Physiology of human cortical neurons adjacent to cavernous malformations and tumors

Kindling in humans: Does secondary epileptogenesis occur?

The relevance of secondary epileptogenesis for human epilepsy remains a controversial subject decades after it was first described in animal models. Whether or not a previously normal brain region can become independently epileptogenic through a kindling-like process has not, and cannot, be definitely proven in humans. Rather than reliance on direct experimental evidence, attempts to answering this question must depend on observational data. In this review, observations based largely upon contemporary surgical series will advance the case for secondary epileptogenesis in humans. As will be argued, hypothalamic hamartoma-related epilepsy provides the strongest case for this process; all the stages of secondary epileptogenesis can be observed. Hippocampal sclerosis (HS) is another pathology where the question of secondary epileptogenesis frequently arises, and observations from bitemporal and dual pathology series are explored. The verdict here is far more difficult to reach, in large part because of the scarcity of longitudinal cohorts; moreover, recent experimental data have challenged the claim that HS is acquired consequent to recurrent seizures. Synaptic plasticity more than seizure-induced neuronal injury is the likely mechanism of secondary epileptogenesis. Postoperative running-down phenomenon provides the best evidence that a kindling-like process occurs in some patients, evidenced by its reversal. Finally, a network perspective of secondary epileptogenesis is considered, as well as the possible role for subcortical surgical interventions.

Synaptic alterations and neuronal firing in human epileptic neocortical excitatory networks

Epilepsy is a prevalent neurological condition, with underlying neuronal mechanisms involving hyperexcitability and hypersynchrony. Imbalance between excitatory and inhibitory circuits, as well as histological reorganization are relatively well-documented in animal models or even in the human hippocampus, but less is known about human neocortical epileptic activity. Our knowledge about changes in the excitatory signaling is especially scarce, compared to that about the inhibitory cell population. This study investigated the firing properties of single neurons in the human neocortex in vitro, during pharmacological blockade of glutamate receptors, and additionally evaluated anatomical changes in the excitatory circuit in tissue samples from epileptic and non-epileptic patients. Both epileptic and non-epileptic tissues exhibited spontaneous population activity (SPA), NMDA receptor antagonization reduced SPA recurrence only in epileptic tissue, whereas further blockade of AMPA/kainate receptors reversibly abolished SPA emergence regardless of epilepsy. Firing rates did not significantly change in excitatory principal cells and inhibitory interneurons during pharmacological experiments. Granular layer (L4) neurons showed an increased firing rate in epileptic compared to non-epileptic tissue. The burstiness of neurons remained unchanged, except for that of inhibitory cells in epileptic recordings, which decreased during blockade of glutamate receptors. Crosscorrelograms computed from single neuron discharge revealed both mono- and polysynaptic connections, particularly involving intrinsically bursting principal cells. Histological investigations found similar densities of SMI-32-immunopositive long-range projecting pyramidal cells in both groups, and shorter excitatory synaptic active zones with a higher proportion of perforated synapses in the epileptic group. These findings provide insights into epileptic modifications from the perspective of the excitatory system and highlight discrete alterations in firing patterns and synaptic structure. Our data suggest that NMDA-dependent glutamatergic signaling, as well as the excitatory synaptic machinery are perturbed in epilepsy, which might contribute to epileptic activity in the human neocortex.

Incidence of Cerebral Cavernous Malformation-Related Epilepsy in Children: A Single Center Survey

INTRODUCTION

Cerebral cavernous malformations (CCMs) are rare developmental cerebrovascular malformations. The risk of epilepsy is high in patients with CCMs, but the incidence of epilepsy has not been reported in a pure pediatric population. We herein present 14 pediatric cases of CCMs, including five with CCM-related epilepsy, and examine the incidence of CCM-related epilepsy in this pediatric population.  Methods: Pediatric patients with CCMs who visited our Hospital between November 1, 2001, to September 31, 2020, were retrospectively screened for inclusion, and 14 were enrolled.  Results: Fourteen enrolled patients were divided into two groups based on the presence or absence of CCM-related epilepsy. The "CCM-related epilepsy group" (n = 5) consisted of five males with a median age of 4.2 (range: 0.3-8.5) years at the first visit. The "non-epilepsy group" (n = 9) consisted of seven males and two females with a median age of 3.5 (range: 1.3-11.5) years at the first visit. The prevalence of CCM-related epilepsy at the time of the present analysis was 35.7%. Follow-up periods in CCM-related epilepsy and non-epilepsy groups were 19.3 and 24.9 patient-years, respectively: the incidence was 11.3% per patient-years. The frequency of seizures due to intra-CCM hemorrhage as the primary symptom was significantly higher in the CCM-related epilepsy group than in the non-CCM-related epilepsy group (p = 0.01). Other clinical characteristics, i.e., primary symptoms including vomiting/nausea and spastic paralysis, magnetic resonance imaging findings, including the number or maximum diameter of CCMs, cortical involvement, intra-CCM hemorrhage, and infratentorial lesions, surgical resection, and non-epileptic sequelae, such as motor disability and intellectual disability, did not significantly differ between the groups.  Discussion: The incidence of CCM-related epilepsy in the present study was 11.3% per patient year, higher than in adults. This discrepancy may be attributed to these studies including both adult and pediatric patients, whereas the present study examined a pure pediatric population. The presence of seizures due to intra-CCM hemorrhage as the initial symptom was a risk factor for CCM-related epilepsy in the present study. To elucidate the pathophysiology of CCM-related epilepsy or the reason for its higher incidence in children than in adults, further analyses of a large number of children with CCM-related epilepsy are warranted.

Epilepsy-related white matter network changes in patients with frontal lobe glioma

PURPOSE

Epilepsy is a common symptom in patients with frontal lobe glioma. Tumor-related epilepsy was recently considered a type of network disease. Glioma can severely influence the integrity of the white matter network. The association between white matter network changes and presurgical epilepsy remains unclear in glioma patients. This study aims to identify alterations to the subcortical brain networks caused by glioma and glioma-related epilepsy.

METHODS

Sixty-one patients with frontal lobe gliomas were enrolled and stratified into the epileptic and non-epileptic groups. Additionally, 14 healthy participants were enrolled after matching for age, sex, and education level. All participants underwent diffusion tensor imaging. Graph theoretical analysis was applied to reveal topological changes in their white matter networks. Regions affected by tumors were excluded from the analysis.

RESULTS

Global efficiency was significantly decreased (p = 0.008), while the shortest path length increased (p = 0.02) in the left and right non-epileptic groups compared to the controls. A total of five edges exhibited decreased fiber count in the non-epileptic group (p < 0.05, false discovery rate-corrected). The topological properties and connectional edges showed no significant differences when comparing the epileptic groups and the controls. Additionally, the degree centrality of several nodes connected to the alternated edges was also diminished.

CONCLUSIONS

Compared to the controls, the epilepsy groups showed raletively intact WM networks, while the non-epileptsy groups had damaged network with lower efficiency and longer path length. These findings indicated that the occurrence of glioma related epilepsy have association with white matter network intergrity.

Unexpected median SEPs fluctuations during brain cavernous malformation resection with no post-operative deficit

Median nerve somatosensory evoked potentials (SEPs) may present changes during cavernous malformation (CM) resection unrelated to new post-operative sensory deficits. We performed intraoperative neurophysiological monitoring of median SEPs (m-SEPs) in three patients who underwent CM resection (surgery) near the sensory-motor cortex. The only preoperative clinical manifestations in all patients were seizures. All patients presented m-SEPs alterations on the side of the lesion during the procedure. Two patients presented permanent changes in the cortical potentials. In the third patient, the cortical and subcortical components suffered temporal fluctuations to return to baselines at the end of the surgery. None of these patients developed new post-operative clinical deficits. During brain cavernous malformation resection, significant fluctuations in the amplitude of different components of m-SEPs may occur. These changes may be due to excitability variations on m-SEP generators and do not translate into new post-operative neurological deficits.

Clinical characteristics and risk factors of cerebral cavernous malformation-related epilepsy

PURPOSE

This study aimed to summarize the clinical characteristics and explore the risk factors for cerebral cavernous malformation (CCM)-related epilepsy (CRE).

METHODS

We retrospectively analyzed the clinical data of patients with CCM in our cerebral vascular malformations database. Descriptive statistics were used to present the clinical characteristics of CRE patients. Patients were divided into a CRE and a non-CRE group according to clinical presentation. Binary logistic regression analysis was used to analyze the risk factors of CRE.

RESULTS

A total of 199 patients with CCM confirmed by postoperative pathological examination were enrolled, 93 of whom were diagnosed with CRE, and 34 patients had drug-resistant epilepsy. The most common seizure type of CRE patients was focal to bilateral tonic-clonic seizure (FBTCS), followed by focal impaired awareness motor seizure. All CCM lesions were supratentorial, 97.8% of which involved the cerebral cortex, 86.0% of lesions had hemosiderin rim, and 50.5% of lesions were located in the temporal lobe. Binary logistic regression analysis indicated that CCM diagnosis age ≤ 44 years (odds ratio [OR] 2.79, p = 0.010), temporal lobe lesion location (OR = 9.07, p = 0.042), medial temporal lobe lesion (OR = 14.09, p = 0.002), cortical involvement of the lesion (OR = 32.77, p = 0.010), and hemosiderin rim around the lesion (OR = 16.48, p = 0.001) significantly increased the risk of CRE.

CONCLUSIONS

The most common seizure type of CRE was FBTCS. Those whose CCM diagnosis age was ≤ 44 years, having a temporal lobe lesion location, especially the medial temporal lobe lesion, cortical involvement, and hemosiderin rim around the lesion had a higher risk of developing CRE.

Evaluating the Role of Perilesional Tissue in Pathobiology of Epileptogenesis of Vascular Malformations of the Central Nervous System

Background and Purpose

Seizures are common presentation of cerebral vascular malformation (CVM). Topography and haemodynamic alterations are proposed as mechanisms for epileptogenesis, but the role of glial/neuronal alterations in perilesional tissue has not received much attention. Identification of the exact pathophysiologic basis could have therapeutic implications. To evaluate whether angioarchitectural factors of CVM or alterations in neuroglial/stroma of the adjacent cortex contribute to seizures.

Method

The clinical, imaging and histological characteristics of arteriovenous malformation (AVM) and cerebral cavernous malformation (CCM) with and without seizures was evaluated using neuroimaging imaging and digital subtraction angiography parameters and histopathology by morphology and immunohistochemistry.

Results

Fifty-six cases of CVM were diagnosed over a 2-year study period. Of these, 32 had adequate perilesional tissue for evaluation (AVM, 24; CCM, 8). Seizures at presentation was seen in 12/24 (50%) of AVM and 5/8 (62.5%) CCM. In AVM, hemosiderin deposition and gliosis in parenchyma (p=0.01) had significant association with seizure. Siderotic vessels in the adjacent cortex was exclusively seen only in CCM with seizures (p=0.018). Angioarchitectural features of CVM on imaging and neuronal alterations in adjacent cortex on histology failed to show any statistically significant difference between the two groups (p>0.05).

Conclusions

We propose that changes in adjacent cortex appear to be epileptogenic rather than the malformation per se. Reactive gliosis and hemosiderin deposits in perilesional tissue in AVM and siderotic vessels in CCM were associated with seizure. This explains the better outcomes following extended lesionectomy that includes epileptogenic perilesional tissues.

Clinical characteristics and long-term outcome of cerebral cavernous malformations-related epilepsy

OBJECTIVE

Cerebral cavernous malformations (CCMs) present variably and epileptic seizures are the most common symptom. The factors contributing to cavernoma-related epilepsy (CRE) and drug resistance remain inconclusive. The outcomes of CRE after different treatment modalities have not yet been fully addressed. This study aimed to characterize the clinical features of patients with CRE and the long-term seizure outcomes of medical and surgical treatment strategies.

METHODS

This was a retrospective cohort of 135 patients with CCM who were diagnosed in 2007~2011 and followed up for 93.6 months on average. The patients were divided into drug-resistant epilepsy (DRE) (n = 29), non-DRE (NDRE) (n = 45), and no epilepsy (NE) (n = 61).

RESULTS

Temporal CCM was the factor most strongly associated with the development of both CRE and DRE. The majority of patients with single temporal CCMs had CRE (86.8%, n = 33) and 50% had DRE, whereas only 14.7% (n = 5) with a non-temporal supratentorial CCM had DRE (P < 0.05). The most common lesion site in the DRE group was the mesiotemporal lobe (50%). Multiple CCMs were more frequently observed in the CRE (29.2%) than the NE (11.5%) group (P < 0.05). In patients with CRE, multiple lesions were associated with a higher rebleeding rate (odds ratio: 11.1), particularly in those with DRE (odds ratio: 15.4). The majority of patients who underwent resective surgery for DRE (76.5%, n = 13) achieved ILAE class I and II seizure outcomes even after a long disease course.

SIGNIFICANCE

Temporal CCM not only predisposes to CRE but is also a major risk factor for drug resistance. The mesiotemporal lobe is the most epileptogenic zone. Multiple CCMs are another risk factor for CRE and increase the rebleeding risk in these patients. Surgical resection could provide beneficial long-term seizure outcomes in patients with DRE.

Angioarchitectural features of brain arteriovenous malformation presented with seizures

Seizures are the second most common manifestations of brain arteriovenous malformations (bAVMs). This study was conducted to investigate the clinical and angioarchitectural features of bAVMs with seizures and provide guidelines for the clinical management of these patients. We collected clinical and radiological data on patients with bAVMs diagnosed by digital subtraction angiography between January 2013 and December 2020 and dichotomized the patients into the seizures and non-seizures groups. We identified differences in demographic and angiographic features. Logistic regression and random forest (RF) models were developed and compared. The diagnostic capacity was assessed using receiver operating characteristic (ROC) curves. A nomogram was constructed, and the clinical impact was determined by decision curve analysis. A total of 414 patients with bAVMs were included in the analysis, of which 78 (18.8%) had bAVM-related seizures. In the multivariable logistic regression model, the location and side of bAVMs were independently associated with seizures. In RF models, the maximal diameter of veins and the cross-sectional area of feeding arteries and draining veins were the most important features. ROC curves showed that the RF model was not better than MLR in predicting seizures. Decision curve analysis revealed that the use of a constructed nomogram to stratify the seizure patients was beneficial at all threshold probabilities in our study. The side and location of bAVMs are specific angioarchitectural features independently associated with the occurrences of seizures with bAVMs.

Bursting of excitatory cells is linked to interictal epileptic discharge generation in humans

Knowledge about the activity of single neurons is essential in understanding the mechanisms of synchrony generation, and particularly interesting if related to pathological conditions. The generation of interictal spikes—the hypersynchronous events between seizures—is linked to hyperexcitability and to bursting behaviour of neurons in animal models. To explore its cellular mechanisms in humans we investigated the activity of clustered single neurons in a human in vitro model generating both physiological and epileptiform synchronous events. We show that non-epileptic synchronous events resulted from the finely balanced firing of excitatory and inhibitory cells, which was shifted towards an enhanced excitability in epileptic tissue. In contrast, interictal-like spikes were characterised by an asymmetric overall neuronal discharge initiated by excitatory neurons with the presumptive leading role of bursting pyramidal cells, and possibly terminated by inhibitory interneurons. We found that the overall burstiness of human neocortical neurons is not necessarily related to epilepsy, but the bursting behaviour of excitatory cells comprising both intrinsic and synaptically driven bursting is clearly linked to the generation of epileptiform synchrony.

Topological Characteristics Associated with Intraoperative Stimulation Related Epilepsy of Glioma Patients: A DTI Network Study

Background: Awake craniotomy with intraoperative stimulation has been utilized in glioma surgical resection to preserve the quality of life. Epilepsy may occur in 5–20% of cases, leading to severe consequences. This study aimed to discuss the mechanism of intraoperative stimulation-related epilepsy (ISE) using DTI-based graph theoretical analysis. Methods: Twenty patients with motor-area glioma were enrolled and divided into two groups (Ep and nEp) according to the presence of ISE. Additionally, a group of 10 healthy participants matched by age, sex, and years of education was also included. All participants underwent T1, T2, and DTI examinations. Graph theoretical analysis was applied to reveal the topological characteristics of white matter networks. Results: Three connections were found to be significantly lower in at least one weighting in the Ep group. These connections were between A1/2/3truL and A4ulL, A1/2/3truR and A4tR, and A6mL and A6mR. Global efficiency was significantly decreased, while the shortest path length increased in the Ep group in at least one weighting. Ten nodes exhibited significant differences in nodal efficiency and degree centrality analyses. The nodes A6mL and A6mR showed a marked decrease in total four weightings in the Ep group. Conclusions: The hub nodes A6mL and A6mR are disconnected in patients with ISE, causing subsequent lower efficiency of global and regional networks. These findings provide a basis for presurgical assessment of ISE, for which caution should be taken when it involves hub nodes during intraoperative electrical stimulation.

Acute Seizures in Cerebral Venous Sinus Thrombosis: Risk Factors and Prognosis

BACKGROUND

Cerebral venous sinus thrombosis (CVST) often presents with acute seizures, and recurrent seizures may also be seen in the long term in some patients. The purpose of this retrospective study was to investigate the frequency and type of acute seizures and to define the risk factors.

METHODS

Sixty-two patients diagnosed with CVST between September 2007 and October 2018 were retrospectively evaluated for the occurrence of acute seizures. Seizures which developed as a presenting symptom or occurred within 2 weeks of diagnosis were defined as acute seizures. Demographic, clinical, and radiologic characteristics were compared between patients with or without acute seizures.

RESULTS

Twenty (32.3%) of the 62 CVST patients had acute seizures. Univariate analysis revealed a significant association between acute seizures and aphasia (P=0.03), motor deficit (P<0.001), sensory deficit (P=0.018), severe (≥3) modified Rankin Scale scores on admission (P=0.017), sagittal sinus thrombosis (P=0.037), cortical vein thrombosis (P<0.001), supratentorial lesions (P<0.001), and hemorrhagic lesions (P<0.001). Multivariate regression analysis identified supratentorial lesions (P=0.015, odds ratio: 9.131, 95% confidence interval: 1.525-54.687) and cortical vein thrombosis (P=0.034, odds ratio: 5.802, 95% confidence interval: 1.146-29.371) as independent factors for acute seizures. Although 25% of patients with acute seizures had recurrent seizures during hospitalization, only 2.6% of the 38 patients with long-term follow-up had recurrent seizures.

CONCLUSIONS

Approximately one third of patients with CVST had acute seizures. Cortical vein thrombosis, supratentorial, and especially hemorrhagic lesions were the most significant risk factors associated with acute seizures. Although seizure recurrence may occur early in the course, long-term recurrence is rare in CVST.

Epilepsy-Related Outcomes in Children With Neonatal Cerebellar Injury

OBJECTIVE

Acute brain injury is a frequent perinatal neurologic complication that can involve the cerebellum. Although short-term outcomes of infants with neonatal cerebellar injury are well described, neurologic sequelae in older children are underreported. Here, we describe epilepsy-related outcomes in young children who suffered from neonatal cerebellar injuries.

METHODS

In-house automated software identified patients with neonatal brain injuries who were evaluated at our institution both as neonates (≤28 days) and as children (≥1 year). Neonatal hospital course, neuroimaging, and outcomes related to epilepsy were reviewed from the medical record. Patients were stratified into 2 groups based on neonatal brain injuries: those with cerebellar injury and those without cerebellar involvement.

RESULTS

Of the 282 neonates followed through childhood over the decade-long study period, 33 (12%) experienced neonatal brain injury. All 33 cases involved supratentorial injury, and 5 (15%) also included cerebellar injury. The development of epilepsy was significantly less likely in the group with cerebellar involvement (40%) compared to that with cerebellar sparing (82%; P = 0.043). In some cases, children with cerebellum-sparing injuries required admission for seizure control and developed drug-resistant epilepsy as well as status epilepticus. These outcomes occurred less frequently in the group with cerebellar involvement.

CONCLUSIONS

Epilepsy-related sequelae may occur less frequently when the cerebellum is involved in neonatal brain injury. Larger prospective studies are needed to clarify how cerebellocortical networks impact functional brain connectivity and epilepsy longitudinally.

Presence of synchrony-generating hubs in the human epileptic neocortex

KEY POINTS

•Initiation of pathological synchronous events such as epileptic spikes and seizures is linked to the hyperexcitability of the neuronal network in both humans and animals. •In the present study, we show that epileptiform interictal-like spikes and seizures emerged in human neocortical slices by blocking GABA_A receptors, following the disappearance of the spontaneously occurring synchronous population activity. •Large variability of temporally and spatially simple and complex spikes was generated by tissue from epileptic patients, whereas only simple events appeared in samples from non-epileptic patients. •Physiological population activity was associated with a moderate level of principal cell and interneuron firing, with a slight dominance of excitatory neuronal activity, whereas epileptiform events were mainly initiated by the synchronous and intense discharge of inhibitory cells. •These results help us to understand the role of excitatory and inhibitory neurons in synchrony-generating mechanisms, in both epileptic and non-epileptic conditions.

ABSTRACT

Understanding the role of different neuron types in synchrony generation is crucial for developing new therapies aiming to prevent hypersynchronous events such as epileptic seizures. Paroxysmal activity was linked to hyperexcitability and to bursting behaviour of pyramidal cells in animals. Human data suggested a leading role of either principal cells or interneurons, depending on the seizure morphology. In the present study, we aimed to uncover the role of excitatory and inhibitory processes in synchrony generation by analysing the activity of clustered single neurons during physiological and epileptiform synchronies in human neocortical slices. Spontaneous population activity was detected with a 24-channel laminar microelectrode in tissue derived from patients with or without preoperative clinical manifestations of epilepsy. This population activity disappeared by blocking GABA_A receptors, and several variations of spatially and temporally simple or complex interictal-like spikes emerged in epileptic tissue, whereas peritumoural slices generated only simple spikes. Around one-half of the clustered neurons participated with an elevated firing rate in physiological synchronies with a slight dominance of excitatory cells. By contrast, more than 90% of the neurons contributed to interictal-like spikes and seizures, and an intense and synchronous discharge of inhibitory neurons was associated with the start of these events. Intrinsically bursting principal cells fired later than other neurons. Our data suggest that a balanced excitation and inhibition characterized physiological synchronies, whereas disinhibition-induced epileptiform events were initiated mainly by non-synaptically synchronized inhibitory neurons. Our results further highlight the differences between humans and animal models, and between in vivo and (pharmacologically manipulated) in vitro conditions.

Neurovascular Lesions in Pediatric Epilepsy

INTRODUCTION

Neurovascular lesions are rare and understudied in the pediatric population. Their initial presentation can range from seizures to focal neurologic deficits, as well as headaches. The goal of this study was to examine the clinical presentation and natural history of neurovascular lesions in children with epilepsy.

METHODS

We reviewed all pediatric epilepsy patients with neurovascular lesions diagnosed between 2006 and 2018 at the University of Alberta and the Stollery Children's Hospital, Edmonton, Canada. Initial clinical presentation and brain imaging, as well as long-term epilepsy and postsurgical outcome, were assessed.

RESULTS

Of the 14 patients, 10 patients had an initial presentation of focal seizures with impaired awareness, whereas 2 patients presented with headache, 1 presented with visual field defects as well as chronic headaches, and 1 with decreased level of consciousness. Seven patients had cavernous angiomas, 6 had arteriovenous malformation, and 1 patient had an arteriovenous fistula. Notably, all patients with cavernous angiomas and 4 of 6 patients with arteriovenous malformations presented with seizures. Among 9 of the 14 who underwent neurovascular corrective surgery, all 9 patients required long-term antiepileptic treatment of at least 1 antiepileptic drug for seizure control after the operation.

CONCLUSION

In this novel case series, we describe focal seizures as the initial presentation of pediatric neurovascular lesions. This clinical presentation appears to be independent of the type of neurovascular lesion. Furthermore, unlike our pediatric surgical patients with epilepsy due to other causes, seizure freedom following neurovascular surgery is limited, and patients require long-term antiepileptic treatment.

Predictors of Epileptic Seizures and Ability to Work in Supratentorial Cavernous Angioma Located Within Eloquent Brain Areas

BACKGROUND

The postoperative outcomes and the predictors of seizure control are poorly studied for supratentorial cavernous angiomas (CA) within or close to the eloquent brain area.

OBJECTIVE

To assess the predictors of preoperative seizure control, postoperative seizure control, and postoperative ability to work, and the safety of the surgery.

METHODS

Multicenter international retrospective cohort analysis of adult patients benefitting from a functional-based surgical resection with intraoperative functional brain mapping for a supratentorial CA within or close to eloquent brain areas.

RESULTS

A total of 109 patients (66.1% women; mean age 38.4 ± 12.5 yr), were studied. Age >38 yr (odds ratio [OR], 7.33; 95% confidence interval [CI], 1.53-35.19; P = .013) and time to surgery > 12 mo (OR, 18.21; 95% CI, 1.11-296.55; P = .042) are independent predictors of uncontrolled seizures at the time of surgery. Focal deficit (OR, 10.25; 95% CI, 3.16-33.28; P < .001) is an independent predictor of inability to work at the time of surgery. History of epileptic seizures at the time of surgery (OR, 7.61; 95% CI, 1.67-85.42; P = .003) and partial resection of the CA and/or of the hemosiderin rim (OR, 12.02; 95% CI, 3.01-48.13; P < .001) are independent predictors of uncontrolled seizures postoperatively. Inability to work at the time of surgery (OR, 19.54; 95% CI, 1.90-425.48; P = .050), Karnofsky Performance Status ≤ 70 (OR, 51.20; 95% CI, 1.20-2175.37; P = .039), uncontrolled seizures postoperatively (OR, 105.33; 95% CI, 4.32-2566.27; P = .004), and worsening of cognitive functions postoperatively (OR, 13.71; 95% CI, 1.06-176.66; P = .045) are independent predictors of inability to work postoperatively.

CONCLUSION

The functional-based resection using intraoperative functional brain mapping allows safe resection of CA and the peripheral hemosiderin rim located within or close to eloquent brain areas.

Imaging biomarkers of epileptogenecity after traumatic brain injury - Preclinical frontiers

Posttraumatic epilepsy (PTE) is a major neurodegenerative disease accounting for 20% of symptomatic epilepsy cases. A long latent phase offers a potential window for prophylactic treatment strategies to prevent epilepsy onset, provided that the patients at risk can be identified. Some promising imaging biomarker candidates for posttraumatic epileptogenesis have been identified, but more are required to provide the specificity and sensitivity for accurate prediction. Experimental models and preclinical longitudinal, multimodal imaging studies allow follow-up of complex cascade of events initiated by traumatic brain injury, as well as monitoring of treatment effects. Preclinical imaging data from the posttraumatic brain are rich in information, yet examination of their specific relevance to epilepsy is lacking. Accumulating evidence from ongoing preclinical studies in TBI support insight into processes involved in epileptogenesis, e.g. inflammation and changes in functional and structural brain-wide connectivity. These efforts are likely to produce both new biomarkers and treatment targets for PTE.

[Surgical treatment of epilepsy in patients with mediobasal temporal cavernous malformations]

OBJECTIVE

Epilepsy is a frequent clinical manifestation of cavernous malformations (CMs) of the mediobasal temporal region (MBTR). Surgical removal of CMs is an excellent technique for treating associated epilepsy and may range from pure lesionectomy to tailored resection of the temporal lobe.

PURPOSE

The study purpose was to determine the optimal surgical management for epilepsy in patients with CMs of the MBTR.

MATERIAL AND METHODS

We retrospectively analyzed the clinical data, neuroimaging findings, surgical techniques, and surgical outcomes in 11 patients with epilepsy and CMs of the MBTR. All patients underwent video-electroencephalography, magnetic resonance imaging, and computed tomography in the pre- and postoperative periods. Nine patients underwent preoperative implantation of foramen ovale electrodes. In all cases, surgery was accompanied by electrocorticography (ECoG).

RESULTS

CMs were located in the anterior MBTR in 7 cases, anterior and middle thirds of the MBTR in 1 case, middle third in 2 cases, and middle and posterior thirds in 1 case. In 8 patients, preoperative monitoring revealed a seizure onset area in the MBTR. These patients underwent cavernomectomy with ECoG-guided resection of the hemosiderin ring and adjacent tissue using the pterional (4 cases) or supracerebellar transtentorial approach (4). In 3 cases, anterior temporal lobectomy with cavernomectomy was additionally used due to spreading of pathological activity to the lateral temporal neocortex. Seizure control after surgery was excellent in 7 patients (class 1 ILAE) and good in 4 (class 2 ILAE).

CONCLUSION

Surgery in patients with epilepsy caused by CMs of the MBTR should be performed based on non-invasive and invasive presurgical evaluation. If the seizure onset area is located in the MBTR, lesionectomy with ECoG-guided resection of the adjacent temporal cortical areas can be performed using the pterional or supracerebellar transtentorial approach. Lateral spread of epileptic activity requires cavernomectomy and anterior temporal lobectomy.

Hyperexcitability of the network contributes to synchronization processes in the human epileptic neocortex

KEY POINTS

Hyperexcitability and hypersynchrony of neuronal networks are thought to be linked to the generation of epileptic activity in both humans and animal models. Here we show that human epileptic postoperative neocortical tissue is able to generate two different types of synchronies in vitro. Epileptiform bursts occurred only in slices derived from epileptic patients and were hypersynchronous events characterized by high levels of excitability. Spontaneous population activity emerged in both epileptic and non-epileptic tissue, with a significantly lower degree of excitability and synchrony, and could not be linked to epilepsy. These results help us to understand better the role of excitatory and inhibitory neuronal circuits in the generation of population events, and to define the subtle border between physiological and pathological synchronies.

ABSTRACT

Interictal activity is a hallmark of epilepsy diagnostics and is linked to neuronal hypersynchrony. Little is known about perturbations in human epileptic neocortical microcircuits, and their role in generating pathological synchronies. To explore hyperexcitability of the human epileptic network, and its contribution to convulsive activity, we investigated an in vitro model of synchronous burst activity spontaneously occurring in postoperative tissue slices derived from patients with or without preoperative clinical and electrographic manifestations of epileptic activity. Human neocortical slices generated two types of synchronies. Interictal-like discharges (classified as epileptiform events) emerged only in epileptic samples, and were hypersynchronous bursts characterized by considerably elevated levels of excitation. Synchronous population activity was initiated in both epileptic and non-epileptic tissue, with a significantly lower degree of excitability and synchrony, and could not be linked to epilepsy. However, in pharmacoresistant epileptic tissue, a higher percentage of slices exhibited population activity, with higher local field potential gradient amplitudes. More intracellularly recorded neurons received depolarizing synaptic potentials, discharging more reliably during the events. Light and electron microscopic examinations showed slightly lower neuron densities and higher densities of excitatory synapses in the human epileptic neocortex. Our data suggest that human neocortical microcircuits retain their functionality and plasticity in vitro, and can generate two significantly different synchronies. We propose that population bursts might not be pathological events while interictal-like discharges may reflect the epileptogenicity of the human cortex. Our results show that hyperexcitability characterizes the human epileptic neocortical network, and that it is closely related to the emergence of synchronies.

A predicted model for postoperative seizure outcomes after the surgical resection of supratentorial cavernous malformations

To explore a predicted model for postoperative seizure outcomes after the surgical resection of supratentorial cavernous malformations.This study was a retrospective review of consecutive patients with cerebral supratentorial cavernous malformations presenting with seizures. All patients underwent surgical resection of CCMs. Univariate and multivariate analyses were performed to determine the predictive value of the preoperative seizure frequency, seizure type, seizure duration, lesion location, lesion size, and the presence of residual hemosiderin.A total of 43 patients met the inclusion criteria. After a mean follow-up period of 40.95 months, 34 patients who were free from postoperative seizures were classified into Engel class I, and the remaining 9 patients were classified into Engel classes II-IV. A univariate analysis showed that the seizure frequency (χ = 13.440, P = 0.004) and seizure duration (χ = 5.145, P = 0.023) prior to surgery were associated with a worse postoperative seizure prognosis. Other covariates including age at onset, gender, a history of the medications taken, smoking status, family history, lesion characteristics, and the role of hemosiderin were not related to seizure outcomes. Logistic regression results demonstrated that the preoperative seizure frequency was an effective predictor (P = 0.004). The receiver operating characteristic curve indicated that area under the curve for the preoperative seizure frequency test was 0.833 (95% confidence interval 0.709-0.957, P = 0.002).The preoperative seizure frequency was a prognostic factor for postoperative seizure outcomes after surgical resection of supratentorial cavernous malformations. To obtain a favorable prognosis for CCM patients with preoperative seizures, early intervention might be a better choice.

The Role of Hemosiderin Excision in Seizure Outcome in Cerebral Cavernous Malformation Surgery: A Systematic Review and Meta-Analysis

Background and Purpose

Whether the excision of hemosiderin surrounding cerebral cavernous malformations (CCMs) is necessary to achieve a seizure-free result has been the subject of debate. Here, we report a systematic review of related literature up to Jan 1, 2015 including 594 patients to assess the effect of hemosiderin excision on seizure outcome in patients with CCMs by meta-analysis.

Methods

Ten studies comparing extended hemosiderin excision with only lesion resection were identified by searching the English-language literature. Meta-analyses, subgroup analyses and sensitivity analysis were conducted to determine the association between hemosiderin excision and seizure outcome after surgery.

Results

Seizure outcome was significantly improved in the patients who underwent an extended excision of the surrounding hemosiderin (OR, 0.62; 95% CI: 0.42–0.91; P = 0.01). In subgroup analysis, studies from Asia (OR, 0.42; 95% CI: 0.25–0.71; P = 0.001), male-majority (female ratio < 50%) studies (OR, 0.56; 95% CI: 0.33–0.96; P = 0.04), low occurrence rate of multiple CCMs (OR, 0.37; 95% CI: 0.20–0.71; P = 0.003), cohort studies (OR, 0.44; 95% CI: 0.28–0.68; P = 0.78), longer duration of seizure symptoms (> 1 year) before surgery (OR, 0.43; 95% CI: 0.22–0.84; P = 0.01), lesion diameter > 2 cm (OR, 0.41; 95% CI: 0.19–0.87; P = 0.02) and short-term (< 3 years) follow-up (OR, 0.48; 95% CI: 0.29–0.80; P = 0.005) tended to correlate with a significantly favorable outcome.

Conclusion

Patients who underwent extended surrounding hemosiderin excision could exhibit significantly improved seizure outcomes compared to patients without hemosiderin excision. However, further well-designed prospective multiple-center RCT studies are still needed.

Animal models of tumour-associated epilepsy

Brain tumours cause a sizeable proportion of epilepsies in adulthood, and actually can be etiologically responsible also for childhood epilepsies. Conversely, seizures are often first clinical signs of a brain tumour. Nevertheless, several issues of brain-tumour associated seizures and epilepsies are far from understood, or clarified regarding clinical consensus. These include both the specific mechanisms of epileptogenesis related to different tumour types, the possible relationship between malignancy and seizure emergence, the interaction between tumour mass and surrounding neuronal networks, and - not least - the best treatment options depending on different tumour types. To investigate these issues, experimental models of tumour-induced epilepsies are necessary. This review concentrates on the description of currently used models, focusing on methodological aspects. It highlights advantages and shortcomings of these models, and identifies future experimental challenges.

Treatment and outcome of epileptogenic temporal cavernous malformations

Background:

The aim of this study is to explore the treatment and outcome of epileptogenic temporal lobe cavernous malformations (CMs).

Methods:

We analyzed retrospectively the profiles of 52 patients diagnosed as temporal lobe CMs associated with epilepsy. Among the 52 cases, 11 underwent a direct resection of CM along with the adjacent zone of hemosiderin rim without electrocorticogram (ECoG) monitoring while the other 41 cases had operations under the guidance of ECoG. Forty-six patients were treated by lesionectomy + hemosiderin rim while the other six were treated by lesionectomy + hemosiderin rim along with extended epileptogenic zone resection. The locations of lesions, the duration of illness, the manifestation, the excision ranges and the outcomes of postoperative follow-up were analyzed, respectively.

Results:

All of the 52 patients were treated by microsurgery. There was no neurological deficit through the long-term follow-up. Outcomes of seizure control are as follows: 42 patients (80.8%) belong to Engel Class I, 5 patients (9.6%) belong to Engel Class II, 3 patients (5.8%) belong to Engel Class III and 2 patients (3.8%) belong to Engel Class IV.

Conclusion:

Patients with epilepsy caused by temporal CMs should be treated as early as possible. Resection of the lesion and the surrounding hemosiderin zone is necessary. Moreover, an extended excision of epileptogenic cortex or cerebral lobes is needed to achieve a better prognosis if the ECoG indicates the existence of an extra epilepsy onset origin outside the lesion itself.

Normotopic cortex is the major contributor to epilepsy in experimental double cortex

OBJECTIVE

Subcortical band heterotopia (SBH) is a cortical malformation formed when neocortical neurons prematurely stop their migration in the white matter, forming a heterotopic band below the normotopic cortex, and is generally associated with intractable epilepsy. Although it is clear that the band heterotopia and the overlying cortex both contribute to creating an abnormal circuit prone to generate epileptic discharges, it is less understood which part of this circuitry is the most critical. Here, we sought to identify the origin of epileptiform activity in a targeted genetic model of SBH in rats.

METHODS

Rats with SBH (Dcx-KD rats) were generated by knocking down the Dcx gene using shRNA vectors transfected into neocortical progenitors of rat embryos. Origin, spatial extent, and laminar profile of bicuculline-induced interictal-like activity on neocortical slices were analyzed by using extracellular recordings from 60-channel microelectrode arrays. Susceptibility to pentylenetetrazole-induced seizures was assessed by electrocorticography in head-restrained nonanesthetized rats.

RESULTS

We show that the band heterotopia does not constitute a primary origin for interictal-like epileptiform activity in vitro and is dispensable for generating induced seizures in vivo. Furthermore, we report that most interictal-like discharges originating in the overlying cortex secondarily propagate to the band heterotopia. Importantly, we found that in vivo suppression of neuronal excitability in SBH does not alter the higher propensity of Dcx-KD rats to display seizures.

INTERPRETATION

These results suggest a major role of the normotopic cortex over the band heterotopia in generating interictal epileptiform activity and seizures in brains with SBH.

Novel approach to temporal lobectomy for removal of a cavernous hemangioma in a dog

OBJECTIVE

To report temporal lobe surgery for a cavernous hemangioma in a dog and outcome.

STUDY DESIGN

Clinical report.

ANIMALS

Dog (n = 1).

METHODS

Magnetic resonance (MR) imaging was used to identify a temporal lobe mass in 9-year-old, male neutered Labrador Retriever that had a 12 hour history of seizures. An approach to the temporal lobe allowed preservation of the zygomatic arch and mass removal.

RESULTS

The mass was confirmed as a cavernous hemangioma on histopathology. Repeat MR imaging at 13 months showed no recurrence of gross structural disease; however, the dog's anti-epileptic medication was administered for adequate seizure control.

CONCLUSION

Temporal lobe surgery can be performed in the dog's for the management of temporal lobe mass lesions.

Cerebral cavernous malformations in the setting of focal epilepsies: pathological findings, clinical characteristics, and surgical treatment principles

Cavernous cerebral malformations (CCMs) are a well-defined epilepsy-associated pathology. They represent lesions/conglomerates of abnormally configured vessels leading to seizures either as a result of physiological changes affecting the cerebral cortex immediately surrounding the CCM (an epileptogenic mechanism that is relevant for both temporal and extratemporal lesions), or as a result of promoting epileptogenicity in remote but anatomo-functionally connected brain regions (a mechanism that is particularly relevant for temporal lobe lesions). This review details the pathological findings in CCMs and discusses the mechanisms of epileptogenicity in this context. The bulk of the review will focus on therapeutic strategies. Medical therapy using antiepileptic drugs is recommended as a first-line therapy, but surgical removal of the CCM with the surrounding cortex should be pursued if seizures prove to be drug resistant. Early timing of the resection and complete removal of any associated epileptic pathology are critical for best outcomes. In addition to reviewing the available data from prior series, we present original research from two specialized epilepsy centers targeted at answering particularly pressing clinical questions mainly related to the ideal timing and extent of surgery. Further research is needed to define the best surgical strategies in patients with temporal lobe CCMs and structurally normal hippocampi.

Brain arteriovenous malformations and seizures: an Italian study

OBJECTIVE

To evaluate seizures as first clinical manifestation of brain arteriovenous malformations (AVMs), in relation to angioarchitectural features of these vascular anomalies.

METHODS

We performed a prospective observational study, collecting records of patients with AVMs consecutively admitted to the Neurological and Neurosurgery Units of Perugia University and to the Neurosurgery Unit of Terni Hospital, during a 10-year period (1 January 2002 to 1 June 2012). Two groups of patients, with or without seizures as AVM first presentation, were analysed to identify differences in demographic and angiographic features. A multivariate logistic regression model was also developed.

RESULTS

We examined 101 patients with AVMs, 55 male and 46 female. Seizures were the initial clinical manifestation in 31 (30.7%) patients. We found a significant difference (p<0.05) between two groups of patients, with or without seizures as AVM first presentation concerning location, side, topography and venous drainage. A multivariate logistic regression model showed that clinical presentation with seizures was correlated with a location in the temporal and frontal lobes, and with a superficial topography. The strongest association (OR 3.48; 95% CI 1.77 to 6.85) was observed between seizures and AVM location in the temporal lobe.

CONCLUSIONS

Vascular remodelling and haemodynamic changes of AVMs might create conditions for epileptogenesis. However, here we show that malformations with specific angiographic characteristics are more likely to be associated with seizures as first clinical presentation. Location is the most important feature related to epilepsy and in particular the temporal lobe might play a crucial role in the occurrence of seizure.

Rates and predictors of seizure freedom in resective epilepsy surgery: an update

Epilepsy is a debilitating neurological disorder affecting approximately 1 % of the world's population. Drug-resistant focal epilepsies are potentially surgically remediable. Although epilepsy surgery is dramatically underutilized among medically refractory patients, there is an expanding collection of evidence supporting its efficacy which may soon compel a paradigm shift. Of note is that a recent randomized controlled trial demonstrated that early resection leads to considerably better seizure outcomes than continued medical therapy in patients with pharmacoresistant temporal lobe epilepsy. In the present review, we provide a timely update of seizure freedom rates and predictors in resective epilepsy surgery, organized by the distinct pathological entities most commonly observed. Class I evidence, meta-analyses, and individual observational case series are considered, including the experiences of both our institution and others. Overall, resective epilepsy surgery leads to seizure freedom in approximately two thirds of patients with intractable temporal lobe epilepsy and about one half of individuals with focal neocortical epilepsy, although only the former observation is supported by class I evidence. Two common modifiable predictors of postoperative seizure freedom are early operative intervention and, in the case of a discrete lesion, gross total resection. Evidence-based practice guidelines recommend that epilepsy patients who continue to have seizures after trialing two or more medication regimens should be referred to a comprehensive epilepsy center for multidisciplinary evaluation, including surgical consideration.

Seizure outcome after surgical resection of supratentorial cavernous malformations plus hemosiderin rim in patients with short duration of epilepsy

OBJECTIVE

The objective of this study was to retrospectively review the postoperative seizure outcome in patients with short duration of epilepsy associated with cavernous malformations and analyze the effect of surgical methods on seizure outcome in such population.

METHODS

36 patients with short duration of epilepsy (shorter than 12 months) associated with cavernous malformations in temporal or frontal lobe underwent microsurgical resection. The patients were retrospectively divided into two groups: Group A (21 patients) with complete removal of hemosiderin rim and Group B (15 patients) with partial removal of hemosiderin rim. Clinical follow-up was achieved with telephone correspondence or outpatient assessment. The seizure outcome was based on Engel's classification.

RESULTS

After a mean follow-up period of 18 months, 77.8% of the patients (28/36) were classified into Engel class I, including 19 patients (90.5%) in the complete removal of hemosiderin rim group (Group A) and 9 patients (60%) in the partial removal of hemosiderin rim group (Group B). Seizure outcome was significantly better in Group A. There was no mortality and all the postoperative neurological deficits were recovered at the time of follow-up.

CONCLUSION

The analysis of the seizure outcome demonstrate patients with short duration of epilepsy associated with cavernous malformations could benefit greatly from complete resection of hemosiderin rim and cavernous malformations.

Significance of horizontal propagation of synchronized activities in human epileptic neocortex investigated by optical imaging and immunohistological study

To characterize the physiological condition of human epileptic neocortex, we employed flavoprotein fluorescence imaging (FFI), an optical imaging method which detects intrinsic signals accompanying neural activation, and immunohistologically studied human cortical specimens. The experimented materials were cortical tissues surrounding various intracerebral lesions obtained from 5 patients with epilepsy (epileptic patients: EPs) and 5 without epilepsy (non-epileptic patients: NEPs). These tissues were immersed in oxygenated artificial cerebrospinal fluid immediately after removal in the operating room. Signal changes of FFI in the cortical layers subjected to electrical stimulation were observed under bicuculline methiodide perfusion. Immunohistological staining for parvalbumin (PV), calbindin, and calretinin were performed on the same specimens to evaluate expressions of calcium-binding protein positive cells. The FFI study showed the characteristic cortical propagation pattern of elicited activities horizontally along the cortical layers in EPs but not in NEPs. The propagated area with more than 0.5% signal changes was significantly larger in EPs than in NEPs (p=0.008). Only the expression of PV positive neurons was significantly lower in EPs than in NEPs (p=0.006). The propagated area on FFI and the decrease in PV positive neurons correlated significantly (R=-0.78, p=0.04). The present study visualized the unique horizontal propagation of signal changes on FFI and demonstrated a correlation of this propagation with immunohistological decreases in PV positive neurons in human epileptic cortex. Further investigations may elucidate the mechanism of hyper-excitability and hyper-synchronization in epileptic cortical tissue itself.

Cliniconeuropathologic correlations show astroglial albumin storage as a common factor in epileptogenic vascular lesions

PURPOSE

Intracerebral vascular malformations including cavernous angiomas (CAs) and arteriovenous malformations (AVMs) are an important cause of chronic pharmacoresistant epilepsies. Little is known about the pathogenetic basis of epilepsy in patients with vascular malformations. Intracerebral deposits of iron-containing blood products have been generally regarded as responsible for the strong epileptogenic potential of CAs. Here, we have analyzed whether blood-brain barrier (BBB) dysfunction and subsequent astrocytic albumin uptake, recently described as critical trigger of focal epilepsy, represent pathogenetic factors in vascular lesion-associated epileptogenesis.

METHODS

We examined the correlation between hemosiderin deposits, albumin accumulation, and several clinical characteristics in a series of 80 drug-refractory epilepsy patients with CAs or AVMs who underwent surgical resection. Analysis of clinical parameters included gender, age of seizure onset, epilepsy frequency, duration of epilepsy before surgery, and postoperative seizure outcome classification according to Engel class scale. Hemosiderin deposits in the adjacent brain tissue of the vascular lesion were semiquantitatively analyzed. Fluorescent double-immunohistochemistry using GFAP/albumin costaining was performed to study albumin extravasation.

KEY FINDINGS

Our results suggest that a shorter duration of preoperative epilepsy is correlated with significantly better postsurgical outcome (p < 0.05), whereas no additional clinical or neuropathologic parameter correlated significantly with the postsurgical seizure situation. Intriguingly, we observed strong albumin immunoreactivity within the vascular lesion and in perilesional astrocytes (57.65 ± 4.05%), but not in different control groups.

SIGNIFICANCE

Our present data on albumin uptake in brain tissue adjacent to AVMs and CAs suggests BBB dysfunction and accumulation of albumin within astrocytes as a new pathologic feature potentially associated with the epileptogenic mechanism for vascular lesions and provides novel therapy perspectives for antiepileptogenesis in affected patients.

Surgical management of cavernous malformations presenting with drug-resistant epilepsy

Cerebral cavernous malformations (CMs) are dynamic lesions characterized by continuous size changes and repeated bleeding. When involving cortical tissue, CMs pose a significant risk for the development of drug-resistant epilepsy, which is thought to be result of an altered neuronal network caused by the lesion itself and its blood degradation products. Preoperative evaluation should comprise a complete seizure history, neurological examination, epilepsy-oriented MRI, EEG, video-EEG, completed with SPECT, PET, functional MRI, and/or invasive monitoring as needed. Radiosurgery shows variable rates of seizure freedom and a high incidence of complications, thus microsurgical resection remains the optimal treatment for CMs presenting with drug-resistant epilepsy. Two thirds of patients reach Engel I class at 3-year follow-up, regardless of lobar location. Those with secondarily generalized seizures, a higher seizure frequency, and generalized abnormalities on preoperative or postoperative EEG, show poorer outcomes, while factors such as gender, duration of epilepsy, lesion size, age, bleeding at the time of surgery, do not correlate consistently with seizure outcome. Electrocorticography and a meticulous removal of all cortical hemosiderin - beyond pure lesionectomy - reduce the risk of symptomatic recurrences.

Predictors of seizure freedom in the surgical treatment of supratentorial cavernous malformations

OBJECT

Seizures are the most common presenting symptom of supratentorial cerebral cavernous malformations (CCMs) and progress to medically refractory epilepsy in 40% of patients. Predictors of seizure freedom in the resection of CCMs are incompletely understood.

METHODS

The authors systematically reviewed the published literature on seizure freedom following the resection of supratentorial CCMs in patients presenting with seizures. Seizure outcomes were stratified across 12 potential prognostic variables. A total of 1226 patients with supratentorial CCMs causing seizures were identified across 31 predominantly retrospective studies; 361 patients had medically refractory epilepsy.

RESULTS

Seventy-five percent of the patients were seizure free after microsurgical lesion removal, whereas 25% continued to have seizures. All patients had had preoperative seizures and > 6 months of postoperative follow-up. Modifiable predictors of postoperative seizure freedom included gross-total resection (OR 36.6, 95% CI 8.5-157.5) and surgery within 1 year of symptom onset (OR 1.83, 95% CI 1.30-2.58). Additional prognostic indicators of a favorable outcome were a CCM size < 1.5 cm (OR 15.4, 95% CI 5.2-45.4), the absence of multiple CCMs (OR 2.02, 95% CI 1.13-3.60), medically controlled seizures (OR 2.38, 95% CI 1.29-4.39), and the lack of secondarily generalized seizures (OR 3.33, 95% CI 2.09-5.30). Other factors, including extended resection of the hemosiderin ring, were not significantly predictive.

CONCLUSIONS

In the surgical treatment of supratentorial CCMs, gross-total resection and early operative intervention may improve seizure outcome. While surgery should not be considered the first-line treatment for CCM-related epilepsy, it is important to understand the variables associated with seizure freedom in CCM resection given the considerable morbidity and diminished quality of life associated with epilepsy.

Spatiotemporal dynamics of epileptiform propagations: imaging of human brain slices

Seizure activities often originate from a localized region of the cerebral cortex and spread across large areas of the brain. The properties of these spreading abnormal discharges may account for clinical phenotypes in epilepsy patients, although the manner of their propagation and the underlying mechanisms are not well understood. In the present study we performed flavoprotein fluorescence imaging of cortical brain slices surgically resected from patients with partial epilepsy caused by various symptomatic lesions. Elicited neural activities in the epileptogenic tissue spread horizontally over the cortex momentarily, but those in control tissue taken from patients with brain tumors who had no history of epilepsy demonstrated only localized responses. Characteristically, the epileptiform propagation comprised early and late phases. When the stimulus intensity was changed gradually, the early phase showed an all-or-none behavior, whereas the late phase showed a gradual increase in the response. Moreover, the two phases were propagated through different cortical layers, suggesting that they are derived from distinct neural circuits. Morphological investigation revealed the presence of hypertrophic neurons and loss of dendritic spines, which might participate in the aberrant activities observed by flavoprotein fluorescence imaging. These findings indicate that synchronized activities of the early phase may play a key role in spreading abnormal discharges in human cortical epilepsies.

Cerebral cavernous malformations and intractable epilepsy: the limited usefulness of current literature

BACKGROUND

Cerebral cavernous malformations (CCM) are known to be highly epileptogenic lesions. A number of studies on CCM surgery deal with CCM-associated seizures and/or epilepsy. In order to counsel patients with CCM-associated epilepsy, clear results from such studies would be highly useful. This study reviews the current literature with the aim to assess its usefulness for presurgical decision-making with emphasis on differentiating outcomes in different epilepsy types.

METHODS

A systematic Medline search identified 27 studies between 1991 and 2009 through the keywords "cavernomas, cavernous, hemangioma, AND epilepsy, AND surgery". They were analysed with regard to clarity of definition of epilepsy subtypes, precision of definition of drug-resistant epilepsy, information on surgical procedure and presurgical workup, seizure outcome and length of follow-up.

RESULTS

Twenty studies included only surgically treated patients. Three types of epilepsy were defined: drug-resistant epilepsy, epilepsy or single/sporadic seizures. In 12 of 27 studies, at least one of these categories remained unclear. The classic definition of drug-resistant epilepsy was not used in the vast majority of studies, with many groups using their own definition. In 30%, the surgical procedure was not described precisely, although 52% of studies used a differentiated preoperative evaluation. Seizure outcome was described using a widely accepted classification in only 48% of series, and in over half of the studies outcome results contained cases with insufficient length of follow-up.

CONCLUSIONS

A large proportion of recent studies on surgery for CCM-associated epilepsy are not using criteria and definitions for the classification of epilepsy and outcome that are commonly used by epileptologists or epilepsy surgeons. This results in the limited usefulness of a large part of the literature for the purpose of preoperative counselling a patient with CCM-associated epilepsy.

Magnetic resonance diffusion tensor imaging and tractography of intracranial cavernous malformations: preliminary observations and characterization of the hemosiderin rim

OBJECT

Cavernous malformations (CMs) can cause symptoms that appear out of proportion to the lesion size, leading one to hypothesize that they may have an effect on adjacent white matter that is not fully explained by local mass effect. The goal of this study was to investigate the diffusion tensor (DT) properties of CMs, the hemosiderin rim, and normal-appearing adjacent white matter.

METHODS

Eighteen cavernous malformations were characterized using standard MR imaging sequences as well as 6-direction DT imaging with single-shot echo planar-gradient echo imaging at 3 tesla.

RESULTS

Diffusion tensor imaging demonstrated that CMs have a characteristic signature on DT imaging, with low fractional anisotropy (FA) and high mean diffusivity centrally within the lesion. The hemosiderin rim had a high FA value relative to the central lesion or adjacent white matter. Tractography revealed that tracts neatly deviate around CMs. Tracts were typically seen to pass through the hemosiderin rim.

CONCLUSIONS

The hemosiderin rim of CMs was intimately associated with white matter tracts that were deviated by the central lesion. These findings are consistent with histopathological reports that the hemosiderin rim is composed of blood breakdown products deposited in viable white matter.

Epileptogenic temporal cavernous malformations: operative strategies and postoperative seizure outcomes

Operative treatment of epileptogenic cavernous malformations (CM) continues under debate. Most studies focus on surgery for supratentorial CM in general. For temporal lobe CM, surgical decision-making concerns in particular whether to perform lesionectomy alone or the additional excision of mesial temporal structures. The purpose of this case series was to evaluate operative strategies used to treat epileptogenic temporal CM and to report resultant postoperative seizure outcomes. Twelve consecutive cases of patients with medically intractable epilepsy who underwent operation for temporal CM between 1996 and 2006 were retrospectively reviewed. When the temporal CM directly invaded the hippocampus or amygdala, the affected structures were resected in addition to the lesion; when the CM was located in the superficial temporal cortex, and there was no radiographic evidence of hippocampal sclerosis, lesionectomy alone was done; with CM located between the superficial temporal cortex and the mesial temporal region, other factors were considered in decision-making, such as lesion proximity to the deep mesiotemporal structures and preoperative epilepsy duration. For six of the twelve patients, extended lesionectomy (EL) alone was done; for the other six, tailored anteromedial temporal resection with hippocampectomy and/or amygdalectomy was performed in addition to EL. Postoperatively, 11 patients - all with preoperative VEM demonstrating electroclinical seizure patterns concordant with lesion location - were seizure-free. We conclude that epileptogenic temporal CM are surgically remediable, when approached with the above operative strategies and presurgical VEM. On the basis of these postoperative seizure control results, we recommend consideration of concurrent resection of mesial temporal structures with EL for certain temporal CM.

Long-term seizure outcomes in adult patients undergoing primary resection of malignant brain astrocytomas

Object

Seizures are a common presenting symptom and cause of morbidity for patients with malignant astrocytomas. The authors set out to determine preoperative seizure characteristics, effects of surgery on seizure control, and factors associated with prolonged seizure control in patients with malignant astrocytomas.

Methods

Cases involving adult patients who underwent primary resection of a hemispheric anaplastic astrocytoma (AA) or glioblastoma multiforme (GBM) at the Johns Hopkins Medical Institutions between 1996 and 2006 were retrospectively reviewed. Multivariate logistical regression analysis was used to identify associations with pre-operative seizures, and multivariate proportional hazards regression analyses were used to identify associations with prolonged seizure control following resection.

Results

Of the 648 patients (505 with GBM, 143 with AA) in this series, 153 (24%) presented with seizures. The factors more commonly associated with preoperative seizures were AA pathology (p = 0.03), temporal lobe involvement (p = 0.04), and cortical location (p = 0.04), while the factors less commonly associated with preoperative seizures were greater age (p = 0.03) and larger tumor size (p ≤ 0.001). Among those patients with a history of seizures, outcome 12 months after surgery was Engel Class I (seizure free) in 77%, Class II (rare seizures) in 12%, Class III (meaningful improvement) in 6%, and Class IV (no improvement) in 5%. Postoperative seizures were rare in patients without a history of preoperative seizures. The factor positively associated with prolonged seizure control was increased Karnofsky Performance Scale score (p = 0.002), while the factors negatively associated with seizure control were preoperative uncontrolled seizures (p = 0.03) and parietal lobe involvement (p = 0.005). Seizure recurrence in patients with postoperative seizure control was independently associated with tumor recurrence (p = 0.006).

Conclusions

The identification and consideration of factors associated with prolonged seizure control may help guide treatment strategies aimed at improving the quality of life for patients with malignant astrocytomas.

Electrocorticography-guided resection of temporal cavernoma: is electrocorticography warranted and does it alter the surgical approach?

OBJECT

Cavernous hemangiomas associated with epilepsy present an interesting surgical dilemma in terms of whether one should perform a pure lesionectomy or tailored resection, especially in the temporal lobe given the potential for cognitive damage. This decision is often guided by electrocorticography (ECoG), despite the lack of data regarding its value in cavernoma surgery. The purpose of the present study was several-fold: first, to determine the epilepsy outcome following resection of cavernomas in all brain regions; second, to evaluate the usefulness of ECoG in guiding surgical decision making; and third, to determine the optimum surgical approach for temporal lobe cavernomas.

METHODS

The authors identified from their surgical database 173 patients who had undergone resection of cavernomas. One hundred two of these patients presented with epilepsy, and 61 harbored temporal lobe cavernomas. Preoperatively, all patients were initially evaluated by an epileptologist. The mean follow-up was 37 months.

RESULTS

Regardless of the cavernoma location, surgery resulted in an excellent seizure control rate: Engel Class I outcome in 88% of patients at 2 years postoperatively. Of 61 patients with temporal lobe cavernomas, the mesial structures were involved in 35. Among the patients with temporal lobe cavernomas, those who underwent ECoG typically had a more extensive parenchymal resection rather than a lesionectomy (p < 0.0001). The use of ECoG in cases of temporal lobe cavernomas resulted in a superior seizure-free outcome: 79% (29 patients) versus 91% (23 patients) of patients at 6 months postresection, 77% (22 patients) versus 90% (20 patients) at 1 year, and 79% (14 patients) versus 83% (18 patients) at 2 years without ECoG versus with ECoG, respectively.

CONCLUSIONS

The surgical removal of cavernomas most often leads to an excellent epilepsy outcome. In cases of temporal lobe cavernomas, the more extensive the ECoG-guided resection, the better the seizure outcome. In addition to upholding the concept of kindling, the data in this study support the use of ECoG in temporal lobe cavernoma surgery in patients presenting with epilepsy.

Benign lesions accompanied by intractable epilepsy in children

Epilepsy surgery has been proposed as a safe alternative treatment for intractable epilepsy in children, especially for patients with structural brain abnormalities. We studied 24 consecutive children who underwent surgery for intractable epilepsy. There were 12 males and 12 females. The mean age was 6.5 years. The seizures' duration ranged from 6 months to 2 years. The histopathological examination of the resected lesions revealed in 12 cases the presence of a ganglioglioma, in 7 cases dysembryoplastic neuroepithelial tumor, in 1 case a low grade glioma, in 2 cases cortical dysplasia, and in 2 cases cavernous malformations. In 18 cases, the lesions were located in the temporal lobe and in 6 cases the lesions were extratemporal. After a mean follow-up period of 4.4 years, 79% (19/24) of patients were seizure free. There were no permanent neurological deficits or deaths. Surgery for focal epilepsy in children is a safe procedure with favorable results.

Cortical hyperexcitability and epileptogenesis: Understanding the mechanisms of epilepsy - part 2

Epilepsy encompasses a diverse group of seizure disorders caused by a variety of structural, cellular and molecular alterations of the brain primarily affecting the cerebral cortex, leading to recurrent unprovoked epileptic seizures. In this two-part review we examine the mechanisms underlying normal neuronal function and those predisposing to recurrent epileptic seizures starting at the most basic cellular derangements (Part 1, Volume 16, Issue 3) and working up to the highly complex epileptic networks and factors that modulate the predisposition to seizures (Part 2). We attempt to show that multiple factors can modify the epileptic process and that different mechanisms underlie different types of epilepsy, and in most situations there is an interplay between multiple genetic and environmental factors.

Seizure characteristics and control following resection in 332 patients with low-grade gliomas

OBJECT

Seizures play an important role in the clinical presentation and postoperative quality of life of patients who undergo surgical resection of low-grade gliomas (LGGs). The aim of this study was to identify factors that influenced perioperative seizure characteristics and postoperative seizure control.

METHODS

The authors performed a retrospective chart review of all cases involving adult patients who underwent initial surgery for LGGs at the University of California, San Francisco between 1997 and 2003.

RESULTS

Three hundred and thirty-two cases were included for analysis; 269 (81%) of the 332 patients presented with >or=1 seizures (generalized alone, 33%; complex partial alone, 16%; simple partial alone, 22%; and combination, 29%). Cortical location and oligodendroglioma and oligoastrocytoma subtypes were significantly more likely to be associated with seizures compared with deeper midline locations and astrocytoma, respectively (p=0.017 and 0.001, respectively; multivariate analysis). Of the 269 patients with seizures, 132 (49%) had pharmacoresistant seizures before surgery. In these patients, seizures were more likely to be simple partial and to involve the temporal lobe, and the period from seizure onset to surgery was likely to have been longer (p=0.0005, 0.0089, and 0.006, respectively; multivariate analysis). For the cohort of patients that presented with seizures, 12-month outcome after surgery (Engel class) was as follows: seizure free (I), 67%; rare seizures (II), 17%; meaningful seizure improvement (III), 8%; and no improvement or worsening (IV), 9%. Poor seizure control was more common in patients with longer seizure history (p<0.001) and simple partial seizures (p=0.004). With respect to treatment-related variables, seizure control was far more likely to be achieved after gross-total resection than after subtotal resection/biopsy alone (odds ratio 16, 95% confidence interval 2.2-124, p=0.0064). Seizure recurrence after initial postoperative seizure control was associated with tumor progression (p=0.001).

CONCLUSIONS

The majority of patients with LGG present with seizures; in approximately half of these patients, the seizures are pharmacoresistant before surgery. Postoperatively, >90% of these patients are seizure free or have meaningful improvement. A shorter history of seizures and gross-total resection appear to be associated with a favorable prognosis for seizure control.