Awake craniotomy with English and British sign language mapping in a patient with a left temporal glioblastoma reveals discordant speech-sign language maps.

The aim of this case study was to describe differences in English and British Sign Language (BSL) communication caused by a left temporal tumour resulting in discordant presentation of symptoms, intraoperative stimulation mapping during awake craniotomy and post-operative language abilities. We report the first case of a hearing child of deaf adults, who acquired BSL with English as a second language. The patient presented with English word finding difficulty, phonemic paraphasias, and reading and writing challenges, with BSL preserved. Intraoperatively, object naming and semantic fluency tasks were performed in English and BSL, revealing differential language maps for each modality. Post-operative assessment confirmed mild dysphasia for English with BSL preserved. These findings suggest that in hearing people who acquire a signed language as a first language, topographical organisation may differ to that of a second, spoken, language.

Connectome reorganization associated with temporal lobe pathology and its surgical resection.

Network neuroscience offers a unique framework to understand the organizational principles of the human brain. Despite recent progress, our understanding of how the brain is modulated by focal lesions remains incomplete. Resection of the temporal lobe is the most effective treatment to control seizures in pharmaco-resistant temporal lobe epilepsy (TLE), making this syndrome a powerful model to study lesional effects on network organization in young and middle-aged adults. Here, we assessed the downstream consequences of a focal lesion and its surgical resection on the brain's structural connectome, and explored how this reorganization relates to clinical variables at the individual patient level. We included adults with pharmaco-resistant TLE (n = 37) who underwent anterior temporal lobectomy between two imaging time points, as well as age- and sex-matched healthy controls who underwent comparable imaging (n = 31). Core to our analysis was the projection of high-dimensional structural connectome data-derived from diffusion MRI tractography from each subject-into lower-dimensional gradients. We then compared connectome gradients in patients relative to controls before surgery, tracked surgically-induced connectome reconfiguration from pre- to postoperative time points, and examined associations to patient-specific clinical and imaging phenotypes. Before surgery, individuals with TLE presented with marked connectome changes in bilateral temporo-parietal regions, reflecting an increased segregation of the ipsilateral anterior temporal lobe from the rest of the brain. Surgery-induced connectome reorganization was localized to this temporo-parietal subnetwork, but primarily involved postoperative integration of contralateral regions with the rest of the brain. Using a partial least-squares analysis, we uncovered a latent clinical imaging signature underlying this pre- to postoperative connectome reorganization, showing that patients who displayed postoperative integration in bilateral fronto-occipital cortices also had greater preoperative ipsilateral hippocampal atrophy, lower seizure frequency and secondarily generalized seizures. Our results bridge the effects of focal brain lesions and their surgical resections with large-scale network reorganization and interindividual clinical variability, thus offering new avenues to examine the fundamental malleability of the human brain.

Cognition in children with arachnoid cysts - A five-year follow-up after microneurosurgical fenestration.

BACKGROUND AND PURPOSE: In recent years there has been a re-evaluation regarding the clinical implications of temporal lobe arachnoid cysts (temporal arachnoid cysts) in children. These cysts have often been considered asymptomatic, or if symptomatic, only causing focal neurological symptoms or signs of increased intracranial pressure. However, several studies have more recently reported on cognitive symptoms improving after surgery. This study aimed to evaluate if reported cognitive improvement after surgery of temporal arachnoid cysts were stable after five years. METHOD: Ten consecutive children (m = 14.65; range 12.1-19.415 were assessed cognitively five years after micro-neurosurgical fenestration of a temporal arachnoid cyst. Results were compared to results from their pre- and post-surgical evaluations. Evaluations included the Wechsler-scales, Boston Naming Test (BNT), Rey Auditory Verbal Learning Test (RAVLT), verbal fluency test (FAS) and Rey Complex Figure Test (RCFT). RESULTS: The analysis revealed significant postsurgical improvement compared to baseline on the Wechsler-scales measures of general intelligence (FSIQ), verbal abilities (VCI) and processing speed (PSI). Mean differences after surgery were 8.3 for FSIQ, (p = 0.026), 8.5 for VI (p = < .01) and 9.9 for PSI (p = 0.03). There were no significant differences in mean test results when comparing postsurgical scores with scores five years after surgery, indicating long-term stability of improvements. CONCLUSION: The results indicate that affected cognitive functions in children with temporal arachnoid cysts improve after surgery and that the improvements remain stable five years later. The improvements and long term stability were also consistent with the experience of both parents and children. The findings provide a strong argument for neurosurgical fenestration of temporal arachnoid cysts in children.

Temporo-Parieto-Occipital Disconnection by Robot-Assisted Magnetic Resonance Imaging-Guided Laser Interstitial Thermal Therapy for Refractory Epilepsy in a Pediatric Patient: Proof-of-Principle Case Report and Surgical Nuances.

OBJECTIVE: Magnetic resonance imaging-guided laser interstitial thermal therapy (MRIgLITT) has been proven safe and effective for the treatment of focal epilepsy of different etiologies. It has also been used to disconnect brain tissue in more extensive or diffuse epilepsy, such as corpus callosotomy and hemispherotomy. METHODS: In this study, we report a case of temporo-parieto-occipital disconnection surgery performed using MRIgLITT assisted by a robotic arm for refractory epilepsy of the posterior quadrant. A highly realistic cadaver simulation was performed before the actual surgery. RESULTS: The patient was a 14-year-old boy whose seizures began at the age of 8. The epilepsy was a result of a left perinatal ischemic event that caused a porencephalic cyst, and despite receiving multiple antiepileptic drugs, the patient continued to experience daily seizures which led to the recommendation of surgery. CONCLUSIONS: A Wada test lateralized language in the right hemisphere. Motor and sensory function was confirmed in the left hemisphere through magnetic resonance imaging functional studies and NexStim. The left MRIgLITT temporo-parieto-occipital disconnection disconnection was achieved using 5 laser fibers. The patient followed an excellent postoperative course and was seizure-free, with no additional neurological deficits 24 months after the surgery.

Comparison of minimally invasive to standard temporal lobectomy approaches to epilepsy surgery: Seizure relief and visual confrontation naming outcomes.

The purpose of this study was to systematically examine three different surgical approaches in treating left medial temporal lobe epilepsy (mTLE) (viz., subtemporal selective amygdalohippocampectomy [subSAH], stereotactic laser amygdalohippocampotomy [SLAH], and anterior temporal lobectomy [ATL]), to determine which procedures are most favorable in terms of visual confrontation naming and seizure relief outcome. This was a retrospective study of 33 adults with intractable mTLE who underwent left temporal lobe surgery at three different epilepsy surgery centers who also underwent pre-, and at least 6-month post-surgical neuropsychological testing. Measures included the Boston Naming Test (BNT) and the Engel Epilepsy Surgery Outcome Scale. Fisher's exact tests revealed a statistically significant decline in naming in ATLs compared to SLAHs, but no other significant group differences. 82% of ATL and 36% of subSAH patients showed a significant naming decline whereas no SLAH patient (0%) had a significant naming decline. Significant postoperative naming improvement was seen in 36% of SLAH patients in contrast to 9% improvement in subSAH patients and 0% improvement in ATLs. Finally, there were no statistically significant differences between surgical approaches with regard to seizure freedom outcome, although there was a trend towards better seizure relief outcome among the ATL patients. Results support a possible benefit of SLAH in preserving visual confrontation naming after left TLE surgery. While result interpretation is limited by the small sample size, findings suggest outcome is likely to differ by surgical approach, and that further research on cognitive and seizure freedom outcomes is needed to inform patients and providers of potential risks and benefits with each.

Temporal lobe injury with middle fossa approach to intracanalicular vestibular schwannomas: a systematic review.

There are several surgical approaches for vestibular schwannoma (VS) resection. However, management has gradually shifted from microsurgical resection, toward surveillance and radiosurgery. One of the arguments against microsurgery via the middle fossa approach (MFA) is the risk of temporal lobe retraction injury or sequelae. Here, we sought to evaluate the incidence of temporal lobe retraction injury or sequela from a MFA via a systematic review of the existing literature. This systematic review was conducted according to the Preferred Reporting Items for Systematic Review and Meta-Analysis (PRISMA) guidelines. Relevant studies reporting temporal lobe injury or sequela during MFA for VS were identified. Data was aggregated and subsequently analyzed to evaluate the incidence of temporal lobe injury. 22 studies were included for statistical analysis, encompassing 1522 patients that underwent VS resection via MFA. The overall rate of temporal lobe sequelae from this approach was 0.7%. The rate of CSF leak was 5.9%. The rate of wound infection was 0.6%. Meningitis occurred in 1.6% of patients. With the MFA, 92% of patients had good facial outcomes, and 54.9% had hearing preservation. Our series and literature review support that temporal lobe retraction injury or sequelae is an infrequent complication from an MFA for intracanalicular VS resection.

Exo- and endoscopic lateral orbital wall approach for the medial temporal lobe glioma: how I do it.

BACKGROUND: The endoscopic transorbital approach provides a direct access to the medial temporal lobe (MTL). However, when excising a highly vascular tumour, a wider access route that enables the concurrent use of standard neurosurgical instruments with both hands is preferable. METHOD: We described the concept and technique of the lateral orbital wall approach (LOWA), which comprises orbitotomy and mini-craniotomy to treat MTL lesions using an exoscope and endoscope. CONCLUSION: The LOWA provides a safe and natural surgical corridor to the MTL and enables 2- or 3-hand surgery. Hence, LOWA can potentially improve safety and efficiency to treat MTL lesions.

[Surgical treatment of focal drug-resistant epilepsy associated with temporal lobe encephalocele]. / Khirurgicheskoe lechenie patsientov so strukturnoi fokal'noi farmakorezistentnoi epilepsiei, assotsiirovannoi s visochnymi entsefalotsele.

BACKGROUND: In recent years, temporal lobe encephalocele has become more common in patients with focal drug-resistant epilepsy. Despite available experience, there are still no clear recommendations for choosing the extent of surgery in these patients. OBJECTIVE: To evaluate the effectiveness of diagnosis and surgical treatment of focal drug-resistant epilepsy associated with temporal lobe encephalocele. MATERIAL AND METHODS: The study included 21 patients with focal temporal lobe epilepsy and temporal lobe encephalocele. All patients underwent continuous video-EEG monitoring and MRI of the brain. There were 12 (57.4%) selective encephalocele resections and 9 (42.6%) anterior temporal lobectomies. The median follow-up period was 31 months. RESULTS: The overall effectiveness of surgical treatment with postoperative Engel class I was 76% (16 cases). Selective encephalocele resection was followed by postoperative Engel class I in 10 patients (83%). There were 6 (67%) patients with similar outcomes after temporal lobectomy. Mean volume of resected tissue adjacent to encephalocele was 8.3 cm3. CONCLUSION: Surgery is a highly effective treatment for patients with epileptic seizures following temporal lobe encephalocele. In our sample, favorable postoperative outcomes were achieved in 76% of patients (Engel class I). There were no significant differences in effectiveness between selective resection and temporal lobectomy. Further research is necessary for a clear protocol of surgical treatment of focal drug-resistant epilepsy associated with encephalocele.

Middle temporal gyrus approach to mesial temporal lobe tumours in children.

AIM OF THE STUDY: To assess whether the middle temporal gyrus (MTG) approach to mesial temporal lobe (MTL) tumours is an effective procedure for the treatment of epilepsy in children. CLINICAL RATIONALE FOR THE STUDY: MTL tumours are a common cause of drug-resistant epilepsy in children. There is as yet no consensus regarding their treatment. One possibility is resection via a MTG approach. MATERIAL AND METHODS: We assessed the medical records of patients treated at the Department of Neurosurgery, Children's Memorial Health Institute,Warsaw, Poland between 2002 and 2020. A prospectively maintained database including clinical, laboratory, and radiographic presentation, as well as pre- and post-operative course, was analysed. Patients with at least a one- -year follow-up were included. RESULTS: There were 14 patients aged 4-18 years who underwent a MTG approach for a MTL tumour. All presented with epileptic seizure, and none had neurological deficit on admission to hospital. Median follow-up was 2.5 years. Neuronavigation was used to adjust the approach, localise the temporal horn, and achieve radical resection of the tumour and the hippocampus. Gross total resection was performed in all cases. In most patients, histopathological examination revealed ganglioglioma. One patient had transient aphasia. Two patients developed hemiparesis after surgery, which later improved. One of them also experienced visual disturbances. Acute complications were more frequent in younger patients (p = 0.024). In all cases, MRI confirmed complete resection and there was no tumour recurrence during the follow-up period. 13/14 patients remained seizure-free (Engel class I). CONCLUSIONS AND CLINICAL IMPLICATIONS: The MTG approach to MTL tumours is an effective procedure for the treatment of epilepsy in children. It avoids removal of the lateral temporal lobe and poses only a minor risk of permanent neurological complications.

Polygenic burden and its association with baseline cognitive function and postoperative cognitive outcome in temporal lobe epilepsy.

OBJECTIVE: Demographic and disease factors are associated with cognitive deficits and postoperative cognitive declines in adults with pharmacoresistant temporal lobe epilepsy (TLE), but the role of genetic factors in cognition in TLE is not well understood. Polygenic scores (PGS) for neurological and neuropsychiatric disorders and IQ have been associated with cognition in patient and healthy populations. In this exploratory study, we examined the relationship between PGS for Alzheimer's disease (AD), depression, and IQ and cognitive outcomes in adults with TLE. METHODS: 202 adults with pharmacoresistant TLE had genotyping and completed neuropsychological evaluations as part of a presurgical work-up. A subset (n = 116) underwent temporal lobe resection and returned for postoperative cognitive testing. Logistic regression was used to determine if PGS for AD, depression, and IQ predicted baseline domain-specific cognitive function and cognitive phenotypes as well as postoperative language and memory decline. RESULTS: No significant findings survived correction for multiple comparisons. Prior to correction, higher PGS for AD and depression (i.e., increased genetic risk for the disorder), but lower PGS for IQ (i.e., decreased genetic likelihood of high IQ) appeared possibly associated with baseline cognitive impairment in TLE. In comparison, higher PGS for AD and IQ appeared as possible risk factors for cognitive decline following temporal lobectomy, while the possible relationship between PGS for depression and post-operative cognitive outcome was mixed. SIGNIFICANCE: We did not observe any relationships of large effect between PGS and cognitive function or postsurgical outcome; however, results highlight several promising trends in the data that warrant future investigation in larger samples better powered to detect small genetic effects.

The role of preoperative [11C]methionine PET in defining tumor-related epilepsy and predicting short-term postoperative seizure control in temporal lobe low-grade gliomas.

OBJECTIVE: Surgery is the mainstay of treatment for low-grade glioma (LGG)-related epilepsy. However, the goal of achieving both oncological radical resection and seizure freedom can be challenging. PET with [11C]methionine (MET) has been recently introduced in clinical practice for the management of patients with LGGs, not only to monitor the response to treatments, but also as a preoperative tool to define the metabolic tumor extent and to predict tumor grading, type, and prognosis. Still, its role in defining tumor-related epilepsy and postoperative seizure outcomes is limited. The aim of this preliminary study was to investigate the role of MET PET in defining preoperative seizure characteristics and short-term postoperative seizure control in a cohort of patients with newly diagnosed temporal lobe low-grade gliomas (tLGGs). METHODS: Patients with newly diagnosed and histologically proven temporal lobe grade 2/3 gliomas (2021 WHO CNS tumor classification) who underwent resection at the authors' institution between July 2011 and March 2021 were included in this retrospective study. MET PET images were acquired, fused with MRI scans, and qualitatively and semiquantitatively analyzed. Any eventual PET/MRI involvement of the temporomesial area, seizure characteristics, and 1-year seizure outcomes were reported. RESULTS: A total of 52 patients with tLGGs met the inclusion criteria. MET PET was positive in 41 (79%) patients, with a median metabolic tumor volume of 14.56 cm3 (interquartile range [IQR] 6.5-28.2 cm3). The median maximum and mean tumor-to-background ratio (TBRmax, TBRmean) were 2.24 (IQR 1.58-2.86) and 1.53 (IQR 1.37-1.70), respectively. The metabolic tumor volume was found to be related to the presence of seizures at disease onset, but only in noncodeleted tumors (p = 0.014). Regarding patients with uncontrolled seizures at surgery, only the temporomesial area PET involvement showed a statistical correlation both in the univariate (p = 0.058) and in the multivariate analysis (p = 0.030). At 1-year follow-up, seizure control was correlated with MET PET-derived semiquantitative data. Particularly, higher TBRmax (p = 0.0192) and TBRmean (p = 0.0128) values were statistically related to uncontrolled seizures 1 year after surgery. CONCLUSIONS: This preliminary study suggests that MET PET may be used as a preoperative tool to define seizure characteristics and outcomes in patients with tLGGs. These findings need to be further validated in larger series with longer epileptological follow-ups.

Clinical utility and safety of a trapezoid-shaped electrode placement for evaluating the mesio-basal temporal lobe during epilepsy surgery.

A trapezoid-shaped electrode (TSE) is used for detecting epileptogenicity in patients with temporal lobe epilepsy (TLE). However, the utility and safety associated with TSE placement have not been reported. In this study, we evaluated the safety and usefulness of TSE by analyzing the seizure detection, surgical outcomes and complications in patients with TLE who underwent intracranial electrodes (ICE) placement. Between April 2000 and August 2019, 50 patients with TLE who underwent 51 ICE placement procedures were examined. A TSE with eight contacts covering the parahippocampal gyrus and basal temporal lobe was used. Among the 37 patients who underwent TSE placement, 26 and 11 patients were diagnosed with mesial TLE (mTLE) and extra-mTLE, respectively. The 14 remaining patients without TSE placement were diagnosed with extra-mTLE. Seizure freedom was achieved in 73% (19/26) of mTLE patients detected by TSE and 50% (14/24) of extra-mTLE patients.Good seizure outcomes (Engel class I and II) were observed in 81% (21/26) patients with mTLE and 67% (16/24) patients with extra-mTLE. Radiographic complications were observed in 20% (10/50) patients who underwent ICE placement. Although 6% (3/50) patients showed transient neurological deficits, none were permanent. The electrodes responsible for the occurrence of complications included nine grid electrodes and one TSE. The complication rate after TSE placement was 3% (1/37). More than 64 electrode contacts and male sex, not TSE placement, were identified as significant risk factors for developing complications. This study demonstrated the usefulness and safety of TSE for evaluating mTLE in patients undergoing ICE placement.

Impairment of unconscious emotional processing after unilateral medial temporal structure resection.

The role of the amygdala in unconscious emotional processing remains a topic of debate. Past lesion studies have indicated that amygdala damage leads to impaired electrodermal activity in response to subliminally presented emotional stimuli. However, electrodermal activity can reflect both emotional and nonemotional processes. To provide behavioral evidence highlighting the critical role of the amygdala in unconscious emotional processing, we examined patients (n = 16) who had undergone unilateral resection of medial temporal lobe structures, including the amygdala. We utilized the subliminal affective priming paradigm in conjunction with unilateral visual presentation. Fearful or happy dynamic facial expressions were presented in unilateral visual fields for 30 ms, serving as negative or positive primes. Subsequently, neutral target faces were displayed, and participants were tasked with rating the valence of these targets. Positive primes, compared to negative ones, enhanced valence ratings of the target to a greater extent when they stimulated the intact hemisphere (i.e., were presented in the contralateral visual field of the intact hemisphere) than when they stimulated the resected hemisphere (i.e., were presented in the contralateral visual field of the resected hemisphere). These results suggest that the amygdala is causally involved in unconscious emotional processing.

Defining the Temporal and Occipital Lobes: Cadaveric Study with Application to Neurosurgery of the Inferior Brain.

BACKGROUND: For surgical interventions, a precise understanding of the anatomical variations of the brain and defined anatomical landmarks to demarcate the regions of the temporal lobe is essential. Many anatomical studies have facilitated important surgical approaches to the temporobasal region. Because there is considerable sulcal variability, morphological analysis of the brain is imperative. The aim of this study was to define the boundaries of the temporal and occipital lobes and to define the variations in sulci and gyri in the inferior aspect. METHODS: In 110 cerebral hemispheres variations were identified and the major landmarks of the gyral-sulcal pattern at the inferior aspect of the brain were defined. RESULTS: The anatomy of the inferior aspect of the brain is defined in detail by morphological analysis of formalin-fixed hemispheres with a view to informing important surgical approaches. CONCLUSIONS: Since the literature defines no clear separation between the temporal and occipital lobes, certain landmarks such as the preoccipital notch and a basal temporo-occipital line were suggested as ways of making the distinction. The parahippocampal ramus is a constant structure that can be used as a reliable landmark for the posterior end of the hippocampus.

Semiautomated electric source imaging determines epileptogenicity of encephaloceles in temporal lobe epilepsy.

OBJECTIVE: We aimed to assess the ability of semiautomated electric source imaging (ESI) from long-term video-electroencephalographic (EEG) monitoring (LTM) to determine the epileptogenicity of temporopolar encephaloceles (TEs) in patients with temporal lobe epilepsy. METHODS: We conducted a retrospective study involving 32 temporal lobe epilepsy patients with TEs as potentially epileptogenic lesions in structural magnetic resonance imaging scans. Findings were validated through invasive intracerebral stereo-EEG in six of 32 patients and postsurgical outcome after tailored resection of the TE in 17 of 32 patients. LTM (mean duration = 6 days) was performed using the 10/20 system with additional T1/T2 for all patients and sphenoidal electrodes in 23 of 32 patients. Semiautomated detection and clustering of interictal epileptiform discharges (IEDs) were carried out to create IED types. ESI was performed on the averages of the two most frequent IED types per patient, utilizing individual head models, and two independent inverse methods (sLORETA [standardized low-resolution brain electromagnetic tomography], MUSIC [multiple signal classification]). ESI maxima concordance and propagation in spatial relation to TEs were quantified for sources with good signal quality (signal-to-noise ratio > 2, explained signal > 60%). RESULTS: ESI maxima correctly colocalized with a TE in 20 of 32 patients (62.5%) either at the onset or half-rising flank of at least one IED type per patient. ESI maxima showed propagation from the temporal pole to other temporal or extratemporal regions in 14 of 32 patients (44%), confirming propagation originating in the area of the TE. The findings from both inverse methods validated each other in 14 of 20 patients (70%), and sphenoidal electrodes exhibited the highest signal amplitudes in 17 of 23 patients (74%). The concordance of ESI with the TE predicted a seizure-free postsurgical outcome (Engel I vs. >I) with a diagnostic odds ratio of 2.1. SIGNIFICANCE: Semiautomated ESI from LTM often successfully identifies the epileptogenicity of TEs and the IED onset zone within the area of the TEs. Additionally, it shows potential predictive power for postsurgical outcomes in these patients.

Pearls & Oy-sters: Mesial Temporal Seizures in the Absence of the Mesial Temporal Lobe. Seizure Onset vs Seizure Network

Seizure semiology represents the clinical expression of the activation of the several brain regions comprising an epileptic network. In mesial temporal lobe epilepsy (MTLE), this network includes the insular-opercular-neocortical temporal-hippocampal (IONTH) regions. In this study, we present the case of a patient with pharmacoresistant seizures characterized by nausea, lip-smacking, semipurposeful hand movements, and speechlessness, suggesting dominant hemisphere MTLE, with scalp video-EEG findings and left hippocampal sclerosis on brain MRI confirming the diagnosis. She underwent anterior temporal lobectomy with amygdalohippocampectomy and was seizure-free for 14 years before relapsing. Recurrent seizure semiology was similar to preoperative seizures, that is, consistent with left MTLE, despite the medial temporal lobe missing. Seizures were therefore assumed to arise from remnant portions of the IONTH network-the insula, operculum, and posterolateral temporal neocortex. Reinvestigation including MEG localization of spikes and acute MRI changes following a seizure cluster suggested a left opercular region epilepsy. Our patient thus demonstrated the principle that seizures with mesial temporal characteristics may arise from outside the mesial temporal lobe (MTL). MTLE semiology arises from the activation of a set of structures (the seizure network) associated with the MTL, which can be triggered by foci both within and outside the MTL itself, and indeed even in its absence. However, it is not necessary to resect the entire extended network to bring about extended periods of seizure freedom in patients with refractory MTLE.

Disruption of the left anterior ventrolateral temporal cortex along with the inferior longitudinal fasciculus impairs the ability to retrieve famous face names: Evidence from three longitudinal case studies.

The cortical distribution of the proper name (PN) retrieval network has been widely studied contrary to its connectional anatomy. Here, we report the case of three patients with a low-grade glioma damaging the mid-to-anterior part of the left temporal lobe. A longitudinal behavioural assessment showed that the surgery caused a long-lasting decline in PN retrieval performances in all patients. Furthermore, a detailed analysis of surgery-related structural disconnections revealed that interruption of the inferior longitudinal fasciculus was the unique common denominator.

Investigating the effect of hippocampal sclerosis on parietal memory network.

OBJECTIVE: We aimed to investigate differences in episodic memory networks between patients with temporal lobe epilepsy (TLE) due to hippocampal sclerosis and healthy controls, especially with regards to the parietal memory network (PMN), as well as their relation to neuropsychological memory performance after mesial temporal resection. METHODS: 28 healthy subjects as well as 21 patients with TLE (12 left, 9 right) were investigated using a spatial memory fMRI paradigm, which has been shown to activate the PMN. Regions of interest (ROI) were defined based on the results of the second-level analyses and activations within the predefined ROIs were compared across groups and correlated with postoperative verbal and nonverbal memory scores. RESULTS: Healthy subjects showed activations within regions belonging to the dorsal visual stream and the PMN as well as the bilateral parahippocampal place area, the bilateral frontal eye field, and the bilateral middle frontal gyrus. Comparison between groups revealed that TLE patients activated significantly less in the left middle occipital gyrus and the right precuneus. The activation pattern in left TLE patients showed further reductions, mainly in areas belonging to the dorsal visual stream and the PMN within the left hemisphere. Activations within the left superior parietal lobulus, bilateral inferior parietal lobulus, bilateral middle temporal gyrus, left precuneus, left frontal eye field, and left middle frontal gyrus correlated significantly with postoperative verbal memory scores, and activations within the left superior parietal lobulus, left inferior parietal lobulus, left middle temporal gyrus, and left precuneus correlated significantly with higher performance in postoperative nonverbal memory scores. SIGNIFICANCE: The PMN is involved in episodic memory encoding. Higher activations in areas belonging to the PMN and the dorsal visual stream, especially within the left hemisphere, before amygdalohippocampectomy may result in higher postoperative memory scores. PLAIN LANGUAGE SUMMARY: This study aims to investigate the effects of epilepsy due to hippocampal sclerosis, i.e. scarring in the temporal lobe, on memory networks in the brain. We discovered that especially patients with left-sided hippocampal sclerosis show reduced brain activations in visual areas and memory networks within the left hemisphere of the brain during orientation in space. Importantly, higher activations within these areas may result in better memory after epilepsy surgery.

MRI evidence for material-specific encoding deficits and mesial-temporal alterations in presurgical frontal lobe epilepsy patients.

OBJECTIVE: Neuroimaging studies reveal frontal lobe (FL) contributions to memory encoding. Accordingly, memory impairments are documented in frontal lobe epilepsy (FLE). Still, little is known about the structural or functional correlates of such impairments. Particularly, material specificity of functional changes in cerebral activity during memory encoding in FLE is unclear. METHODS: We compared 24 FLE patients (15 right-sided) undergoing presurgical evaluation with 30 healthy controls on a memory fMRI-paradigm of learning scenes, faces, and words followed by an out-of-scanner recognition task as well as regarding their mesial temporal lobe (mTL) volumes. We also addressed effects of FLE lateralization and performance level (normal vs. low). RESULTS: FLE patients had poorer memory performance and larger left hippocampal volumes than controls. Volume increase seemed, however, irrelevant or even dysfunctional for memory performance. Further, functional changes in FLE patients were right-sided for scenes and faces and bilateral for words. In detail, during face encoding, FLE patients had, regardless of their performance level, decreased mTL activation, while during scene and word encoding only low performing FLE patients had decreased mTL along with decreased FL activation. Intact verbal memory performance was associated with higher right frontal activation in FLE patients but not in controls. SIGNIFICANCE: Pharmacoresistant FLE has a distinct functional and structural impact on the mTL. Effects vary with the encoded material and patients' performance levels. Thus, in addition to the direct effect of the FL, memory impairment in FLE is presumably to a large part due to functional mTL changes triggered by disrupted FL networks. PLAIN LANGUAGE SUMMARY: Frontal lobe epilepsy (FLE) patients may suffer from memory impairment. Therefore, we asked patients to perform a memory task while their brain was scanned by MRI in order to investigate possible changes in brain activation during learning. FLE patients showed changes in brain activation during learning and also structural changes in the mesial temporal lobe, which is a brain region especially relevant for learning but not the origin of the seizures in FLE. We conclude that FLE leads to widespread changes that contribute to FLE patients' memory impairment.