Ipsilateral and contralateral thalamic hypometabolism as a predictor of outcome after temporal lobectomy for seizures.

FDG PET is often used to help localize the seizure focus before surgery in patients with medically refractory temporal lobe epilepsy. However, the ability of certain patterns of metabolic landscape to predict postsurgical seizure outcome has not been well characterized. The purpose of this retrospective study was to determine whether FDG PET abnormalities elsewhere in the brain, in combination with those in the temporal lobes, can be used to predict seizure outcome after surgery. METHODS: Eighty patients with refractory temporal lobe seizures were imaged with PET after intravenous administration of 115 microCi/kg FDG. Images were interpreted without knowledge of clinical information by an experienced reviewer to determine seizure focus and regional metabolic changes in the brain. Metabolic activity scores were assigned for cortical and subcortical structures using the following criteria: 4 = normal activity, 3 = mildly decreased activity, 2 = moderately decreased activity, 1 = severely decreased activity, and 0 = no activity. A laterality index for each region was calculated using the equation 100 x [right - left]/[1/2 x (right + left)]. Seizure focus localization was based on the laterality of temporal lobe metabolic activity and was compared with that determined by scalp and depth electrodes and MRI results. Comparisons were made between asymmetries in metabolic activity in various brain structures and postoperative seizure frequency. Postoperative outcome was determined on the basis of cessation (complete disappearance of seizures) or continuation of seizure activity, regardless of frequency, compared with the preoperative state. RESULTS: All 64 patients who were free of seizures postoperatively had either no thalamic asymmetry or reduced metabolism on the side from which the temporal lobe was removed. In contrast, 5 of 16 patients (31%) with postoperative seizures of any frequency had hypometabolism in the thalamus contralateral to that of the removed temporal lobe. All 5 patients with reverse thalamic asymmetry had postoperative seizures. Patients with thalamic hypometabolism ipsilateral to the removed temporal lobe also had an increased risk of postoperative seizures, but this risk was not as high as in patients with the contralateral abnormality. In these patients, the temporal lobe (which appeared hypometabolic on PET) was determined to be the site of the seizure on the basis of information besides that provided by PET before surgery. CONCLUSION: This study indicated that, in patients with temporal lobe epilepsy, thalamic metabolic asymmetry, particularly in the reverse direction to that of the temporal lobe asymmetry, was associated with a poor postsurgical outcome compared with no or matched asymmetry. This determination may be important in evaluating patients for, and selecting optimal candidates for, surgical intervention.     

Temporal hypometabolism at the onset of cryptogenic temporal lobe epilepsy

Most patients with intractable temporal lobe epilepsy (TLE) exhibit temporal glucose hypometabolism. The reasons for the development of this abnormality are as yet unclear. The current notion is that an initial injury causes seizures, which in turn give rise to hypometabolism. The aim of this study was to assess whether temporal reductions in glucose metabolism in non-lesional TLE are the result of repeated seizures or whether hypometabolism represents an initial disturbance at the onset of disease. Glucose consumption was assessed with fluorine-18 fluorodeoxyglucose positron emission tomography (¹⁸F-FDG PET) in 62 patients with cryptogenic non-refractory TLE in different stages of disease. Twelve subjects without neurological illness served as controls. Patients with onset of epilepsy at least 3 years prior to the PET scan were defined as having chronic TLE. Using this criterion, the whole patient cohort included 27 patients with de novo TLE and 35 patients with chronic TLE. The groups were matched for age and sex. The appearance of high-resolution magnetic resonance images of the brain was unremarkable in all patients. In the total cohort, number, duration and frequency of seizures had a significant relation to the magnitude of hypometabolism. Temporal hypometabolism was exhibited by 26 of the 62 patients (42%), including 8 out of 27 (30%) with newly diagnosed TLE and 18 out of 35 (51%) with chronic TLE. The disturbances were more extensive and more severe in patients with chronic TLE. It is concluded that temporal hypometabolism may already be present at the onset of TLE, but is less frequent and less severe in newly diagnosed than in chronic TLE. The metabolic disturbance correlates with the number of seizures. These findings suggest that an initial dysfunction is present in a considerable number of patients and that hypometabolism is worsened by continuing epileptic activity.     

Temporal hypometabolism at the onset of cryptogenic temporal lobe epilepsy

Most patients with intractable temporal lobe epilepsy (TLE) exhibit temporal glucose hypometabolism. The reasons for the development of this abnormality are as yet unclear. The current notion is that an initial injury causes seizures, which in turn give rise to hypometabolism. The aim of this study was to assess whether temporal reductions in glucose metabolism in non-lesional TLE are the result of repeated seizures or whether hypometabolism represents an initial disturbance at the onset of disease. Glucose consumption was assessed with fluorine-18 fluorodeoxyglucose positron emission tomography (18F-FDG PET) in 62 patients with cryptogenic non-refractory TLE in different stages of disease. Twelve subjects without neurological illness served as controls. Patients with onset of epilepsy at least 3 years prior to the PET scan were defined as having chronic TLE. Using this criterion, the whole patient cohort included 27 patients with de novo TLE and 35 patients with chronic TLE. The groups were matched for age and sex. The appearance of high-resolution magnetic resonance images of the brain was unremarkable in all patients. In the total cohort, number, duration and frequency of seizures had a significant relation to the magnitude of hypometabolism. Temporal hypometabolism was exhibited by 26 of the 62 patients (42%), including 8 out of 27 (30%) with newly diagnosed TLE and 18 out of 35 (51%) with chronic TLE. The disturbances were more extensive and more severe in patients with chronic TLE. It is concluded that temporal hypometabolism may already be present at the onset of TLE, but is less frequent and less severe in newly diagnosed than in chronic TLE. The metabolic disturbance correlates with the number of seizures. These findings suggest that an initial dysfunction is present in a considerable number of patients and that hypometabolism is worsened by continuing epileptic activity.     

Correlation between PET and SISCOM in temporal lobe epilepsy.

The subtraction of interictal from ictal SPECT coregistered to 3-dimensional (3D) MRI (SISCOM) and (18)F-FDG PET are 2 techniques that are involved in the definition of the epileptogenic zone in refractory partial temporal lobe epilepsy (TLE). The aim of this study was compare, region by region, the functional patterns obtained by both strategies, SISCOM and PET, in patients with unilateral TLE. METHODS: Perfusion data using SISCOM and metabolic data using (18)F-FDG PET scans were acquired from 17 patients with unilateral TLE. The functional metabolism and perfusion maps were overlaid onto a 3D rendering of the patient's anatomic MRI scans. RESULTS: The functional patterns that were observed with PET and SISCOM were found mainly in the ipsilateral and contralateral temporal lobes, in the orbitofrontal and insular cortices. Despite the high rate of concordance, in some cases discrepancies could be observed between PET and SISCOM abnormalities: In the mesial regions, as in the anterior neocortex, PET abnormalities were found more frequently than SISCOM changes. SISCOM abnormalities were found more frequently in the posterior temporal neocortex. In the extratemporal cortex, SISCOM abnormalities were more widespread. CONCLUSION: The marked rate of concordance between PET and SISCOM abnormalities observed in relatively extensive regions shows that, in TLE, seizures were generated and spread in metabolically abnormal regions.     

Modified CT techniques in the evaluation of temporal lobe epilepsy prior to lobectomy

The outcome of temporal lobectomy performed for seizure control is improved by preoperative identification of structural lesions. We used cranial CT, modified to improve visualization of mesial temporal structures, as a means of preoperative evaluation in 48 patients with partial complex seizures. The axial views, parallel to the temporal fossa, improved visualization of five lesions, including two that were not diagnosed by routine cranial CT. In 12 patients, intrathecal metrizamide was used; the rest received intravenous contrast. These modified techniques could not reliably predict mesial temporal herniation; however, modified axial CT with intravenous contrast is recommended for evaluation of suspected temporal lobe pathology.     

White matter abnormalities in the anterior temporal lobe suggest the side of the seizure foci in temporal lobe epilepsy

Introduction White matter abnormalities in the anterior temporal lobe (WAATL) are sometimes observed on magnetic resonance (MR) images of patients with temporal lobe epilepsy (TLE). Our purpose was to determine whether WAATL could indicate if the seizure foci are ipsilateral on electroencephalograms (EEG) in TLE patients.Methods We reviewed 112 consecutive patients with medically intractable TLE. We compared the side of seizure foci on EEG (preoperative and intraoperative) and MR images.Results Both loss of gray–white matter demarcation and increased signal intensity changes in the anterior white matter (positive WAATL) were observed in 54 of 112 patients (48.2%) with TLE. WAATL were present on the same side as the seizure foci on preoperative intracranial EEG with subdural electrodes (iEEG) and on intraoperative electrocorticography (ECG) in all the patients. In 47 patients, MR images showed WAATL and focal lesions that were possibly epileptogenic for TLE. In 2 of the 47 patients, the seizure foci on iEEG and ECG were contralateral to the focal lesion; in the remaining 45 patients, the seizure foci on surface EEG (sEEG) and ECG and the focal lesion were on the same side. In three patients, no focal lesions were seen but WAATL were present on the same side as the seizure foci on sEEG and ECG. In four patients, MR images showed focal lesions for which epileptogenicity was questionable, and WAATL on the same side as the seizure foci on EEG.Conclusion WAATL are clinically useful because they indicate the side of the seizure foci.     

Effect of seizure on hippocampus in mesial temporal lobe epilepsy and neocortical epilepsy: an MRS study

This study was performed to evaluate the effect of seizures on the bilateral hippocampus in mesial temporal lobe epilepsy (mTLE) and neocortical epilepsy by single voxel proton magnetic resonance spectroscopy (MRS). Forty-one patients with mTLE having unilateral hippocampal sclerosis and 43 patients with a neocortical epilepsy who underwent subsequent epilepsy surgery were recruited. Ninety-five percent confidence intervals of N-acetyl aspartate/choline (NAA/Cho) and NAA/creatine (NAA/Cr) ratios in 20 healthy control subjects were used as threshold values to determine abnormal NAA/Cho and NAA/Cr. NAA/Cho and NAA/Cr were significantly lower in the ipsilateral hippocampus of mTLE and neocortical epilepsy. Using asymmetry indices for patients with bilaterally abnormal ratios of NAA/Cho and NAA/Cr in addition to using unilateral abnormal ratio, the seizure focus was correctly lateralized in 65.9% of patients with mTLE and 48.8% of neocortical epilepsy patients. Bilateral NAA/Cho abnormality was significantly related to a poor surgical outcome in mTLE. No significant relationship was found between the results of NAA/Cho or NAA/Cr and surgical outcome in neocortical epilepsy. The mean contralateral NAA/Cr ratio of the hippocampus in mTLE was significantly lower in patients with a history of secondary generalized tonic-clonic seizure (SGTCS) than in those without. Our results demonstrate effects of seizures on the hippocampi in neocortical epilepsy and the relation between SGTCS and NAA/Cr of the contralateral hippocampus in mTLE. This proves the presence of a seizure effect on the hippocampus in neocortical epilepsy as well as in mTLE.     

Pre-surgical identification of epileptogenic areas in temporal lobe epilepsy by 123I-iomazenil SPECT: a comparison with IMP SPECT and FDG PET

OBJECTIVES: The aim of this study was to evaluate the usefulness of (123)I-iomazenil (IMZ) single photon emission computed tomography (SPECT) for the pre-surgical identification of epileptogenic areas in patients with temporal lobe epilepsy and to compare the results with those of (123)I-IMP SPECT and (18)Fluorodeoxyglucose positron emission tomography (FDG PET). METHODS: We examined seven patients with medically refractory temporal lobe epilepsy (five men and two women; mean age, 28 years) with no remarkable findings on magnetic resonance imaging. Before surgery, IMZ SPECT, IMP SPECT and FDG PET were all performed in the interictal state. Then, visual assessment and region-of-interest (ROI) analysis were performed on each image. Final definitions of the epileptogenic areas were made by electrocorticography and histopathology. RESULTS: By IMZ SPECT, a decreased IMZ uptake in the ipsilateral temporal lobe was found in all patients, while a similar decrease in the contralateral temporal lobe was also found in one patient. In comparison to IMP SPECT, the extent of the abnormal area on IMZ SPECT was equal to that on IMP SPECT in one patient while it was more restricted to the epileptogenic area in five patients. In comparison to FDG PET, the extent of the abnormal area on IMZ SPECT was equal to that on FDG PET in three patients while it was more restricted in the epileptogenic area in four patients. In ROI analysis, decreases of IMZ, IMP and FDG uptake were observed in the epileptogenic area, although they were not statistically significant. CONCLUSIONS: IMZ SPECT was considered to be useful for pre-surgical determination of the epileptogenic areas in temporal lobe epilepsy with no remarkable MRI findings, and it was also found to be superior to IMP SPECT and FDG PET for this purpose.     

Early and delayed MR and PET changes after selective temporomesial radiosurgery in mesial temporal lobe epilepsy

We report a patient with medically refractory mesial temporal lobe epilepsy treated by gamma knife radiosurgery. In lieu of a microsurgical procedure, an entorhinoamygdalohippocampectomy was performed with a gamma knife and low marginal doses (25 Gy). The clinical and imaging studies, including CT, MR imaging, 18F-fluorodeoxyglucose positron emission tomography (FDG-PET), and long-term follow-up MR examinations, are reported. The patient has been seizure-free since the day of treatment, with no clinical complications. MR studies accurately depicted the effect on the target structures and the transient secondary changes around them. FDG-PET scans showed decreased metabolism after gamma knife surgery throughout the anteromesial part of the epileptogenic temporal lobe. This metabolic decrease was reversible in the lateral temporal cortex. Our case suggests that gamma knife surgery is a promising tool for use as a minimally invasive approach to the treatment of epilepsy.     

Degree of hippocampal atrophy is related to side of seizure onset in temporal lobe epilepsy

BACKGROUND AND PURPOSE: Temporal lobe epilepsy (TLE) is associated with pathologic changes in hippocampal physiology and morphology. Our aim was to quantify volume reduction of the right and left hippocampus in patients with TLE and to investigate whether the degree of hippocampal atrophy is related to the side of seizure onset. METHODS: The volume of the right and left hippocampus was estimated for 50 controls and 101 patients with TLE, by applying the unbiased Cavalieri method on MR images. RESULTS: Pairwise comparisons, within a multivariate analysis of variance and adjusted by using the Bonferroni correction, revealed that both right and left hippocampal volumes were, on average, significantly smaller in patients with right-sided seizure onset (R-patients) relative to those of controls (P < .001 and P = .04, respectively). Furthermore, left hippocampal volume was significantly smaller in patients with left-sided seizure onset (L-patients) compared with controls (P < .001), but the right-sided hippocampal volume was not significantly smaller (P = .71). Moreover, a correlation analysis revealed that the strong linear association between the right and left hippocampal volumes existing in the control population (r = 0.73) is partially lost in patients with TLE (r < or = 0.48), and this loss in correlation appears to be more pronounced in L-patients than in R-patients. CONCLUSION: Our MR imaging results suggest that although the major damage in patients with TLE is located in the hippocampus ipsilateral to the side of seizure onset, R-patients are more likely to have bilateral hippocampal volume reduction. These findings support the hypothesis that cerebral hemispheres may not only differ in their functionality organization but also in their vulnerability to a neurologic insult.     

FDG PET as a predictor of response to resynchronisation therapy in patients with ischaemic cardiomyopathy

Purpose Although resynchronisation therapy (CRT) is a promising addition to heart failure therapy, a substantial number of patients do not respond to CRT. As FDG PET has routinely been used for prediction of improvement after revascularisation in ischaemic cardiomyopathy, it was hypothesised that there is also a relationship between the extent of viable tissue and improvement as a result of CRT. Methods Thirty-nine patients with ischaemic cardiomyopathy (ejection fraction 27 ± 9%) and a wide QRS complex underwent temporary pacing to determine the optimal pacing combination, i.e. that with the highest increase in cardiac index (CI) compared with baseline (measured by Doppler echocardiography). All patients also underwent FDG PET imaging. In 19 patients, CI measurements were repeated 10–12 weeks after permanent biventricular pacemaker implantation. Results Echocardiography (13-segment model) showed a mean of 9.8 ± 1.6 dyssynergic segments, with preserved FDG uptake in 4.1 ± 2.4 segments. CI improvement at the optimal pacing site was 20 ± 9%. There was a linear relationship between the extent of viable tissue and CI improvement during pacing (p < 0.001). Using a cut-off value of more than three viable segments (ROC analysis), FDG PET had a sensitivity of 72% and a specificity of 71% for detection of the presence of haemodynamic improvement (i.e. a CI improvement >15%). The relation between CI improvement and viable tissue was similar at follow-up. Conclusion A correlation was found between the extent of viable tissue and the haemodynamic response to CRT in patients with ischaemic cardiomyopathy, suggesting that FDG PET imaging may be useful to discriminate between responders and non-responders to CRT.     

Thalamic hypometabolism in a patient undergoing vagal nerve stimulation seen on F-18 FDG PET imaging

A 31-year-old man with a vagal nerve stimulator for seizure control was noted to have decreased metabolism within the thalamus as visualized by F-18 fluorodeoxyglucose (FDG) positron emission tomography (PET). Some investigators think the thalamus plays an important role in the regulation of seizure activity. Vagal nerve stimulation (VNS) may reduce thalamic activity, which in turn may reduce seizure activity. However, because the thalamus has diffuse connections throughout the brain, its role in seizure activity is likely complex. Observing decreased thalamic activity during VNS is just 1 small step toward understanding this role.     

FDG PET as a prognostic predictor in the early post-therapeutic evaluation for unresectable hepatocellular carcinoma

Purpose

To elucidate the prognostic role of post-therapeutic ¹⁸F-fluorodeoxyglucose (¹⁸F-FDG) positron emission tomography (PET), we conducted a retrospective cohort study analysing the clinical factors that affect overall survival after non-operative therapy for unresectable hepatocellular carcinoma (HCC).

Methods

Sixty-seven cases with unresectable HCC who received non-operative therapy (transcatheter arterial chemoembolization: n?=?24, transcatheter arterial infusion chemotherapy: n?=?31, radiofrequency ablation: n?=?5 or systemic chemotherapy: n?=?7) and had received FDG PET for the evaluation of the therapeutic effect within 1 month after the end of the therapy were evaluated. Overall survival rate was evaluated using the univariate and multivariate analyses of relevant clinical and laboratory parameters before and after therapy, including visual PET analysis and quantitative analysis using maximum standardized uptake value (SUV).

Results

Visual PET diagnosis of post-therapeutic lesions was a good predictor of overall survival of unresectable HCC patients. The low FDG group showed significantly longer survival (average: 608 days) than that (average: 328 days) of the high FDG group (p?<?0.0001). Multivariate analysis showed four significant prognostic factors for the survival: post-therapeutic alpha-fetoprotein (αFP) level (=400 ng/ml, p?=?0.004), post-therapeutic visual PET diagnosis (p?=?0.006), post-therapeutic clinical stage (UICC stage IV, p?=?0.04) and post-therapeutic Milan criteria (p?=?0.03), while pre-therapeutic clinical factors, SUV by post-therapeutic FDG PET (5.0 or more) or others did not show significance.

Conclusion

The present study suggests that post-therapeutic PET performed within 1 month after non-operative therapy can be a good predictor of overall survival in unresectable HCC patients, while pre-therapeutic evaluation including PET, tumour markers and clinical staging may not be useful.     

The significance of bilateral CSI changes for the postoperative outcome in temporal lobe epilepsy

PURPOSE: In a prospective study, we evaluated the significance of preoperative bilateral chemical shift spectroscopy imaging (CSI) changes for the prognosis of postoperative seizure outcome in the surgical treatment of patients with temporal lobe epilepsy (TLE). METHOD: CSI using multivoxel spectroscopy was performed. Twenty-six consecutive TLE patients scheduled for epilepsy surgery were included. To evaluate the value of the CSI with respect to postoperative seizure outcome, discriminant analysis with ipsilateral and contralateral CSI was performed. RESULTS: The discriminant analysis showed that the contralateral metabolic changes alone are able to predict seizure outcome whereby 92.3% of cases were correctly classified. Upon comparison of the two groups of seizure-free and non-seizure-free patients with respect to contralateral metabolic changes, the difference proved to be highly significant (paired t test: t = -6.3, df = 24, p < 0.001). CONCLUSION: Bilateral metabolic CSI changes have a predictive value for the postoperative outcome in patients with TLE. In patients with severe bilateral metabolic changes, poor seizure outcome is a likely result.     

Developmental abnormalities of the medial temporal lobe in patients with temporal lobe epilepsy.

PURPOSETo evaluate MR temporal lobe malformations and their frequency in patients with temporal lobe epilepsy.METHODSTwo hundred twenty-two consecutive adult patients with temporal lobe epilepsy of varying severity were investigated with 1.0-T or 1.5-T MR units using three-dimensional T1-weighted acquisition protocol.RESULTSSixteen patients (7.2%) presented with malformations of the temporal lobe. Four patterns of malformations were encountered: (a) heterotopia (n = 1), lining the temporal horn of the lateral ventricle; (b) focal neocortical dysgenesis (n = 6), which consisted of cortical thickening, poor gray/white matter demarcation, abnormal gyration (n = 5), or limited schizencephaly (n = 1); (c) hippocampal malformations (n = 5), which presented as abnormal hippocampal formation associated with a cyst (n = 2), isolated malformation of the subiculum (n = 1), or bilateral hippocampal malformation (n = 2) consisting of an abnormal shape and a misplaced fimbria; (d) complex malformations of the temporal lobe, combining categories a, b, and c (n = 4). The age at onset, severity of the disease, and occurrence of generalized tonicoclonic seizures were not significantly different between patients with malformations and the entire population of patients with temporal lobe epilepsy.CONCLUSIONMR analysis of temporal lobe malformations allowed a precise determination of the extent of the malformations and the presence or absence of associated hippocampal disease, all of which are of great help in the preoperative evaluation of patients with intractable epilepsy.     

Morphological abnormalities of limbic lobe structures in partial temporal lobe epilepsy

PURPOSE: To evaluate lesions of the different structures of the Papez circuit in association with hippocampal sclerosis. MATERIAL: and methods. 13 patients (32.1+/-8.2 y.o.) suffering from partial, temporal lobe, drug-resistant epilepsy and 20 normal volunteers (31.8+/-7.7 y.o.) were evaluated by MRI on a 1.5 T scanner (Philips): axial T1w 3D Gradient Echo acquisitions, thickness: 1.5mm. Hippocampus and cingulate gyrus volume were calculated after semi-automated segmentation of intrasulcal gray matter using the "Surgiscope Scopeplan" Elekta((R)). The thickness of the posterior column of the fornix and the thickness of the mamillary bodies were also measured. RESULTS: We found 10 cases of ipsolateral hippocampal sclerosis, 6 cases of ipsolateral atrophy of the mamillary body and 4 cases of ipsolateral atrophy of the fornix. We did not find any atrophy of the cingulate gyrus. CONCLUSION: Hippocampal sclerosis can be associated with lesions of limbic lobe structures (fornix and mamillary body), excluding the cingulate gyrus.