Peri-ictal yawning (PY) is an autonomic manifestation associated with temporal lobe epilepsy (TLE), typically appearing during the late ictal or postictal phase.1 Some reports suggest that PY is specific to the non-dominant hemisphere and may indicate seizure lateralization. However, previous studies inferred hemispheric dominance mainly from scalp electroencephalography (EEG) or handedness, with limited evaluation. To our knowledge, only Du et al. reported PY lateralization, with no case employing the Wada test for hemispheric dominance and stereoelectroencephalography (SEEG) for seizure-onset zone (SOZ).2 Here, we report a case of PY with left hemispheric dominance confirmed by Wada test and SOZ in the left temporal lobe demonstrated by SEEG. A right-handed woman in her 30s with no significant history developed epilepsy at 27. She mainly had focal seizures with impaired consciousness with autonomic aura, occasionally progressing to focal to bilateral tonic–clonic seizures. Magnetic resonance imaging (MRI) revealed multiple transmantle signs in the left temporal lobe (Figure S1). No clear epileptiform discharges were observed on interictal scalp EEG. Despite medication adjustments, sleep-related seizures persisted several times weekly. On neuropsychological testing, Verbal Memory, General Memory, and Delayed Recall indices were predominantly impaired (Table S1). Long-term video EEG captured 10 seizures, showing head turning without lateral predominance and simultaneous tonic extension of all four limbs, rendering localization of the SOZ difficult. Therefore, SEEG was performed with seven electrodes (70 contacts) (Figure 1A). Interictal SEEG revealed frequent spikes in the right parahippocampal gyrus and left posterior parahippocampal gyrus, and intermittent slow waves in the left anterior parahippocampal gyrus. Three focal to bilateral tonic–clonic seizures were recorded, characterized by head turning without lateral predominance and tonic extension of limbs (Figure 1B). The seizures originated from a contact located in the left anterior parahippocampal gyrus. Ictal EEG propagation was observed to the contacts in the right parahippocampal gyrus an average of 17.1 s after seizure onset, followed by propagation to the left posterior parahippocampal gyrus at an average of 20.8 s. The ictal EEG pattern, characterized by bursts of high-amplitude activity, was also identified in more than 200 nocturnal seizures, including subclinical seizures, yawnings, and oral automatisms. After the emergence of EEG changes accompanied by oral automatisms that persisted for several seconds, PY was observed in the late ictal or postictal phase. All seizures originated from contact A28, implanted in the left anterior parahippocampal gyrus (Figure 1C). A Wada test was conducted to determine the dominant hemisphere, which was confirmed to be the left. Anterior temporal lobectomy was performed 2 weeks after SEEG. Pathological examination confirmed a diagnosis of focal cortical dysplasia (FCD) type Ib, given the absence of balloon cells and dysmorphic neurons. The patient had no postoperative complications or seizures. Consent for submission was obtained (Video 1). In this study, frequent PY was observed in a patient with TLE, with left hemispheric dominance confirmed by the Wada test and left temporal seizure onset demonstrated by SEEG. PY is a rare peri-ictal manifestation, usually reported in the late ictal or postictal phase of non-dominant TLE1 and regarded as a lateralizing sign to the non-dominant hemisphere. In our case, however, the Wada test confirmed left hemispheric dominance, and SEEG showed PY arising from the left parahippocampal gyrus, suggesting that PY may not be restricted to seizures of the non-dominant hemisphere. Abnormal yawning involves pathways linking the insula, basal ganglia, and hypothalamic paraventricular nucleus (PVN) to limbic structures, and occurs in various neurological disorders.3 While more common with right-hemisphere lesions, left-sided cases have also been reported,4, 5 possibly reflecting right-hemisphere dominance in autonomic regulation. However, as SEEG sampling in this case was limited, the coverage was insufficient to fully evaluate activity in structures considered to be involved in yawning or the related deep neural networks, rendering the underlying mechanism speculative. Nonetheless, this case indicates that PY is not confined to non-dominant seizures and can occur in dominant TLE. In this case, a patient with left hemispheric dominance confirmed by the Wada test and seizures arising from the left mesial temporal lobe on SEEG repeatedly exhibited PY in the late ictal and postictal phases. This demonstrates that PY, traditionally considered a sign of the non-dominant hemisphere, can also occur in the dominant hemisphere. NK: writing—original draft, writing—review and editing. SN: conceptualization, resources, investigation, writing—review and editing. MK: resources, investigation, writing—review and editing. YH: supervision, writing—review and editing. The authors declare that no financial support was received for the research, authorship, and/or publication of this article. The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest. Informed consent was obtained from the patient for publication of this report. Detailed data are available upon request from any qualified investigator. Figure S1. Table S1. Data S1. Data S2. Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article. Which of the following statements about peri-ictal yawning (PY) is correct? Which of the following correctly describes focal cortical dysplasia (FCD) type Ib in focal epilepsy? Which combination of tests is most reliable for precisely evaluating hemispheric dominance in patients? Answers may be found in the Supporting information.
Kawase et al. (Tue,) studied this question.