Abstracts

Rationale: Temporal lobe epilepsy determined by MTS have a higher incidence of depression. Studies using animal models and neuroimaging in humans suggest a common serotonergic mechanism. There is a lack of studies in human brain. Measurement of serotonin in brain is a research strategy commonly used in animal models. We compared the concentration of 5HT in hippocampus of patients with TLE-MTS with and without psychiatric disorders (PD). We also compared [5HT] with the severity of epilepsy. Methods: Thirty-five surgically treated patients with TLE-MTS, 16 (45,7%) with PD were included. [5HT] was measured using High Pressure Liquid Chromatography with fluorescence detection. Results: No differences were found between groups regarding the dose of carbamazepine or oxcarbazepine, monotherapy or polytherapy. The mean [5HT] was 0,3359ng/mg. There was a correlation between lower levels of [5HT] and the presence of generalized tonic clonic seizures (GTC) (p=0,48), but not frequency (p=0.138) of GTC. There was also a correlation between the use of SSRIs and lower frequency of GTC (p=0,028).There was no difference among [5HT] and the presence of PD, age of onset and duration of epilepsy, seizure frequency and history of febrile seizures or status epilepticus. However, the use of antipsychotic drug was correlated with lower [5HT] (p = 0.029). No significant differences were found between the presence of psychosis and lower [5HT]. Conclusions: This is the first study measuring the concentration of serotonin in human brain and comparing groups with TLE-MTS with and without PD. In our study, we showed that [5HT] is related to the severity of epilepsy, but not to the presence of PD. Patients with and without PD, as well as patients who did or did not had GTC seizures, were similar regarding AEDs, considering dose and monotherapy/polytherapy. AEDs effect is unlikely to interfere with the results of the [5HT] levels. We demonstrated a correlation between a greater presence of GTC seizures in patients who did not use SSRIs. The hypothesis that patients with depression have more GTC seizures is in contradicted by the lack of correlation between presence of GTC seizures with PD. Another possibility is an antiepileptic effect of the SSRI providing an adjuvant effect in the treatment of these patients. We found a correlation between antipsychotic use and lower levels of serotonin. Although a relationship between serotonin levels and PD was not found, this finding can be explained by a lower concentration of serotonin in patients with a more severe presentation of psychosis. However this sample was too small for this assumption. In conclusion, the relationship between epilepsy and PD probably involve more intricate mechanisms than serotonin concentration. We also suggest that SSRIs may have an antiepileptic effect, which has been recently documented in literature.