Kosugi, Kenzo

写真a

Affiliation

School of Medicine, Department of Neurosurgery ( Shinanomachi )

Position

Instructor
Scopus Paper Info  
Paper Count: 48 Citation Count: 520 h-index: 11

Click to view the Scopus page. The data was downloaded from Scopus API in August 16, 2026, via http://api.elsevier.com and http://www.scopus.com .

Page Top ▲
 

Papers 【 Display / hide 】

  • Effect of body position on cerebral perfusion: a comparison of supine and seated positions assessed using conventional and upright CT perfusion

    Mizutani K., Yamada Y., Yamada M., Yokoyama Y., Kosugi K., Yoshida K., Takahashi S., Akiyama T., Toda M., Jinzaki M.

    European Radiology Experimental 10 ( 1 )  2026.12

    　View Summary

    Objective: Postural changes influence systemic hemodynamics and may affect cerebral perfusion; however, quantitative evaluation remains limited in vivo under physiological gravitational conditions. We aimed to assess posture-dependent alterations in cerebral perfusion using upright multidetector computed tomography perfusion (CTP), with whole-brain cerebral blood flow (CBF) as the primary outcome. Materials and methods: This was a single-center observational study of healthy volunteers approved by the institutional review board. Eighteen volunteers underwent CTP imaging in both the supine and seated positions on the same day using two 320-row multidetector CT scanners with identical systems. Whole-brain CBF was defined as the primary endpoint. Mean transit time (MTT) and cerebral blood volume (CBV) were evaluated as secondary outcomes. Paired comparisons were performed between postures, and exploratory analyses assessed regional changes and interindividual variability. Results: Whole-brain CTP-derived CBF was significantly higher in the seated position than in the supine position (32.9 ± 6.0 [mean ± standard deviation] versus 29.2 ± 5.6 mL/100 g/min; p = 0.010), representing a 1.15 ± 0.19-fold increase. CTP-derived MTT was significantly shorter in the seated position (4.25 ± 0.61 versus 4.63 ± 0.72 s; p = 0.035), and CTP-derived CBV showed a modest but significant increase (2.23 ± 0.16 versus 2.16 ± 0.17 mL/100 g; p = 0.044). Regional perfusion changes were consistent across brain segments with interindividual variability in postural responses. Conclusions: Upright CTP detected posture-associated differences in whole-brain CTP-derived perfusion metrics, suggesting potential utility for investigating physiological and pathological alterations in cerebral hemodynamics associated with postural change. Relevance statement: Upright CTP enables physiological evaluation of posture-related cerebral hemodynamics under gravitational loading and may provide new insights into cerebral circulation in both health and disease. Key Points: Whole-brain cerebral blood flow increased by 15% in the seated position compared with supine using upright CT perfusion. Mean transit time shortened by 7% and cerebral blood volume increased modestly by 4% in the seated position. Perfusion responses showed marked interindividual variability, suggesting different physiological adaptations to posture.

  • Vagal afferents gate cortical excitability in a kainate-induced mouse model of temporal lobe epilepsy

    Sayanagi T., Kosugi K., Ascencao L.C., Makino K., Takabatake Y., Merante M., Suzuki T., Abe Y., Teratani T., Toda M., Tanaka K.F.

    Brain Stimulation 19 ( 4 )  2026.07

    ISSN  1935861X

    　View Summary

    Background: Vagus nerve stimulation (VNS) is an established therapy for refractory epilepsy, indicating that enhanced vagal activity can suppress excessive brain excitability. However, whether endogenous vagal tone itself serves as an intrinsic antiepileptic mechanism remains unclear. We aimed to determine if endogenous vagal activity restrains epileptic dynamics and to elucidate the neural pathways involved. Methods: We employed an intrahippocampal kainate-induced mouse model of temporal lobe epilepsy and an optogenetic model of hippocampal excitability. We performed gain-of-function studies using cervical VNS (30 Hz) and loss-of-function studies using bilateral subdiaphragmatic vagotomy and selective ablation of VGluT2-positive vagal afferents. Results: Cervical VNS attenuated network hyperexcitability, significantly reducing delta power and root mean square (RMS) amplitude, consistent with its clinical efficacy. By contrast, bilateral subdiaphragmatic vagotomy increased delta power, RMS amplitude, and mortality, demonstrating that endogenous vagal activity restrains epileptic dynamics. In the optogenetic model, VNS suppressed, whereas vagotomy exacerbated, light-evoked after-discharges. Crucially, selective ablation of VGluT2-positive vagal afferents largely abolished the electrophysiological signatures of VNS, including power suppression and network desynchronization, establishing that the antiseizure action of VNS depends on intact afferent pathways. Conclusions: These findings identify endogenous vagal afferent signaling as a tonic brake on epileptic network activity and provide mechanistic evidence that cervical VNS suppresses seizures by amplifying this endogenous pathway. This work presents a conceptual and mechanistic framework for afferent-targeted neuromodulation strategies aimed at improving therapeutic precision in epilepsy.

  • The “en bloc” shift: ipsilateral and contralateral abducens nerve palsy following microvascular decompression for trigeminal neuralgia caused by vertebrobasilar dolichoectasia. Illustrative cases

    Ito S., Kosugi K., Fukumoto H., Sayanagi T., Ishikawa K., Watanabe N., Akiyama T., Toda M.

    Journal of Neurosurgery Case Lessons 11 ( 21 )  2026.05

    　View Summary

    BACKGROUND Microvascular decompression (MVD) for trigeminal neuralgia (TN) caused by vertebrobasilar dolichoectasia (VBD) is technically challenging due to the vessel’s size and stiffness. While ipsilateral abducens nerve (cranial nerve [CN] VI) palsy is a known complication, contralateral palsy resulting from force transmission remains unreported. OBSERVATIONS The authors describe 2 cases of CN VI palsy following MVD for VBD-associated TN. Case 1 developed ipsilateral palsy after caudal transposition of the vertebral artery, resulting from a paradoxical medial shift of the proximal vessel segment. Case 2 presented with a rare contralateral CN VI palsy. Postoperative imaging indicated that mobilizing the rigid VBD caused an “en bloc” shift of the entire vertebrobasilar system, resulting in secondary compression of the contralateral CN VI. Both patients achieved immediate pain relief, and the palsies recovered with conservative management. LESSONS Mobilizing a dolichoectatic VBD transmits mechanical force to distant segments via an en bloc shift, potentially injuring CN VI on either the operative or contralateral side. Preoperative identification of risk factors—specifically severe calcification, preexisting contralateral deviation, and minimal contralateral CSF space—is crucial. Surgeons should recognize that vascular transposition can transmit force bilaterally and must counsel patients regarding these risks.

  • Enhanced Precision in Personalized Intraoperative Monitoring of Facial Nerves: A Comparative Analysis of Functional MRI-Guided and Conventional Electrode Placement for Transcranial Motor-Evoked Potentials During Skull Base Surgery

    Sayanagi T., Tamura R., Tomio R., Sogano J., Karatsu K., Ishikawa K., Kosugi K., Akiyama T., Ueda R., Toda M.

    Operative Neurosurgery  2026

    ISSN  23324252

    　View Summary

    BACKGROUND AND OBJECTIVES: – Facial nerve preservation is critical in skull base surgery. Transcranial facial motor-evoked potential (tfMEP) monitoring can be limited by interindividual primary motor cortex (M1) facial cortex variability and intraoperative perturbations. We evaluated a functional MRI (fMRI)–guided, neuronavigation-assisted montage to personalize stimulating electrode placement and reduce thresholds during cerebellopontine angle tumor surgery.METHODS: – In a prospective cohort (n = 20), tfMEPs were recorded simultaneously using 2 montages: (1) fMRI-guided electrode directly over the patient-specific M1 facial hotspot identified by preoperative task fMRI and (2) conventional C3/C4. Train-of-five stimulation elicited compound muscle action potentials from orbicularis oculi/oris. The primary end point was stimulation threshold (mA) to elicit >50 µV, measured at predefined stages (precraniotomy through closure). Secondary analyses assessed threshold changes after durotomy/cerebrospinal fluid (CSF) drainage and postoperative House–Brackmann (HB) grades.RESULTS: – fMRI-guided placement yielded lower baseline thresholds than conventional within patients (mean 65.5 vs 73.5 mA; Δ = −8.9 mA; P < .0001). The advantage persisted at closure (85.3 vs 96.3 mA; P < .0001). After durotomy/CSF drainage, thresholds increased modestly with both montages (+3.3 vs +4.0 mA; between-group P = .65). Monitoring feasibility was 100%, providing continuous data early in the case when direct nerve stimulation was not yet possible. At the latest follow-up, 17/20 (85%) had HB I and 3/20 (15%) HB II; no patient had permanent moderate/severe palsy.CONCLUSION: – Neuronavigation-assisted, fMRI-guided tfMEP reliably targets the individual M1 facial area and significantly lowers stimulation thresholds vs conventional C3/C4, without increasing susceptibility to threshold drift after CSF loss. This simple, adoptable workflow may enhance intraoperative decision making for facial nerve preservation. Larger multicenter studies are warranted to validate outcome prediction and refine threshold-based alarm criteria.

  • Intraoperative Language mapping in a Japanese-English-French trilingual patient with a left Temporal lobe glioma: a case report

    Yamamoto K., Tamura R., Ganaha S., Karatsu K., Ishizawa T., Kojima K., Ando M., Kosugi K., Kitamura Y., Ueda R., Ishikawa A., Imanishi T., Tsuji T., Toda M.

    Brain Structure and Function 230 ( 9 )  2025.12

    ISSN  18632653

    　View Summary

    Background: Awake surgery with intraoperative language mapping has become increasingly refined, allowing assessment not only of motor but also higher brain functions. Language remains the most critical function to evaluate and preserve. However, reports of multilingual patients undergoing such procedures are still limited, particularly those involving Japanese, a linguistically and structurally unique language. Case description: We present the case of a 32-year-old right-handed multilingual male (Japanese L1, English L2, French L3), a film director and actor, who underwent awake craniotomy for a recurrent low-grade glioma involving the left temporal lobe. Preoperative functional MRI confirmed left hemispheric language dominance across all three languages, although French and English showed broader activation than Japanese during semantic fluency tasks. During surgery, cortical mapping with object naming and reading tasks was performed in Japanese, English, and French. Naming errors were observed in the posterior superior temporal gyrus across all three languages, whereas semantic paraphasia in the posterior middle temporal gyrus and reading impairment in the posterior inferior temporal gyrus were specific to Japanese. Postoperative MRI revealed subtotal resection with preservation of language function. Histopathology confirmed astrocytoma, IDH-mutant, WHO grade 3. Conclusion: This case represents the first report of intraoperative language mapping in a Japanese–English–French trilingual patient, demonstrating both overlapping and language-specific cortical regions. The findings underscore the importance of individualized and multimodal language mapping in multilingual patients, particularly when typologically distant languages such as Japanese are involved.

display all >>

Page Top ▲

Papers, etc., Registered in KOARA 【 Display / hide 】

Page Top ▲

Reviews, Commentaries, etc. 【 Display / hide 】

Page Top ▲

Research Projects of Competitive Funds, etc. 【 Display / hide 】

  • Development of a novel immunothereapy targeting tumor microenvironment of NF2

    2020.04
    -
    2023.03

    MEXT,JSPS, Grant-in-Aid for Scientific Research, Grant-in-Aid for Early-Career Scientists , Principal investigator

Page Top ▲
 

Courses Taught 【 Display / hide 】

  • LECTURE SERIES, NEUROSURGERY

    2026

Page Top ▲