Biomedical subjects

Masato Matsumoto

Publications and source records attributed to Masato Matsumoto.

22 records · Page 2Linked to original sources

PubMed2002

Glossopharyngeal nerve evoked potentials after stimulation of the posterior part of the tongue in dogs.

OBJECTIVE: Lower cranial nerve palsy is one of the most critical complications after posterior fossa surgery. However, no established monitoring procedures exist for glossopharyngeal nerve function. Therefore, glossopharyngeal nerve evoked potentials after stimulation of the posterior part of the tongue in dogs was studied to analyze whether glossopharyngeal nerve compound action potentials and evoked potentials are useful in the intraoperative monitoring of patients undergoing brainstem and cerebellopontine angle surgery. METHODS: Glossopharyngeal nerve action potentials and cortical potentials were evoked by stimulating the posterior part of the tongue in mongrel dogs. The potentials were evoked by supramaximal constant current electrical stimuli delivered with bipolar stainless steel needle electrodes and recorded with silver ball electrodes. RESULTS: Compound nerve action potentials were recorded from the exposed intracranial portion of the glossopharyngeal nerve. The latency of the initial negative peak of the action potentials was 2.8 +/- 0.6 milliseconds (mean +/- standard deviation; n = 17). Evoked cortical potentials were recorded on the coronal gyrus by stimulating the contralateral side. The latencies of the initial positive peak and negative peak were 20.1 +/- 3.7 and 35.7 +/- 8.2 milliseconds, respectively (n = 6). Ipsilateral tongue stimulation elicited biphasic evoked potentials on the coronal gyrus, which had small amplitudes and delayed latencies. Both compound nerve action potentials and cortical evoked potentials disappeared after sectioning of the glossopharyngeal nerve. CONCLUSION: The glossopharyngeal nerve action potentials and cortical potentials elicited by the stimulation of the posterior one-third of the tongue can be recorded. These evoked potentials represent a new means for intraoperative monitoring of patients undergoing surgery in the brainstem via the cerebellopontine angle, which involves the lower cranial nerves.

Action Potentials↗

PubMed2002

Origins of surface potentials evoked by electrical stimulation of oculomotor nerves: are they related to electrooculographic or electromyographic events?

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.

Abducens Nerve↗

PubMed2002

Acute aneurysm surgery using three-dimensional CT angiogrphy without conventional catheter angiography.

The object of this study is to assess whether aneurysm surgery can be performed in patients with ruptured cerebral aneurysms by using three-dimensional computerized tomography angiography (3D-CTA) alone, without conventional catheter angiography (CCA). Between May 1994 and November 1996, a consecutive series of 60 cases of ruptured cerebral aneurysms was evaluated by both 3D-CTA and CCA prospectively and compared the detectability of cerebral aneurysms. Both 3D-CTA and CCA demonstrated a 100% diagnostic accuracy of ruptured cerebral aneurysms. In the associated unruptured cerebral aneurysms, the diagnostic accuracies of 3D-CTA and CCA were 96% and 92%, respectively. Based on the results, we have operated on 128 consecutive patients with ruptured aneurysms in the acute stage based on 3D-CTA findings since December 1996. One hundred twenty eight ruptured aneurysms including 50 associated unruptured aneurysms were detected by 3D-CTA. In seven of 128 ruptured aneurysms, which included four dissecting vertebral artery aneurysms, two basilar artery (BA) tip aneurysms, and one BA-superior cerebellar artery (SCA) aneurysm, 3D-CTA was followed by CCA to obtain diagnostic confirmation or information concerning 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. One hundred twenty one patients who underwent surgery with 3D-CTA findings only had no complications related to the lack of information of CCA. The authors considered that 3D-CTA could replace CCA in the diagnosis of ruptured aneurysms and that surgery could be performed in almost all acutely ruptured aneurysms by using only 3D-CTA without CCA.

Acute Disease↗

PubMed2002

Effects of methylprednisolone on axonal depression induced by hypoxia, gamma-aminobutyric acid, and (+/-)-8-hydroxy-dipropylaminotetralin hydrobromide.

OBJECTIVE: We sought to confirm the effects of methylprednisolone (MP) on axonal depression induced by hypoxia, gamma-aminobutyric acid (GABA), and (+/-)-8-hydroxy-dipropylaminotetralin hydrobromide (8-OH-DPAT). METHODS: Compound action potentials were recorded to assess the effects of MP in neonatal rat spinal cord axons. Longitudinally hemisected spinal cords were superfused for 120 minutes in Ringer's solution saturated with 95% N2 and 5% CO2. The effect of MP on GABA- and 8-OH-DPAT-induced axonal depression was analyzed with oxygenated isolated dorsal columns. RESULTS: Hypoxia (120 min) significantly reduced the response amplitudes in hemicord preparations. MP (30 micromol/L) prevented hypoxia-induced depression of action potential amplitudes. In oxygenated dorsal column preparations, GABA (50 micromol/L) significantly reduced action potential amplitudes. At 10, 30, and 100 micromol/L, MP had no effect on axonal excitability and GABA-induced axonal depression. 8-OH-DPAT (100 micromol/L) significantly reduced the action potential amplitude. MP (10, 30, 50, and 100 micromol/L) reduced 8-OH-DPAT-induced amplitude depression in a dose-dependent manner. CONCLUSION: At the higher concentrations, MP protected spinal cord axons against hypoxia-induced excitability loss. It had an effect on serotonin 1A-induced axonal depression but not on GABA-induced depression.

8-Hydroxy-2-(di-n-propylamino)tetralin↗