Satoko Ochi

Intraoperative Subcortical Fiber Mapping with Subcortico-Cortical Evoked Potentials

OBJECTIVE During brain surgery, there are difficulties associated with identifying subcortical fibers with no clear landmarks. We evaluated the usefulness of cortical evoked potentials with subcortical stimuli (subcortico-cortical evoked potential [SCEP]) in identifying subcortical fibers intraoperatively. METHODS We used SCEP to identify the pyramidal tract in 4 patients, arcuate fasciculus in 1 patient, and both in 2 patients during surgical procedures. After resection, a 1 × 4-electrode plate was placed on the floor of the removal cavity and 1-Hz alternating electrical stimuli were delivered to this electrode. A 4 × 5 recording electrode plate was placed on the central cortical areas to map the pyramidal tract and temporoparietal cortical areas for the arcuate fasciculus. SCEPs were obtained by averaging electrocorticograms time locked to the stimulus onset. RESULTS The subcortical stimulation within 15 mm of the target fiber induced cortical evoked potentials in the corresponding areas, whereas the stimulation apart from 20 mm did not. Five patients showed transient worsening of neurologic symptoms after surgery. However, all patients recovered. CONCLUSIONS SCEP was useful for identifying subcortical fibers and confirmed the preservation of these fibers. This technique is expected to contribute to the effectiveness and safety of resective surgery in patients with lesions close to eloquent areas.

Infant Motor Development Recovery after Surgery of Post TraumaticEpilepsy (PTE) - Meaningful Change of Fractional Anisotropy (FA) of MRIDiffusion Tensor Imaging (DTI) in a Case of Growing Skull Fracture

Epileptic seizure in pediatric patients affects neurodevelopment, and surgical treatment of intractable epilepsy improved comorbidities, but the mechanism is not fully uncovered yet. By measurement of MRI-DTI Fractional Anisotropy (FA) of posterior limb of internal capsule (PIC) of infants, we presented its change by seizure propagation and control in a case of an infant post traumatic epilepsy (PTE) caused by growing skull fracture. Her motor developmental delay and hemiparesis with non-convulsive status epilepticus (NCSE) started 2 months after injury, recovered after surgical repair and seizure control. FA of PIC was lower than normal (0.29 ipsilateral, 0.37 contralateral) had increased to normal range in one week after surgical treatment and seizure control (0.62, 0.66). Comparing with normal time course of FA of motor tract of infant, this dynamic change of FA indicated the effect of seizure control after surgical treatment. As measurement of other brain lesion also showed increased FA in both ipsilateral and contralateral deep white matter, indicated the effect of NCSE for wide network of brain, and influenced infant neuronal development. These result indicated one mechanism why NCSE affected motor developmental delay and surgical intervention for regional infant intractable epilepsy prevented further developmental delay. By handy method of measuring FA of motor tract, we had one possibility to predict motor tract injury in infancy. We also reviewed and discussed about the mechanism of FA increase and decrease in early infancy and how PTE caused FA change.

Location and Threshold of Electrical Cortical Stimulation for Functional Brain Mapping

BACKGROUND AND OBJECTIVE Although many studies have investigated functional localization by electrical stimulation, the threshold to identify each area remains controversial. The present study aimed to elucidate the threshold of a cortical stimulation for functional mapping. METHODS We analyzed data from 17 patients with medically intractable epilepsy who underwent a 50-Hz electrical cortical stimulation for functional mapping between October 2013 and May 2017. The symptoms induced by the stimulation and the thresholds of the stimulation for these responses were evaluated. RESULTS Motor responses were observed after the stimulation of the primary motor cortex, supplementary motor area, and frontal eye field, and sensory responses after the stimulation of the primary and secondary sensory cortex. Regarding negative responses, language impairment was observed after the stimulation of the anterior, posterior, and basal temporal language areas, negative motor responses after the stimulation of the premotor cortex, posterior parietal cortex, and the pre- supplementary motor area, and an impairment in spatial recognition after the stimulation of the right posterior parietal cortex. Negative or positive auditory symptoms were observed with the stimulation of the posterior superior temporal gyrus. The thresholds for positive phenomena were significantly lower than those for negative phenomena (Mann-Whitney U test, P < 0.01), and sensory responses were induced at significantly lower intensities than motor responses (P < 0.01). CONCLUSIONS Positive and sensory effects are induced by lower intensities than negative and motor responses, respectively. The present results provide not only a practical guide for functional mapping, but also a hierarchal concept of processing in the brain.

Threshold and distribution of afterdischarges with electrical cortical stimulation

OBJECTIVE The present study aimed to investigate the threshold and distribution of afterdischarges (ADs) with cortical electrical stimulation for functional brain mapping. METHOD We retrospectively analyzed data from 11 patients with medically intractable epilepsy who underwent 50-Hz cortical electrical stimulation for functional mapping followed by resection. These patients became seizure free for more than six months. The threshold and distribution of ADs induced by the stimulation were evaluated. RESULTS The median threshold was 6 mA (range: 2-15 mA) for the frontal lobe, 8 mA (3-15 mA) for the temporal lobe, 6 mA (2-15 mA) for the parietal lobe, and 6 mA (4-12 mA) for the occipital lobe. No significant interlobar differences were observed in AD thresholds. No significant differences were noted between within and outside epileptogenic zones. The distribution of ADs, remote spread was observed in all patients, reflecting fronto-parieto-temporal connections, as well as contiguous spread. The stimulation of premotor areas, the inferior parietal lobule, supplementary motor area, and basal temporal areas appeared to induce ADs in remote cortices. CONCLUSION While no locational differences were observed in AD thresholds, each brain region showed a characteristic pattern for AD spread. Remote AD spread needs to be considered for safe functional mapping.

The auditory cortex network in the posterior superior temporal area

OBJECTIVE This study investigated the function and networks of the auditory cortices in the posterior lateral superior temporal area (PLST) using a combination of electrical cortical stimulation and diffusion tensor imaging (DTI). METHODS Seven patients with intractable focal epilepsy in which the PLST auditory cortices were identified during the electrical cortical stimulation were enrolled in this study (left side: four patients, right side: three patients). Electrical stimulation at 50 Hz was applied to the chronically implanted subdural electrodes to identify the PLST auditory cortices. DTI was used to identify the subcortical fibers originating from the PLST auditory cortices found by electrical stimulation. RESULTS Electrical stimulation of the right PLST auditory cortices induced hearing impairment in three patients and left side stimulation elicited hearing illusory sounds in four patients. DTI detected the middle longitudinal fasciculus (MLF) in all patients, the superior longitudinal fasciculus (SLF) in six patients and the inferior fronto-occipital fasciculus (IFOF) in three patients, originating from the PLST auditory cortices. CONCLUSION This study suggests different functional roles between the right and left PLST auditory cortices, and the networks originating from these areas. SIGNIFICANCE MLF, SLF and IFOF might be associated with the auditory processing.

Distribution and Network of Basal Temporal Language Areas: A Study of the Combination of Electric Cortical Stimulation and Diffusion Tensor Imaging

OBJECTIVE The basal temporal language area (BTLA) is considered to have several functions in language processing; however, its brain network is still unknown. This study investigated the distribution and networks of the BTLA using a combination of electric cortical stimulation and diffusion tensor imaging (DTI). METHOD 10 patients with intractable focal epilepsy who underwent presurgical evaluation with subdural electrodes were enrolled in this study (language dominant side: 6 patients, language nondominant side: 4 patients). Electric stimulation at 50 Hz was applied to the electrodes during Japanese sentence reading, morphograms (kanji) reading, and syllabograms (kana) reading tasks to identify the BTLA. DTI was used to identify the subcortical fibers originating from the BTLA found by electric stimulation. RESULTS The BTLA was found in 6 patients who underwent implantation of the subdural electrodes in the dominant hemisphere. The BTLA was located anywhere between 20 mm and 56 mm posterior to the temporal tips. In 3 patients, electric stimulation of some or all areas within the BTLA induced disturbance in reading of kanji words only. DTI detected the inferior longitudinal fasciculus (ILF) in all patients and the uncinate fasciculus (UF) in 1 patient, originating from the BTLA. ILF was detected from both kanji-specific areas and kanji-nonspecific areas. CONCLUSION This study indicates that the network of the BTLA is a part of a ventral stream and is mainly composed of the ILF, which acts as a critical structure for lexical retrieval. ILF is also associated with the specific processing of kanji words.

The Involvement of Sensory-motor Networks in Reflex Seizure

Reflex seizures are epileptic events triggered by specific external stimuli, or less commonly, internal mental stimuli. Understanding the characteristics of reflex seizures is important to elucidate the mechanisms underlying network abnormalities in epileptic conditions. This report details a patient with medically intractable reflex seizures provoked by sensory stimuli to the patient’s right foot. Single-photon emission computed tomography (SPECT) during the seizure induced by sensory stimulation showed hyperperfusion in broad sensory-motor networks (dorsal column-medial lemniscus pathway, left thalamus, bilateral postcentral gyri and posterior parietal cortices, left supplementary motor area (SMA), and left paracentral lobule) and left caudateputamen. The irritative zones and ictal onset zone were localized to the left medial frontoparietal (SMA, anterior and middle cingulate gyrus, and paracentral lobule) and lateral posterior parietal cortices, as evidenced by amelioration of reflex seizures following intracranial electroencephalography and surgical resection of these areas. The neuroradiological and electrophysiological findings in our case study illustrate that the mechanism of reflex seizures may be associated with hyperexcitability of the broad sensory-motor networks, including the basal ganglia. Disconnection of these networks is necessary to treat reflex seizures.

Etiology of Sudden Cardiac Arrest in Patients with Epilepsy: Experience of Tertiary Referral Hospital in Sapporo City, Japan

It has been reported that epilepsy patients had higher risk of sudden death than that of the general population. However, in Japan, there is very little literature on the observational research conducted on sudden fatal events in epilepsy. We performed a single-center, retrospective study on all the out-of-hospital cardiac arrest (OHCA) patients treated in our emergency department between 2007 and 2013. Among the OHCA patients, we extracted those with a history of epilepsy and then analyzed the characteristics of the fatal events and the background of epilepsy. From 1,823 OHCA patients, a total of 10 cases were enrolled in our study. The median age was 34 years at the time of the incident [9–52 years; interquartile range (IQR), 24–45]. We determined that half of our cases resulted from external causes of death such as drowning and suffocation and the other half were classified as sudden unexpected death in epilepsy (SUDEP). In addition, asphyxia was implicated as the cause in eight cases. Only the two near-drowning patients were immediately resuscitated, but the remaining eight patients died. The median age of first onset of epilepsy was 12 years (0.5–30; IQR, 3–21), and the median disease duration was 25 years (4–38; IQR, 6–32). Patients with active epilepsy accounted for half of our series and they were undergoing poly anti-epileptic drug therapy. The fatal events related to epilepsy tended to occur in the younger adult by external causes. An appropriate therapeutic intervention and a thorough observation were needed for its prevention.

Subcortical heterotopia appearing as huge midline mass in the newborn brain.

IntroductionWe report the case of a 2-year-old boy who showed a huge midline mass in the brain at prenatal assessment.Case reportAfter birth, magnetic resonance imaging (MRI) revealed a conglomerate mass with an infolded microgyrus at the midline, which was suspected as a midline brain-in-brain malformation. MRI also showed incomplete cleavage of his frontal cortex and thalamus, consistent with lobar holoprosencephaly. The patient underwent an incisional biopsy of the mass on the second day of life. The mass consisted of normal central nervous tissue with gray and white matter, representing a heterotopic brain. The malformation was considered to be a subcortical heterotopia. With maturity, focal signal changes and decreased cerebral perfusion became clear on brain imaging, suggesting secondary glial degeneration. Coincident with these MRI abnormalities, the child developed psychomotor retardation and severe epilepsy focused on the side of the intracranial mass.

Exophytic glioblastoma multiforme originating from the medulla oblongata

Glioblastoma multiforme (GBM) is most frequently located in the supratentorial region of the brain. In this paper, we report the case of a 25-year-old man who presented with a heterogeneous tumor with exophytic features and located in the caudal fourth ventricle. The tumor was subtotally resected and the patient underwent radiotherapy at a dosage of 50 Gy and concurrent chemotherapy with temozolomide. Histopathological examination revealed the typical features of conventional GBM. The patient independently performed the activities of daily living for 11 months. However, after identifying a recurrence of the tumor in the dorsal medulla oblongata, the patient suddenly died at home 12 months after diagnosis, likely due to respiratory arrest. To the best of our knowledge, it is extremely rare for GBM to occur in the medulla oblongata and only eight cases have been described in detail. Patients with intrinsic GBM of the medulla oblongata died within three months. In contrast, patients with exophytic GBMs of the medulla oblongata survived for more than one year. Patients with GBMs that occurred in the medulla oblongata and exhibited exophytic growth patterns had a better prognosis than patients with intrinsic GBMs because the tumors could be more radically and safely resected. Correspondence to: Masahiko Wanibuchi, M.D, Department of Neurosurgery, Sapporo Medical University, Minami 1 Jo Nishi 16 Chome, Chuo-ku, Sapporo, Hokkaido 060-8543 (Japan), Tel: +81-11-611-2111, Fax: +81-11-614-1662; E-mail: wanibuti@sapmed.ac.jp