Ictal SPECT in Psychogenic Nonepileptic and Epileptic Seizures

Psychogenic nonepileptic seizures (PNES) are a common and debilitating problem in patients with epilepsy. They can be virtually indistinguishable from epileptic seizures, demanding video-electroencaphalogram monitoring, which is costly and not widely available, for differential diagnosis. Specific functional brain correlates of PNES have not been demonstrated so far. We hypothesized that PNES and epileptic seizures have distinct brain activation patterns, assessed by functional neuroimaging during ictal events of both conditions.

Compare ictal brain activation patterns of PNES and epileptic seizures using single-photon emission computerized tomography.

We prospectively assessed brain functional activation using single-photon emission computerized tomography 99mTc-ethyl cysteinate dimer in 26 patients with PNES, confirmed by trained psychiatrists in epileptology, who had their seizures induced by provocative tests compared with 22 age- and sex-matched subjects with temporal lobe epilepsy who underwent prolonged intensive video-electroencaphalogram monitoring.

In PNES patients compared with temporal lobe epilepsy group, we found a consistent increase in regional cerebral blood flow in the right precuneus (Brodmann area 7; P = 0.003) and right posterior cingulate cortex (Brodmann area 31; P = 0.001), as well as a decrease in regional cerebral blood flow in the right amygdala (P = 0.027).

Activation of default mode network brain areas and temporoparietal junction may be a distinct feature of ictal PNES and could be explained by a disruption between movement prediction input and sensory outcome. Such information mismatch might be the neurobiological underpinning of dissociative episodes.