Cognitive changes in people with temporal lobe epilepsy over a 13-year period

Topological regularization of networks in temporal lobe epilepsy: a structural MRI study

Objective

Patients with temporal lobe epilepsy (TLE) often exhibit neurocognitive disorders; however, we still know very little about the pathogenesis of cognitive impairment in patients with TLE. Therefore, our aim is to detect changes in the structural connectivity networks (SCN) of patients with TLE.

Methods

Thirty-five patients with TLE were compared with 47 normal controls (NC) matched according to age, gender, handedness, and education level. All subjects underwent thin-slice T1WI scanning of the brain using a 3.0 T MRI. Then, a large-scale structural covariance network was constructed based on the gray matter volume extracted from the structural MRI. Graph theory was then used to determine the topological changes in the structural covariance network of TLE patients.

Results

Although small-world networks were retained, the structural covariance network of TLE patients exhibited topological irregularities in regular architecture as evidenced by an increase in the small world properties (p < 0.001), normalized clustering coefficient (p < 0.001), and a decrease in the transfer coefficient (p < 0.001) compared with the NC group. Locally, TLE patients showed a decrease in nodal betweenness and degree in the left lingual gyrus, right middle occipital gyrus and right thalamus compared with the NC group (p < 0.05, uncorrected). The degree of structural networks in both TLE (Temporal Lobe Epilepsy) and control groups was distributed exponentially in truncated power law. In addition, the stability of random faults in the structural covariance network of TLE patients was stronger (p = 0.01), but its fault tolerance was lower (p = 0.03).

Conclusion

The objective of this study is to investigate the potential neurobiological mechanisms associated with temporal lobe epilepsy through graph theoretical analysis, and to examine the topological characteristics and robustness of gray matter structural networks at the network level.

Abnormalities of regional brain activity and executive function in patients with temporal lobe epilepsy: A cross-sectional and longitudinal resting-state functional MRI study

PURPOSE

We decided to track changes in regional brain activity and executive function in temporal lobe epilepsy (TLE) patients based on cross-sectional and longitudinal designs and sought potential imaging features for follow-up observation.

METHODS

Thirty-two TLE patients and thirty-three healthy controls (HCs) were recruited to detect changes in fractional amplitude of low-frequency fluctuation (fALFF) and regional homogeneity (ReHo) and to evaluate executive function both at baseline and at two-year (23.3 ± 8.3 months) follow-up. Moreover, multivariate pattern analysis (MVPA) was used for follow-up observation.

RESULTS

TLE patients displayed lower fALFF values in the right superior frontal gyrus (SFG) and higher ReHo values in the left putamen (PUT) relative to the HCs. Longitudinal analysis revealed that TLE patients at follow-up exhibited higher fALFF values in the left postcentral gyrus (PoCG), higher ReHo values in the left PoCG and the right middle frontal gyrus (MFG), lower ReHo values in the bilateral PUT and the right fusiform gyrus (FFG) compared with these patients at baseline. The executive function was impaired in TLE patients but didn't deteriorate over time. No correlations were discovered between regional brain activity and executive function. The MVPA based on ReHo performed well in differentiating the follow-up group from the baseline group.

CONCLUSION

We revealed the abnormalities in regional brain activity and executive function as well as their longitudinal trends in TLE patients. The ReHo might be a good imaging feature for follow-up observation.

Cognitive decline in adult-onset temporal lobe epilepsy: Insights from aetiology

PURPOSE

To identify patients with adult-onset temporal lobe epilepsy (TLE) at risk of developing cognitive decline. Detecting which patients, aetiologies, or factors are most closely related with memory decline would allow us to identify patients that would eventually benefit from more specific treatment.

METHODS

Single centre, retrospective analysis of a prospectively followed-up cohort study, including all patients with the diagnosis of adult-onset TLE during 2013, with a minimum follow-up of five years. Memory and cognitive decline were analysed at 5 years and at last follow-up.

RESULTS

Of 89 initially selected patients, 71 were included. After 5 years, 11/71 (15.5%) patients suffered cognitive decline, of which 1/71 (4%) developed dementia. At last follow-up (range 65-596 m) a total of 34/71 (47.8%) patients were diagnosed with cognitive decline, specifically either memory decline or dementia. Cognitive decline at 5 years was related to: 1. Age at onset: 62.65 years (SD 9.04) in the group with cognitive decline vs 50.33 y. (SD 13.02 in the group without cognitive decline; p=0.004); 2. Onset as status epilepticus (3/6 in patients with memory decline vs 8/65 in patients without cognitive decline; p=0.04); 3. Immune aetiology: 42% compared with unknown (10%) and structural (10%) aetiologies; p=0.036; 4. Hippocampal sclerosis on MRI: 5/11 patients with cognitive decline vs 9/51 patients without cognitive decline; p=0.035. Cognitive decline was not related to seizure frequency, sex, or age (p=0.78; p=0.40; p=0.95, respectively).

CONCLUSIONS

Older age at epilepsy onset, onset as status epilepticus, immune aetiology, and hippocampal sclerosis are risk factors for developing cognitive decline in patients with adult-onset temporal lobe epilepsy.

Longer-term verbal and visual memory patterns in patients with temporal lobe and genetic generalized epilepsies

OBJECTIVE

To compare forgetting patterns between patients with temporal lobe (TLE) and generalized (GGE) epilepsies and to assess whether recall is associated with epileptic activity.

METHODS

Thirty-three patients with TLE (13 left, 17 right, and 3 nonlateralized TLE), 42 patients with GGE, and 57 healthy controls (HCs) were asked to recall words, verbal story material, and the Rey-Osterrieth complex figure at two delays. Accelerated long-term forgetting (ALF) was defined by group performance comparable to HCs at 30 min and worse recall than HCs after 4 weeks. ALF was assessed by comparing raw test scores in a two-way repeated measures analysis of variance (ANOVA) adjusted for the learning capacity.

RESULTS

Compared to HCs, patients with R-TLE remembered fewer items of the word list after 30 min as well as after 4 weeks. Patients with L-TLE and GGE had comparable learning-adjusted performance to HCs at the 30 min delay but scored less after 4 weeks (group by delay interaction F(3, 124) = 3.2, P = 0.026,η p 2  = 0.07). The epilepsy group (patients with TLE and GGE combined) performed as well as HCs at 30 min but worse after 4 weeks irrespective of experienced seizures during the 4-week delay or interictal bilateral (TLE) or generalized (GGE) activity before the study. We noted no statistically significant differences between patient and HC verbal story (group by delay interaction F(3, 124) = 0.7, P = 0.570,η p 2  = 0.02) or complex figure (F(3, 124) = 0.8, P = 0.488,η p 2  = 0.02) recall.

SIGNIFICANCE

Our data support verbal and visual memory impairment in both TLE and GGE with different performances between these groups in the task of word recall. We suggest the presence of ALF in patients with GGE and left TLE after adjusting for learning capacity. We could not confirm the influence of epileptic activity on long-term forgetting patterns. Future studies are required to better define domain-specific differences in memory impairment in TLE and GGE.

The relationship between memory and quality of life is mediated by trait anxiety in patients with temporal lobe epilepsy

PURPOSE

Memory deficits are very frequent in patients with drug-resistant epilepsy, but they predict a small proportion of variance of their quality of life (QOL) in previous studies, possibly due to the lack of consideration of mediating factors of this relationship. This study aimed to examine whether trait anxiety mediates the relationship between memory and QOL in this population, controlling the influence of demographic and seizure-related factors.

METHODS

In this cross-sectional study, 119 adults with drug-resistant temporal lobe epilepsy (TLE) underwent a neuropsychological evaluation, in which memory, anxiety, and QOL were assessed.

RESULTS

In the total sample, better delayed memory had an effect on better QOL indirectly through lower trait anxiety (B = 0.13, SE = 0.06, p = 0.04, ab_cs = 0.13; κ² = 0.18; PM_ind = 0.76). Additionally, delayed memory has not a direct association with QOL (B = 0.04, SE = 0.09, p = 0.64, Cohen's f ² = 0.005; PM_dir = 0.24), and the total effect of delayed memory on QOL tended to reach statistical significance (B = 0.17, SE = 0.10, p = 0.08). The proposed mediation model yielded excellent fit (CFI = 1.00, RMSEA = 0.0001, SRMR = 0.009, and χ² (1) = 0.50, p = 0.48) and explained 38% of the variance of QOL.

CONCLUSION

These findings suggest that trait anxiety is an important factor in understanding the relationship between memory and QOL in patients with TLE, considering the influence of demographic and seizure-related variables, and may have relevant implications for decision-making in this population.

Prevalence and Factors Influencing Visual Memory Dysfunction among Epilepsy Patients-A Single-Center Study

Background

Epilepsy is associated with cognitive impairment due to the disease itself or side-effects of antiepileptic drugs.

Objective

We aimed to study the prevalence of visual memory dysfunction among epilepsy patients and identify the predictors that could contribute to the impairment.

Materials and Methods

This was a cross-sectional study. We analyzed 250 patients with epilepsy from neurology clinic at our tertiary center. Assessment of visual memory was done using Wechsler Memory Scale-IV (WMS-IV) with scores from subsets of visual reproduction I, II and designs I, II contributing to visual memory index (VMI) score. The correlation between continuous variables was analyzed using Pearson correlation; whereas the VMI scores of different factors were analyzed via a 1-way ANOVA test. The statistical significance was set at P < 0.05.

Results

The prevalence of visual memory dysfunction in our epilepsy population was 37.2%. Analysis of individual predictors showed that older patients, lower educational level, combined generalized and focal types of epilepsy, longer duration of epilepsy, greater number of antiepileptic drugs (AEDs) used, and abnormal neuroimaging contributed to poor visual memory. Multiple logistic regression analysis showed that educational level, types of epilepsy, and the number of AEDs used were significant predictors for visual memory impairment.

Conclusion

Visual memory dysfunction in patients with epilepsy was due to manifold confounding factors. Our findings enabled us to identify patients with visual memory dysfunction and modifiable factors that contribute to it. WMS-IV is a suitable assessment tool to determine visual memory function, which can help clinicians to optimize the patients' treatment.

Associations of individual and structural socioeconomic status with cognition and mental distress in pharmacoresistant focal epilepsy

OBJECTIVE

Epilepsy is often associated with low socioeconomic status (SES). People with epilepsy (PWE) also suffer from cognitive dysfunction and mental distress. In the general population, these constraints are related to individual and structural SES. However, in PWE, cognitive dysfunction and mental distress have been mainly attributed to biological factors such as brain lesions or pharmacological treatment, whereas comprehensive studies on possible social determinants are missing. Here, we study associations of individual and structural SES with cognition and mental distress in PWE.

METHODS

We retrospectively studied 340 adult patients with pharmacoresistant focal epilepsy from Berlin treated at a tertiary epilepsy center. Individual SES (education, employment, and income), structural SES (social index of district and neighborhood), and their interactions were examined. Associations between social variables and verbal learning, psychomotor speed, and mental distress were analyzed with multiple regression analyses, controlling for demographic and medical variables and intelligence.

RESULTS

Our sample had lower educational levels and lived more frequently in low SES neighborhoods compared to the general population of Berlin. Thirty percent showed reduced verbal learning, 31% had deficits in psychomotor speed, and 20% revealed significant mental distress. Lower structural SES was related to lower psychomotor speed (ΔR² = 0.9%) and higher mental distress (ΔR² = 1.6%). Employment was related to verbal learning (ΔR² = 0.7%) and psychomotor speed (ΔR² = 1.2%). Income and education were linked to mental distress (ΔR² = 5%). Neighborhood and individual SES covered more than half of the explained variance in mental distress. Furthermore, interactions between individual and structural SES were identified.

CONCLUSION

We confirm cognitive deficits, significant mental distress, and individual and structural social disadvantage in PWE. Our findings indicate that individual and structural SES are related to cognitive and emotional well-being beyond demographic and medical characteristics. As a clinical implication, individual and structural SES should be considered when interpreting neuropsychological findings.

One-Year Analysis of Risk Factors Associated With Cognitive Impairment in Newly Diagnosed Epilepsy in Adults

Cognitive impairment (CI) occurs in people with epilepsy, affecting their quality of life. This study aimed to identify factors associated with CI in adult patients with newly diagnosed epilepsy. Additionally, we sought to determine whether any particular cognitive function is impaired predominantly by anti-seizure medications or by other factors. We enrolled 229 patients with newly diagnosed epilepsy and 191 participants were followed up for 1 y. We used the Montreal Cognitive Assessment as a tool to quantify CI. The sub-item scores were also collected to assess whether any aspects of CI are predominantly affected by anti-seizure medication treatment. Subjective memory decline due to anti-seizure medications was also recorded. One-hundred-and-two participants (44.5%) had CI onset before anti-seizure medication treatment. Aging, low education level, stroke or brain surgery etiology, and anxious symptoms were identified as risk factors for CI before anti-seizure medications use. Brain surgery for the young, anxious status for the middle-aged, and depressive status for the elderly were risk factors for CI at different ages. The elderly PWE had worse memory than the others. PWE with TLE had worse cognition, especially in memory and naming. The overall impact of anti-seizure medications on cognition was mild. Refractory epilepsy was a predictor of cognitive decline. Subjective memory decline was predicted by high-risk treatment and by a finding of refractory epilepsy. Clarifying the risk factors for CI can help the physician to assess the probable risk of CI for each individual before the start of anti-seizure medication treatment, which may lead to better compliance.

Alterations Functional Connectivity in Temporal Lobe Epilepsy and Their Relationships With Cognitive Function: A Longitudinal Resting-State fMRI Study

Background: Cognitive impairments in temporal lobe epilepsy (TLE) patients has been described as a chronically progressive feature of the disease. However, how severe recurrent seizures modify neuronal circuits in the human brain and subsequently degrade cognitive function, remains largely unknown. Here, we aimed to investigate longitudinal alterations by functional magnetic resonance imaging (fMRI) in TLE patients and to assess how those alterations are related to cognitive function performance.

Methods: Sixteen TLE patients and 20 normal controls (NCs) were recruited for a study to observe longitudinal alterations in resting-state functional connectivity (FC) and to estimate alertness, orientation, and executive function both at baseline and at a follow-up time ~3 years later.

Results: TLE patients, compared with NCs, showed impaired executive function, intrinsic alertness, and phasic alertness and exhibited lengthened reaction time (RT) in the spatial cue and center cue conditions at baseline. The orienting function of TLE patients was declined at follow-up compared to the baseline. Cross-sectional analysis demonstrated that TLE patients displayed significantly greater positive correlation than NCs between the right dorsolateral prefrontal cortex (DLPFC) and the right inferior parietal lobule (IPL) and right superior frontal gyrus (SFG). Furthermore, among TLE patients, the longitudinal study revealed a decrease in correlation between the right DLPFC and the right SFG compared to the baseline. In addition, there was a significant negative correlation between the longitudinal change in FC and the change in orienting function in TLE subjects.

Conclusions: Abnormal connectivity between the DLPFC and the SFG suggests the potential of longitudinal resting-state fMRI to delineate regions relevant to cognitive dysfunction for disease progression.

Long-term cognitive outcomes in patient with epilepsy

In contrast to short-term cognitive outcomes, long-term cognitive outcomes (over 5 years) has been scarcely assessed so far. Yet, predicting long-term outcomes at any time point of the epilepsy, from initial diagnosis, to medically intractability is very important for therapeutic decision-making, patient information, and orientation. Assessing long-term cognitive outcomes in patients with epilepsy would ideally require longitudinal studies and a comparison with a healthy controls group. This issue has been addressed extensively, but with controversial results. However, there is a general consensus about the fact that cognitive outcome is not the same in all groups of patients with epilepsy. Possible prognostic factors include age at onset, duration of epilepsy, syndrome and etiology, seizure outcome and therapeutics. The multiplicity of factors makes it very difficult to assess their relative weight in individuals. Although long-term cognitive outcome studies are scarce, this issue has been specifically studied in newly diagnosed epilepsies and in focal drug-resistant epilepsies. In the first clinical setting, i.e. newly diagnosed epilepsy, it appears that cognitive deficits are already present at epilepsy onset in a significant proportion of patients but seem to remain stable over time. In focal drug-resistant epilepsies, cognitive deficits (mainly verbal memory) were generally shown to remain stable provided that seizures were controlled either by medication or by surgery. Beyond the possible correlation between seizure and cognitive outcome, no causal link however has been demonstrated between these two important outcomes.

Memory response and neuroimaging correlates of a novel cognitive rehabilitation program for memory problems in epilepsy: A pilot study

BACKGROUND

Memory deficits are very common in epilepsy, but no standard of care exists to effectively manage them.

OBJECTIVE

We assessed effectiveness of cognitive rehabilitation (CR) on memory and neural plasticity in people with epilepsy (PWE) reporting memory impairments.

METHODS

Nine PWE completed 6 weekly sessions adapted from 2 generic CR programs enriched with information regarding epilepsy. Participants completed neuropsychological, mood, and quality of life (QOLIE-31) measures prior and after completion of CR; 5/9 participants also completed pre- and post-CR fMRI while performing a verbal paired associates learning task. FMRI data were analyzed using group spatial independent components analysis methods; paired t-tests compared spatial activations for pre-/post-CR.

RESULTS

Improvements were seen in immediate recall in Rey Auditory Verbal Learning Task, QOLIE-31, and read word recognition in paired associates task (all p's≤0.05). FMRI changes comparing pre-to-post CR were noted through increased activation in the left inferior frontal gyrus (IFG) and anterior cingulate and decreased activation in the left superior temporal gyrus; also noted were decreased activations in the default mode network (DMN), right cingulate, right middle temporal gyrus, right supramarginal gyrus, and increased DMN activation in the left cuneus.

CONCLUSIONS

This study demonstrates feasibility of conducting CR program in PWE with fMRI as a mechanistic biomarker. Improvements in cognition and cortical plasticity await confirmation in larger samples.

Antiepileptic drugs are not independently associated with cognitive dysfunction

OBJECTIVE

To test the hypothesis that individual antiepileptic drugs (AEDs) are not associated with cognitive impairment beyond other clinically relevant factors, we performed a cross-sectional study of patients admitted to an inpatient video-EEG monitoring unit.

METHODS

We prospectively enrolled patients admitted to an inpatient specialist epilepsy program between 2009 and 2016. Assessments included objective cognitive function, quality of life subscales for subjective cognitive function, and questionnaires for anxiety and depressive symptoms. Bayesian model averaging identified predictors of cognitive function. Bayesian model selection approach investigated effect of individual AEDs on cognition. Conventional frequentist analyses were also performed.

RESULTS

A total of 331 patients met inclusion criteria. Mean age was 39.3 years and 61.9% of patients were women. A total of 45.0% of patients were prescribed AED polypharmacy, 25.1% AED monotherapy, and 29.9% no AED. Age, seizure frequency, and a diagnosis of concomitant epilepsy and psychogenic nonepileptic seizure were predictors of objective cognitive function. Depression, anxiety, and seizure frequency were predictors of subjective cognitive function. Individual AEDs were not independently associated with impaired cognitive function beyond other clinically relevant variables.

CONCLUSIONS

This study found that no AED was independently associated with cognitive dysfunction. Significant determinants of objective and subjective cognitive dysfunction included seizure frequency and depression, respectively. These findings suggest that optimizing therapy to prevent seizures is not likely to occur at the expense of cognitive function.

Longitudinal assessment of resting-state fMRI in temporal lobe epilepsy: A two-year follow-up study

In this study, we aimed to detect longitudinal alterations in local spontaneous brain activity and functional connectivity (FC) of the default mode network (DMN) in patients with temporal lobe epilepsy (TLE) over a two-year follow-up. We used amplitude of low-frequency fluctuation (ALFF) analysis and independent component analysis (ICA) to explore differences in local spontaneous brain activity and FC strength. In total, 33 participants (16 patients with TLE and 17 age- and gender-matched healthy controls (HCs)) were recruited in this study. All participants performed the Attention Network Test (ANT) for evaluation of the executive control function. Compared with healthy patients at baseline, patients with TLE at follow-up exhibited increased ALFF values in the left medial frontal gyrus, as well as reduced FC values in the left inferior parietal gyrus (IPG) within the DMN. Patients with TLE revealed executive dysfunction, but no progressive deterioration was observed during follow-up. This study revealed the abnormal distribution of ALFF values and Rs-FC changes over a two-year follow-up period in TLE, both of which demonstrated different reorganization trajectories and loss of efficiency.

White matter correlates of disease duration in patients with temporal lobe epilepsy: updated review of literature

BACKGROUND

Medial temporal lobe epilepsy (mTLE) has been associated with widespread white mater (WM) alternations in addition to mesial temporal sclerosis (MTS). Herein, we aimed to investigate the correlation between disease duration and WM structural abnormalities in mTLE using diffusion MRI (DMRI) connectometry approach.

METHOD

DMRI connectometry was conducted on 24 patients with mTLE. A multiple regression model was used to investigate white matter tracts with microstructural correlates to disease duration, controlling for age and sex. DMRI data were processed in the MNI space using q-space diffeomorphic reconstruction to obtain the spin distribution function (SDF). The SDF values were converted to quantitative anisotropy (QA) and used in further analyses.

RESULTS

Connectometry analysis identified impaired white matter QA of the following fibers to be correlated with disease duration: bilateral retrosplenial cingulum, bilateral fornix, right inferior longitudinal fasciculus (ILF), and genu of corpus callosum (CC) (FDR = 0.009).

CONCLUSION

Our results were obtained from DMRI connectometry, which indicates the connectivity and the level of diffusion in nerve fibers rather just the direction of diffusion. Compared to previous studies investigating the correlation between duration of epilepsy and white matter integrity in mTLE patients, we detected broader and somewhat different associations in midline structures and component of limbic system. However, further studies with larger sample sizes are required to elucidate previous and current results.

Pre- and long-term postoperative courses of hippocampus-associated memory impairment in epilepsy patients with antibody-associated limbic encephalitis and selective amygdalohippocampectomy

OBJECTIVE

Limbic encephalitis (LE) is defined by mesiotemporal lobe structure abnormalities, seizures, memory, and psychiatric disturbances. This study aimed to identify the long-term clinical and neuropsychological outcome of selective amygdalohippocampectomy (sAH) in drug-resistant patients with temporal lobe epilepsy due to known or later diagnosed subacute LE not responding to immunotherapy associated with neuronal autoantibodies.

METHODS

In seven patients with temporal lobe epilepsy due to antibody positive LE (glutamic acid decarboxylase (GAD65): n=5; voltage-gated potassium channel complex (VGKC), N-methyl d-aspartate receptor (NMDAR): n=1; Ma-2/Ta: n=1) sAH (6 left, 1 right) was performed. Those patients underwent repeated electroencephalography (EEG) recordings, magnetic resonance imaging (MRI) volumetry of the amygdala and hippocampus, and neuropsychological examinations and were followed up for 6-7years on average.

RESULTS

Verbal memory and figural memory were affected in 57% of patients at baseline and 71% at the last follow-up. At the last follow-up, 14% of the patients had declined in verbal memory and figural memory. We observed improved memory in 43% of patients regarding figural memory, but not in a single patient regarding verbal memory. Repeated evaluations across the individual courses reveal cognitive and MRI dynamics that appear to be unrelated to surgery and drug treatment. Three of the seven patients with LE with different antibodies (NMDAR: n=1, Ma-2/Ta: n=1 and GAD65: n=1) achieved persistent seizure freedom along with no accelerated memory decline after surgery. Two of the five GAD65-antibody patients positive with LE showed progressive memory decline and a long-term tendency to contralateral hippocampus atrophy.

CONCLUSIONS

While memory demonstrated some decline in the long run, what is most important is that a progressive decline in memory is seldom found after sAH in patients with LE. Moreover, the dynamics in performance and MRI before and after surgery reveal disease dynamics independent of surgery. Selective amygdalohippocampectomy can lead to seizure freedom, but should be considered as a last resort treatment option for drug-resistant patients with temporal lobe epilepsy due to LE. Particular caution is recommended in patients with GAD65-LE.

Verbal memory decline from hippocampal depth electrodes in temporal lobe surgery for epilepsy

OBJECTIVE

To explore whether patients with refractory mesial temporal lobe epilepsy risk aggravated verbal memory loss from intracranial electroencephalography (EEG) recording with longitudinal hippocampal electrodes in the language-dominant hemisphere.

METHODS

A long-term neuropsychological follow-up (mean 61.5 months, range 22-111 months) was performed in 40 patients after ictal registration with left hippocampal depth electrodes (study group, n = 16) or no invasive EEG, only extracranial registration (reference group, n = 24). The groups were equal with respect to education, age at seizure onset, epilepsy duration, and prevalence of pharmacoresistant temporal lobe epilepsy (TLE; 75%) versus seizure freedom (25%). Retrospective neuropsychological data from preoperative surgical workup (T1) and prospective follow-up neuropsychological data (T2) were compared. A ≥1 SD intrapatient decline was considered as clinically relevant deterioration of verbal memory.

RESULTS

Significant decline in verbal memory was seen in 56% of the patients in the study group compared to 21% in the reference group. At T1, there were no statistical between-group differences in memory performance. At T2, between-group comparison showed significantly greater verbal memory decline for the study group (Claeson Dahl Learning and Retention Test, Verbal Learning: p = 0.05; Rey Auditory Verbal Learning Test, Total Learning: p = 0.04; Claeson Dahl Learning and Retention Test, Verbal Retention: p = 0.04). An odds ratio (OR) of 7.1 (90% confidence interval [CI] 1.3-37.7) for verbal memory decline was seen if right temporal lobe resection (R TLR) had been performed between T1 and T2. The difference between groups remained unchanged when patients who had undergone R TLR were excluded from the analysis, with a remaining aggravated significant decline in verbal memory performance for the study group compared to the reference group.

SIGNIFICANCE

Our results suggest a risk of verbal memory deterioration after the use of depth electrodes along the longitudinal axis of the hippocampus. Until this issue is further investigated, caution regarding depth electrodes in the language-dominant hemisphere hippocampus seems advisable.

Volumetric Changes in Hippocampal Subregions and Memory Performance in Mesial Temporal Lobe Epilepsy with Hippocampal Sclerosis

In the present study we explored the different patterns of volumetric atrophy in hippocampal subregions of patients with left and right mesial temporal lobe epilepsy with hippocampal sclerosis (TLE-HS). Meanwhile, the memory impairment patterns in Chinese-speaking TLE-HS patients and potential influencing factors were also determined. TLE-HS patients (21 left and 17 right) and 21 healthy controls were recruited to complete T2-weighted imaging and verbal/nonverbal memory assessment. The results showed that both left and right TLE-HS patients had overall reduced hippocampal subregion volumes on the sclerotic side, and cornu ammonis sectors (CA1) exhibited maximum atrophy. The verbal memory of left TLE-HS patients was significantly impaired (P < 0.001) and was not associated with the volumes of the left hippocampal subregions. Verbal or nonverbal memory impairment was not found in the patients with right TLE-HS. These results suggested that the atrophy of hippocampal subregion volumes cannot account for the verbal memory impairment, which might be related to the functional network.

Impact of hippocampal subfield histopathology in episodic memory impairment in mesial temporal lobe epilepsy and hippocampal sclerosis

OBJECTIVE

The objective of the study was to analyze preoperative visual and verbal episodic memories in a homogeneous series of patients with mesial temporal lobe epilepsy (MTLE) and unilateral hippocampal sclerosis (HS) submitted to corticoamygdalohippocampectomy and its association with neuronal cell density of each hippocampal subfield.

METHODS

The hippocampi of 72 right-handed patients were collected and prepared for histopathological examination. Hippocampal sclerosis patterns were determined, and neuronal cell density was calculated. Preoperatively, two verbal and two visual memory tests (immediate and delayed recalls) were applied, and patients were divided into two groups, left and right MTLE (36/36).

RESULTS

There were no statistical differences between groups regarding demographic and clinical data. Cornu Ammonis 4 (CA4) neuronal density was significantly lower in the right hippocampus compared with the left (p=0.048). The groups with HS presented different memory performance - the right HS were worse in visual memory test [Complex Rey Figure, immediate (p=0.001) and delayed (p=0.009)], but better in one verbal task [RAVLT delayed (p=0.005)]. Multiple regression analysis suggested that the verbal memory performance of the group with left HS was explained by CA1 neuronal density since both tasks were significantly influenced by CA1 [Logical Memory immediate recall (p=0.050) and Logical Memory and RAVLT delayed recalls (p=0.004 and p=0.001, respectively)]. For patients with right HS, both CA1 subfield integrity (p=0.006) and epilepsy duration (p=0.012) explained Complex Rey Figure immediate recall performance. Ultimately, epilepsy duration also explained the performance in the Complex Rey Figure delayed recall (p<0.001).

SIGNIFICANCE

Cornu Ammonis 1 (CA1) hippocampal subfield was related to immediate and delayed recalls of verbal memory tests in left HS, while CA1 and epilepsy duration were associated with visual memory performance in patients with right HS.