Magnetoencephalographic analysis of paroxysmal fast activity in patients with epileptic spasms

This study sought to demonstrate the origin and propagation of paroxysmal fast activity (PFA) in patients with epileptic spasms (ESs), using time-frequency analyses of magnetoencephalogram (MEG) PFA recordings.

A 204-channel helmet-shaped MEG, with a 600Hz sampling rate, was used to examine PFA in 3 children with ESs. We analyzed MEG recordings of PFA by short-time Fourier transform and the aberrant area or high-power spectrum was superimposed onto reconstructed three-dimensional magnetic resonance images as moving images. One ictal discharge was collected. One child and one adult with PFA due to Lennox-Gastaut syndrome were also examined for comparison.

All four PFAs in Patient 1 and five PFAs in Patient 3 were generated from one hemisphere. In Patient 2, four of seven PFAs were generated from one hemisphere and the remaining three were generated from both hemispheres. In Patient 3, one ictal MEG showed ictal discharges that were generated from the same area as the PFA, although the electroencephalogram showed no discharge. In Patients with Lennox-Gastaut syndrome, all 10 PFAs were generated from bilateral hemispheres simultaneously.

Short-time Fourier transform analyses of MEG PFA can show the origin and form of propagation of PFA. These results suggest that ESs are representative of focal seizures and the mechanism of PFA is different between ESs and Lennox-Gastaut syndrome.