Epilepsy and the subsequent risk of cerebral tumour: record linkage retrospective cohort study

Shedding light on glioma growth

Cancer is known for opportunistically utilizing resources from its surroundings for its own growth and survival. In this issue of Cell, Venkatesh et al. demonstrate that this also occurs in the brain, identifying neuronal activity-induced secretion of neuroligin-3 as a novel mechanism promoting glioma proliferation.

Development and validation of an epidemiologic case definition of epilepsy for use with routinely collected Australian health data

OBJECTIVES

We report the diagnostic validity of a selection algorithm for identifying epilepsy cases.

STUDY DESIGN AND SETTING

Retrospective validation study of International Classification of Diseases 10th Revision Australian Modification (ICD-10AM)-coded hospital records and pharmaceutical data sampled from 300 consecutive potential epilepsy-coded cases and 300 randomly chosen cases without epilepsy from 3/7/2012 to 10/7/2013. Two epilepsy specialists independently validated the diagnosis of epilepsy. A multivariable logistic regression model was fitted to identify the optimum coding algorithm for epilepsy and was internally validated.

RESULTS

One hundred fifty-eight out of three hundred (52.6%) epilepsy-coded records and 0/300 (0%) nonepilepsy records were confirmed to have epilepsy. The kappa for interrater agreement was 0.89 (95% CI=0.81-0.97). The model utilizing epilepsy (G40), status epilepticus (G41) and ≥1 antiepileptic drug (AED) conferred the highest positive predictive value of 81.4% (95% CI=73.1-87.9) and a specificity of 99.9% (95% CI=99.9-100.0). The area under the receiver operating curve was 0.90 (95% CI=0.88-0.93).

CONCLUSION

When combined with pharmaceutical data, the precision of case identification for epilepsy data linkage design was considerably improved and could provide considerable potential for efficient and reasonably accurate case ascertainment in epidemiological studies.

A role for intracellular zinc in glioma alteration of neuronal chloride equilibrium

Glioma patients commonly suffer from epileptic seizures. However, the mechanisms of glioma-associated epilepsy are far to be completely understood. Using glioma-neurons co-cultures, we found that tumor cells are able to deeply influence neuronal chloride homeostasis, by depolarizing the reversal potential of γ-aminobutyric acid (GABA)-evoked currents (EGABA). EGABA depolarizing shift is due to zinc-dependent reduction of neuronal KCC2 activity and requires glutamate release from glioma cells. Consistently, intracellular zinc loading rapidly depolarizes EGABA in mouse hippocampal neurons, through the Src/Trk pathway and this effect is promptly reverted upon zinc chelation. This study provides a possible molecular mechanism linking glioma invasion to excitation/inhibition imbalance and epileptic seizures, through the zinc-mediated disruption of neuronal chloride homeostasis.

[Glioma-associated epilepsy]

BACKGROUND

Epileptic seizures are a common symptom in patients with primary brain tumours of the glioma type. The paper presents a discussion of epileptogenesis, choice of medication and follow-up of these patients.

METHOD

The article is based on a search in PubMed and selection of articles based on the authors' discretionary judgement and clinical experience with this patient group.

RESULTS

Epileptic seizures are a common symptom of glioma, particularly the low-grade types. The background to glioma-associated epilepsy is multifactorial, and the molecular biological characteristics of the tumour probably play a central part in the epileptogenesis. Effective treatment of epileptic seizures is of great importance to the quality of life of the glioma patient. Seizure frequency and the effectiveness of anti-epileptic treatment vary, and some patients require treatment with several anti-epileptic drugs. Surgical and oncological treatment of the tumour will also often reduce the frequency of seizures.

CONCLUSION

As a general rule, antiepileptics without enzyme-inducing properties and with low protein-binding should be preferred for glioma patients. This will reduce the risk of interactions with chemotherapy or steroid therapy. Patients with brain tumours are particularly vulnerable to the effects on wakefulness, moods and cognition, and this should be borne in mind in the choice of medication and in follow-up. Haematological status should be monitored particularly closely when there is concomitant use of chemotherapy and antiepileptic drugs that may affect the bone marrow function.

Coexistence of schizophrenia and epilepsy: record-linkage studies

For many years, there has been interest in a possible link between epilepsy and schizophrenia. A recent study found a strong, bidirectional link between the two conditions: people with one had a higher than average risk of having the other. Using two large data sets of hospital admission data, we investigated whether schizophrenia and epilepsy occur together in individuals more commonly than expected by chance. We undertook a retrospective cohort study using the Oxford Record Linkage Study (ORLS) and English national linked Hospital Episode Statistics to investigate the coexistence of these conditions. There was an elevated risk of epilepsy in people admitted to hospital with schizophrenia (ORLS rate ratio 2.1, 95% confidence interval 1.6-2.6; England 3.0, 2.9-3.1) and an elevated risk of schizophrenia in people admitted to hospital with epilepsy (ORLS 5.1, 4.1-6.2; England 4.5, 4.3-4.6). We found no consistent difference between male and female patients. Schizophrenia and epilepsy occur together in individuals more frequently than expected by chance.