Proton magnetic resonance spectroscopic imaging suggests progressive neuronal damage in human temporal lobe epilepsy

Whether temporal lobe epilepsy (TLE) is the result of an isolated, early injury or whether there is ongoing neuronal damage due to seizures is often debated. We attempted to examine the long-term effect of seizures using proton magnetic resonance spectroscopic imaging (1H-MRSI), which can quantify neuronal loss or dysfunction based on reduced signals from the neuronal marker N-acetylaspartate (NAA). We performed 1H-MRSI in 82 consecutive patients with medically intractable, non-foreign-tissue TLE to determine whether there was a correlation between seizure frequency, type or duration of epilepsy and NAA to creatine ratios (NAA/Cr). Spectroscopic resonance intensities were categorized as to whether they were measured from the temporal lobe ipsilateral or contralateral to the predominant EEG focus. Ipsilateral and contralateral NAA/Cr was negatively correlated with duration of epilepsy. Furthermore, patients with frequent generalized tonic-clonic seizures had lower NAA/Cr than patients with no or rare generalized tonic-clonic seizures. The results suggest that although an early injury may cause asymmetric temporal lobe damage that is present at the onset of epilepsy, generalized seizures may induce additional neuronal damage that progresses over the course of the disease.