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Namio Kodama, Masato Matsumoto and Tatsuya Sasaki

✓ The authors describe an intraoperative technique, in which oxycellulose is placed between an aneurysm and its surrounding arteries, allowing a space to be secured for inserting the clip blades without occlusion of the arteries. This method is useful in preserving the blood vessels, especially perforating arteries, around the aneurysm.

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Tomoyoshi Oikawa, Masato Matsumoto, Tatsuya Sasaki and Namio Kodama

Object. The goal of this study was to develop a new method of intraoperative monitoring of functions located in the lateral portion of the medulla oblongata. Based on the fact that the spinal trigeminal nucleus and tract are located in the lateral portion of the medulla oblongata, the authors intended to investigate the efficacy of trigeminal evoked potentials (TEPs) in intraoperative monitoring for assessing functions of the medulla oblongata.

Methods. Trigeminal evoked potentials induced by electrical stimulation of the infraorbital nerve were recorded from the dorsolateral portion of the medulla oblongata (M-TEP) and the cerebral sensory cortex (C-TEP) in dogs. When the lateral one-sixth portion of the medulla was cut, the amplitude of the M-TEP decreased markedly, but the amplitude of the C-TEP and the somatosensory evoked potential (SSEP) did not decrease. When the lateral one-third portion of the medulla was cut, the amplitude of the SSEP decreased, but that of the C-TEP showed no change. When the medulla was retracted, the amplitude of the M-TEP was more sensitive than that of SSEP. Pathological examinations revealed that retraction force less than 10 g and a reduction in the amplitude of the M-TEP less than 50% were safe.

Conclusions. These results suggest that M-TEPs obtained from the dorsolateral portion of the medulla oblongata by electrical stimulation of the trigeminal nerve are clinically applicable as a new means of intraoperative monitoring of the functions of the medulla oblongata.

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Tatsuya Sasaki, Kyouichi Suzuki, Masato Matsumoto, Taku Sato, Namio Kodama and Keiko Yago

Object. Evoked potentials elicited by electrical stimulation of the oculomotor nerve and recorded from surface electrodes placed on the skin around the eyeball reportedly originate in the eye and are represented on electrooculograms. Because evoked potentials recorded from surface electrodes are extremely similar to those of extraocular muscles, which are represented on electromyograms, the authors investigated the true origin of these potentials.

Methods. Evoked potentials elicited by electrical stimulation of the canine oculomotor nerve were recorded from surface electrodes placed on the skin around the eyeball. A thread sutured to the center of the cornea was pulled and the potentials that were evoked during the resultant eye movement were recorded. These potentials were confirmed to originate in the eye and to be represented on electrooculograms because their waveforms were unaffected by the administration of muscle relaxant. To eliminate the influence of this source, the retina, a main origin of standing potentials of the eyeball, was removed. This resulted in the disappearance of electrooculography (EOG) waves elicited by eye movement. Surface potentials elicited by oculomotor nerve stimulation were the same before and after removal of the retina. Again the oculomotor nerve was electrically stimulated and electromyography (EMG) response of the extraocular muscles was recorded at the same time that potentials were recorded from the surface electrodes. In their peak latencies, amplitudes, and waveforms, the evoked potentials obtained from surface electrodes were almost identical to EMG responses of extraocular muscles.

Conclusions. Evoked potentials elicited by electrical stimulation of the oculomotor nerves and obtained from surface electrodes originated from EMG responses of extraocular muscles. These evoked potentials do not derive from the eye.

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Kyouichi Suzuki, Namio Kodama, Tatsuya Sasaki, Masato Matsumoto, Yutaka Konno, Jun Sakuma, Masahiro Oinuma and Masahiro Murakawa

Object. The lack of a specified intraoperative method for monitoring anterior choroidal artery (AChA) blood flow insufficiency (BFI) led the authors to devise a method for checking the BFI in this artery during aneurysm surgery. To this end, the authors relied on the intraoperative motor evoked potentials (MEPs) elicited by electrical stimulation of the hand motor cortex.

Methods. The study population consisted of 108 patients with internal carotid artery (ICA) aneurysms who underwent surgery via a standard frontotemporal craniotomy. After the dura mater had been opened, a grid electrode strip with 16 small electrodes was inserted subdurally into the hand motor cortex from the edge of the craniotomy. To check BFI in the AChA, the hand motor cortex was stimulated at an intensity level between 10 and 18 mA. The MEPs were successfully recorded from the contralateral thenar muscles in all 108 patients. There was no postoperative motor paresis in 88 patients in whom the MEPs remained unchanged during the performance of various surgical maneuvers. Among the other 20 patients, 19 manifested transient MEP changes, but 15 of those patients experienced no postoperative motor paresis. In four patients who exhibited transient MEP changes, either after aneurysm clipping or during temporary occlusion of the ICA and/or AChA, hemiparesis occurred postoperatively but disappeared within 24 hours. In one patient with an ICA—posterior communicating artery aneurysm, the MEP disappeared and did not reappear by the time of dural closure. Severe hemiplegia developed in this patient and a computerized tomography scan obtained postoperatively revealed a new low-density area in the internal capsule.

Conclusions. The findings of this study suggest that the monitoring method that is introduced here is safe and reliable for detecting intraoperative BFI in the AChA.

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Masato Matsumoto, Masanori Sato, Masayuki Nakano, Yuji Endo, Youichi Watanabe, Tatsuya Sasaki, Kyouichi Suzuki and Namio Kodama

Object. The aim of this study was to assess whether aneurysm surgery can be performed in patients with ruptured cerebral aneurysms by using three-dimensional computerized tomography (3D-CT) angiography alone, without conventional catheter angiography.

Methods. In a previous study, 60 patients with subarachnoid hemorrhage (SAH) from ruptured aneurysms were prospectively evaluated using both 3D-CT and conventional angiography, which resulted in a 100% accuracy for 3D-CT angiography in the diagnosis of ruptured aneurysms, and a 96% accuracy in the identification of associated unruptured aneurysms. The results led the authors to consider replacing conventional angiography with 3D-CT angiography for use in diagnosing ruptured aneurysms, and to perform surgery aided by 3D-CT angiography alone without conventional angiography. Based on the results, 100 consecutive patients with SAH who had undergone surgery in the acute stage based on 3D-CT angiography findings have been studied since December 1996. One hundred ruptured aneurysms, including 41 associated unruptured lesions, were detected using 3D-CT angiography. In seven of 100 ruptured aneurysms, which included four dissecting vertebral artery aneurysms, two basilar artery (BA) tip aneurysms, and one BA—superior cerebellar artery aneurysm, 3D-CT angiography was followed by conventional angiography to acquire diagnostic confirmation or information about the vein of Labbé, which was needed to guide the surgical approach for BA tip aneurysms. All of the ruptured aneurysms were confirmed at surgery and treated successfully. Ninety-three patients who underwent operation with the aid of 3D-CT angiography only had no complications related to the lack of information gathered by conventional angiography. The 3D-CT angiography studies provided the authors with the aneurysm location as well as surgically important information on the configuration of its sac and neck, the presence of calcification in the aneurysm wall, and its relationship to the adjacent vessels and bone structures.

Conclusions The authors believe that 3D-CT angiography can replace conventional angiography in the diagnosis of ruptured aneurysms and that surgery can be performed in almost all acutely ruptured aneurysms by using only 3D-CT angiography without conventional angiography.

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Kyouichi Suzuki, Namio Kodama, Tatsuya Sasaki, Masato Matsumoto, Tsuyoshi Ichikawa, Ryoji Munakata, Hiroyuki Muramatsu and Hiromichi Kasuya


The authors performed fluorescein cerebral angiography in patients after aneurysm clip placement to confirm the patency of the parent artery, perforating artery, and other arteries around the aneurysm.


Twenty-three patients who underwent aneurysm surgery were studied. Aneurysms were located in the internal carotid artery in 12 patients, middle cerebral artery in six, anterior cerebral artery in three, basilar artery bifurcation in one, and junction of the vertebral artery (VA) and posterior inferior cerebellar artery in one. After aneurysm clip placement, the target arteries were illuminated using a beam from a blue light-emitting diode atop a 7-mm diameter pencil-type probe. In all patients, after intravenous administration of 5 ml of 10% fluorescein sodium, fluorescence in the vessels was clearly observed through a microscope and recorded on videotape.


The excellent image quality and spatial resolution of the fluorescein angiography procedure facilitated intra-operative real-time assessment of the patency of the perforating arteries and branches near the aneurysm, including: 12 posterior communicating arteries; 12 anterior choroidal arteries; four lenticulostriate arteries; three recurrent arteries of Heubner; three hypothalamic arteries; one ophthalmic artery; one perforating artery arising from the VA; and one posterior thalamoperforating artery. All 23 patients experienced an uneventful postoperative course without clinical symptoms of perforating artery occlusion.


Because the fluorescein angiography procedure described here allows intraoperative confirmation of the patency of perforating arteries located deep inside the surgical field, it can be practically used for preventing unexpected cerebral infarction during aneurysm surgery.

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Narihide Shinoda, Osamu Hirai, Shinya Hori, Kazuyuki Mikami, Toshiaki Bando, Daisuke Shimo, Takahiro Kuroyama, Yoji Kuramoto, Masato Matsumoto and Yasushi Ueno


The presence of disproportionately enlarged subarachnoid space hydrocephalus (DESH) on brain imaging is a recognized finding of idiopathic normal pressure hydrocephalus (iNPH), but the features of DESH can vary across patients. The aim of this study was to evaluate the utility of MRI-based DESH scoring for predicting prognosis after surgery.


In this single-center, retrospective cohort study, the DESH score was determined by consensus between a group of neurosurgeons, neurologists, and a neuroradiologist based on the preoperative MRI findings of the patients with suspected iNPH. The DESH score was composed of the following 5 items, each scored from 0 to 2 (maximum score 10 points): ventriculomegaly, dilated sylvian fissures, tight high convexity, acute callosal angle, and focal sulcal dilation. The association between the DESH score and improvement of the scores on the modified Rankin Scale (mRS), iNPH Grading Scale (iNPHGS), Mini–Mental State Examination (MMSE), Trail Making Test-A (TMT-A), and Timed 3-Meter Up and Go Test (TUG-t) was examined. The primary end point was improvement in the mRS score at 1 year after surgery, and the secondary outcome measures were the iNPHGS, MMSE, TMT-A, and TUG-t scores at 1 year after surgery. Improvement was determined as improvement of 1 or more levels on mRS, ≥ 1 point on iNPHGS, ≥ 3 points on MMSE, a decrease of > 30% on TMT-A, and a decrease of > 10% on TUG-t.


The mean DESH score for the 50 patients (mean age 77.6 ± 5.9 years) reviewed in this study was 5.58 ± 2.01. The mean rate of change in the mRS score was −0.50 ± 0.93, indicating an inverse correlation between the DESH score and rate of change in the mRS score (r = −0.749). Patients who showed no improvement in mRS score tended to have a low DESH score as well as low preoperative MMSE and TMT-A scores. There were no differences in the areas of deep white matter hyperintensity and periventricular hyperintensity on the images between patients with and without an improved mRS score (15.6% vs 16.7%, respectively; p = 1.000). The DESH score did differ significantly between patients with and without improved scores on the iNPHGS (6.39 ± 1.76 vs 4.26 ± 1.69, respectively; p < 0.001), MMSE (6.63 ± 1.82 vs 5.09 ± 1.93; p = 0.010), TMT-A (6.32 ± 1.97 seconds vs 5.13 ± 1.93 seconds; p = 0.042), and TUG-t (6.48 ± 1.81 seconds vs 4.33 ± 1.59 seconds; p < 0.001).


MRI-based DESH scoring is useful for the prediction of neurological improvement and prognosis after surgery for iNPH.

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Tatsuya Sasaki, Namio Kodama, Masato Matsumoto, Kyouichi Suzuki, Yutaka Konno, Jun Sakuma, Yuji Endo and Masahiro Oinuma


The object of this study was to investigate patients with cerebral infarction in the area of the perforating arteries after aneurysm surgery.


The authors studied the incidence of cerebral infarction in 1043 patients using computed tomography or magnetic resonance imaging and the affected perforating arteries, clinical symptoms, prognosis, and operative maneuvers resulting in blood flow disturbance.


Among 46 patients (4.4%) with infarction, the affected perforating arteries were the anterior choroidal artery (AChA) in nine patients, lenticulostriate artery (LSA) in nine patients, hypothalamic artery in two patients, posterior thalamoperforating artery in five patients, perforating artery of the vertebral artery (VA) in three patients, anterior thalamoperforating artery in nine patients, and recurrent artery of Heubner in nine patients. Sequelae persisted in 21 (45.7%) of the 46 patients; 13 (28.3%) had transient symptoms and 12 (26.1%) were asymptomatic. Sequelae developed in all patients with infarctions in perforating arteries in the area of the AChA, hypothalamic artery, or perforating artery of the VA; in four of five patients with posterior thalamoperforating artery involvement; and in two of nine with LSA involvement. The symptoms of anterior thalamoperforating artery infarction or recurrent artery of Heubner infarction were mild and/or transient. The operative maneuvers leading to blood flow disturbance in perforating arteries were aneurysmal neck clipping in 21 patients, temporary occlusion of the parent artery in nine patients, direct injury in seven patients, retraction in five patients, and trapping of the parent artery in four patients.


The patency of the perforating artery cannot be determined by intraoperative microscopic inspection. Intraoperative motor evoked potential monitoring contributed to the detection of blood flow disturbance in the territory of the AChA and LSA.