The challenge of localizing hyperkinetic seizures: timing matters!

Hyperkinetic seizures (HSs), which are generally associated with the frontal lobe (although they may indeed originate from other regions too), are characterized by complex motor movements with high amplitude and short duration.

To differentiate HSs originating from the frontal and extrafrontal lobes via electroencephalographic (EEG) features, notably timing.

Clinical and video-EEG data of patients with HS were examined retrospectively. The localization of the ictal and interictal discharges, the onset and duration of the hyperkinetic movements, as well as the ictal-postictal electrophysiological and semiological features, were reviewed. The patients were divided into two groups according to their HS onset timing: if the onset of hyperkinetic semiology was in the first 10 seconds, they were classified as early-onset HS; if later, as late-onset HS.

We included 29 patients (171 seizures); seizure onset was localized to the frontal region in 21 patients, and to the temporal and temporo-occipital regions in 6 patients, and it could not be determined in 2 patients. The HSs started in the early period in 21 patients, and in the late period in 8 patients; HSs originating from the frontal region started earlier than those originating from the temporal region (6.2 versus 25.7 seconds respectively; p = 0.002). Electrophysiological (35.4 versus 95.7 seconds respectively; p = 0.004) and clinical (34.3 versus 94.6 seconds respectively; p = 0.003) seizure durations were shorter in frontal-onset seizures compared with temporal-onset seizures.

The timing of HS onset and the duration of the seizures are informative in terms of localization. Earlier onset of hyperkinetic semiology and shorter duration may point to a frontal origin.