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Takehiro Uda, Michiharu Morino, Hirotaka Ito, Noriaki Minami, Atsushi Hosono, Taiki Nagai, and Takahiro Matsumoto

Object

Amygdalohippocampectomy is a well-established, standard surgery for medically intractable mesial temporal lobe epilepsy (MTLE). However, in the case of MTLE without hippocampal atrophy or sclerosis, amygdalohippocampectomy is associated with decreased postoperative memory function. Hippocampal transection (HT) has been developed to overcome this problem. In HT the hippocampus is not removed; rather, the longitudinal hippocampal circuits of epileptic activities are disrupted by transection of the pyramidal layer of the hippocampus. The present study describes a less invasive modification of HT (transsylvian HT) and presents the seizure and memory outcomes for this procedure.

Methods

Thirty-seven patients with MTLE (18 men and 19 women; age range 9–63 years; 19 with surgery on the right side and 18 with surgery on the left side; seizure onset from 3 to 34 years) who were treated with transsylvian HT were retrospectively analyzed. All patients had left-side language dominance, and follow-up periods ranged from 12 to 94 months (median 49 months). Seizure outcomes were evaluated for all patients by using the Engel classification. Memory function was evaluated for 22 patients based on 3 indices (verbal memory, nonverbal memory, and delayed recall), with those scores obtained using the Wechsler Memory Scale–Revised. Patients underwent evaluation of the memory function before and after surgery (6 months–1 year).

Results

Engel Class I (completely seizure free) was achieved in 25 patients (67.6%). Class II and Class III designation was achieved in 10 (27%) and 2 patients (5.4%), respectively. There were differences in memory outcome between the sides of operation. On the right side, verbal memory significantly increased postoperatively (p = 0.003) but nonverbal memory and delayed recall showed no significant change after the operation (p = 0.718 and p = 0.210, respectively). On the left side, all 3 indices (verbal memory, nonverbal memory, and delayed recall) showed no significant change (p = 0.331, p = 0.458, and p = 0.366, respectively).

Conclusions

Favorable seizure outcome and preservation of verbal memory were achieved with transsylvian HT for the treatment of MTLE without hippocampal atrophy or sclerosis.

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Michiharu Morino, Tsutomu Ichinose, Takehiro Uda, Kyoko Kondo, Satoko Ohfuji, and Kenji Ohata

Object

It remains unclear whether selective amygdalohippocampectomy, an operative technique developed for use in epilepsy surgery to spare unaffected brain tissue and thus minimize the cognitive consequences of temporal lobe surgery, actually leads to a better memory outcome. The present study was performed to determine the effects of selective surgery on memory outcome in patients with intractable mesial temporal lobe epilepsy due to hippocampal sclerosis treated using transsylvian selective amygdalohippocampectomy (TSA).

Methods

The study population consisted of 62 patients with left hemisphere language dominance who underwent left-(31 patients) or right-sided (31 patients) TSA. All patients underwent comprehensive neuropsychological testing before and 1 month and 1 year after unilateral TSA. Verbal Memory I, Nonverbal Memory I, Total Memory, Attention, and Delayed Recall were assessed using the Wechsler Memory Scale–Revised, whereas Verbal Memory II was assessed using the Miyake Verbal Retention Test (MVRT), and Nonverbal Memory II was assessed using the Benton Visual Retention Test. Separate repeated-measures multivariate analysis of variance (MANOVA) were performed for these intervals with memory scores.

Results

The results of MANOVA indicated that patients who underwent right-sided TSA showed significant improvements in Verbal Memory I (preoperatively vs 1 month postoperatively, p < 0.0001; and preoperatively vs 1 year postoperatively, p = 0.0002), Nonverbal Memory I (preoperatively vs 1 month postoperatively, p = 0.0003; and preoperatively vs 1 year postoperatively, p = 0.006), and Delayed Recall (preoperatively vs 1 month postoperatively, p = 0.028) at both 1-month and 1-year follow-ups. In addition, Verbal Memory II (MVRT) was also significantly improved 1 year after surgery (p = 0.001). In the group of patients who underwent left-sided TSA, both Verbal Memory I and II were maintained at the same level 1 month after surgery, whereas the Verbal Memory I score 1 year after surgery increased with marginal significance (p = 0.074). In addition, Verbal Memory II showed significant improvement 1 year after surgery (p = 0.049). There were no significant changes in Nonverbal Memory I and II, Attention, or Delayed Recall at either the 1-month or 1-year follow-up.

Conclusions

Results of the present study indicated that left-sided TSA for hippocampal sclerosis tends to improve verbal memory function with the preservation of other types of memory function. Moreover, right-sided TSA for hippocampal sclerosis can lead to significant improvement in memory function, with memory improvement observed 1 month after right-sided TSA and persisting 1 year after surgery.

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Takehiro Uda, Ichiro Kuki, Takeshi Inoue, Noritsugu Kunihiro, Hiroharu Suzuki, Hiroshi Uda, Toshiyuki Kawashima, Kosuke Nakajo, Yoko Nakanishi, Shinsuke Maruyama, Takashi Shibata, Hiroshi Ogawa, Shin Okazaki, Hisashi Kawawaki, Kenji Ohata, Takeo Goto, and Hiroshi Otsubo

OBJECTIVE

Epileptic spasms (ESs) are classified as focal, generalized, or unknown onset ESs. The classification of ESs and surgery in patients without lesions apparent on MRI is challenging. Total corpus callosotomy (TCC) is a surgical option for diagnosis of the lateralization and possible treatment for ESs. This study investigated phase-amplitude coupling (PAC) of fast activity modulated by slow waves on scalp electroencephalography (EEG) to evaluate the strength of the modulation index (MI) before and after disconnection surgery in children with intractable nonlesional ESs. The authors hypothesize that a decreased MI due to surgery correlates with good seizure outcomes.

METHODS

The authors studied 10 children with ESs without lesions on MRI who underwent disconnection surgeries. Scalp EEG was obtained before and after surgery. The authors collected 20 epochs of 3 minutes each during non–rapid eye movement sleep. The MI of the gamma (30–70 Hz) amplitude and delta (0.5–4 Hz) phase was obtained in each electrode. MIs for each electrode were averaged in 4 brain areas (left/right, anterior/posterior quadrants) and evaluated to determine the correlation with seizure outcomes.

RESULTS

The median age at first surgery was 2.3 years (range 10 months–9.1 years). Two patients with focal onset ESs underwent anterior quadrant disconnection (AQD). TCC alone was performed in 5 patients with generalized or unknown onset ESs. Two patients achieved seizure freedom. Three patients had residual generalized onset ESs. Disconnection surgeries in addition to TCC consisted of TCC + posterior quadrant disconnection (PQD) (1 patient); TCC + AQD + PQD (1 patient); and TCC + AQD + hemispherotomy (1 patient). Seven patients became seizure free with a mean follow-up period of 28 months (range 5–54 months). After TCC, MIs in 4 quadrants were significantly lower in the 2 seizure-free patients than in the 6 patients with residual ESs (p < 0.001). After all 15 disconnection surgeries in 10 patients, MIs in the 13 target quadrants for each disconnection surgery that resulted in freedom from seizures were significantly lower than in the 26 target quadrants in patients with residual ESs (p < 0.001).

CONCLUSIONS

In children with nonlesional ESs, PAC for scalp EEG before and after disconnection surgery may be a surrogate marker for control of ESs. The MI may indicate epileptogenic neuronal modulation of the interhemispheric corpus callosum and intrahemispheric subcortical network for ESs. TCC may be a therapeutic option to disconnect the interhemispheric modulation of epileptic networks.

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Hiroki Ohata, Takeo Goto, Alhusain Nagm, Narasinga Rao Kannepalli, Kosuke Nakajo, Hiroki Morisako, Hiroyuki Goto, Takehiro Uda, Shinichi Kawahara, and Kenji Ohata

OBJECTIVE

The endoscopic endonasal approach (EEA) for skull base tumors has become an important topic in recent years, but its use, merits, and demerits are still being debated. Herein, the authors describe the nuances and efficacy of the endoscopic endonasal extradural posterior clinoidectomy for maximal tumor exposure.

METHODS

The surgical technique included extradural posterior clinoidectomy following lateral retraction of the paraclival internal carotid artery and extradural pituitary transposition. In cases with prominent posterior clinoid process, a midline sellar dura cut was added to facilitate extradural exposure. Forty-four consecutive patients, in whom this technique was performed between 2016 and 2018 at Osaka City University Hospital, were reviewed. The pathology included 19 craniopharyngiomas, 7 chordomas, 6 meningiomas, 6 pituitary adenomas, 4 chondrosarcomas, and 2 miscellaneous. Utilization and effectiveness of this approach were further demonstrated with neuroimaging.

RESULTS

Extradural posterior clinoidectomies were successfully applied in all patients without permanent neurovascular injury and with better maneuverability and greater resection rate of the tumors. Four patients experienced transient postoperative abducens nerve paresis, and 1 patient experienced transient postoperative oculomotor nerve paresis; however, the patients with deficits recovered within 3 months. On radiological examination, the surgical field was 2.2 times wider in cases with bilateral posterior clinoidectomy than in cases without posterior clinoidectomy.

CONCLUSIONS

The extended EEA with extradural posterior clinoidectomy creates an extra working space and allows adequate accessibility with safe surgical maneuverability to remove tumors that extend behind the posterior clinoid and dorsum sellae.