Biomedical subjects

Graeme D Jackson

Publications and source records attributed to Graeme D Jackson.

At least 19 recordsLinked to original sources

PubMed2005

How reliable are fMRI-EEG studies of epilepsy? A nonparametric approach to analysis validation and optimization.

Simultaneously acquired functional magnetic resonance imaging (fMRI) and electroencephalography (EEG) data hold great promise for localizing the spatial source of epileptiform events detected in the EEG trace. Despite a number of studies applying this method, there has been no independent and systematic validation of the approach. The present study uses a nonparametric method to show that interictal discharges lead to a blood oxygen level dependent (BOLD) response that is significantly different to that obtained by examining random 'events'. We also use this approach to examine the optimization of analysis strategy for detecting these BOLD responses. Two patients with frequent epileptiform events and a healthy control were studied. The fMRI data for each patient were analyzed using a model derived from the timings of the epileptiform events detected on EEG during fMRI scanning. Twenty sets of random pseudoevents were used to generate a null distribution representing the level of chance correlation between the EEG events and fMRI data. The same pseudoevents were applied to control data. We demonstrate that it is possible to detect blood oxygen level-dependent (BOLD) changes related to interictal discharges with specific and independent knowledge about the reliability of this activation. Biologically generated events complicate the fMRI-EEG experiment. Our proposed validation examines whether identified events have an associated BOLD response beyond chance and allows optimization of analysis strategies. This is an important step beyond standard analysis. It informs clinical interpretation because it permits assessment of the reliability of the connection between interictal EEG events and the BOLD response to those events.

Analysis of Variance↗

PubMed2005

Effect of prior cognitive state on resting state networks measured with functional connectivity.

To address the extent to which functional connectivity measures an absolute brain state, we observed the effect of prior performance of a language task on resting-state networks in regions associated with language. Six subjects were imaged during rest before and after a block-design language task. Connectivity maps were generated for each of four language regions (identified from analysis of the language activation portion of the study) in each subject for both rest periods. Conjunction analysis demonstrated distinct networks of voxels for each seed region, indicating separate functional subnetworks associated with the different regions. In a comparison of rest before and after the activation task widespread and significant changes were observed in all individuals, suggesting that the measured resting state network reflects a dynamic image of the current brain state. At the group level, an extended network was observed that was largely persistent over time. Even at the group level an increase in connectivity was observed between left and right middle frontal gyri, and between posterior cingulate cortex and medial frontal cortex in the rest after the language task. These results suggest that functional connectivity may be a powerful measure of cognitive state, sensitive to differences between controls and patients together with the particular cognitive processing occurring during the rest state.

Brain Mapping↗

PubMed2004

A high-field functional MRI study of quadri-lingual subjects.

We assessed six multilingual subjects by functional MRI using a Noun Verb Generation task in four different languages. We hypothesised that the degree of proficiency in each language would be related to the extent of functional activity measured in a region of interest analysis. Proficiency in each language was quantified using two neuropsychological tests. All four languages activated overlapping brain areas, corresponding to the major language regions. The number of activated voxels correlated with proficiency, so that the activated volume increased for languages in which a subject had poorer proficiency. Activation did not appear to be dependent on the age at which the language was learnt.

Adult↗

PubMed2004

Stable ratio of ipsilateral to contralateral sensory motor cortex activity despite varying effort and peripheral nerve block.

BACKGROUND: Ipsilateral sensory motor cortex (SMC) activation can occur during hand movements following cerebral injury. We studied the effect of increasing task difficulty and temporary peripheral paralysis on patterns of motor system activation. METHODS: Six healthy subjects completed a functional MRI paradigm of right finger abduction with four stages; light resistance, strong resistance, imagined movement and attempted abduction after ulnar nerve blockade. Activation maps compared images acquired during rest and task, while region of interest analysis measured numbers of activated pixels. RESULTS: All subjects showed some ipsilateral SMC activation. Across all subjects and all tasks involving hand movement, contralateral activation was proportional to ipsilateral activation (2.1:1; r=0.86). CONCLUSIONS: The relationship between ipsilateral and contralateral SMC activation remained stable despite differing effort or hand paralysis. The contralateral and ipsilateral SMC appear to act in a coordinated fashion during unilateral hand movements.

Adult↗

PubMed2004

Voxel-based relaxometry: a new approach for analysis of T2 relaxometry changes in epilepsy.

The measurement of the T2 relaxation time (T2 relaxometry) had been established as a reliable tool for the assessment of certain conditions such as temporal lobe epilepsy. The standard procedure for analysis of T2 data uses manually drawn regions of interest (ROIs). This approach is limited by its subjective nature and its restricted scope of investigation within selected regions of the brain. In this study, we introduce a voxel-based analysis approach termed voxel-based relaxometry (VBR). Tissue signal changes were assessed in 19 patients with hippocampal sclerosis (HS) and in 38 healthy controls using (i) conventional ROI-based analysis with several bilateral ROIs and also (ii) the VBR method in which the T2 maps are warped to a stereotactic space, smoothed and statistically compared. Conventional ROI analysis identified the expected T2 increase in the sclerotic hippocampus in all HS patients. Furthermore, 13 of the 19 patients displayed a T2 increase in at least one of the other ROIs. The VBR analysis showed a similar pattern of statistically significant areas of increased T2 within the sclerotic hippocampus. In addition, extrahippocampal areas of increased T2 were apparent including the anterior temporal lobe white matter and the parahippocampal gyrus. The results of the VBR analysis are in agreement with the conventional ROI analysis. The VBR analysis has the advantage of providing an even-handed assessment of T2 differences through the brain. We recommend VBR as an alternative means of relaxometry data analysis that provides an objective assessment of differences between subjects.

Adult↗

PubMed2004

Subtle microscopic abnormalities in hippocampal sclerosis do not predict clinical features of temporal lobe epilepsy.

PURPOSE: Subtle microdysplastic features are found in some patients with hippocampal sclerosis (HS) and refractory temporal lobe epilepsy. The significance of these findings is unknown. We investigated their frequency, relation to the pattern of HS, and clinical associations. METHODS: One-hundred forty patients with histologically confirmed HS (mean age at operation, 35 years; 85 women) were analyzed. The presence of HS and subtle structural abnormalities (SSAs) in the mesial temporal lobe and in the lateral neocortical tissue was assessed in detail. Antecedents, seizure characteristics, two verbal memory tests, and outcome in HS patients with and without SSAs were determined. RESULTS: SSAs were found in 60 (43%) of the 140 HS patients, being mesial only in 32 of the 60 cases, and lateral only in nine cases; the remaining 19 cases had both mesial and lateral abnormalities. The frequency of SSA was not related to the pattern of HS or other tested variables. Prolonged febrile convulsions were present in 26 (44%) patients with SSAs, and in 26 (34%) patients (not significant) without SSAs. The outcome after surgery did not differ between patients with SSAs (incidence rate ratio for seizure recurrence, 0.9; 95% confidence interval, 0.5-1.6) compared with patients without SSAs (reference ratio, 1). CONCLUSIONS: Forty-three percent of HS patients have SSAs in their lobectomy specimens. The presence of SSAs does not predict clinical characteristics, such as presence of prolonged febrile convulsions, postsurgical outcome, or neuropsychological performance, nor does it correlate with the histologic pattern of HS.

Adult↗

PubMed2004

Increased anterior temporal lobe T2 times in cases of hippocampal sclerosis: a multi-echo T2 relaxometry study at 3 T.

BACKGROUND AND PURPOSE: Increased T2 relaxation times in the ipsilateral hippocampus are present in patients with hippocampal sclerosis. Visual assessment of T2-weighted images of these patients suggests increased signal intensity in the anterior temporal lobe as well. Our aim was to assess hippocampal and anterior temporal T2 relaxation times in patients with partial epilepsy by using a new T2-relaxometry sequence implemented by using a 3-T General Electric imaging unit. METHODS: Coronal view T2 maps were generated by using an eight-echo Carr-Purcell-Meiboom-Gill sequence (TE, 28-231) with an acquisition time of 7 min on a 3-T General Electric Signa Horizon LX imaging unit. T2 relaxation times were measured in the hippocampus and anterior temporal lobe of 30 healthy control volunteers and 20 patients with partial epilepsy. RESULTS: For the 30 control volunteers, the mean hippocampal T2 relaxation time was 98 +/- 2.8 ms. In all measured areas, the asymmetry index was small (<0.01). For the 15 patients with independent evidence of hippocampal sclerosis established by visual, volumetric, and, when available, pathologic criteria, mean hippocampal T2 relaxation times were 118 +/- 7 ms (P <.0001) on the ipsilateral side and 101 +/- 4 ms (P =.005) on the contralateral side. The T2 values were also increased in the anterior temporal lobe (ipsilateral: 82 +/- 6 ms, P <.0001; contralateral: 79 +/- 6 ms, P =.01) as compared with the values for the control volunteers (75 +/- 3 ms). The five patients with focal cortical dysplasia had hippocampal T2 relaxation times that were not different from control values. CONCLUSION: T2 relaxometry at 3 T is feasible and useful and confirmed marked ipsilateral hippocampal signal intensity increase in patients with hippocampal sclerosis. Importantly, definite signal intensity change was also present in the anterior temporal lobe. T2 relaxometry is a sensitive means of identifying abnormalities in the hippocampus and other brain structures.

Adult↗

PubMed2004

MR imaging and spectroscopic study of epileptogenic hypothalamic hamartomas: analysis of 72 cases.

BACKGROUND AND PURPOSE: Reports of MR imaging in hypothalamic hamartomas associated with epilepsy are few, and the number of patients studied is small. We aimed to detail the relationship of hypothalamic hamartomas to surrounding structures, to determine the frequency and nature of associated abnormalities, and to gain insight into mechanisms of epileptogenesis. METHODS: We systematically examined MR imaging studies of 72 patients with hypothalamic hamartoma and refractory epilepsy (patient age, 22 months to 31 years). A dedicated imaging protocol was used in 38 cases. Proton MR spectroscopy of the hypothalamic hamartoma was performed for 19 patients and compared with the metabolite profile of the thalamus in 10 normal children and the frontal lobe in 10 normal adults. RESULTS: Compared with normal gray matter, hypothalamic hamartomas were hyperintense on T2-weighted images (93%), hypointense on T1-weighted images (74%), and had reduced N-acetylaspartate and increased myoinositol content shown by MR spectroscopy. Hypothalamic hamartomas always involved the mammillary region of the hypothalamus, with attachment to one or both mammillary bodies. Intrahypothalamic extension (noted in 97%) tended to displace the postcommissural fornix and hypothalamic gray matter anterolaterally, such that the hypothalamic hamartomas nestled between the fornix, the mammillary body, and the mammillothalamic tract. Larger hamartoma size was associated with central precocious puberty. Associated findings of questionable epileptic significance included anterior temporal white matter signal intensity abnormalities (16%) and arachnoid cysts (6%). Malformations of cortical development were observed in only two patients, and hippocampal sclerosis was not observed. CONCLUSIONS: Hypothalamic hamartomas can be readily distinguished from normal hypothalamic gray and adjacent myelinated fiber tracts, best appreciated on thin T2-weighted images. MR imaging and spectroscopy suggest reduced neuronal density and relative gliosis compared with normal gray matter. Associated epileptogenic lesions are rare, supporting the view that the hypothalamic hamartoma alone is responsible for the typical clinical features of the syndrome. The intimate relationship to the mammillary body, fornix, and mammillothalamic tract suggests a role for these structures in epileptogenesis associated with hypothalamic hamartomas.

Adolescent↗

PubMed2004

Temporal lobe dysembryoplastic neuroepithelial tumour: significance of discordant interictal spikes.

PURPOSE: Dysembryoplastic neuroepithelial tumours (DNET) are an important cause of refractory partial epilepsies. They usually occur within dysplastic cortex and tend to affect the temporal lobes. The EEG of these patients is characterised by slowing and/or epileptiform abnormalities with a multifocal distribution. We studied the EEG features of epilepsy patients with a temporal lobe DNET to assess the relationship of EEG abnormalities with the localisation of the tumour and the clinical features. METHODS: We retrospectively reviewed 16 patients with unilateral, temporal lobe DNET on MRI. The EEG abnormalities were classified as concordant to the lesion when the EEG discharges were confined to the ipsilateral temporal lobe or discordant when EEG discharges were found in other areas. Clinical and epilepsy characteristics were compared between patients with concordant and discordant EEG. RESULTS: Focal EEG abnormalities were found in 81% of the patients; 6/16 patients had concordant EEG abnormalities, and 7/16 patients had discordant EEG abnormalities. Epilepsy severity prior to the operation, antecedents and post-operative outcome were not different between patients with concordant or discordant EEG abnormalities. CONCLUSION: Patients with temporal lobe DNET often show EEG discharges discordant to the tumour. However, they do not appear to predict the clinical and epilepsy characteristics of these patients.

Adult↗

PubMed2003

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.

Adolescent↗

PubMed2003

fMRI "deactivation" of the posterior cingulate during generalized spike and wave.

Using spike-triggered fMRI, we sought to document regional changes in blood oxygen level-dependent (BOLD) activity associated with spontaneous generalised spike and slow-wave discharges (S&W). Five adult patients were studied who had idiopathic generalised epilepsy (IGE) and frequent S&W. EEG was recorded inside a 3T MRI, allowing acquisition of single, whole-brain fMRI images following S&W, as well as baseline images. Between 4 and 25 spike and wave complexes were captured in individuals. Four of the five individuals showed significant S&W-related BOLD signal reductions ("deactivation") in the posterior cingulate (P<0.001 uncorrected). Significant changes were absent only in the individual with fewest spikes. Group analysis including all five subjects confirmed fMRI deactivation in the posterior cingulate. Some S&W-related BOLD signal increases were seen in the depths of the precentral sulci in individuals and on group analysis. No significant S&W-related changes in thalamic BOLD activity were observed. The posterior cingulate may have a role in the electroclinical phenomenon of S&W and "absence." Possibilities include a causative role, with reduced activity in the cingulate facilitating the onset of S&W, a secondary role, explaining the cognitive changes observed during prolonged S&W, or an epiphenomenon.

Adolescent↗

PubMed2003

Benign epilepsy with centro-temporal spikes: spike triggered fMRI shows somato-sensory cortex activity.

OBJECTIVE: We performed spike triggered functional MRI (fMRI) in a 12 year old girl with Benign Epilepsy with Centro-temporal Spikes (BECTS) and left-sided spikes. Our aim was to demonstrate the cerebral origin of her interictal spikes. METHODS: EEG was recorded within the 3 Tesla MRI. Whole brain fMRI images were acquired, beginning 2-3 seconds after spikes. Baseline fMRI images were acquired when there were no spikes for 20 seconds. Image sets were compared with the Student's t-test. RESULTS: Ten spike and 20 baseline brain volumes were analysed. Focal activiation was seen in the inferior left sensorimotor cortex near the face area. The anterior cingulate was more active during baseline than spikes. CONCLUSIONS: Left sided epileptiform activity in this patient with BECTS is associated with fMRI activation in the left face region of the somatosensory cortex, which would be consistent with the facial sensorimotor involvement in BECT seizures. The presence of BOLD signal change in other regions raises the possibility that the scalp recorded field of this patient with BECTs may reflect electrical change in more than one brain region.

Adolescent↗

PubMed2003

Myoinositol abnormalities in temporal lobe epilepsy.

PURPOSE: This study used magnetic resonance spectroscopy (MRS) to examine metabolite abnormalities in the temporal and frontal lobe of patients with temporal lobe epilepsy (TLE) of differing severity. METHODS: We investigated myoinositol in TLE by using short-echo MRS in 34 TLE patients [26 late onset (LO-TLE), eight hippocampal sclerosis (HS-TLE)], and 16 controls. Single-voxel short-echo (35 ms) MR spectra of temporal and frontal lobes were acquired at 1.5 T and analyzed by using LCModel. RESULTS: The temporal lobe ipsilateral to seizure origin in HS-TLE, but not LO-TLE, had reduced N-acetylaspartate (NA) and elevated myoinositol (MI; HS-TLE NA, 7.8 +/- 1.9 mM, control NA, 9.2 +/- 1.3 mM; p < 0.05; HS-TLE MI, 6.1 +/- 1.6 mM, control mI 4.9 +/- 0.8 mM, p< 0.05). Frontal lobe MI was low in both patient groups (LO-TLE, 4.3 +/- 0.8 mM; p < 0.05; HS-TLE, 3.6 +/-.05 mM; p < 0.001; controls, 4.8 +/- 0.5 mM). Ipsilateral frontal lobes had lower MI (3.8 +/- 0.7 mM; p < 0.01) than contralateral frontal lobes (4.3 +/- 0.8 mM; p < 0.05). CONCLUSIONS: MI changes may distinguish between the seizure focus, where MI is increased, and areas of seizure spread where MI is decreased.

Adult↗

PubMed2003

Correlation between language organization and diffusion tensor abnormalities in refractory partial epilepsy.

PURPOSE: Atypical language organization is more frequently found in patients with refractory partial epilepsy than in healthy controls; however, the reasons for this are not well known. Here we assess the relation between language laterality index (LI) and white-matter tract changes. METHODS: Nine patients with refractory partial epilepsy were assessed with a 3-T GE scanner. Functional magnetic resonance imaging (fMRI) of language and diffusion tensor imaging (DTI) were acquired. For the fMRI, a noun-verb generation task was performed, all images were motion corrected, and activated pixels in classic language areas were counted. The DTI images were acquired in six standard directions with an initial non-diffusion-weighted scan. The "average anisotropy" was determined in a region of interest in the frontal lobe, temporal lobe, and parietal lobe white matter. An asymmetry index (AI) was calculated for language and DTI. Atypical language lateralization was diagnosed if the lateralization index (LI)-language was smaller than 0.4. RESULTS: Two of the nine patients had atypical language localization (LI-language, -0.6, and 0.3); both had left temporal DTI asymmetry (LI-DTI, -0.3 and -0.2). The remaining seven patients had typical language localization, and no marked DTI abnormalities. Asymmetry in temporal lobe DTI correlated with LI-language (r= 0.8; p = 0.006). CONCLUSIONS: Atypical language lateralization in patients with partial epilepsy may be associated with white-matter tract abnormalities.

Adolescent↗

PubMed2003

MR imaging of epilepsy: state of the art at 1.5 T and potential of 3 T.

Shortly after being introduced in the nineteen eighties, magnetic resonance imaging (MRI) became a key tool for the investigation of patients with epilepsy, due to its ability to acquire high quality images. The strength of the magnetic field of a scanner is measured in tesla (T). This review addresses the clinical and research potential in epilepsy of MR imaging at 1.5 T and 3 T. A typical clinical scanning protocol at 1.5 T for a patient with refractory epilepsy may include T1- and T2-weighted imaging, fluid-attenuated inversion recovery (FLAIR) imaging, and a 3D volume acquisition sequence. A research protocol may add quantification of structural imaging, such as volumetric assessment and T2-relaxometry, together with functional measures, such as MR-spectroscopy, functional MRI and diffusion weighted sequences. MR-spectroscopy assesses the metabolites of the seizure focus and other brain areas. Functional MRI allows localisation of cognitive and sensori-motor function and the ability to assess the spatial relationship of these functions to the seizure focus. Whereas these techniques can be performed at 1.5 T, particularly MR-spectroscopy and functional MRI benefit from increased magnetic field-strength. Higher magnetic field-strength is associated with a higher signal-to-noise ratio (SNR). The increased SNR can allow shorter imaging times for a given resolution, higher resolution for a given imaging time, or combination of both. The use of higher magnetic field-strengths is therefore indicated for the (fast) imaging of ill subjects, for long protocols, including structural, metabolic and functional imaging, and for novel applications, such as continuous EEG recording and functional MRI for the detection of the seizure focus. Disadvantages of MR imaging in epilepsy at a high field-strength of 3 T and above are, apart from engineering and technical challenges, the greater energy deposition into tissue and increased susceptibility to artefacts. So far, magnets of 3 T and above have been used mainly for research applications, however the benefits of high field-strength for MR spectroscopy and functional MRI, and the usefulness of these techniques for the investigation of epilepsy patients are obvious incentives for the use of 3 T systems in routine clinical investigations.

Electroencephalography↗

PubMed2003

Anterior temporal changes on MR images of children with hippocampal sclerosis: an effect of seizures on the immature brain?

BACKGROUND AND PURPOSE: Ipsilateral loss of anterior temporal gray-white matter definition, due mainly to white matter signal intensity abnormality, is frequently seen on MR images of patients with hippocampal sclerosis. Our aim was to determine the prevalence and clinical correlations of these anterior temporal changes in pediatric cases of hippocampal sclerosis and to determine whether cumulative damage from seizures is important for their development. METHODS: We reviewed the MR images and clinical details of 54 children (age range, 1.5-19 years) with typical hippocampal sclerosis. Specific imaging features noted included hippocampal sclerosis, anterior temporal changes, anterior temporal atrophy, and extra-hippocampal abnormality. RESULTS: Thirty-one (57%) of 54 children with hippocampal sclerosis had associated ipsilateral anterior temporal changes. Ipsilateral anterior temporal atrophy was associated with anterior temporal changes (P <.03). Children whose images showed anterior temporal changes were younger at onset of epilepsy (P <.01) and younger at antecedent cerebral insult (P <.03) than those with normal anterior temporal lobes. Most (84%) children whose images showed anterior temporal changes had experienced the onset of epilepsy or antecedent cerebral insult before the age of 2 years (P <.0009). Eighty-one percent of children with anterior temporal changes shown on their images experienced seizures at the time of antecedent insult. CONCLUSION: Ipsilateral anterior temporal changes identical to those observed in adult cases are seen on the MR images of young children with hippocampal sclerosis, with a similar prevalence, and are associated with either epilepsy onset or seizure-related cerebral insult before the age of 2 years. We suggest that the loss of gray-white matter definition may represent a persistent immature appearance, including an abnormality of myelin or myelination, possibly a result of seizures occurring during maturation of the temporal pole.

Adolescent↗

PubMed2002

Hippocampal pathology in refractory temporal lobe epilepsy: T2-weighted signal change reflects dentate gliosis.

BACKGROUND: The MR and pathologic features of hippocampal sclerosis (HS) are well described and include volume decrease and T2-weighted signal increase for MRI, and neuron cell loss and gliosis for pathology. OBJECTIVE: To confirm the established correlation between hippocampal volumes and neuron cell counts, and to study the still controversial association between signal change and gliosis. METHODS: The authors studied 44 patients (22 men and 22 women; mean age at surgery, 37 years) with refractory temporal lobe epilepsy. Quantitative assessment of hippocampal volumes and T2 relaxometry, and neuron and glial cell count in the region CA1 and molecular layer of the dentate gyrus was performed. The proportion of glial fibrillary acidic protein (GFAP)-positive glial cells (reactive astrocytes) was indicated. RESULTS: In a stepwise regression, the ipsilateral hippocampal volume was predicted best by the neuron cell count in the dentate gyrus (p = 0.005, r = 0.4). Hippocampal T2 time, however, was predicted best by the glial cell count in the dentate gyrus (p = 0.01, r = 0.4). None of the other cell counts contributed to either model. In the dentate, 31% of the glial cells were reactive astrocytes, whereas in CA1, 5% were reactive. CONCLUSION: The results confirmed the correlation between hippocampal volumes and neuron cell counts. T2-weighted signal increase in the hippocampus was mainly influenced by gliosis in the dentate gyrus, where a high proportion of glial cells show abnormal activity. This activity may reflect changes important in the development of hippocampal epileptogenicity.

Adult↗

PubMed2002

Seizure-associated hippocampal volume loss: a longitudinal magnetic resonance study of temporal lobe epilepsy.

This longitudinal quantitative magnetic resonance imaging study of 24 patients with mild temporal lobe epilepsy shows an ipsilateral hippocampal volume decrease of 9% (range, -30 to +0.5%; p = 0.002, paired t test) over a period of 3.5 +/- 0.7 years. The hippocampal volume loss was correlated to the number of generalized seizures between the scans (p = 0.0007, r = 0.6), suggesting seizure-associated hippocampal damage.

Adolescent↗