Lateralization of human temporal lobe epilepsy by 31P NMR spectroscopic imaging at 4.1 T

Whole-body radiofrequency coil for (31) P MRSI at 7 T

Widespread use of ultrahigh-field (31) P MRSI in clinical studies is hindered by the limited field of view and non-uniform radiofrequency (RF) field obtained from surface transceivers. The non-uniform RF field necessitates the use of high specific absorption rate (SAR)-demanding adiabatic RF pulses, limiting the signal-to-noise ratio (SNR) per unit of time. Here, we demonstrate the feasibility of using a body-sized volume RF coil at 7 T, which enables uniform excitation and ultrafast power calibration by pick-up probes. The performance of the body coil is examined by bench tests, and phantom and in vivo measurements in a 7-T MRI scanner. The accuracy of power calibration with pick-up probes is analyzed at a clinical 3-T MR system with a close to identical (1) H body coil integrated at the MR system. Finally, we demonstrate high-quality three-dimensional (31) P MRSI of the human body at 7 T within 5 min of data acquisition that includes RF power calibration. Copyright © 2016 John Wiley & Sons, Ltd.

High-performance radiofrequency coils for (23)Na MRI: brain and musculoskeletal applications

(23)Na RF coil design for brain and MSK applications presents a number of challenges, including poor coil loading for arrays of small coils and SNR penalties associated with providing (1)H capability with the same coil. The basics of RF coil design are described, as well as a review of historical approaches to dual tuning. There follows a review of published high performance coil designs for MSK and brain imaging. Several coil designs have been demonstrated at 7T and 3T which incorporate close-fitting receive arrays and in some cases design features which provide (1)H imaging with little penalty to (23)Na sensitivity. The "nested coplanar loop" approach is examined, in which small transmit-receive (1)H elements are placed within each (23)Na loop, presenting only a small perturbation to (23)Na performance and minimizing RF shielding issues. Other designs incorporating transmit-receive arrays for (23)Na and (1)H are discussed including a 9.4 T (23)Na/(1)H brain coil. Great gains in (23)Na SNR have been made with many of these designs, but simultaneously achieving high performance for 1H remains elusive.

Extratemporal abnormalities in phosphorus magnetic resonance spectroscopy of patients with mesial temporal sclerosis

ABSTRACT Objective We evaluated extratemporal metabolic changes with phosphorus magnetic resonance spectroscopy (31P-MRS) in patients with unilateral mesial temporal sclerosis (MTS). Method 31P-MRS of 33 patients with unilateral MTS was compared with 31 controls. The voxels were selected in the anterior, posterior insula-basal ganglia (AIBG, PIBG) and frontal lobes (FL). Relative values of phosphodiesters- PDE, phosphomonoesters-PME, inorganic phosphate - Pi, phosphocreatine- PCr, total adenosine triphosphate [ATPt = γ- + a- + b-ATP] and the ratios PCr/ATPt, PCr/γ-ATP, PCr/Pi and PME/PDE were obtained. Results We found energetic abnormalities in the MTS patients compared to the controls with Pi reduction bilaterally in the AIBG and ipsilaterally in the PIBG and the contralateral FL; there was also decreased PCr/γ-ATP in the ipsilateral AIBG and PIBG. Increased ATPT in the contralateral AIBG and increased γ-ATP in the ipsilateral PIBG were detected. Conclusion Widespread energy dysfunction was detected in patients with unilateral MTS.

Proton MR Spectroscopy in Patients with Structural MRI-Negative Temporal Lobe Epilepsy

BACKGROUND AND PURPOSE

With conventional magnetic resonance imaging (MRI), 20-30% of patients with temporal lobe epilepsy (TLE) have negative pathological MRI findings. Further investigations of the role of magnetic resonance spectroscopy (MRS) in the pre-surgical evaluation of patients with MRI-negative TLE are important to avoid intracranial EEG recording and to better understand the mechanism of the epileptogenic process. This study aimed to compare the measurements of N-acetylaspartate (NAA), creatine (Cr), and choline (Cho) in the hippocampi of MRI-negative TLE patients and normal subjects.

METHODS

Twenty patients with MRI-negative TLE and 10 age-matched healthy control subjects underwent MRI and MRS. The concentrations of NAA, Cr, and Cho and the ratios of NAA/Cr and NAA/(Cr+Cho) were measured. Seven of these 20 patients also underwent surgical treatment for TLE. Their pathological results and surgical outcomes were evaluated.

RESULTS

In the hippocampi ipsilateral to the seizure side, the NAA/Cr and NAA/(Cr+Cho) ratios were significantly decreased compared with the ratios of the hippocampi contralateral to the seizure side and the normal control hippocampi. There was no significant difference between the hippocampi contralateral to the seizure side and the normal control hippocampi. The pathological results from the patients who underwent temporal lobe resection indicated mild to moderate gliosis and minimal loss of neurons. Five patients were seizure-free during the follow-up period of 9- 47 months (mean 27.7 months).

CONCLUSIONS

In MRI-negative TLE, significant reductions in the NAA/Cr and NAA/(Cr+Cho) ratios ipsilateral to the seizure side may help lateralize and localize the epileptogenic zone.

PCr/ATP ratio mapping of the human head by simultaneously imaging of multiple spectral peaks with interleaved excitations and flexible twisted projection imaging readout trajectories at 9.4 T

Quantitative (31)P magnetic resonance imaging of the whole human brain is often time-consuming even at low spatial resolution due to the low concentrations, long T(1) relaxation times, and low detection sensitivity of phosphorus metabolites. We report herein the results of combining the increased detection sensitivity of an ultra-high field 9.4 T scanner designed for human imaging with a new pulse sequence termed simultaneously imaging of multiple spectral peaks with interleaved excitations and flexible twisted projection imaging readout trajectories to rapidly sample multiple resonances in the (31)P spectrum. The phosphocreatine and γ-adenosine triphosphate images, obtained simultaneously from the entire human head, are demonstrated at 1.5 cm isotropic nominal resolution in a total acquisition time of 33 min. The phosphocreatine/γ-adenosine triphosphate ratio calculated for brain parenchyma (1-2) and the superficial temporalis muscle (3-5) are in agreement with literature values.

Novel approaches to imaging epilepsy by MRI

As the concept of a network of injury has emerged in the treatment of epilepsy, the importance of evaluating that network noninvasively has also grown. Recently, studies utilizing magnetic resonance spectroscopic imaging, manganese-enhanced MRI and functional (f)MRI measures of resting state connectivity have demonstrated their ability to detect injury and dysfunction in cerebral networks involved in the propagation of seizures. The ability to noninvasively detect neuronal injury and dysfunction throughout cerebral networks should improve surgical planning, provide guidance for placement of devices that target network propagation and provide insights into the mechanisms of recurrence following resective surgery.

Brain-mapping techniques for evaluating poststroke recovery and rehabilitation: a review

Brain-mapping techniques have proven to be vital in understanding the molecular, cellular, and functional mechanisms of recovery after stroke. This article briefly summarizes the current molecular and functional concepts of stroke recovery and addresses how various neuroimaging techniques can be used to observe these changes. The authors provide an overview of various techniques including diffusion-tensor imaging (DTI), magnetic resonance spectroscopy (MRS), ligand-based positron emission tomography (PET), single-photon emission computed tomography (SPECT), regional cerebral blood flow (rCBF) and regional metabolic rate of glucose (rCMRglc) PET and SPECT, functional magnetic resonance imaging (fMRI), near infrared spectroscopy (NIRS), electroencephalography (EEG), magnetoencephalography (MEG), and transcranial magnetic stimulation (TMS). Discussion in the context of poststroke recovery research informs about the applications and limitations of the techniques in the area of rehabilitation research. The authors also provide suggestions on using these techniques in tandem to more thoroughly address the outstanding questions in the field.

Neurometabolism in human epilepsy

PURPOSE

Because of the large and continuous energetic requirements of brain function, neurometabolic dysfunction is a key pathophysiologic aspect of the epileptic brain. Additionally, neurometabolic dysfunction has many self-propagating features that are typical of epileptogenic processes, that is, where each occurrence makes the likelihood of further mitochondrial and energetic injury more probable. Thus abnormal neurometabolism may be not only a chronic accompaniment of the epileptic brain, but also a direct contributor to epileptogenesis.

METHODS

We examine the evidence for neurometabolic dysfunction in epilepsy, integrating human studies of metabolic imaging, electrophysiology, microdialysis, as well as intracranial EEG and neuropathology.

RESULTS

As an approach of noninvasive functional imaging, quantitative magnetic resonance spectroscopic imaging (MRSI) measured abnormalities of mitochondrial and energetic dysfunction (via 1H or 31P spectroscopy) are related to several pathophysiologic indices of epileptic dysfunction. With patients undergoing hippocampal resection, intraoperative 13C-glucose turnover studies show a profound decrease in neurotransmitter (glutamate-glutamine) cycling relative to oxidation in the sclerotic hippocampus. Increased extracellular glutamate (which has long been associated with increased seizure likelihood) is significantly linked with declining energetics as measured by 31P MR, as well as with increased EEG measures of Teager energy, further arguing for a direct role of glutamate with hyperexcitability.

DISCUSSION

Given the important contribution that metabolic performance makes toward excitability in brain, it is not surprising that numerous aspects of mitochondrial and energetic state link significantly with electrophysiologic and microdialysis measures in human epilepsy. This may be of particular relevance with the self-propagating nature of mitochondrial injury, but may also help define the conditions for which interventions may be developed.

Differential glutamate dehydrogenase (GDH) activity profile in patients with temporal lobe epilepsy

PURPOSE

Pathophysiologic mechanisms underlying temporal lobe epilepsy (TLE) are still poorly understood. One major hypothesis links alterations in energy metabolism to glutamate excitotoxicity associated with seizures in TLE. The purpose of this study was to determine whether changes in the activities of enzymes critical in energy and neurotransmitter metabolism contributed to the alterations in metabolic status leading to the excitotoxic effects of glutamate.

METHODS

Activities of four key enzymes involved in energy metabolism and glutamate cycling in the brain [aspartate aminotransferase (AAT), citrate synthase (CS), glutamate dehydrogenase (GDH), and lactate dehydrogenase (LDH)] were measured in anterolateral temporal neocortical and hippocampal tissues obtained from three different groups of medically intractable epilepsy patients having either mesial, paradoxical, or mass lesion-associated temporal lobe epilepsy (MTLE, PTLE, MaTLE), respectively.

RESULTS

We found that GDH activity was significantly decreased in the temporal cortex mainly in the MTLE group. A similar trend was recognized in the hippocampus of the MTLE. In all three patient groups, GDH activity was considerably lower, and AAT and LDH activities were higher in cortex of MTLE as compared with the corresponding activities in hippocampus (p<0.05). In the MTLE cortex and hippocampus, GDH activities were negatively correlated with the duration since the first intractable seizure.

CONCLUSIONS

Our results support the hypothesis suggesting major alteration in GDH activity mainly in the MTLE group. It is proposed that significant alterations in the enzyme activities may be contributing to decreased metabolism of glutamate, leading to its accumulation.

Metabolic alteration transients during paroxysmal activity in an epileptic patient with fixation-off sensitivity: a case study

The purpose of this study was to investigate short-time metabolic variations related to continuous epileptic activity elicited by fixation-off sensitivity (FOS). Time-resolved magnetic resonance spectroscopy was performed on a patient on whom previous clinical findings clearly indicated presence of FOS. The epileptic focus was localized with a simultaneous electroencephalographic and functional magnetic resonance imaging study. The results showed a linear increase of the sum of glutamate and glutamine with time of paroxysmal activity in epileptic focus and much greater concentration of choline-containing compounds in focus than in the contralateral side.

Seizure-associated Abnormalities in Epilepsy: Evidence from MR Imaging

Acute seizure-associated changes have been described in the animal and human literature. Controversy exists over whether seizures cause permanent damage to the brain, and whether a (prolonged) seizure can induce changes that lead to an epileptic lesion, resulting in habitual seizures and epilepsy. Current magnetic resonance imaging (MRI) offers a variety of imaging tools and is capable of detecting acute seizure-associated changes. In contrast to the histologic examination, serial MRI studies are possible and allow longitudinal observation of the fate of these changes. This report reviews the literature on acute seizure-associated effects emphasizing the MRI evidence.

Clinical applications of MR spectroscopy in epilepsy

1H and 31P spectroscopy detects relevant metabolite changes in patients with TLE. Numerous studies confirm reduction in NAA and in the ratio of PCr/Pi. In his 1999 review, Kuzniecky concluded that proton MRS, using single-voxel or chemical shift imaging, lateralizes temporal lobe epilepsy in 65% to 96% of cases, with bilateral changes seen in 35% to 45% of cases, whereas phosphorus MRS shows a lateralizing PCr/Pi ratio in 65% to 75% of the TLE patients. There are indications that these changes are reversible with seizure treatment. Improvements in MRS technology, such as the ability to calculate absolute concentrations, to account for differences be-tween gray and white matter and to achieve better spectral resolution by use of a higher magnetic field strength, will now allow more extensive use of this technique for patients with epilepsy.

1H and 31P Spectroscopic Imaging of Epilepsy: Spectroscopic and Histologic Correlations

Although MRS measurements are useful in assessing the biochemical alterations underlying human epilepsy, to date their use has been limited primarily by three factors: (a) the lack of widespread methods and appropriate hardware for acquiring high-resolution spectroscopic imaging data, (b) difficulties in spectral interpretation associated with metabolic heterogeneity, and (c) difficulties in biological interpretation due to a lack of correlative histologic studies. In this work, we (a) describe approaches to overcome these hurdles, and (b) discuss the biological interpretation of the spectroscopic findings in TLE.

Neural damage due to temporal lobe epilepsy: dual-nuclei (proton and phosphorus) magnetic resonance spectroscopy study

The aim of this study was to evaluate the usefulness of proton and phosphorus (1H and 31P) magnetic resonance spectroscopy (MRS) for temporal lobe epilepsy (TLE) patients, and to evaluate neural damage and metabolite dysfunction in the TLE patient brain. We performed 1H and 31P MRS of medial temporal lobes (MTL) in the same TLE patients (n = 14) with a relatively wide range of severity from almost seizure-free to intractable, and calculated the ratio of N-acetylasparate to choline-containing compounds and creatine + phosphocreatine (NAA/Cho + Cr) in 1H MRS and inorganic phosphate to all main peaks (%Pi) in 31P MRS. There was no significant correlation between NAA/(Cho + Cr) and %Pi in each side (ipsilateral, r = -0.20; contralateral, r =-0.19). The values of NAA/(Cho + Cr) showed a significant difference between ipsilateral and contralateral MTLs to the focus of TLE patients (P < 0.01, paired t-test). Although %Pi also had a tendency to show the laterality of TLE, there was no significance. Ipsilateral (r = -0.90, P < 0.0001) and contralateral (r = -0.70, P < 0.005) NAA/(Cho + Cr) decreases and contralateral %Pi increase (r = 0.81, P < 0.001) had significant correlation with seizure frequency. 1H MRS provides more important information concerning neuronal dysfunction in MTL of TLE patients than 31P MRS.

Identifying potential surgical candidates in patients with evidence of bitemporal epilepsy

PURPOSE

To determine which patients with evidence of medically refractory bitemporal epilepsy are potentially good candidates for surgical therapy.

METHODS

We reviewed 42 adults with intractable seizures who were found to have bitemporal ictal onsets, based on scalp video-EEG long-term monitoring (LTM). All underwent invasive LTM before surgery. Surgical outcomes were classified as seizure free, >75% reduction in seizures, or <75% reduction in seizures, >or=1 year after resection. We related the following factors to outcome: (a). >75% preponderance of interictal scalp EEG discharges to one temporal region; (b). magnetic resonance imaging (MRI) findings; (c). lateralizing deficits on verbal or visual reproduction memory testing; and (d). memory failure with injection contralateral to side of surgery on Wada testing.

RESULTS

Twenty-six (62%) of 42 patients had unilateral ictal onsets based on intracranial studies. Seizure freedom (occurring in 64% of this group), or >75% seizure reduction (found in 12% of subjects) occurred only when at least one of the following three factors was concordant with the side of surgery: preponderance of interictal scalp EEG discharges, unilateral temporal lesion on MRI, or lateralizing verbal or visual reproduction memory deficits on neuropsychological tests (p = 0.004). Seven subjects with bilateral ictal onsets based on intracranial studies had resections based on preponderance of seizures to one side, or other lateralizing noninvasive abnormality. Five of these (all of whom had >or=80% of seizures originating from one side) had >75% reduction in seizures.

CONCLUSIONS

Invasive monitoring to pursue possible surgical therapy for patients with surface EEG evidence of bitemporal epilepsy may be justified only when some lateralizing feature is found in other noninvasive assessments.

In vivo 31P magnetic resonance spectroscopy of human brain at 7 T: an initial experience

In vivo (31)P spectra were acquired from the human primary visual cortex at 7 T. The relaxation times of the cerebral metabolites, intracellular pH, rate constant (k(f)) of the creatine kinase (CK) reaction, and nuclear Overhauser enhancement (NOE) on the detected phosphorus moieties from irradiation of the water spins were measured from normal subjects. With a 5-cm-diameter surface coil, 3D (31)P chemical shift imaging was performed with a spatial resolution of 7.5 ml and an acquisition resolution of 8 min, resulting in a signal-to-noise ratio (SNR) for phosphocreatine (PCr) resonance of 32. The apparent T(1) and T(2) of PCr measured at 7 T were 3.37 +/- 0.29 s and 132.0 +/- 12.8 ms, respectively, which were considerably longer than those of adenosine triphosphate (ATP) (T(1): 1.02-1.27 s; T(2): 25-26 ms). The NOE measured in this study was 24.3% +/- 1.6% for PCr, and 10% for ATP. The k(f) measured in the human primary visual cortex was 0.24 +/- 0.03 s(-1). The results from this study suggest that ultra-high-field strength is advantageous for performing in vivo (31)P magnetic resonance spectroscopy (MRS) in the human brain.

1H and 31P spectroscopy and bioenergetics in the lateralization of seizures in temporal lobe epilepsy

Over the past decade, (1)H and (31)P spectroscopy measurements have demonstrated that significant metabolic alterations occur in temporal lobe epilepsy. However, to most accurately interpret these changes, metabolic heterogeneity and differences between gray and white matter must be accounted for. These alterations, decreased NAA and the ratio of phosphocreatine/inorganic phosphate, can be reversed with successful treatment of seizures. The reversibility of these two measures is consistent with the localization of NAA synthesis to neuronal mitochondria and the important role for bioenergetics in the pathophysiology of temporal lobe epilepsy.

Fast kappa-space sample selection in MRSI with a limited region of support

One of the primary drawbacks in the application of magnetic resonance spectroscopic imaging is the long acquisition times required to obtained the desired resolution. When region of support information is available, the number of phase-encoding steps and thus time can be reduced without loss of information if the kappa-space locations are chosen well. We propose to select locations using a rectangular sampling array that is shifted to various positions in kappa-space to obtain the necessary sampling density. This method allows multiple samples to be selected simultaneously and reduces the computation required to evaluate the selection criterion. We present an efficient forward selection algorithm for optimizing the shift pattern so that the image can be reconstructed as reliably as possible from a periodic nonuniform set of samples. The proposed algorithm has important practical potential in that it can finish the selection in less than half a minute for typical image sizes and can reconstruct the image with fewer samples than regular sampling. With appropriate imaging hardware, this new algorithm makes selective sampling possible in a real-time image acquisition setting.

Alkaline pH changes in the cerebellum of asymptomatic HIV-infected individuals

Human immunodeficiency virus (HIV) infection of the brain causes a complex cascade of cellular events involving several different cell types that eventually leads to neuronal cell death and the manifestation of the AIDS-associated dementia complex (ADC). Upon autopsy HIV-infected individuals show lesions within subcortical regions of the brain, including the cerebellum. Previously we have demonstrated, in primary and cell culture models of rat and human astrocytes, a change in intracellular pH (pH(i)) due to increased Na(+)/H(+) exchange following exposure to inactivated virus or gp120, the major HIV envelope glycoprotein. To further investigate whether any such in vivo pH(i) changes occur in human brains subsequent to HIV infection, we measured the pH(i) of the cerebellum in eight HIV-positive individuals and nine healthy volunteers using (31)P magnetic resonance spectroscopy imaging (MRSI) at high field strength (4.1 T). The results showed a significant difference between the age-adjusted mean pH(i) in the cerebellum in control group and patient groups (7.11 +/- 0.03 vs 7.16 +/- 0.04), and further HIV-infected individuals displayed a significant increase in the number of cerebellar volume elements that were alkaline. We hypothesize that this propensity towards alterations in cerebellar pH(i) may portend later neurological involvement resulting from HIV infection.

Quantitative (31)P spectroscopic imaging of human brain at 4 Tesla: assessment of gray and white matter differences of phosphocreatine and ATP

This report describes the implementation and application of a multicompartment analysis of (31)P spectroscopic imaging data to determine the tissue-specific heterogeneities in metabolite content in the human brain and surrounding tissue. Using this information and a multicompartment regression analysis the phosphocreatine and ATP content of "pure" cerebral gray and white matter, the cerebellum, and skeletal muscle was determined in a group of 10 healthy volunteers. The data were converted to mM units using previously reported values for the T(1)s of phosphocreatine and ATP at 4 T, the water content of human brain, and an external reference for absolute quantification. The phosphocreatine concentration in cerebral gray and white matter, the cerebellum, and skeletal muscle was 3.53 +/- 0.33, 3.33 +/- 0.37, 3.75 +/- 0.66, and 25.8 +/- 2.3 mM, respectively. The ATP concentration in cerebral gray and white matter, the cerebellum, and skeletal muscle was 2.19 +/- 0.33, 3.41 +/- 0.33, 1.75 +/- 0.58, and 8.5 +/- 1.9 mM, respectively. Magn Reson Med 45:46-52, 2001.

Optimal k-space sampling in MRSI for images with a limited region of support

Magnetic resonance spectroscopic imaging requires a great deal of time to gather the data necessary to achieve satisfactory resolution. When the image has a limited region of support (ROS), it is possible to reconstruct the image from a subset of k-space samples. Therefore, we desire to choose the best possible combination of a small number of k-space samples to guarantee the quality of the reconstructed image. Sequential forward selection (SFS) is appealing as an optimization method because the previously selected sample can be observed while the next sample is selected. However, when the number of selected k-space samples is less than the number of unknowns at the beginning of the selection process, the optimality criterion is undefined and the resulting SFS algorithm cannot be used. In this paper, we present a modified form of the criterion that overcomes this problem and develop an SFS algorithm for the new criterion. Then we develop an efficient computational strategy for this algorithm as well as for the standard SFS algorithm. The combined algorithm efficiently selects a reduced set of k-space samples from which the ROS can be reconstructed with minimal noise amplification.

A filter design method for minimizing ringing in a region of interest in MR spectroscopic images

Magnetic resonance spectroscopic imaging (MRSI) requires a relatively long time to sample k-space (the spatial frequency domain), effectively lowpass filtering the resulting reconstructed image. Ringing is especially problematic when a region of interest (ROI) is close to a bright region outside the ROI, since the bright region tends to create a ringing artifact into the ROI due to the lowpass nature of the data. In this paper, we propose a method that reduces the effect of a stronger signal region on a weaker signal in a nearby ROI by designing a postprocessing filter that steers the strong interference away from the ROI. The proposed method is computationally simple both in the design stage and in applying it to images. We present experiments that illustrate the value of the technique.

The stiff-person syndrome: an autoimmune disorder affecting neurotransmission of gamma-aminobutyric acid

The stiff-person syndrome, a rare and disabling disorder, is characterized by muscle rigidity and episodic spasms that involve axial and limb musculature. Continuous contraction of agonist and antagonist muscles caused by involuntary motor-unit firing at rest are the hallmark clinical and electrophysiologic signs of the disease. Except for global muscle stiffness, results of neurologic examination are usually normal. Results of conventional computed tomography and magnetic resonance imaging of the brain are also normal. The cause of the stiff-person syndrome is unknown; however, an autoimmune pathogenesis is suspected because of 1) the presence of antibodies against glutamic acid decarboxylase (GAD), the rate-limiting enzyme for the synthesis of the inhibitory neurotransmitter gamma-aminobutyric acid (GABA); 2) the association of the disease with other autoimmune conditions; 3) the presence of various autoantibodies; and 4) a strong immunogenetic association. Anti-GAD antibodies, which are found in high titers in most patients, seem to be directed against conformational forms of GAD. New evidence suggests that these antibodies may be pathogenic because they interfere with the synthesis of GABA. In addition, a reduction in brain levels of GABA, which is prominent in the motor cortex, has been demonstrated with magnetic resonance spectroscopy in patients with the stiff-person syndrome. The stiff-person syndrome is clinically elusive but potentially treatable and should be considered in patients with unexplained stiffness and spasms. Drugs that enhance GABA neurotransmission, such as diazepam, vigabatrin, and baclofen, provide mild to modest relief of clinical symptoms. Immunomodulatory agents, such as steroids, plasmapheresis, and intravenous immunoglobulin, seem to offer substantial improvement. Results of an ongoing controlled trial will elucidate the role of these agents in the treatment of the disease.

Applications of neural network analyses to in vivo 1H magnetic resonance spectroscopy of epilepsy patients

A total of 67 in vivo water-suppressed proton magnetic resonance spectra of the temporal lobes were recorded from 15 patients with long standing temporal lobe epilepsy and 13 healthy volunteers. Conventional data analysis indicated slightly lower N-acetyl aspartate levels in epileptic patients compared with controls. For further analysis of data, a spectral region (4.0-1.5 ppm) was used as input for artificial neural network analysis. Correct classification of spectra was obtained in 66 out of 67 cases, disregarding from which side of the brain the spectra were recorded. The ability of the trained network to recognize spectra recorded both contalaterally and ipsilaterally to the epileptic focus strongly indicates bilateral metabolic changes. Artificial neural networks could also be trained to recognize whether the spectra were recorded from the ipsilateral or contralateral side of the epileptic focus, indicating that neural network analysis of in vivo proton MR spectra can be used as an additional tool for pre-surgical lateralization of seizure foci.

Hippocampal or neocortical lesions on magnetic resonance imaging do not necessarily indicate site of ictal onsets in partial epilepsy

Advances in neuroimaging techniques, particularly high-resolution magnetic resonance imaging (MRI), have proved invaluable in identifying structural brain lesions in patients with epilepsy. The assumption that such focal lesions invariably predict the site of seizure origin may not be correct, however. We report a series of 20 adults with medically intractable partial epilepsy, where high-resolution brain MRI disclosed a unilateral, focal, hippocampal, or neocortical lesion as the only abnormality in each case; nevertheless, based on electroencephalographic (EEG) recordings, ictal onsets arose from a completely different location than that of the MRI lesion. All patients underwent epilepsy surgery, with the operations based on ictal EEG findings, and all were followed at least 2 years after the resection. After the most recent follow-up examination, 50% (10/20) of the patients were completely seizure-free, 35% (7/20) had at least a 75% reduction in the number of seizures, and 15% (3/20) had less than a 75% reduction in the number of seizures. We conclude that the identification of a focal, structural, hippocampal, or neocortical lesion on brain MRI is not always indicative of the site of seizure origin in partial epilepsy. Furthermore, in cases of discordance between MRI and EEG data, a good outcome after epilepsy surgery is possible if EEG ictal onsets are definitive.