Diagnostic challenges in the evaluation of chronic epilepsy-related surgical neuropathology

Seizure-outcome after surgery of low-grade epilepsy associated neuro-epithelial tumors

BACKGROUND

Most patients with glioneuronal tumors present with seizures. Although several studies have shown that greater extent of resection improves overall patient survival, few studies have focused on postoperative seizure outcome after resection of these tumors. The aim of this study was to characterize seizure control rates in patients undergoing glioneuronal tumor resection and evaluate the association between poor seizure outcome and tumor recurrence or progression.

METHODS

The study population included patients who had undergone resection of glioneuronal tumors between 2014 and 2019 at our institution. Seizure outcome was assessed using Engel grading. Preoperative seizure characteristics, tumor characteristics, surgical factors, and postoperative seizure outcomes were reviewed.

RESULTS

Twenty-six patients (N.=16, temporal lobe; N.=6, frontal lobe; N.=4, parietal lobe) with mean seizures duration of 56.9-months, were assessed. Histopathologically, N.=15 dysembryoplastic neurepithelial tumor, N.=7 ganglioglioma and N.=4 Diffuse lepto-meningeal neuroepithelial tumor. There were 2 cases of complex DNET and one case of DLMNT had associated cortical dysplasia. At mean follow-up of 49.7 months, N.=20 Engel 1, N.=4 Engel 2 and N.=2 had Engel 3 outcome. N.=20 underwent gross total excision (N.=18 Engel 1 and N.=2 Engel 2) and N.=6 sub-total excision. Among the 4 patients who needed re-surgery, two were in Engel 2 and another two were in Engel 3.

CONCLUSIONS

Good seizure-outcome is likely associated with extent of resection. Younger age of patient, less than one-year of seizure duration and absence of generalization of seizure are good prognostic indicators. The best seizure-control can be achieved by early surgical intervention.

Analysis of Intraoperative Seizures During Bipolar Brain Mapping in Eloquent Areas: Intraoperative Seizures in brain mapping

OBJECTIVES

Awake Craniotomy (AC) is a very well described technique that is performed to make an adequate tumor resection preserving the functionality of the patient. Intraoperative Seizures (IS) are reported as a failure of such procedure. We analyze the incidence and risk factor during AC.

METHODS

We made a review of the database of the National Institute of Neurology and Neurosurgery between January 2017 and May 2019 for intrinsic tumors located in eloquent areas of the brain. An analysis of ISconcerning the clinical history, clinical presentation, imaging techniques, histological findings and surgical technique was made. The factors associated with Mapping Failure (MF) were also evaluated.

RESULTS

45 patients were included of whom 7 patients (15.6%) developed IS after cortical-subcortical stimulation, 5 presented partial motor seizures (11.1%) and 2 experimented generalized secondary seizures (4.5%). Of the patients that had a MF, one patient (14%) was due to generalized tonic-clonic seizures which couldn't be managed by cold saline irrigation and administration of anti-seizures drugs and was then converted to a general anesthetic technique. We observed that the patients that had a bigger tumoral volume (112.2 cm3 85.3, P = 0,07) had a bigger positive relation in presenting IS, having a peak sensibility and specificity above 70 cc (ROC).

CONCLUSIONS

In our analysis IS are more common in patients with high presurgical tumor volume. Even though the majority of the patients that presented IS didn't develop MF, it is important to acknowledge that the multidisciplinary group in the operating room must be prepared to detect these complications, treat them promptly and avoid MF.

Glioneuronal tumors: clinicopathological findings and treatment options

Glioneuronal tumors are very rare CNS neoplasms that demonstrate neuronal differentiation, composed of mixed glial and neuronal cells. The majority of these lesions are low grade and their correct classification is crucial in order to avoid misidentification as ‘ordinary’ gliomas and prevent inappropriate aggressive treatment; nevertheless, precise diagnosis is a challenge due to phenotypic overlap across different histologic subtype. Surgery is the standard of therapeutic approach; literature concerning the benefit of adjuvant treatments is inconclusive and a globally accepted treatment of recurrence does not exist. Targetable mutations in the genes BRAF and FGFR1/2 are recurrently found in these tumors and could take a promising role in future treatment management.

Diffuse Low-Grade Glioma - Changing Concepts in Diagnosis and Management: A Review

Though diffuse low-grade gliomas (dLGGs) represent only 15% of gliomas, they have been receiving increasing attention in the past decade. Significant advances in knowledge of the natural history and clinical diversity have been documented, and an improved pathological classification of gliomas that integrates histological features with molecular markers has been issued by the WHO. Advances in the radiological assessment of dLGG, particularly new magnetic resonance imaging scanning sequences, allow improved diagnostic and prognostic information. The management paradigms are evolving from “wait and watch” of the past to more active interventional therapy to obviate the risk of malignant transformation. New surgical technologies allow more aggressive surgical resections with a reduction of morbidity. Many reports suggest the association of gross total resection with longer overall survival and progression-free survival in addition to better seizure control. The literature also shows the use of chemotherapeutics and radiation therapy as important adjuncts to surgery. The goals of management have has been increasing survival with increasing stress on quality of life. Our review highlights the recent advances in the molecular diagnosis and management of dLGG with trends toward multidisciplinary and multimodality management of dLGG with an aim to surgically resect the primary disease, followed by chemoradiation in cases of progressive or recurrent disease.

Lesional Temporal Lobe Epilepsy: Beware the Deceitful "Panic Attack"

BACKGROUND

Ganglioglioma is a rare, benign, intraaxial glioneuronal tumor but a relatively common cause of pharmacoresistant temporal lobe epilepsy (TLE). Given its often nonspecific neuropsychiatric manifestations and frequently negative electroencephalographic workup, TLE can be easily misdiagnosed as a psychiatric disorder, particularly panic attacks.

CASE DESCRIPTION

We present a case of a 17-year-old boy who was found to have lesional TLE secondary to a left temporal ganglioglioma, 5 years after having been misdiagnosed with panic disorder and having undergone ineffective and unnecessary psychotherapy. He was successfully cured by surgery. Although a few similar cases of TLE masquerading as a panic disorder have been previously reported in the literature, this is the youngest and only pediatric patient described to date.

CONCLUSION

This report underscores the challenges in making an accurate clinical diagnosis of TLE and the importance of timely brain imaging whenever an atypical or medically refractory panic disorder is encountered.

Rare glial tumors

This chapter describes the epidemiology, pathology, molecular characteristics, clinical and neuroimaging features, treatment, outcome, and prognostic factors of the rare glial tumors. This category includes subependymal giant cell astrocytoma, pleomorphic xanthoastrocytoma, astroblastoma, chordoid glioma of the third ventricle, angiocentric glioma, ganglioglioma, desmoplastic infantile astrocytoma and ganglioma, dysembryoplastic neuroepithelial tumor, papillary glioneuronal tumor, and rosette-forming glioneuronal tumor of the fourth ventricle. Many of these tumors, in particular glioneuronal tumors, prevail in children and young adults, are characterized by pharmacoresistant seizures, and have an indolent course, and long survival following surgical resection. Radiotherapy and chemotherapy are reserved for recurrent and/or aggressive forms. New molecular alterations are increasingly recognized.

What is New in the Management of Epilepsy in Gliomas?

OPINION STATEMENT

Seizures represent a common symptom in low- and high-grade gliomas. Tumor location and histology influence the risk for epilepsy. Some molecular factors (BRAF V 600E mutations in glioneuronal tumors and IDH1/2 mutations in diffuse grade II and III gliomas) are molecular factors that are relevant for diagnosis and prognosis and have been associated with the risk of epilepsy as well. Glutamate plays a central role in epileptogenicity and growth of glial and glioneuronal tumors, based on the release of glutamate from tumor cells that enhances excitotoxicity, and a downregulation of the inhibitory GABAergic pathways. Several potential targets for therapy have been identified, and m-TOR inhibitors have already shown activity. Gross total resection is the strongest predictor of seizure freedom in addition to clinical factors, such as preoperative seizure duration, type, and control with antiepileptic drugs (AEDs). Radiotherapy and chemotherapy with alkylating agents (procarbazine, CCNU, vincristine, temozolomide) are effective in reducing the frequency of seizures in patients with pharmacoresistant epilepsy. Newer AEDs (in particular levetiracetam and lacosamide) seem to be better tolerated than the old AEDs (phenobarbital, phenytoin, carbamazepine), but randomized clinical trials are needed to prove their superiority in terms of efficacy.

Post-surgical outcome for epilepsy associated with type I focal cortical dysplasia subtypes

Focal cortical dysplasias are a well-recognized cause of medically intractable seizures. The clinical relevance of certain subgroups of the International League Against Epilepsy (ILAE) classification scheme remains to be determined. The aim of the present work is to assess the effect of the focal cortical dysplasia type Ib and Ic histologic subtypes on surgical outcome with respect to seizure frequency. This study also provides an opportunity to compare the predictive value of the ILAE and Palmini et al classification schemes with regard to the type I focal cortical dysplasias. We retrospectively reviewed 91 focal cortical dysplasia patients (55% female; median age: 19 years (interquartile range 8-34); median seizure duration: 108 months (interquartile range 36-204)) with chronic epilepsy who underwent surgery. We compared the pathological subtypes, evaluating the patients' post-surgical outcome with respect to seizure frequency according to the Engel's classification and the ILAE outcome classification. Both the ILAE classification scheme and Palmini et al classification scheme were utilized to classify the histologic subtype. Using χ(2) and Fisher's exact tests, we compared the post-surgical outcomes among these groups. Of the 91 patients, there were 50 patients with ILAE focal cortical dysplasia type Ib, 41 with ILAE focal cortical dysplasia type Ic, 63 with Palmini et al focal cortical dysplasia type IA, and 28 with Palmini et al focal cortical dysplasia type IB. After surgery, 44 patients (48%) were seizure-free. Crude analysis revealed no significant difference between patients with subtypes of ILAE focal cortical dysplasia type I or Palmini et al focal cortical dysplasia type I concerning postoperative outcome according to the Engel and ILAE scoring systems on seizure frequency. Our findings revealed no significant difference concerning surgical outcome with respect to seizure frequency for the histologic subtypes of ILAE focal cortical dysplasia type I (Ib vs Ic) or Palmini et al focal cortical dysplasia type I (IA vs IB). In isolation, the histologic subtype of focal cortical dysplasia type I does not appear predictive of postoperative outcome.

Investigation of Deaths in Seizure Patients

Epilepsy is commonly encountered in forensic pathology and is ultimately determined to be the cause of death in 1–2% of medicolegal death investigations. Epilepsy is a risk factor for death from external causes, including accidents and drowning. More commonly, deaths result from the underlying epilepsy pathology, including intracranial neoplasms, cerebrovascular disease, status epilepticus, and sudden unexpected death in epilepsy (SUDEP). SUDEP refers to the sudden death in an epilepsy patient that lacks an alternative anatomic or toxicological cause of death. At autopsy, intracranial pathology is present in the majority of epilepsy-related deaths and is more likely to be identified following brain fixation. Common findings include brain tumors, mesial temporal sclerosis, and malformations of cortical development. Death investigators should pay particular attention to clinical history to establish a clear history of epilepsy and to determine seizure type, frequency, underlying etiology, and prior medical and surgical treatments as well as other comorbid medical conditions. A complete autopsy with toxicology is necessary to identify other causes of death, particularly in cases of suspected SUDEP. While toxicology may be helpful in some cases, caution must be taken in interpreting postmortem antiepileptic drug concentrations as levels decrease postmortem.

Seizure control after subtotal lesional resection

Reports on seizure outcomes following surgery for lesional epilepsy consistently cite extent of resection as a significant predictor of outcome. Unfortunately, gross-total resection is not technically feasible in all cases of medically refractory tumor-associated epilepsy. Here, the authors present the case of a 4-year-old girl whose epilepsy was medically controlled after 1-stage electrocorticography-guided subtotal resection (STR) of a large diffuse protoplasmic astrocytoma. They also review the modern literature on epilepsy associated with brain tumors. Outcomes are compared with those following surgical treatment of focal cortical dysplasia and vascular lesions. Gross-total lesional resection shows significant superiority across pathologies and anatomical regions. Despite a considerable number of STRs yielding seizure freedom, other favorable treatment factors have not been defined. Although gross-total lesional resection, if possible, is clearly superior, tailored surgery may still offer patients a significant opportunity for a good outcome. Treatment factors yielding successful seizure control following STR remain to be fully elucidated.

Pharmacoeconomic outcomes for pregabalin: a systematic review in neuropathic pain, generalized anxiety disorder, and epilepsy from a Spanish perspective

INTRODUCTION

Pregabalin is an anticonvulsant approved in Europe for the treatment of neuropathic pain, as an adjunct therapy for epileptic seizures, and recently for generalized anxiety disorder. The aim of this study was to conduct a systematic review to evaluate the cost-effectiveness of pregabalin associated with the treatment of its labeled indications from a societal perspective in Spain.

METHODS

Data from the MEDLINE database were searched using algorithms to identify relevant economic evaluations published in English or Spanish on pregabalin for the management of neuropathic pain, generalized anxiety disorder (GAD), and epilepsy in Spanish patients over the last 10 years.

RESULTS

In total, 52 potentially relevant abstracts were identified from the MEDLINE database. Twenty manuscripts met the inclusion criteria. The majority of the selected papers (14/20) evaluated pregabalin for neuropathic pain from a societal perspective in Spain (5 economic models of pregabalin vs. gabapentin, 4 economic analyses of pregabalin in comparison with usual care, 4 economic evaluations comparing pregabalin monotherapy with add-on strategies, and one that evaluated different times of initiating pregabalin therapy). Five studies analyzed the use of pregabalin in Spain for the management of GAD (one cost-effectiveness model that compared pregabalin with venlafaxine, 2 secondary analyses in benzodiazepine-refractory patients, and 2 studies evaluating pregabalin vs. usual care in patients refractory to standard regimens). The last manuscript described a cost-effectiveness model that compared pregabalin versus levetiracetam use for the treatment of refractory partial epilepsy.

CONCLUSION

The majority of published evidence supports the possibility that pregabalin could be a cost-effective and/or cost-saving alternative for the treatment of refractory epilepsy, GAD, and neuropathic pain, in both treatment-naïve patients and in those who have demonstrated inadequate response or intolerance to previous therapy.

The pathology of magnetic-resonance-imaging-negative epilepsy

Patients with magnetic-resonance-imaging (MRI)-negative (or 'nonlesional') pharmacoresistant focal epilepsy are the most challenging group undergoing presurgical evaluation. Few large-scale studies have systematically reviewed the pathological substrates underlying MRI-negative epilepsies. In the current study, histopathological specimens were retrospectively reviewed from MRI-negative epilepsy patients (n=95, mean age=30 years, 50% female subjects). Focal cortical dysplasia cases were classified according to the International League Against Epilepsy (ILAE) and Palmini et al classifications. The most common pathologies found in this MRI-negative cohort included: focal cortical dysplasia (n=43, 45%), gliosis (n=21, 22%), hamartia+gliosis (n=12, 13%), and hippocampal sclerosis (n=9, 9%). The majority of focal cortical dysplasia were ILAE type I (n=37) or Palmini type I (n=39). Seven patients had no identifiable pathological abnormalities. The existence of positive pathology was not significantly associated with age or temporal/extratemporal resection. Follow-up data post surgery was available in 90 patients; 63 (70%) and 57 (63%) attained seizure freedom at 6 and 12 months, respectively. The finding of positive pathology was significantly associated with seizure-free outcome at 6 months (P=0.035), but not at 12 months. In subgroup analysis, the focal cortical dysplasia group was not significantly correlated with seizure-free outcome, as compared with the negative-pathology groups at either 6 or 12 months. Of note, the finding of hippocampal sclerosis had a significant positive correlation with seizure-free outcome when compared with the negative-pathology group (P=0.009 and 0.004 for 6- and 12-month outcome, respectively). Absence of a significant histopathology in the resected surgical specimen did not preclude seizure freedom. In conclusion, our study highlights the heterogeneity of epileptic pathologies in MRI-negative epilepsies, with focal cortical dysplasia being the most common finding. The existence of positive pathology in surgical specimen may be a good indication for short-term good seizure outcome. There is a small subset of cases in which no pathological abnormalities are identified.

Seizures in low-grade gliomas: natural history, pathogenesis, and outcome after treatments

Seizures represent a common symptom in low-grade gliomas; when uncontrolled, they significantly contribute to patient morbidity and negatively impact quality of life. Tumor location and histology influence the risk for epilepsy. The pathogenesis of tumor-related epilepsy is multifactorial and may differ among tumor histologies (glioneuronal tumors vs diffuse grade II gliomas). Gross total resection is the strongest predictor of seizure freedom in addition to clinical factors, such as preoperative seizure duration, type, and control with antiepileptic drugs (AEDs). Epilepsy surgery may improve seizure control. Radiotherapy and chemotherapy with alkylating agents (procarbazine + CCNU+ vincristine, temozolomide) are effective in reducing the frequency of seizures in patients with pharmacoresistant epilepsy. Newer AEDs (levetiracetam, topiramate, lacosamide) seem to be better tolerated than the old AEDs (phenobarbital, phenytoin, carbamazepine), but there is lack of evidence regarding their superiority in terms of efficacy.

Seizure outcome of surgical treatment of focal epilepsy associated with low-grade tumors in children

OBJECT

Low-grade tumor (LGT) is an increasingly recognized cause of focal epilepsies, particularly in children and young adults, and is frequently associated with cortical dysplasia. The optimal surgical treatment of epileptogenic LGTs in pediatric patients has not been fully established.

METHODS

In the present study, the authors retrospectively reviewed 30 patients (age range 3-18 years) who underwent surgery for histopathologically confirmed LGTs, in which seizures were the only clinical manifestation. The patients were divided into 2 groups according to the type of surgical treatment: patients in Group A (20 cases) underwent only tumor removal (lesionectomy), whereas patients in Group B (11 cases) underwent removal of the tumor and the adjacent epileptogenic zone (tailored surgery). One of the patients, who underwent 2 operations, is included in both groups. Follow-up ranged from 1 to 17 years.

RESULTS

Sixteen (80%) of 20 patients in Group A had an Engel Class I outcome. In this group, 3 of 4 patients who were in Engel Classes II and III had temporomesial lesions. All patients in Group B had temporomesial tumors and were seizure free (Engel Class I). In this series, in temporolateral and extratemporal tumor locations, lesionectomy yielded a good seizure outcome. In addition, a young age at seizure onset (in particular < 4 years) was associated with a poor seizure outcome.

CONCLUSIONS

Tailored resection in temporomesial LGTs was associated with excellent seizure outcome, indicating that an adequate presurgical evaluation including extensive neurophysiological evaluation (long-term videoelectroencephalography monitoring) to plan appropriate surgical strategy is advised.

Neuropathology of pediatric epilepsy

The preoperative study of patients who are candidates for epilepsy surgery often classifies their epileptic foci as "lesional" or "non-lesional" based upon evidence from neuroimaging. Many lesions not detected by MRI are found by microscopic examination of the resected tissue. Advances have been made in neuropathological techniques to study resected brain tissue and to specify the types of focal cortical dysgeneses and other lesions by extending microscopic findings by applying immunocytochemical markers that identify specific types and distributions of neurons and glial cells that denote tissue architecture. There may be etiological differences between focal and extensive cortical dysplasias involving many gyri or entire lobes of cerebral cortex. Of additional importance in pediatric brain resections is that these modern techniques also denote cellular maturation and can identify abnormal cells with mixed lineage. α-B-crystallin can serve as a metabolic tissue marker of epileptic activity, regardless of the presence or absence of a "structural" lesion by MRI or by conventional histopathology. Satellitosis may contribute to epileptogenic neurons and later to death of those neurons. The classification of malformations of the brain is a process requiring continuous updates that include genetics, neuroimaging, and neuropathology as new data emerge, but should not be exclusive to one region of the brain, such as cerebral cortex or cerebellum. Standardization in neuropathological terminology enhances scientific communication. The ILAE recently published a useful consensus classification of focal cortical dysplasias that is flexible to enable future revisions and changes as new data become available.

Dual Pathology in Rasmussen's Encephalitis: A Report of Coexistent Focal Cortical Dysplasia and Review of the Literature

Rasmussen's encephalitis is a well-established, albeit rare cause of medically intractable epilepsy. In a small number of Rasmussen's cases, a second pathology is identified, which independently can cause medically intractable seizures (dual pathology). This paper documents a case of a 13-year-old male who presented with medically intractable epilepsy. The patient underwent a series of surgical resections, early on resulting in a diagnosis of focal cortical dysplasia and later yielding a diagnosis of coexistent Rasmussen's encephalitis, marked by chronic inflammation, microglial nodules, and focal cortical atrophy, combined with focal cortical dysplasia (Palmini et al. type IIA, ILAE type IIA). The literature on dual pathology in the setting of Rasmussen's encephalitis is reviewed.

Utilization of frozen sections in the evaluation of chronic epilepsy-related cases

The role of frozen section consultation in the evaluation of chronic epilepsy-associated surgical excisions of brain tissue has not been previously examined. The study retrospectively reviews 335 cases in which a frozen section consultation was obtained in the setting of a resection for chronic epilepsy. In most cases (n = 323), 3 or fewer frozen sections were performed. The most commonly identified pathologies on final diagnosis included tumor or tumorlike lesions (79.1% of cases) and focal cortical dysplasia (20.9% of cases). Frozen section diagnoses discrepant with final diagnoses due to sampling error or misinterpretation were noted in 39 cases and most commonly involved a diagnosis of gliosis or tumor in the setting of a focal cortical dysplasia or diagnosis of gliosis in the setting of a low-grade tumor. In conclusion, frozen section consultation may be particularly useful in the evaluation of neoplasms arising in the setting of chronic epilepsy. Some epilepsy-associated pathology, such as focal cortical dysplasia, may be difficult to diagnose at the time of frozen section and such cases may not be an ideal target for intraoperative frozen section consultation.

Surgical management of glioneuronal tumors with drug-resistant epilepsy

In this review, we discuss the options for the surgical management of glioneuronal tumors (GNTs) associated with drug-resistant epilepsy, with an emphasis on the surgical issues involved in addressing the epileptogenic nature of these lesions. We briefly summarize the pathological hallmarks of these lesions in order to outline how these tumors contribute to seizure activity. Understanding the pathophysiology of these lesions is important in discussing the advantages and disadvantages of different surgical strategies. There have been a number of studies that have investigated the utility of different surgical approaches in improving seizure outcome, and we highlight some of these studies in order to shed light on surgical issues related to these tumors.

Histopathological evaluation of the nervous system in National Toxicology Program rodent studies: a modified approach

This article outlines the changes and underlying rationale for modifications to the histopathological evaluation of the nervous system during toxicology and carcinogenesis studies conducted by the National Toxicology Program (NTP). In the past, routine evaluation of the nervous system was mostly limited to three sections of brain, and occasionally the spinal cord and peripheral nerves. Factors such as the increasing occurrence of human neurological diseases and associated economical cost burden, the role of unidentified environmental stressors in neurodegenerative disorders, multiple therapeutic drug-induced neuropathies noted in human clinical trials, and the exponential use of environmental chemicals with unknown neurotoxic potential necessitate a more extensive evaluation of the nervous system. The NTP has modified its protocol to include examination of key anatomic subsites related to neurodegenerative diseases such as Parkinson's disease. Modifications include four additional sections of the brain. Increasing the number of brain sections permits examination of a greater number of specific anatomic subsites with unique vulnerability. In addition, the spinal cord, peripheral nerves, trigeminal ganglion, and intestinal autonomic ganglia will be evaluated as needed. It is expected that this modified approach will increase the sensitivity of detecting neurotoxicants and neurocarcinogens important in human neurologic and neurodegenerative disorders.

Epilepsy and brain tumors

PURPOSE OF REVIEW

To present an overview of the recent findings in pathophysiology and management of epileptic seizures in patients with brain tumors.

RECENT FINDINGS

Low-grade gliomas are the most epileptogenic brain tumors. Regarding pathophysiology, the role of peritumoral changes [hypoxia and acidosis, blood-brain barrier (BBB) disruption, increase or decrease of neurotransmitters and receptors] are of increasing importance. Tumor-associated epilepsy and tumor growth could have some common molecular pathways. Total/subtotal surgical resection (with or without epilepsy surgery) allows a seizure control in a high percentage of patients. Radiotherapy and chemotherapy as well have a role. New antiepileptic drugs are promising, both in terms of efficacy and tolerability. The resistance to antiepileptic drugs is still a major problem: new insights into pathogenesis are needed to develop strategies to manipulate the pharmakoresistance.

SUMMARY

Epileptic seizures in brain tumors have been definitely recognized as one of the major problems in patients with brain tumors, and need specific and multidisciplinary approaches.