What is the current evidence on decision-making after referral for temporal lobe epilepsy surgery?

The added clinical and economic value of diagnostic testing for epilepsy surgery

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We assess the added value of diagnostic imaging for epilepsy surgery.

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A cost-effectiveness evaluation is conducted considering a range of strategies.

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We find that additional PET and invasive EEG investigations are most cost-effective.

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The long-term effectiveness of surgery has a large impact on the optimal strategy.

The costs, benefits and risks associated with diagnostic imaging investigations for epilepsy surgery necessitate the identification of an optimal pathway in the pre-surgical workup. In order to assess the added value of additional investigations a full cost-effectiveness evaluation should be conducted, taking into account all of the life-time costs and benefits associated with undertaking additional investigations. This paper considers and applies the appropriate framework against which a full evaluation should be assessed.

We conducted a systematic review to evaluate the progression of the literature through this framework, finding that only isolated elements of added value have been appropriately evaluated. The results from applying the full added value framework are also presented, identifying an optimal strategy for pre-surgical evaluation for temporal lobe epilepsy surgery. Our results suggest that additional FDG–PET and invasive EEG investigations after an initially discordant MRI and video-EEG appears cost-effective, and that the value of subsequent invasive-EEGs is closely linked to the maintenance of longer-term benefits after surgery.

It is integral to the evaluation of imaging technologies in the work-up for epilepsy surgery that the impact of the use of these technologies on clinical decision-making, and on further treatment decisions, is considered fully when informing cost-effectiveness.

Epilepsy surgery: how accurate are multidisciplinary teams in predicting outcome?

BACKGROUND

Since epilepsy surgery is an elective procedure, patients need to weigh the risks of the procedure against the likely outcome if they are to make an informed decision to proceed. The aim of this study was to examine the accuracy of multidisciplinary team predictions of postoperative outcome in epilepsy surgery candidates.

METHODS

An experienced multidisciplinary team provided preoperative predictions of postoperative outcome in 94 temporal lobe epilepsy patients who subsequently proceeded to surgery and were followed up one year later.

RESULTS

Team predictions of postoperative outcome were generally accurate for groups of patients judged to have a 30%, 40%, 50% or 60% chance of becoming seizure free. Team estimates of odds tended to regress towards the mean. Logistic regression analyses were more accurate than the team estimates in identifying patients with a very good (>70%) or very poor (<20%) chance of complete seizure freedom. Non localising scalp EEG, necessitating the need for an invasive EEG study prior to surgery was a significant predictor of poor postoperative outcome in this series.

CONCLUSIONS

Probabilities based on logistic regression models may augment and improve the accuracy of clinical estimates of postoperative outcome in patients with a very good or very poor chance of being rendered seizure free by surgery, by counteracting the tendency of regression towards the mean in team decision making.

Anticonvulsant activity of DNS II fraction in the acute seizure models

AIM OF THE STUDY

Delphinium nordhagenii belongs to family Ranunculaceae, it is widely found in tropical areas of Pakistan. Other species of Delphinium are reported as anticonvulsant and are traditionally used in the treatment of epilepsy. Delphinium nordhagenii is used by local healer in Pakistan but never used for scientific investigation as anticonvulsant. Thus, Delphinium nordhagenii was subjected to bioassay-guided fractionation and the most active fraction, i.e. DNS II acetone was chosen for further testing in the acute seizure models of epilepsy to study the antiepileptic potential in male mice.

MATERIALS AND METHODS

Different doses (60, 65 and 70mg/kg, i.p.) of DNS II acetone fraction of Delphinium nordhagenii was administered 30min prior the chemoconvulsant's injection in the male mice. Convulsive doses of chemoconvulsants (pentylenetetrazole 90mg/kg, s.c. and picrotoxin 3.15mg/kg, s.c.) were used. The mice were observed 45-90min for the presence of seizures. Moreover, four different doses of DNS II (60, 65, 70 and 100mg/kg, i.p.) were tested in the MES test.

RESULTS

The DNS II acetone fraction of Delphinium nordhagenii has exhibited the anticonvulsant actions by preventing the seizures against PTZ- and picrotoxin-induced seizure as well as 100% seizure protection in MES test. The results are comparable with standard AEDs (diazepam 7.5mg/kg, i.p. and phenytoin 20mg/kg, i.p.).

CONCLUSIONS

These findings suggest that the Delphinium nordhagenii possesses the anticonvulsant activity. Further analysis is needed to confirm the structure and target the extended activity profile.

The added value of [18F]-fluoro-D-deoxyglucose positron emission tomography in screening for temporal lobe epilepsy surgery

PURPOSE

[18F]-Fluoro-d-deoxyglucose positron emission tomography (FDG-PET) is an expensive, invasive, and not widely available technique used in the presurgical evaluation of temporal lobe epilepsy. We assessed its added value to the decision-making process in relation to other commonly used tests.

METHODS

In a retrospective study of a large series of consecutive patients referred to the national Dutch epilepsy surgery program between 1996 and 2002, the contribution of FDG-PET, magnetic resonance imaging (MRI), and video-electroencephalogram (video-EEG) monitoring findings, alone or in combination, to the decision whether to perform surgery was investigated. The impact of FDG-PET was quantified by comparing documented decisions concerning surgery before and after FDG-PET results.

RESULTS

Of 469 included patients, 110 (23%) underwent FDG-PET. In 78 of these patients (71%), FDG-PET findings led clinicians to change the decision they had made based on MRI and video-EEG monitoring findings. In 17% of all referred patients, the decision regarding surgical candidacy was based on FDG-PET findings. FDG-PET was most useful when previous MRI results were normal (p < 0.0001) or did not show unilateral temporal abnormalities (p < 0.0001), or when ictal EEG results were not consistent with MRI findings (p < 0.0001) or videotaped seizure semiology (p = 0.027). The positive and negative predictive values for MRI and video-EEG monitoring, which ranged from 0.48 to 0.67, were improved to 0.62 to 0.86 in combination with FDG-PET.

CONCLUSIONS

In patients referred for TLE surgery, FDG-PET findings can form the basis for deciding whether a patient is eligible for surgery, and especially when MRI or video-EEG monitoring are nonlocalizing.