Cortical reorganization following anterior temporal lobectomy in patients with temporal lobe epilepsy

BACKGROUND

Functional MRI was used to study the impact of temporal lobe epilepsy (TLE) and anterior temporal lobectomy (ATL) on the cortical language network in patients with medically refractory TLE.

METHODS

Nineteen patients with medically refractory TLE and 11 healthy control subjects were enrolled in this study. Ten patients underwent left ATL (mean age 35.2 +/- 3.8 years), and 9 underwent right ATL (mean age 35.9 +/- 2.6 years). The subjects silently generated verbs in response to a series of visually presented nouns inside the scanner. Correlation analysis was performed between the subjects' performance on the clinical language tests and their neural response in the a priori cortical regions.

RESULTS

Preoperative data revealed that the patients with TLE showed increased neural activity in the right inferior frontal gyri (IFG) and middle frontal gyri (MFG). The right TLE patients demonstrated strong correlation between their language performance and the level of cortical activation within the typical language areas. However, such a correlation was absent in the left TLE patients. After the ATL surgery, the left TLE patients showed reduced activation in the left MFG and right IFG, whereas no difference was observed in the right TLE patients. In the right TLE patients, the correlation between language performance and neural response shifted from the typical language areas to the anterior cingulate cortex.

CONCLUSION

This study demonstrates that the cortical language network is affected differently by the left and right temporal lobe epilepsy and is reorganized after anterior temporal lobectomy.

Lorentz effect imaging

This paper presents a method that can detect minute electrical activity in a strong magnetic field. It uses displacement encoding to detect small spatial displacement induced by Lorentz force on the conducting materials, hence the term Lorentz effect imaging (LEI). With increased sensitivity from improved hardware capabilities or signal averaging, this technique may be used to detect spatial displacements induced by small currents comparable to neuronal electrical current. The initial results using the LEI technique may provide insight in assessing the feasibility of using MRI to non-invasively detect the neuronal electrical activities.

Genetic engineering of stent grafts with a highly efficient pseudotyped retroviral vector

PURPOSE

The purpose of this study was first to compare the gene transfer efficiency of amphotrophic murine leukemia viral vector (ampho-MuLV) with the efficiency of MuLV pseudotyped with the vesicular stomatitis virus G glycoprotein (VSVG-MuLV) in tissue of vascular origin. The second purpose of this study was to determine cell retention after the implantation of genetically engineered stent grafts.

METHODS

Gene transfer efficiency was ascertained with the b-galactosidase assay. The target tissues included endothelial cells (ECs), smooth muscle cells (SMCs), and human saphenous veins (HSVs). Polyurethane stent grafts were suffused with lac Z-transduced ECs and SMCs that were harvested from porcine jugular vein. The grafts were implanted into the iliac artery of each pig whose jugular vein had been harvested. Cell retention was analyzed at 1 and 4 weeks with X-Gal staining.

RESULTS

VSVG-MuLV transduction efficiency exceeded that of ampho-MuLV in human ECs (VSVG-MuLV, n = 24, 89% +/- 6%; ampho-MuLV, n = 18, 14% +/- 6%; P <. 001), human SMCs (VSVG-MuLV, n = 5, 92% +/- 3%; ampho-MuLV, n = 4, 17% +/- 2%; P <.001), pig ECs (VSVG-MuLV, n = 4, 81% +/- 2%; ampho-MuLV, n = 4, 13% +/- 3%; P <.001), and pig SMCs (VSVG-MuLV, n = 5, 89% +/- 3%; ampho-MuLV, n = 4, 16% +/- 1%; P <.001). As much as a 10-fold higher transduction efficiency was observed with VSVG-MuLV in HSVs. After the stent graft implantation, the engineered cells were retained and proliferated on the stent membrane, with ingrowth into the underlying intima.

CONCLUSION

VSVG-MuLV significantly increased the gene transfer efficiency in vascular SMCs and ECs and in organ-cultured HSVs. The cells were retained and proliferated on stent grafts for the short term in the pig.

Functional MRI of human brain during breath holding by BOLD and FAIR techniques

BOLD (blood oxygenation level-dependent) and FAIR (flow-sensitive alternating inversion recovery) imaging techniques were used to investigate the oxygenation and hemodynamic responses of human brain during repeated challenges of breath holding and prolonged single breath holding. The effects of different breathing techniques on BOLD and FAIR image contrasts were carefully examined. With a periodic breath-holding paradigm of 30 s, global changes in gray matter were observable both in T*2-weighted and FAIR images. T*2-weighted images showed 1-4% relative signal intensity increases, while FAIR images demonstrated relative cerebral blood flow (CBF) increase up to 30-70%. The activated pixels depicted in FAIR images were about three times less than those seen in T*2-weighted images. With prolonged breath holding, it was observed that signal intensities in T*2-weighted and FAIR images were dependent on the breathing techniques used. Breath holding after expiration gave rise to immediate signal intensity increases in T*2-weighted and FAIR images, whereas breath holding performed after deep inspiration signals showed a biphasic change both in flow and T*2-weighted. T*2-weighted and FAIR signals showed a transient decrease before rising above the baseline level.

ADC mapping by means of a single-shot spiral MRI technique with application in acute cerebral ischemia

Diffusion-weighted MRI based on single-shot echo planar imaging (EPI) has been established as a useful tool to study acute cerebral ischemia. However, EPI is prone to spatial distortion and ghosting artifacts. In this study, a pulse sequence for diffusion-weighted imaging (DWI) based on a single-shot spiral readout is presented. Using this technique, multislice apparent diffusion coefficient (ADC) mapping can be performed in an interleaved fashion with the same temporal resolution as EPI. Other advantages associated with ADC mapping by the single-shot spiral method include minimal ghosting artifacts, reduced spatial distortion, and capability to scan in arbitrary planes. This technique has been successfully tested in five normal volunteers and three stroke patients. It has been demonstrated that the single-shot spiral technique is capable of producing high quality DWI and ADC trace maps (128 x 128) in the axial, sagittal, and coronal planes, which facilitate clinical diagnosis.

Integration of stereoscopic DSA and 3D MRI for image-guided neurosurgery

We demonstrate the feasibility and utility of using anatomical/vascular correlation in image-guided surgery, by interfacing a PC-based stereoscopic Digital Subtraction Angiography (DSA) analysis system to a three-dimensional (3D) image based surgical workstation that has been modified to allow presentation of stereoscopic images. Numerical values representing the position and angulation of a hand-held probe are transmitted to both systems simultaneously, enabling the probe to be visualized stereoscopically in both anatomical and vascular images during the surgical procedure. The integration of the patient's vascular and anatomical data in this way provides the surgeon with a complete overview of brain structures through which he is passing the electrode-guiding cannulas, enabling him to avoid critical vessels en route to the targets.