No abstract

SUMMARYStartle seizures belong to reflex epilepsy syndromes. They usually occur in patients with mental deficiency and showing widely extended cortical lesions, often involving the sensorimotor area. Here we report three cases who did not fulfill these criteria, and in whom stereotactic electroencephalography (SEEG) recordings demonstrated the prominent involvement of the supplementary motor area (SMA). Visual analysis was complemented by time-frequency analysis of SEEG signals using a neuroimaging approach (Epileptogenicity Maps), which showed at seizure onset a significant increase of high frequency oscillations (HFOs, 60-100 Hz) over the premotor and prefrontal areas. Critically, in all cases, the SMA showed ictal HFOs at seizure onset and was included in the surgical resection. All patients became seizure-free after surgery, and histopathological examinations showed no specific lesion. These cases suggest the prominent but not exclusive role of SMA in startle seizures, and highlight the fact that surgery can be considered even in the absence of any magnetic resonance imaging (MRI) lesion.

Refractory extratemporal lobe epilepsy (ETLE) tends to have a less favourable surgical outcome in comparison to temporal lobe epilepsy. ETLE poses specific diagnostic and therapeutic challenges, particularly in cases where seizures develop from the midline. This review focuses on the diagnostic challenges and therapeutic strategies in mesial ETLE. The great diversity of interhemispheric functional areas and extensive connectivity to extramesial structures results in very heterogeneous seizure semiology. Specific signs, such as ictal body turning, can suggest a mesial onset. The hidden cortex of the mesial wall furthermore gives rise to specific diagnostic difficulties due to the low localizing value of scalp EEG. Advanced imaging, as well as targeted intracranial studies, can substantially contribute to depict the seizure onset zone since electroclinical findings are difficult to interpret in most cases. Surgical accessibility of the interhemispheric space can be challenging, both for the placement of subdural grids, as well as for resective surgery. When facing the hidden cortex on the mesial wall of the hemispheres, targeted intra‐ or extra‐operative intracranial recordings can lead to satisfactory outcomes in properly selected cases.