ABSTRACT
We present a case of MRI negative SMA seizure with the seizure onset zone in the secondary leg area on the superior bank of the Sylvian fissure, localized with multiscale electro-clinical and neuroradiological examinations. The 34-year-old female patient's intractable epilepsy started at age 14. She had diffuse pain aura in her left leg followed by tonic posturing with fully preserved consciousness suggesting parieto-fronto-medial seizure propagation. Her daily nocturnal SMA seizures became drug-resistant. Multiple 3T MRI images and neuropsychological evaluations were normal. Interictal PET detected a right parietal and insular FDG hypometabolism. The seizure onset zone and the symptomatogenic zone were localized by invasive electrophysiology. The insular deep electrode showed the propagation of ictal activity with an onset in the secondary sensory leg area through the insula to the fronto-medial surface. Eighteen spontaneous seizures, electrical cortical stimulation and cortical mapping confirmed the designated area of the resection, which was later proved macroscopically abnormal during surgery. The histological and immunohistological workup confirmed focal cortical dysplasia (IIb type). Postoperative postprocessing morphometry of the preoperative MRI study confirmed the lesion in the right inferior parietal lobe. The patient remained seizure free after surgery for more than 4 years, and medication free for the last two years. Our results concluded that the insula has a "relay" or "node" function in the parieto-opercular-fronto-medial epileptic network. The insular functional connectivity predisposed frontal propagation of the epileptic activity in the connectome of her epilepsy. The three-way insular structural connectivity has determining function on the seizure propagation.