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Purpose: To retrospectively analyse a single-centre consecutive surgical series of patients with temporal lobe epilepsy (TLE) and negative MRI. To identify factors associated with postoperative seizure outcome among several presurgical, surgical and postsurgical variables., Methods: Clinical records of 866 patients who received temporal lobe resections and with a minimum follow-up of 12 months were retrospectively searched for MRI-negative cases. Anamnestic, clinical, neurophysiological, surgical, histopathological and postsurgical data were collected. Seizure outcome was categorised as favourable (Engel's class I) and unfavourable (Engel's classes II-IV). Uni- and multivariate statistical analysis was performed to identify variables having a significant association with seizure outcome., Results: Forty-eight patients matched the inclusion criteria. 26 (54.1%) patients required invasive EEG evaluation with Stereo-electro-encephalography (SEEG) before surgery. Histological evaluation was unremarkable in 34 cases (70.8%), revealed focal cortical dysplasias in 13 cases and hippocampal sclerosis in 2. 28 (58.3%) patients were in Engel's class I after a mean follow-up of 82 months (SD ± 74; range 12-252). Multivariate analysis indicated auditory aura, contralateral diffusion of the discharge at Video-EEG monitoring and use of 18 F-FDG PET as variables independently associated with seizure outcome., Conclusion: Carefully selected patients with MRI-negative TLE can be good candidates for surgery. Surgery should be considered with caution in patients with clinical features of neocortical seizure onset and contralateral propagation of the discharge. Use of 18 F-FDG PET may be helpful to improve SEEG and surgical strategies. The presented data help in optimising the selection of patients with MRI-negative TLE with good chances to benefit from surgery.

The vestibular system is unique among the senses because of the entirely multisensory nature of its cortical projections. Neuroanatomical and neuroimaging studies show that vestibular stimulation activates somatosensory areas, and particularly the so-called parieto-insular vestibular cortex (PIVC) in the monkey, while deactivating visual areas. Further, recent psychophysical studies showed that vestibular stimulation facilitates detection of electrocutaneous stimuli, suggesting a vestibular-somatosensory perceptual interaction. However, the functional mechanism underlying this perceptual facilitation remains unclear. We therefore recorded somatosensory potentials evoked by left median nerve stimulation, before and immediately after left cold caloric vestibular stimulation (CVS), in a small-scale study of eight healthy volunteers. CVS selectively enhanced the N80 component recorded over both ipsilateral and contralateral somatosensory areas, without significantly affecting earlier or later components. Interestingly, the N80 component has been localised to the parietal operculum, which includes the human homologue of the monkey PIVC, and is thus a prime neuroanatomical candidate for vestibular-somatosensory convergence. As a control, we measured visual evoked potentials to reversing checkerboard patterns and found no effects of vestibular stimulation. This rules out explanations based on indirect effects of vestibular modulations, such as general arousal or supramodal spatial attention. We believe our results provide the first clue linking brain structure to function for the interaction between vestibular and somatosensory systems.