The chapeau de gendarme sign can be evoked by lateral prefrontal epileptic seizures

The 'chapeau de gendarme' (CDG) sign, characterised by a symmetric down-turned mouth, has been considered as a semiological hallmark of focal epileptic seizures with cingulate or insular involvement. We report three cases in which the CDG sign featured in habitual seizures.

The epileptogenic zones of these three patients were localized in the lateral prefrontal cortex by video-stereoelectroencephalography monitoring. A sulcal resection has led to a seizure-free outcome in each patient.

Ictal stereoelectroencephalography demonstrated that ictal discharges arising from the lateral prefrontal cortices were immediately followed by low-voltage fast activity, concomitantly involving the anterior insulo-cingulate cortices, and preceding the onset of the CDG signs. Limited sulcal resection and seizure freedom after surgery confirmed the restricted distributions of the epileptogenic zones in the lateral prefrontal cortex.

Our observations led us to speculate that the epileptic discharges could enter the emotional insulo-cingulate cortical system through the prefrontal-cingulate inhibitory projections (feedforward pattern) -arising from the supragranular layers of the lateral prefrontal cortex-and proceed to the deeper layers of the anterior-middle cingulate cortex, trigger the co-occurrence of gamma bands, and evoke a set of exaggerated behaviours, which is often accompanied by the unique facial sign.