Focal cortical release of endogenous opioids during reading-induced seizures.

Background: Studies in animals implicate endogenous release of opioid peptides as a mechanism for terminating partial and generalised seizures. To localise dynamic changes in opioid neurotransmission associated with partial seizures and higher cognitive function, we investigated the release of endogenous opioids in patients with reading-induced seizures compared with healthy controls.

Methods: Five patients who had reading epilepsy and six controls had 11C-diprenorphine (DPN) positron-emission-tomography (PET) scans while reading a string of symbols (baseline) or a scientific paper (activation). Statistical parametric mapping was used to find areas with differences in opioid-receptor binding.

Findings: On activation scans mean 11C-DPN binding to opioid receptors was significantly lower (p<0.05 corrected for multiple non-independent comparisons) in the left parieto-temporo-occipital cortex (Brodmann area 37) in reading-epilepsy patients compared with controls.

Interpretation: These findings suggest that opioid-like substances are involved in the termination of reading-induced seizures.