with repeated ultrasound stimulation is achieved by regulating the changes in glutamate and γ-Aminobutyric acid levels, as confirmed by measurements of expressed c-Fos and GAD65 and multitemporal analysis of neurotransmitters in the interstitial fluid obtained via microdialysis.

Therapeutic Quadrisected Annular Array for Improving Magnetic Resonance Compatibility.

OBJECTIVE: Focused ultrasound has been applied in brain therapeutics. Although focusing ultrasonic beams on multiple arbitrary regions under the guidance of magnetic resonance imaging(MRI) is needed for precise treatments, current therapeutic transducers with large pitch sizes have been optimized to focus on deep brain regions. While annular arrays can adjust the beam foci from cortical to deep regions, their circular shape may generate eddy current-induced magnetic flux during MRI. In this study, a quadrisected annular array is proposed to address these limitations. METHODS: Conventional and quadrisected annular arrays with three elements were implemented by loading the electrode patterns onto an 850 kHz 1-3 composite PZT disc, with a diameter of 31 mm, including three rings. MR compatibilities were demonstrated by imaging an MRI phantom with pulse sequences for B0 and B1 mapping and spin-echo imaging. Acoustic beam profiles, with and without a macaque monkey skull, were measured. A quadrisected transducer was also used to open the blood-brain barrier(BBB). RESULTS: The flip angle distortion improved by 20% in spin-echo MR imaging. The acoustic beam distortions shifting the focal point from 36 to 41mm and elongating the focal zone from 10 to 15 mm could be recovered to nearly the original values. BBB openings in the hippocampus and basal region were also demonstrated. CONCLUSION: The MR compatibility was improved by the increased resistance of the electrodes in the quadrisected array maintaining dynamic focusing capabilities. SIGNIFICANCE: The quadrisected annular design can be a fundamental structure for a larger MR-compatible segmented array transducer generating multiple acoustic foci.

Analysis of hippocampal subfields in sickle cell disease using ultrahigh field MRI.

Sickle cell disease (SCD) is an inherited hemoglobinopathy that causes organ dysfunction, including cerebral vasculopathy and neurological complications. Hippocampal segmentation with newer and advanced 7 Tesla (7T) MRI protocols has revealed atrophy in specific subregions in other neurodegenerative and neuroinflammatory diseases, however, there is limited evidence of hippocampal involvement in SCD. Thus, we explored whether SCD may be also associated with abnormalities in hippocampal subregions. We conducted 7T MRI imaging in individuals with SCD, including the HbSS, HbSC and HbS/beta thalassemia genotypes (n = 53), and healthy race and age-matched controls (n = 47), using a customized head coil. Both T1- and T2-weighted images were used for automatic segmentation of the hippocampal subfields. Individuals with SCD had, on average, significantly smaller volume of the region including the Dentate Gyrus and Cornu Ammonis (CA) 2 and 3 as compared to the control group. Other hippocampal subregions also showed a trend towards smaller volumes in the SCD group. These findings support and extend previous reports of reduced volume in the temporal lobe in SCD patients. Further studies are necessary to investigate the mechanisms that lead to structural changes in the hippocampus subfields and their relationship with cognitive performance in SCD patients.

Anaphylactic reaction with hydroxyethyl starch during anesthesia - A case report.

BACKGROUND: Hydroxyethyl starch (HES), a class of synthetic colloid solutions, has been widely used to treat perioperative hypovolemia. The use of HES, however, is associated with the risk of allergic reactions. CASE: An 83-year-old man was scheduled to undergo an open reduction and internal fixation of a pertrochanteric fracture under spinal anesthesia. He had no history of allergy. Five minutes after HES administration, hypotension, agitation, and skin rash were developed. HES infusion was terminated due to a suspected anaphylactic reaction. The vital signs recovered following administration of phenylephrine, dexamethasone, and hydrocortisone. Serum tryptase and total immunoglobulin E levels were elevated in plasma samples collected following the commencement of the allergic reaction during surgery. CONCLUSIONS: In the present report, the risk of anaphylactic reaction with HES and the laboratory tests needed to support the diagnosis are highlighted.

In-vivo and numerical analysis of the eigenmodes produced by a multi-level Tic-Tac-Toe head transmit array for 7 Tesla MRI.

Radio-frequency (RF) field inhomogeneities and higher levels of specific absorption rate (SAR) still present great challenges in ultrahigh-field (UHF) MRI. In this study, an in-depth analysis of the eigenmodes of a 20-channel transmit Tic-Tac-Toe (TTT) RF array for 7T neuro MRI is presented. The eigenmodes were calculated for five different Z levels (along the static magnetic field direction) of the coil. Four eigenmodes were obtained for each Z level (composed of 4 excitation ports), and they were named based on the characteristics of their field distributions: quadrature, opposite-phase, anti-quadrature, and zero-phase. Corresponding finite-difference time-domain (FDTD) simulations were performed and experimental B1+ field maps were acquired using a homogeneous spherical phantom and human head (in-vivo). The quadrature mode is the most efficient and it excites the central brain regions; the opposite-phase mode excites the brain peripheral regions; anti-quadrature mode excites the head periphery; and the zero-phase mode excites cerebellum and temporal lobes. Using this RF array, up to five eigenmodes (from five different Z levels) can be simultaneously excited. The superposition of these modes has the potential to produce homogeneous excitation with full brain coverage and low levels of SAR at 7T MRI.

The effects of the Trendelenburg position and intrathoracic pressure on the subclavian cross-sectional area and distance from the subclavian vein to pleura in anesthetized patients.

BACKGROUND: The effects of maneuvers to increase intrathoracic pressure and of Trendelenburg position on the cross-sectional area (CSA) of the subclavian vein (SCV) and the relationship between the SCV and adjacent structures have not been investigated. METHODS: In ultrasonography-guided SCV catheterization (N = 30), the CSA of the SCV and the distance between the SCV and pleura (DSCV-pleura) were determined during 10-second airway opening, and 10-second positive inspiratory hold with 20 cm H2O in the supine position (S-0, and S-20) and the 10° Trendelenburg position (T-0, and T-20). In addition to a statistical significance of P < 0.05, CSA and DSCV-pleura differences of ≥15% were defined as clinically relevant changes. RESULTS: CSA (mean [95% confidence interval]) in S-20, T-0, and T-20 (1.02 [0.95-1.14] cm(2), 1.04 [0.95-1.15] cm(2), and 1.14 [1.04-1.24] cm(2), respectively) was significantly larger than a CSA in S-0 (0.93 [0.86-1.00] cm(2), all P < 0.001). However, only the increase of CSA in T-20 vs S-0 (0.21 cm(2), 23.2%) was clinically meaningful (≥15%). The number of patients who showed CSA increase ≥15% was more in S-0 to T-20 (57%) compared with those in S-0 to S-20 (23%) and S-0 to T-0 (27%). DSCV-pleura measurements (mean) in S-20 and T-20 (0.61 and 0.60 cm) were significantly shorter than those in S-0 (0.70 cm, all P < 0.001), but the reductions of DSCV-pleura were not clinically meaningful (≥15%). CONCLUSIONS: The combined application of inspiratory hold and Trendelenburg position provided a greater and more relevant degree of CSA increase without compromising DSCV-pleura, which may facilitate SCV catheterization. Further investigations are needed to determine whether these results affect the success rate of catheterization and the risk of procedural injury.

Clinical factors affecting the pain on injection of propofol.

BACKGROUND: Pain on propofol injection is a well-known adverse effect. We evaluated the clinical factors that affect the pain on injection of propofol to develop a strategy to prevent or reduce pain. METHODS: We conducted a prospective, observational study of 207 adult patients (ASA I-II), and the patients were classified according to gender, age, the body mass index (BMI), the IV site and the side of the IV site. During the 10 seconds after propofol injection, pain intensity was measured on an 11-point numerical rating scale (0 = no pain and 10 = worst possible pain). Pain in excess of 3 on the numerical scale was regarded as moderate to severe pain. RESULTS: THE SUBGROUPS OF GENDER (FEMALE: 55.6% vs. male: 25.0%; P < 0.01) and the IV site (dorsum of hand: 61.2% vs. wrist: 40.0% vs. antecubital fossa: 22.5%; P < 0.01) had significantly different frequencies for the incidence of pain on injection on the univariate and multivariate analyses. For the subgroup of females, the incidence of pain was statistically different according to the age group (20-40 yr: 71.0% vs. 41-60: 54.8% vs. 61-80: 38.5%; P = 0.014). CONCLUSIONS: Our results showed that the younger age patients, the patients with a peripheral IV site and female patients are more sensitive to pain on the injection of propofol.