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Query: UMLS:C0036572 (seizures)
 80,221 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

To investigate alterations of brain metabolism associated with temporal lobe epilepsy, [31P]MRS studies were performed on the anterotemporal lobes of patients with medically refractory complex partial seizures. Interictally, the pH was significantly more alkaline in the temporal lobe ipsilateral to the seizure focus (7.25 vs. 7.08, p less than 0.05), and the inorganic phosphorous concentration was greater on the side of the epileptogenic focus (1.9 vs. 1.1 mM, p less than 0.05). These changes in pH and inorganic phosphate may represent metabolic alterations secondary to seizures. Alternatively, because alkalosis enhances neural excitability and may enhance seizure activity, the increased pH of the seizure focus may provide insight into the pathophysiologic mechanism of epileptic seizures.
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PMID:Increased pH and inorganic phosphate in temporal seizure foci demonstrated by [31P]MRS. 162 74

Elevations of brain concentrations of arachidonic acid and other free fatty acids (FFAs) by seizures induced in animals were demonstrated some years ago. Similarly, large shifts of potassium (K+) from intra- to extracellular space during seizure activity have been documented in numerous studies. More recent studies of cell membrane function demonstrated a direct effect of FFAs on membrane K+ conductance, suggesting that FFAs may play a primary role in seizure evolution in brain tissue. Using electroconvulsive therapy (ECT), in which generalized seizures are induced in patients by passage of electrical current, as a controlled human model of seizures, we studied the in vivo biochemical effects of single generalized seizures with localized proton magnetic resonance spectroscopy (1H MRS). We found that ECT reliably induces an elevation in the lipid signal that resonates at approximately 1.2 ppm. We observed a similar increase in brain lipids in a patient with temporal lobe epilepsy temporarily off medication; the signal disappeared after re-medication. Similar observations were noted for a subject with focal gliosis bordering a resected brain tumor. Finally, acute alcohol effects seem also to induce observable lipid changes. The 1H MRS technique does not yet permit direct identification of the specific lipids involved but analysis of cerebrospinal fluid obtained by lumbar puncture before and immediately after ECT may permit more precise characterization of the observed lipid increases. Theoretical and clinical implications of these results for the study of brain FFAs and epilepsy will be discussed.
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PMID:Induced and spontaneous seizures in man produce increases in regional brain lipid detected by in vivo proton magnetic resonance spectroscopy. 163 96

This review has attempted to indicate areas of investigation that in vivo MRS methodology is particularly suited for and would answer important questions related to neonatal cerebral development or injury. There are several metabolites (PEth, PCr, NAA, taurine, glutamate) and lipids detectable by in vivo 31P or 1H MRS, which show substantial changes in concentration during ontogenesis. Do these biochemical markers correlate with major morphological changes, such as myelination? If they do, can this be used to quantitate abnormalities in brain development from congenital abnormalities or metabolic encephalopathies? In the neutral to mild acidic range (7.0 greater than pHi greater than 6.5) adult and neonatal brain appear to have similar intrinsic physicochemical buffering capacity. However, at the extremes of pHi induced by respiratory alkalosis or severe acidosis from partial ischemia, the possibility exists that the buffering capacities of adult and neonatal brain differ. Whether this is true requires further investigations using both neonates and adults, or perhaps more preferably, multiple measurements on a single species throughout its developmental period. Such studies are now feasible because multinuclear in vivo MRS can provide a large body of information from individual animals. A similar study design could prove useful for investigations of changes in cerebral resistance to hypoxia, ischemia, or asphyxia during development. The roles that blood pressure, glucose, temperature, or the administration of extrinsic buffers and drugs have on modulating the severity of and relationship between changes in blood flow, energy metabolites, or pHi, are all amenable to study using in vivo MRS. Furthermore, all of these variables can be measured simultaneously. The kinetics of brain acid and lactate homeostasis during chronic cerebral insults or following acute insults has not been thoroughly examined in either neonates or adult animals. There is evidence to suggest that following ischemia or seizures, brain acidosis resolves before brain lactosis. However, the clinical diagnostic significance of this post-insult uncoupling between pHi and lactate remains to be established. Finally, the application of in vivo MRS methodology to study the effects of trauma, drugs, environmental toxins, and other metabolic encephalopathies on neonatal cerebral perfusion and metabolism are virtually unexplored. Hopefully, the material presented here will prompt researchers to consider the application of in vivo MRS to new avenues of investigation.
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PMID:In vivo multinuclear magnetic resonance spectroscopy investigations of cerebral development and metabolic encephalopathy using neonatal animal models. 219 84

Clinical studies using 31P and 1H MRS with a whole body 2.0 T MRI/MRS system are described. In most cases, techniques to quantitate absolute molar concentrations of metabolites in various organs were used. In the brain, AIDS, chronic stroke, and white matter lesions were associated with alterations of brain 31P metabolites. Epilepsy was associated with increased pH in the seizure focus. In the heart, dilated cardiomyopathy was associated with increased PDE/ATP while PCr/ATP was unchanged. In the liver, alcoholic hepatitis and cirrhosis were associated with diminished hepatic ATP while alcoholic hepatitis had increased pH and cirrhosis had decreased pH. This allowed differentiation of normal liver, alcoholic hepatitis, and alcoholic cirrhosis without biopsy. In the prostate, malignancy was associated with increased PME/ATP and decreased PCr/ATP. The PME/PCr was greatly increased in malignant prostate with no overlap in normals. Other cancers outside the brain had increased PME and effective treatment was often associated with diminished PME. 1H MRS of the brain was performed using ISIS and outer volume suppression pulses for volume localization. Excellent high resolution 1H water-suppressed spectra were obtained at echo times as short as 30 ms, showing well resolved peaks for lactate, N-acetylaspartate, glutamate, choline, creatinine, and inositol. 1H MRS demonstrated that the uptake of ethanol by the brain was slower than the rise of ethanol in blood. 31P spectroscopic imaging of the brain with resolution of 2.25 x 2.25 x 2.5 cm produced metabolic images and high resolution spectra from desired regions of interest.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Clinical magnetic resonance spectroscopy of brain, heart, liver, kidney, and cancer. A quantitative approach. 270 9

MRS techniques can aide in confirming the location of seizure foci in temporal lobe epilepsy. N-acetyl aspartate (NAA), creatine plus phosphocreatine, choline-containing compounds, and lactate are most often the clinically relevant metabolites in these studies. We examined the importance of partial volume effects from tissue heterogeneity in temporal lobe spectroscopy on the metabolite ratios. Our study shows that localized spectroscopy, using three different voxel sizes, centered on the anterior body of the hippocampus, produces significantly different values for the NAA to the creatine ratio. The spectroscopy was performed at 1.5 T using the PRESS pulse sequence and a phased-array coil system specifically designed for the temporal lobe. The data exhibits a clear trend of increasing NAA to creatine ratios with increasing voxel size. This trend demonstrates that partial volume effects can contribute to variation of NAA to creatine ratios in healthy subjects.
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PMID:Partial volume effects in volume-localized phased-array proton spectroscopy of the temporal lobe. 754 6

We assessed performance on selected tests of verbal memory in 48 patients who had undergone either anterior temporal lobectomy or selective amygdalo-hippocampectomy for the relief of pharmacologically intractable epilepsy. We related performance both to the side of surgical excision and to the presence or absence of abnormalities in the contralateral, unoperated, temporal lobe, as revealed by proton magnetic resonance spectroscopy (1H MRS) or T2 relaxometry. There were abnormalities on the unoperated side detected by 1H MRS in 50% of the 34 patients who successfully underwent spectroscopy, and by T2 relaxometry in 33% of the complete series of 48 patients. There was no systematic relationship between seizure outcome and the presence or absence of abnormalities on the unoperated side. Verbal memory deficits were present in patients with left-sided excision, regardless of whether there were abnormalities on the unoperated side. The patients with right-sided excision also had verbal memory deficits, but only in the group with magnetic resonance abnormalities on the contralateral (ie, left) side and only on delayed recall. The study extends previous findings on the role of the temporal lobes in memory and highlights the role of these new magnetic resonance techniques in relating cognitive processes to brain structures.
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PMID:Verbal memory impairment after right temporal lobe surgery: role of contralateral damage as revealed by 1H magnetic resonance spectroscopy and T2 relaxometry. 772 73

We used proton magnetic resonance spectroscopy (1H MRS) to determine concentrations of N-acetylaspartate (NAA), creatine and choline in vivo (63 MHz) and in vitro (400 MHz) in seven patients undergoing surgical treatment of intractable temporal lobe epilepsy (TLE). Nine healthy volunteers were used as controls for in vivo MRS. NAA concentrations in vivo on the ipsilateral and contralateral sides were 6.5 +/- 1.3 (s.d.) and 7.9 (+/- 2.1) mmol l-1, respectively and 8.6 (+/- 0.8) mmol l-1 in the volunteers. NAA concentration in vitro was 3.2 (+/- 0.9) mumol g-1 wet weight (ww) and the corresponding concentration from the macroscopically intact brain tissue was 4.7 (+/- 1.0) mumol g-1 ww. Thus, in vivo quantitative 1H MRS identified the size of seizure focus in patients with temporal lobe epilepsy.
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PMID:Reduced N-acetylaspartate concentration in temporal lobe epilepsy by quantitative 1H MRS in vivo. 782 19

We used proton magnetic resonance spectroscopy (1H MRS) to investigate the temporal lobes of 25 patients with temporal lobe epilepsy. Spectra were obtained from 2 x 2 x 2 cm cubes in the medial region of the temporal lobe, and were analyzed on the basis of signals from N-acetylaspartate (NAA), creatine + phosphocreatine (Cr), and choline-containing compounds (Cho). In comparison with control subjects, the temporal lobes ipsilateral to the seizure focus showed a mean reduction of 22% in the NAA signal, with a 15% increase in the Cr signal and a 25% increase in the Cho signal. There were smaller effects in the contralateral temporal lobes. These spectral abnormalities may reflect neuronal loss or damage, together with reactive astrocytosis. The NAA/Cho+Cr ratio was abnormally low in 88% of the patients, 40% showing bilateral effects. On the basis of the NAA/Cho+Cr ratio, we correctly achieved lateralization in 15 cases, with three incorrect. Two of the incorrect lateralizations also had imaging abnormalities on the contralateral side, and the other had severe bilateral abnormalities on MRS. We conclude that 1H MRS provides useful information in the preoperative investigation of patients with temporal lobe epilepsy, contributing to lateralization and detecting bilateral abnormalities.
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PMID:Magnetic resonance spectroscopy in temporal lobe epilepsy. 805 40

Functional and anatomical neuroimaging has had a dramatic effect on the evaluation of patients for seizure surgery. The demonstration by PET that the epileptogenic focus has interictal metabolic abnormalities has allowed a greater number of patients to come to seizure surgery, with fewer of these patients requiring intracranial electrode evaluations. Metabolic changes have also been demonstrated utilizing single voxel and whole brain 1H and 31P MRS imaging techniques with the interictal focus characterized by increased Pi, pH, and decreased PME and NAA. These findings can be used to accurately lateralize temporal lobe as well as frontal lobe epilepsy. Furthermore, there is evidence that these findings can be used to localize the seizure focus with the changes specific for the epileptogenic region; although, more diffuse changes both ipsilaterally and contralaterally have been seen. In patients with anterior hippocampal seizure foci the pH is significantly alkaline only in the ipsilateral hippocampus, whereas the increased Pi and decreased PME can be seen throughout the ipsilateral temporal lobe. When compared to controls the contralateral hemisphere is acidotic. Decreased NAA concentrations as well as NAA/Cr ratios have been demonstrated in the epileptogenic region in temporal and frontal lobe epilepsy. The decreased NAA has been correlated with the severity of cell loss, and may be a more sensitive measure than qualitative or quantitative measures of the hippocampal atrophy; however, the NAA decrease is more widespread than just the epileptogenic focus but may be maximal at the site of seizure initiation. In preliminary work, NAA maps of deviation from normality have suggested that the maximal change to coincide with the epileptogenic region. These results suggest that in focal epilepsy there is abnormal metabolic activity throughout the brain detectable by MRS, with patterns of metabolic asymmetry that are useful for seizure localization.
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PMID:Application of spectroscopic imaging in epilepsy. 875 Mar 34

Proton magnetic resonance spectra include signals from N-acetylaspartate, creatine + phosphocreatine, and choline-containing compounds. Abnormalities in these signals can be used in the assessment of patients with intractable epilepsy. In particular, they provide a means of identifying metabolic abnormalities within the temporal lobes, detecting bilateral and diffuse pathology, and aiding lateralization of the seizure focus. The pathology demonstrated on MRS can also be related to cognitive dysfunction.
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PMID:N-acetylaspartate and epilepsy. 875 Mar 36


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