Introduction from Dr Markus Reuber, editor-in-chief of Seizure
Treatment decisions in chronic medical disorders are based on studies only capturing likely outcomes in the short term. This is problematic enough for interventions with fully reversible effects but more profoundly troubling when the treatment cannot simply be stopped with the expectation that the patient would return to their pre-treatment baseline. The reasons for this are obvious: researchers are keen to learn quickly whether new treatments work – or work better than the previous therapeutic options. Long-term follow-up studies are difficult to conduct because participants may be lost to follow up or subject to personal and medical changes with potential effects on the outcome after the intervention of interest. These and other methodological problems mean that long-term follow up data is relatively hard to come by and sometimes difficult to interpret.
My Editor’s Choice from the current issue of Seizure makes an important contribution to our understanding an intervention which can only really be evaluated in a meaningful way by looking at long-term follow-up data: temporal lobe epilepsy surgery (1). The main neurological concern in relation to this form of epilepsy surgery is damage to brain structures supporting memory functions. Previous cross-sectional and short-term longitudinal investigations raised the possibility that temporal lobe epilepsy may be associated with an acceleration of “normal” age-related memory decline (2, 3). The new longitudinal study by Helmstaedter et al. in the current issue of Seizure describes cognitive outcomes a mean of eight years (5-22) after epilepsy surgery (3). On the whole the findings are reassuring. Although the major immediate losses of memory functions with temporal lobe epilepsy surgery were confirmed, these functions did not continue to decline at the speed of “normal” age-related memory decline (i.e. the rate at which memory performance declines in healthy individuals). Over the longer term, memory functions in patients with temporal lobe epilepsy (TLE) who had undergone surgery did not differ from those whose seizure disorder had been treated with medication alone. Although successful epilepsy surgery was not found to be associated with a group-level improvement of memory functions directly, a reduction in antiepileptic drug load (perhaps made possible by successful epilepsy surgery) was. The study also provided some additional evidence for the concept of “double winners” and “double losers” from epilepsy surgery. Patients were more likely to be seizure-free after epilepsy surgery. In those who had become seizure free, a degree of recovery of verbal memory was more and memory decline less likely than among those still experiencing seizures. From a neuropsychological point of view, epilepsy surgery therefore comes out as a good treatment for TLE – as long as it is offered to patients who will become seizure-free with this intervention!
(1) Helmstaedter C, Elger C, Vogt V. Cognitive outcomes more than 5 years after temporal lobe epilepsy surgery: Remarkable functional recovery when seizures are controlled. Seizure 2018 – please add bibliographic details.
(2) Helmstaedter C, Reuber M, Elger CC. Interaction of cognitive aging and memory deficits related to epilepsy surgery. Ann.Neurol. 2002;52(1):89-94.
(3) Helmstaedter C, Kurthen M, Lux S, Reuber M, Elger CE. Chronic epilepsy and cognition: a longitudinal study in temporal lobe epilepsy. Ann.Neurol. 2003;54(4):425-432.