Hippocampal T2 Relaxometry Research Articles

A Study of Hippocampal T2 Relaxometry Value in Temporal Lobe Epilepsy Patient

In the advancement of the current imaging technique for detection of mesial temporal sclerosis in temporal lobe epilepsy patient, there are multiple Magnetic resonance imaging (MRI) quantitative techniques. One of the long known to be valuable quantitative technique is T2 relaxometry where it has overall better accuracy for detection of mesial temporal sclerosis compared with the qualitative assessment only. A comparative cross-sectional study was conducted in Hospital Universiti Sains Malaysia from August 2021 to January 2023 which include 51 participants, 19 (36.5%) were temporal lobe epilepsy patient and 33 (63.5%) were control. The hippocampal T2 relaxometry was calculated for temporal lobe epilepsy patient and control. The mean T2 relaxometry reading for these groups were compared using Independent T-test. The correlation of T2 relaxometry value with age, duration of epilepsy and seizure frequency were analysed using Pearson correlation. Cohen Kappa inter-rater reliability was done for MR qualitative assessment. The participant age range was from 15 to 65 years old. Total of 23 samples were male (44.2%). The mean T2 relaxometry for epilepsy patient was higher than control. For correlation, moderate to good positive correlation was seen between the duration of epilepsy with T2 relaxometry of right hippocampus. Whereas poor positive correlation between the right hippocampus T2 relaxometry with age (P>0.01), as well poor positive correlation between both hippocampus T2 relaxometry with seizure frequency (P>0.01). There was one patient (5.2%) reported to be negative for mesial temporal sclerosis by qualitative assessment, but the T2 relaxometry reading however was raised. As a conclusion, T2 relaxometry sequence can be use as adjunct to the current qualitative assessment to increase sensitivity and specificity in detecting mesial temporal sclerosis.
 Keywords: Temporal lobe epilepsy, Mesial temporal sclerosis, T2 relaxometry, MRI epilepsy protocol

Role of T2 relaxometry in localization of mesial temporal sclerosis and the degree of hippocampal atrophy in patients with intractable temporal lobe epilepsy: A cross sectional study.

Mesial temporal lobe epilepsy is one of the most common causes of refractory epilepsy worldwide. A good percentage of patients do not have detectable hippocampal atrophy on magnetic resonance imaging (MRI). The objective of this study is to evaluate whether T2 relaxometry can identify hippocampal pathology and lateralize the epileptic focus in patients with intractable temporal lobe epilepsy (TLE). T2 relaxometry can also be used to correlate the clinical severity of the disease with the relaxometry readings in those who have hippocampal atrophy as well as those who do not. Thirty two patients having clinical and electrophysiological features of TLE were enrolled and a MRI brain with T2 relaxometry was done. Hippocampal T2 relaxometry values were calculated in the head, body, and tail of the hippocampus and average T2 relaxometry values were calculated, and a comparison was done with the controls. For patients with unilateral involvement, the contralateral side was taken as control and in cases of bilateral involvement, controls were identified from normal subjects. T2 relaxometry is found to be superior to MR visual analysis in the early detection of cases of hippocampal sclerosis where there is no atrophy on visual analysis. Nine out of 32 patients (28%) were normal on MR visual analysis; however, showed increased values on T2 relaxometry, correlating with clinical and electrophysiological diagnosis. The rest of the patients with hippocampal atrophy showed a correlation of T2 relaxometry values with the degree of atrophy. The hippocampal T2 measurement is thus more sensitive and specific. The study was clinically significant (p < .0001). There was a mild female predilection of the disease and there was no significant correlation with comorbidities. There was a strong positive correlation with patients having a history of febrile seizures in childhood. T2 relaxometry may accurately lateralize the majority of patients with persistent TLE and offers evidence of hippocampus injury in those patients who do not show evidence of atrophy on MRI and also the T2 relaxometry values correlated with the degree of atrophy. Early identification of hippocampal sclerosis is crucial for prompt management which offers better outcomes.

Combined quantitative T2 mapping and [18F]FDG PET could improve lateralization of mesial temporal lobe epilepsy

ObjectivesTo investigate whether quantitative T2 mapping is complementary to [18F]FDG PET in epileptogenic zone detection, thus improving the lateralization accuracy for drug-resistant mesial temporal lobe epilepsy (MTLE) using hybrid PET/MR.MethodsWe acquired routine structural MRI, T2-weighted FLAIR, whole brain T2 mapping, and [18F]FDG PET in 46 MTLE patients and healthy controls on a hybrid PET/MR scanner, followed with computing voxel-based z-score maps of patients in reference to healthy controls. Asymmetry indexes of the hippocampus were calculated for each imaging modality, which then enter logistic regression models as univariate or multivariate for lateralization. Stereoelectroencephalography (SEEG) recordings and clinical decisions were collected as gold standard.ResultsRoutine structural MRI and T2w-FLAIR lateralized 47.8% (22/46) of MTLE patients, and FDG PET lateralized 84.8% (39/46). T2 mapping combined with [18F]FDG PET improved the lateralization accuracy by correctly lateralizing 95.6% (44/46) of MTLE patients. The asymmetry indexes of hippocampal T2 relaxometry and PET exhibit complementary tendency in detecting individual laterality, especially for MR-negative patients. In the quantitative analysis of z-score maps, the ipsilateral hippocampus had significantly lower SUVR (LTLE, p < 0.001; RTLE, p < 0.001) and higher T2 value (LTLE, p < 0.001; RTLE, p = 0.001) compared to the contralateral hippocampus. In logistic regression models, PET/T2 combination resulted in the highest AUC of 0.943 in predicting lateralization for MR-negative patients, followed by PET (AUC = 0.857) and T2 (AUC = 0.843).ConclusionsThe combination of quantitative T2 mapping and [18F]FDG PET could improve lateralization for temporal lobe epilepsy.Key Points• Quantitative T2 mapping and18F-FDG PET are complementary in the characterization of hippocampal alterations of MR-negative temporal lobe epilepsy patients.• The combination of quantitative T2 and18F-FDG PET obtained from hybrid PET/MR could improve lateralization for temporal lobe epilepsy.

Correlations between Limbic White Matter and Cognitive Function in Temporal-Lobe Epilepsy, Preliminary Findings.

The limbic system is presumed to have a central role in cognitive performance, in particular memory. The purpose of this study was to investigate the relationship between limbic white matter microstructure and neuropsychological function in temporal-lobe epilepsy (TLE) patients using diffusion tensor imaging (DTI). Twenty-one adult TLE patients, including 7 non-lesional (nlTLE) and 14 with unilateral mesial temporal sclerosis (uTLE), were studied with both DTI and hippocampal T2 relaxometry. Correlations were performed between fractional anisotropy (FA) of the bilateral fornix and cingulum, hippocampal T2, neuropsychological tests. Positive correlations were observed in the whole group for the left fornix and processing speed index. In contrast, memory tests did not show significant correlations with DTI findings. Subgroup analysis demonstrated an association between the left fornix and processing speed in nlTLE but not uTLE. No correlations were observed between hippocampal T2 and test scores in either the TLE group as a whole or after subgroup analysis. Our findings suggest that integrity of the left fornix specifically is an important anatomical correlate of cognitive function in TLE patients, in particular patients with nlTLE.

Is streamlined evaluation of children for epilepsy surgery possible?

The presurgical evaluation of children with intractable epilepsy includes evaluation by an experienced clinician, MRI, video EEG, and functional imaging techniques to localize seizure onset. However, the contributions of each investigation to surgical decision making has not been systematically assessed. Data used for decision on eligibility for surgery on 353 children was discussed at a presurgical multidisciplinary meeting and systematically recorded. The relationships between MRI, EEG, SPECT findings, and the probability of being offered epilepsy surgery were investigated retrospectively using a quick unbiased statistical tree (QUEST). Sixteen children were offered nonresective surgery. Of the remaining, 236 (70%) were offered resective surgery. The proportion of children with a localized lesion on MRI offered resective surgery was 92%[95% CI: 88 to 95%], and EEG telemetry did not modify decision making in this group (p < 0.001). In children with bilateral MRI changes or normal scan the probability of being offered resective surgery was 78% in those with localized ictal onset on EEG compared to 9% with nonlocalized EEG (p < 0.001). SPECT did not appear to systematically influence decision making in any group. Children with medically intractable epilepsy and localized lesions on MRI may not necessarily need ictal EEG recordings or SPECT prior to offering resective surgery. More targeted use of EEG telemetry could allow more children with less obvious surgical targets to be investigated without increasing resources.

T2‐Weighted and T2 Relaxometry Images in Patients with Medial Temporal Lobe Epilepsy

Quantification of increased T2-weighted MRI signal that is associated with hippocampal sclerosis (HS) can be performed through (1) mean of hippocampal signal in single-echo T2 MRI and (2) hippocampal T2 relaxometry. It is not clear whether these two techniques are equivalent. In this study, we compare the hippocampal signal, detected by single-echo T2 quantification and by T2 relaxometry, in patients with medial temporal lobe epilepsy (MTLE). We studied magnetic resonance images from 50 MTLE patients and 15 healthy subjects. We compared the quantification of a T2 signal from single echo images to T2 relaxometry, both obtained from a manually traced region of interest (ROI) in coronal slices involving the whole hippocampus. Repeated measures ANOVA was used to evaluate the differences in the distribution of the Z-scores from single-echo T2 quantification and T2 relaxometry within subjects. We observed a significant difference between the measurements obtained from single-echo T2 quantification and T2 relaxometry (P < .001). Measurements from head, body, and tail of the hippocampus were different (P=.04), with a significant interaction between anatomic location and type of measurement used (P= .008). Post hoc paired comparisons revealed that T2 relaxometry yielded greater Z-scores for the body (P= .002) and tail (P < .0001). For each subject with MTLE, T2 relaxometry was able to detect a higher signal in the body and tail of the hippocampus compared to single-echo T2. This is a possible indicator that T2 relaxometry is more sensitive in detecting T2 abnormalities within the body and tail of the hippocampus in patients with MTLE.

Abnormalities in hippocampi remote from the seizure focus: a T2 relaxometry study.

The aim of this study was to determine whether partial epilepsy is associated with abnormalities in hippocampi that are not the primary seizure focus. As hippocampal T2 relaxometry is useful for identifying abnormalities that are not obvious on visual assessment of MRI, this was the method employed. Of 457 consecutive children and young adults from whom T2 relaxometry data were obtained, 96 had well characterized partial epilepsy and were enrolled, along with 27 control subjects. The patients were divided on the basis of clinical, video-EEG and visual MRI assessment into three groups: (i) those with temporal lobe epilepsy (TLE) and mesial temporal sclerosis (MTS) (MTS-TLE); (ii) lesional TLE (l-TLE); or (iii) extratemporal epilepsy (ETE). There was a significant and similar prolongation of T2 relaxation time identified in hippocampi remote from the seizure focus in all patient groups when compared with control subjects. In the non-sclerotic hippocampus of patients with MTS, T2 relaxation time was prolonged by a mean of 3.3 ms [95% confidence interval (CI), 0.8-5.9 ms; P = 0.01], patients with l-TLE had prolongation of T2 relaxation time by a mean of 4.3 ms (95% CI, 1.8-7.1 ms; P = 0.001) and those with ETE had prolongation of T2 relaxation time by a mean of 3.7 ms (95% CI, 1.6-6.6 ms; P = 0.006) compared with control subjects after adjustment for age. Unsurprisingly, in patients with MTS-TLE, T2 relaxation time in the sclerotic hippocampus was prolonged by a mean of 19 ms (95% CI = 14.6-22.4 ms; P < 0.001). The similarity in the extent of prolongation of T2 relaxation time in hippocampi that are not the primary epileptogenic focus, the wide variety of structural associations and the varied sites of epileptogenic foci, considered together, suggest that the abnormalities are likely to be caused by ongoing seizure activity rather than by underlying aetiology or site of epileptogenic focus.

Chronic Epilepsy Does Not Cause Measurable Structural Changes on MRI

The Structural Consequences of Newly Diagnosed SeizuresLiu RSN, Lemieux L, Bell GS, Sisodiya SM, Bartlett PA, Shorvon SD, Sander JWAS, Duncan JSAnn Neurol 2002;52:573–580Intractable epilepsy may be associated with widespread structural cerebral damage. We determined whether structural damage occurs to the hippocampus, cerebellum, and neocortex in the first few years after a diagnosis of seizures. Sixty-eight patients older than 14 years with newly diagnosed seizures and 90 matched controls underwent serial magnetic resonance imaging (MRI) brain scans 3.5 years apart. Using quantitative analysis of serial scans, we determined changes in hippocampal volume, hippocampal T2 relaxometry, and total and regional brain volumes. Thirty-four (50%) patients had recurrent unprovoked seizures between baseline and follow-up scans. One patient with preexisting hippocampal sclerosis (HS) did not develop progressive hippocampal damage. Group analyses found no difference in change in cerebral measures between patients and ...

Chronic Epilepsy Does Not Cause Measurable Structural Changes on MRI.

The Structural Consequences of Newly Diagnosed Seizures Liu RSN, Lemieux L, Bell GS, Sisodiya SM, Bartlett PA, Shorvon SD, Sander JWAS, Duncan JS Ann Neurol 2002;52:573–580 Intractable epilepsy may be associated with widespread structural cerebral damage. We determined whether structural damage occurs to the hippocampus, cerebellum, and neocortex in the first few years after a diagnosis of seizures. Sixty-eight patients older than 14 years with newly diagnosed seizures and 90 matched controls underwent serial magnetic resonance imaging (MRI) brain scans 3.5 years apart. Using quantitative analysis of serial scans, we determined changes in hippocampal volume, hippocampal T2 relaxometry, and total and regional brain volumes. Thirty-four (50%) patients had recurrent unprovoked seizures between baseline and follow-up scans. One patient with preexisting hippocampal sclerosis (HS) did not develop progressive hippocampal damage. Group analyses found no difference in change in cerebral measures between patients and controls or between patients with and without recurrent seizures. Significant quantitative changes in individuals were largely attributable to preexisting cerebral lesions or alcohol abuse. Subtle changes detected in individuals over a 3.5-year period but were not related to a history of overt seizures. Our results show patients with newly diagnosed seizures are not generally at increased risk of seizure-induced structural cerebral damage as detected with MRI. Cerebral damage may occur before the onset of seizures or develop insidiously over a more prolonged period

The structural consequences of newly diagnosed seizures.

Intractable epilepsy may be associated with widespread structural cerebral damage. We determined whether structural damage occurs to the hippocampus, cerebellum and neocortex in the first few years following a diagnosis of seizures. Sixty-eight patients over the age of 14 years with newly diagnosed seizures and 90 matched controls underwent serial magnetic resonance imaging (MRI) brain scans 3.5 years apart. Using quantitative analysis of serial scans, we determined changes in hippocampal volume, hippocampal T2 relaxometry and total and regional brain volumes. Thirty-four (50%) patients had recurrent unprovoked seizures between baseline and follow-up scans. One patient with pre-existing hippocampal sclerosis (HS) did not develop progressive hippocampal damage. Group analyses found no difference in change in cerebral measures between patients and controls or between patients with and without recurrent seizures. Significant quantitative changes in individuals were largely attributable to pre-existing cerebral lesions or alcohol abuse. Subtle changes detected in individuals over 3.5 years but were not related to a history of overt seizures. Our results show patients with newly diagnosed seizures are not generally at increased risk of seizure-induced structural cerebral damage as detected with MRI. Cerebral damage may occur before the onset of seizures or develop insidiously over a more prolonged period.

Prolonged Febrile Convulsions Produce More Severe Mesial Temporal Sclerosis

Quantitative Magnetic Resonance Characterization of Mesial Temporal Sclerosis in ChildhoodScott RC, Gadian DG, Cross JH, Wood SJ, Neville BG, Connelly ANeurology 2001;56:1659–1665ObjectiveTo investigate whether quantitative magnetic resonance (MR) techniques can be used to distinguish between mesial temporal sclerosis in patients with a history of prolonged febrile convulsion and in patients without such a history.MethodsQuantitative hippocampal T2 relaxometry, hippocampal volumetry, and single-voxel 1H-magnetic resonance spectroscopy (MRS) data were acquired from 16 children who subsequently underwent temporal lobe resections for intractable temporal lobe epilepsy and histologically were shown to have sclerosis of the horn of Ammon. Eight children had a history of prolonged febrile convulsion in early childhood, and eight children had other or no associations.ResultsPatients with a history of prolonged febrile convulsion had smaller hippocampi (p = 0.02) and prolonged T2 relaxation time (p = 0.03) ipsila...

Prolonged Febrile Convulsions Produce More Severe Mesial Temporal Sclerosis.

Quantitative Magnetic Resonance Characterization of Mesial Temporal Sclerosis in Childhood Scott RC, Gadian DG, Cross JH, Wood SJ, Neville BG, Connelly A Neurology 2001;56:1659–1665 Objective To investigate whether quantitative magnetic resonance (MR) techniques can be used to distinguish between mesial temporal sclerosis in patients with a history of prolonged febrile convulsion and in patients without such a history. Methods Quantitative hippocampal T2 relaxometry, hippocampal volumetry, and single-voxel 1H-magnetic resonance spectroscopy (MRS) data were acquired from 16 children who subsequently underwent temporal lobe resections for intractable temporal lobe epilepsy and histologically were shown to have sclerosis of the horn of Ammon. Eight children had a history of prolonged febrile convulsion in early childhood, and eight children had other or no associations. Results Patients with a history of prolonged febrile convulsion had smaller hippocampi (p = 0.02) and prolonged T2 relaxation time (p = 0.03) ipsilateral to the seizure focus when compared with patients without such a history. There was also more side-to-side asymmetry of T2 relaxation time (p = 0.004) and hippocampal volume (p = 0.02) in the patients with a history of prolonged febrile convulsion than in those with other or no associations. No differences between the groups were identified by using 1H-MRS Conclusions These data support the view that there are at least two types of mesial temporal sclerosis. There may be several pathogenetic pathways from initial insult to later mesial temporal sclerosis, and these pathways are, at least in part, dependent on the initial insult.

Quantitative magnetic resonance characterization of mesial temporal sclerosis in childhood.

To investigate whether quantitative MR techniques can be used to distinguish between mesial temporal sclerosis in patients with a history of prolonged febrile convulsion and in patients without such a history. Quantitative hippocampal T2 relaxometry, hippocampal volumetry, and single voxel (1)H-MRS data were acquired from 16 children who subsequently underwent temporal lobe resections for intractable temporal lobe epilepsy and histologically were shown to have sclerosis of the horn of Ammon. Eight children had a history of prolonged febrile convulsion in early childhood and eight children had other or no associations. Patients with a history of prolonged febrile convulsion had smaller hippocampi (p = 0.02) and prolonged T2 relaxation time (p = 0.03) ipsilateral to the seizure focus when compared with patients without such a history. There was also more side-to-side asymmetry of T2 relaxation time (p = 0.004) and hippocampal volume (p = 0.02) in the patients with a history of prolonged febrile convulsion than in those with other or no associations. No differences between the groups were identified using (1)H-MRS. These data support the view that there are at least two types of mesial temporal sclerosis. There may be several pathogenetic pathways from initial insult to later mesial temporal sclerosis, and these pathways are, at least in part, dependent on the initial insult.

A fast FLAIR dual-echo technique for hippocampal T2 relaxometry: first experiences in patients with temporal lobe epilepsy.

To evaluate the use of cerebrospinal fluid (CSF) signal nulling in MR T2 measurements of the hippocampus in normal control subjects and patients with temporal lobe epilepsy (TLE), dual-echo acquisitions covering the whole brain were used. T2 relaxation times were estimated in 12 standard Eurospin II MR test objects and in the hippocampi of 10 control subjects, using T2 maps constructed from conventional spin-echo (CSE), fast spin-echo (FSE), and fast FLAIR (FF) dual-echo sequences on a 1.5-T MR scanner. Hippocampal T2 values (HCT2) were measured on contiguous coronal 5-mm slices throughout the antero-posterior extent of each hippocampus in the 10 controls and 12 TLE patients, using both CSE and FF. Scan-rescan reproducibility in Eurospin II standard MR test objects was high for all sequences. There was a good correlation between T2 values from CSE, FF, and FSE sequences in test objects and in control hippocampi. In controls, the coefficient of variation of mean HCT2 values differed between slice positions, but was lowest for FF, followed by CSE data. The intrarater coefficient of reliability between repeated measurements in control subjects was lowest for FF HCT2, at 2.3%. The interrater coefficient of reliability for CSE HCT2 measurements in controls (4.8%) was slightly lower than the interrater coefficient for FF HCT2 (5.4%). HCT2 measurement with both CSE and FF identified abnormal values in the same 10 hippocampi of 12 patients. Hippocampal dual-echo T2 relaxometry using CSF nulling is reliable in control subjects, and identifies the abnormal hippocampi in patients with TLE. The increases in hippocampal T2 signal demonstrated using FF HCT2 measurements are unlikely to be partial volume effects from CSF.

Occurrence of hippocampal sclerosis: is one hemisphere or gender more vulnerable?

We analyzed a large group of patients investigated for suspected seizures to test whether gender or side are important factors in the origins of hippocampal sclerosis (HS). We studied 996 consecutive patients (48% men, 52% women) by using standard hippocampal T2-relaxometry methods. HS was associated with a highly abnormal T2 time (< or =113 ms). Categoric analysis showed that hippocampal T2 time was independent of gender and side. T2 time was bilaterally normal in 81% of men and in 79% of women; it was unilaterally abnormal in 15% of both men and women; and bilaterally abnormal in 4% of men and in 6% of women. Highly abnormal T2 relaxometry, suggesting HS, occurred with equal frequency in men and women and on the right and left sides. Quantitative analysis of hippocampal T2 times showed values not differing significantly between men and women or between the right and left hemispheres. There was no significant interaction between gender and side. In patients with seizure disorders, hippocampal T2 relaxometry is not different in adult men and women and in the right and left hemispheres.

The relation between quantitative MRI measures of hippocampal structure and the intracarotid amobarbital test.

The increasing sophistication of quantitative magnetic resonance imaging (MRI) techniques has generated hopes that they may eventually supersede the intracarotid amobarbital procedure (IAP) in the presurgical screening for bilateral abnormalities in prospective candidates for temporal lobe epilepsy surgery. As the first step toward this aim, the purpose of this study was to examine the relationship between these measures of structural and functional integrity. We examined the relation between memory performance and pass/fail rates on the IAP and two MRI measures of hippocampal integrity: hippocampal volumes, adjusted for intracranial volume (HCvol) and hippocampal T2 relaxometry (HCT2), in 48 patients with medically intractable temporal lobe epilepsy, who underwent the IAP as part of their presurgical evaluation for temporal lobectomy. The unilateral memory scores from the IAP were not significantly correlated with the corresponding HCvol or HCT2 measures in the right- and left-temporal-lobe groups. However, the MRI measures of hippocampal asymmetry (right minus left HCvol, right minus left HCT2) were significantly correlated with our measure of functional asymmetry, the right minus left hemisphere memory score from the IAP, supporting the role of the IAP in lateralising temporal lobe dysfunction. Forty-six patients with unilateral hippocampal sclerosis and concordant EEG studies passed the IAP. Two patients failed the memory component of the IAP. In both cases, other presurgical investigations suggested bilateral abnormalities. We conclude that patients with unilateral hippocampal sclerosis, established by a rigorous quantitative MRI protocol, and concordant ictal and interictal EEG findings may not be at risk for postoperative amnesia, despite baseline neuropsychological deficits suggestive of bilateral disturbance.

Multimodality MRI in mesial temporal sclerosis: relative sensitivity and specificity.

Our objectives were to determine the relative sensitivity and specificity of different MRI sequences and analysis techniques for the detection of mesial temporal sclerosis (MTS). Mesial temporal sclerosis is the most common pathologic finding in patients undergoing temporal lobe epilepsy surgery. Magnetic resonance imaging is the most reliable preoperative imaging technique for the detection of MTS. We analyzed the abnormalities in preoperative MRIs of 44 consecutive patients who had undergone temporal lobectomy and who had pathologic confirmation of MTS. Techniques included inversion recovery (IR); T1-weighted, volume-acquired images; hippocampal T2 relaxometry (HT2); volumetric assessment; and visual analysis. Sensitivity was 86% with IR, 90% with T1-weighted qualitative visual analysis, and 97% with quantitative volumetry. Pathologic prolongation of HT2 (> 2 SD of normal) was present in 79%. Analysis of variance showed statistically significant differences in sensitivity between HT2, volumetric measurements (p < 0.01), and qualitative visual atrophy (p < 0.05). Concordance between all MRI modalities was 68%. Inversion recovery and qualitative analysis lateralized the side of surgery in 93%. The combination of IR and T1-weighted images correctly identify MTS in most patients. Hippocampal volumetry provided localization in an additional small number of patients.