Ictal vomiting as a sign of temporal lobe epilepsy confirmed by stereo-EEG and surgical outcome

Abstract

Vomiting is uncommon in patients with epilepsy and has been reported in both idiopathic and symptomatic epilepsies. It is presumed to originate in the anterior part of the temporal lobe or insula. To date, 44 cases of nonidiopathic focal epilepsy and seizures associated with ictal vomiting have been reported. Of the 44 cases, eight were studied using invasive exploration (3 stereo-EEG/5 subdural grids). Here, we report a 4-year-and-7-month-old patient with a history of febrile convulsion in the second year of life and who developed episodes of vomiting and complex partial seizures at 3 years of age. Scalp EEG showed no electrical modification during vomiting while the complex partial seizure displayed a clear right temporal origin. Brain MR showed hippocampal volume reduction with mild diffuse blurring of the temporal lobe. Stereoelectroencephalography study confirmed the mesiotemporal origin of the seizures and showed that the episodes of vomiting were strictly related to an ictal discharge originating in the mesial temporal structures without insular diffusion. The patient is now seizure-free (18 months) after removal of the right anterior and mesial temporal structures. In all the reported patients, seizures seemed to start in mesial temporal structures. The grid subgroup is more homogeneous, and the most prominent characteristic (4/5) is the involvement of both mesial and lateral temporal structures at the time of vomiting. In the S-EEG group, there is evidence of involvement of either the anterior temporal structures alone (2/3) or both insular cortices (1/3). Our case confirms that vomiting could occur when the ictal discharge is limited to the anterior temporal structure without insular involvement. Regarding the pathophysiology of vomiting, the role of subcortical structures such as the dorsal vagal complex and the central pattern generators (CPG) located in the reticular area is well established. Vomiting as an epileptic phenomenon seems to be related to the involvement of temporal structures, mainly mesial structures (amygdala) and with an uncertain role of the insula. An intriguing hypothesis is that the ictal discharge in mesial structures determines seizure manifestation that could be explained not only by tonic activation of the cortex, but also by 'release' (reduction of inhibition?) of the CPG responsible for involuntary motor behaviors.

Keywords: Amygdala; Central pattern generators; Ictal vomiting; Stereo-EEG; Temporal lobe epilepsy.