石下 洋平

BACKGROUND: Temporal encephaloceles (TEs) are increasingly recognized as epileptogenic lesions in drug-resistant temporal lobe epilepsy. However, endoscopic endonasal surgery performed primarily to resect epileptogenic lesions remains extremely rare, largely because defining the optimal extent of resection is challenging without direct electrophysiological confirmation. OBSERVATIONS: A 41-year-old right-handed man presented with drug-resistant focal impaired consciousness seizures. MRI revealed a right TE herniating into the lateral recess of the sphenoid sinus. Scalp EEG suggested seizure onset in the right anterior temporal region with no evidence of a widespread temporal epileptogenic network. Through an endoscopic endonasal transpterygoid approach, the encephalocele and adjacent temporal dura mater were exposed. Depth electrodes placed into the encephalocele and adjacent cortex demonstrated frequent spikes in both sites, confirming epileptogenicity. The encephalocele and a 7-mm margin of adjacent cortex were resected, followed by multilayer skull base reconstruction. The patient experienced no complications and remained seizure free for 48 months. LESSONS: Endonasal depth EEG enables direct confirmation of epileptogenicity in encephalocele-associated epilepsy and supports minimally invasive, tailored lesionectomy. In appropriately selected patients, particularly those without evidence of a widespread mesial temporal epileptogenic network, use of an endoscopic endonasal approach may avoid craniotomy while achieving durable seizure freedom. https://thejns.org/doi/10.3171/CASE25965.

BACKGROUND: Hair shaving during craniotomy is traditionally performed to facilitate skin preparation and improve intraoperative visibility, but it may cause cosmetic and psychological concerns for patients. Evidence supporting its role in reducing postoperative infections is limited. In this study, we evaluated patient satisfaction with a shave-free craniotomy technique and examined postoperative infection rates. METHODS: We retrospectively reviewed patients who underwent shave-free craniotomy performed by the author between April 2018 and April 2023. Procedures that did not require shaving, as well as surgeries in which additional or extended incisions were anticipated, were excluded. Eligible patients were mailed a questionnaire between July and October 2023. The survey assessed (1) preoperative anxiety related to shaving, (2) expectations regarding shaving before preoperative explanations, and (3) satisfaction with the shave-free procedure (0-100 scale). Postoperative wound infections were also assessed. RESULTS: A total of 116 surgeries were performed on 115 patients. Fifty-five patients (48%) responded to the questionnaire. Shaving-related anxiety accounted for 10.7% of overall preoperative anxiety. Before receiving preoperative explanations, 18% of patients expected total shaving, 80% expected partial shaving, and 1.8% expected no shaving. Satisfaction scores were high for both women (95.8 ± 16.9) and men (96.7 ± 5.7). Two postoperative wound infections (1.7%) were observed, one of which required bone flap removal. CONCLUSION: Shave-free craniotomies were associated with high patient satisfaction and did not increase the risk of postoperative infections. Although cosmetic concerns differ among individuals, avoiding hair removal may help reduce anxiety in some patients without compromising surgical safety.

OBJECTIVE: Patients with temporal lobe epilepsy (TLE) suffer from epileptic seizures and memory decline. While focal resection eliminates seizures in 60-70% of patients, surgery carries the risk of further compromising memory. We hypothesized that hippocampal neurofeedback (NF) will induce targeted brain activity associated with memory function. METHODS: Patients with intracranial electrodes implanted in bilateral hippocampi performed a memory NF task, developed specifically for this project. The NF task involved real-time analysis of hippocampal activity using the electrode in the less-affected hippocampus while conducting a memory task. Changes in theta activity and task performance were assessed. RESULTS: The NF task was conducted in seven TLE patients. In five patients, theta activity increased significantly in the targeted hippocampus (Mann-Kendall test; p < 0.05). Mixed linear model analysis across all sessions revealed a significant increase in theta activity in the targeted hippocampus (p = 0.0032), with no significant change contralaterally (p = 0.19). Three additional TLE patients underwent random NF to assess if theta activity was induced merely by the encoding process, but none of them showed significant changes in theta activity. CONCLUSION: Memory NF task effectively induced targeted hippocampal activity in TLE patients. SIGNIFICANCE: Hippocampal NF may enhance memory function in TLE patients prior to focal resection.

Sound frequency and duration are essential auditory components. The brain perceives deviations from the preceding sound context as prediction errors, allowing efficient reactions to the environment. Additionally, prediction error response to duration change is reduced in the initial stages of psychotic disorders. To compare the spatiotemporal profiles of responses to prediction errors, we conducted a human electrocorticography study with special attention to high gamma power in 13 participants who completed both frequency and duration oddball tasks. Remarkable activation in the bilateral superior temporal gyri in both the frequency and duration oddball tasks were observed, suggesting their association with prediction errors. However, the response to deviant stimuli in duration oddball task exhibited a second peak, which resulted in a bimodal response. Furthermore, deviant stimuli in frequency oddball task elicited a significant response in the inferior frontal gyrus that was not observed in duration oddball task. These spatiotemporal differences within the Parasylvian cortical network could account for our efficient reactions to changes in sound properties. The findings of this study may contribute to unveiling auditory processing and elucidating the pathophysiology of psychiatric disorders.

The action observation network (AON) has been extensively studied using short, isolated motor acts. How activity in the network is altered when these isolated acts are embedded in meaningful sequences of actions remains poorly understood. Here we utilized intracranial electrocorticography to characterize how the exchange of information across key nodes of the AON-the precentral, supramarginal, and visual cortices-is affected by such embedding and the resulting predictability. We found more top-down beta oscillation from precentral to supramarginal contacts during the observation of predictable actions in meaningful sequences compared to the same actions in randomized, and hence less predictable, order. In addition, we find that expectations enabled by the embedding lead to a suppression of bottom-up visual responses in the high-gamma range in visual areas. These results, in line with predictive coding, inform how nodes of the AON integrate information to process the actions of others.