Fig 1A (modified from Blauwblomme et al., 2010). Top: coronal and lateral representation of the stereotaxic implantation scheme. Bottom: reflex seizure showing ictal onset in the right insula and secondary spreading in the hippocampus.
Reflex epilepsy is a rare neurological condition in which seizures are triggered by a specific type of sensory input (Xue & Ritaccio, 2006). The most common reflex seizures are induced by light, but other reported triggers have included reading, Mah-Jong, music, the voice of a specific television performer,1 bathing, orgasm, and eating.
The present case involved a 28 year old woman who had refractory partial seizures triggered by eating, which were preceded by an unpleasant taste in her mouth. Strawberry syrup ingestion was noted to be the easiest way to induce seizures. Nine years earlier, she had surgery to remove a vascular malformation from the right frontal operculum/insular cortex. This region contains gustatory cortex encoding for taste. Because of the uncontrolled nature of her seizures, the surgical team implanted intracranial electrodes to determine the focus of abnormal EEG activity.
Two reflex seizures to strawberry syrup intake were recorded, which started with loss of consciousness, followed by facial flushing, oro-alimentary automatisms, repeated swallowing and sialorrhoea [excessive salivation], and ended with postictal confusion and amnesia. From a visual analysis of SEEG (Fig. 1A), seizures began in the anterior inferior portion of the insula with a high-amplitude spike followed by a low-voltage high-frequency discharge with secondary spreading to the hippocampus and then to the temporal neocortex.In the early ictal state, fast gamma band activity (30-120 Hz) showed increased power in the anterior inferior portion of the insula, accompanied by decreased power in the hippocampus.
Functional MRI was also performed during strawberry syrup intake to map gustatory cortex, and another session recorded simultaneous resting state fMRI/EEG activity.
Fig. 1C (modified from Blauwblomme et al., 2010). Overlay of fMRI and SEEG results. Left: crosshairs on the dorsolateral fronto-parietal region. Right: crosshairs on the anterior insula.
The authors reported three major findings from the fMRI/EEG mapping (see Fig 1C):
The dorsolateral anterior parietal cortex showed pre-ictal γ [gamma] power decrease (red) and belonged to the fMRI gustatory network (yellow). In the vicinity, the dorsolateral posterior frontal cortex showed preictal γ power increase (magenta) and interictal fMRI/EEG activations (green).
Early ictal γ power increase (cyan) showed up in the inferior/middle part of the anterior insula, which also responded to taste fMRI (yellow). A preictal increase in γ power (magenta) was observed in the upper part of the anterior insula.
Hippocampus showed early ictal decrease in γ activity (blue).
The surgical team identified the specific region of the insula that was the problematic seizure focus (the middle short gyrus in cyan), and removed it. Two years later, the patient remains seizure-free, and presumably can enjoy strawberry syrup once again.
1 The identity of said performer was revealed to be Mary Hart, host of Entertainment Tonight. From Science News (Vol. 140, No. 3, p. 45):
...the woman had seizures only while watching "Entertainment Tonight."Systematic testing ruled out all but one of the cast members -- cohost Mary Hart, whose voice pattern consistently caused the seizures. [Dr. Venkat] Ramani prescribed anticonvulsant drugs and advised the patient not to watch the program. In the two years since, she has remained "relatively seizure free," he reports.
Blauwblomme, T., Kahane, P., Minotti, L., Grouiller, F., Krainik, A., Vercueil, L., Chabardes, S., Hoffmann, D., & David, O. (2010). Multimodal imaging reveals the role of γ activity in eating-reflex seizures. Journal of Neurology, Neurosurgery & Psychiatry DOI: 10.1136/jnnp.2010.212696
Xue LY, Ritaccio AL. (2006). Reflex seizures and reflex epilepsy. Am J Electroneurodiagnostic Technol. 46:39-48.