The Experts below are selected from a list of 138 Experts worldwide ranked by ideXlab platform
Atsushi Umemura - One of the best experts on this subject based on the ideXlab platform.
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Contribution of cerebrovascular parasympathetic and sensory innervation to the development of cerebral edema in rat focal ischemia and reperfusion
Neuroscience letters, 1996Co-Authors: Atsushi Umemura, Kazuo YamadaAbstract:The purpose of this study was to investigate the contribution of cerebrovascular parasympathetic and sensory innervation to the development of ischemic brain edema. We measured the cerebral water content in rat focal ischemia and reperfusion model. A chronic transection of neither parasympathetic fiber nor sensory fiber (Nasociliary Nerve) modified the cerebral water content after 2 h ipsilateral middle cerebral artery (MCA) occlusion. However, a chronic transection of sensory fiber, but not the parasympathetic fiber, significantly attenuated the increase of the cerebral water content after 2 h occlusion of ipsilateral MCA followed by 2 h reperfusion. This result indicates that the cerebrovascular sensory innervation contributes to the development of cerebral edema in the postischemic reperfusion.
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cerebrovascular parasympathetic innervation contributes to coupling of neuronal activation and blood flow in rat somatosensory cortex
Neuroscience Letters, 1995Co-Authors: Atsushi Umemura, Neil M BranstonAbstract:Abstract We measured the increase of regional cerebral blood flow (rCBF) in the somatosensory cerebral cortex occurring in response to a standard stimulation of the L. side mystacial vibrissae (facial whiskers) in rats anaesthetised with halothane, in conjunction with blocking of activity in the R. side parasympathetic (PS) and sensory fibres innervating the cerebral vessels. Blocking was achieved reversibly and repeatedly by means of a cooling probe. When the PS fibres and the Nasociliary Nerve (NCN) were blocked together, but not when the NCN was blocked alone, the R. side rCBF increase occurring with whisker stimulation was significantly reduced. Our results indicate that, in addition to the intrinsic cortical factors demonstrated in earlier studies, the cerebrovascular PS innervation, but not the NCN, contributes to the increase in cortical rCBF associated with somatosensory cortical neuronal activation.
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contribution of cerebrovascular parasympathetic and sensory innervation to the short term control of blood flow in rat cerebral cortex
Journal of Cerebral Blood Flow and Metabolism, 1995Co-Authors: Neil M Branston, Atsushi Umemura, Achamma KoshyAbstract:In two groups of normotensive rats anaesthetised with halothane, either the Nasociliary Nerve (NCN) or the NCN and parasympathetic (PS) fibres together (NCN-PS) were functionally blocked at the right ethmoidal foramen. Blocking was achieved reversibly and repeatedly using a cooling probe. Cortical regional CBF (rCBF) was measured bilaterally using laser–Doppler probes. In Group 1, bilateral common carotid occlusion (CCO) was applied for 1 min both with and without block. In Group 2, CCO was applied permanently followed by stages of controlled haemorrhagic hypotension to deepen the ischaemia and the block applied at each stage. In Group 1, during CCO, rCBF was unaffected by blocking NCN-PS. However, during the transient postocclusive hyperaemia, blocking NCN-PS, but not NCN alone, significantly increased right side rCBF. In Group 2 and in Group 1 in the absence of CCO (normotension), rCBF was unaffected by blocking either set of fibres. We conclude that neither NCN nor PS fibres contribute to the tonic lev...
M Tschabitscher - One of the best experts on this subject based on the ideXlab platform.
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Transnasal approach to the medial intraconal space: anatomic study and clinical considerations.
Minimally invasive neurosurgery : MIN, 2010Co-Authors: I Dallan, V Seccia, R Lenzi, P Castelnuovo, M Bignami, P Battaglia, L Muscatello, S Sellari-franceschini, M TschabitscherAbstract:The aim of this study was to illustrate the anatomy of the medial compartment of the orbit by comparing the endoscopic transnasal perspective with the external ones. 8 orbits from 5 double-injected heads were carefully dissected. An endoscopic anterior transconjunctival dissection was performed in one orbit while an endoscopic transnasal intraconal dissection was conducted in 3 orbits. External dissections (from medial, superior and anterior perspective) were also performed. The role of the medial rectus muscle is emphasised. It represents the first important landmark encountered, covering all the other structures during transnasal approaches. By displacing it, the medial intraconal space with its contents becomes visible: the ophthalmic artery and related branches, the superior ophthalmic vein, the Nasociliary Nerve and, in the deepest part of the medial compartment, the optic Nerve. The medial compartment of the orbit can be addressed transnasally. By displacing the medial rectus muscle, it is possible to gain adequate space for the instruments and to control all of the medial compartment, including the medial aspect of the optic Nerve. © Georg Thieme Verlag KG Stuttgart · New York.
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Transnasal approach to the medial intraconal space: anatomic study and clinical considerations.
Minimally Invasive Neurosurgery, 2010Co-Authors: I Dallan, V Seccia, R Lenzi, P Castelnuovo, M Bignami, P Battaglia, L Muscatello, S Sellari-franceschini, M TschabitscherAbstract:BACKGROUND: The aim of this study was to illustrate the anatomy of the medial compartment of the orbit by comparing the endoscopic transnasal perspective with the external ones. METHODS: 8 orbits from 5 double-injected heads were carefully dissected. An endoscopic anterior transconjunctival dissection was performed in one orbit while an endoscopic transnasal intraconal dissection was conducted in 3 orbits. External dissections (from medial, superior and anterior perspective) were also performed. RESULTS: The role of the medial rectus muscle is emphasised. It represents the first important landmark encountered, covering all the other structures during transnasal approaches. By displacing it, the medial intraconal space with its contents becomes visible: the ophthalmic artery and related branches, the superior ophthalmic vein, the Nasociliary Nerve and, in the deepest part of the medial compartment, the optic Nerve. CONCLUSION: The medial compartment of the orbit can be addressed transnasally. By displacing the medial rectus muscle, it is possible to gain adequate space for the instruments and to control all of the medial compartment, including the medial aspect of the optic Nerve.
Peter J. Goadsby - One of the best experts on this subject based on the ideXlab platform.
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Nitric oxide synthase inhibitors can antagonize neurogenic and calcitonin gene‐related peptide induced dilation of dural meningeal vessels
British journal of pharmacology, 2002Co-Authors: Simon Akerman, David J. Williamson, Holger Kaube, Peter J. GoadsbyAbstract:The detailed pathophysiology of migraine is beginning to be understood and is likely to involve activation of trigeminovascular afferents. Clinically effective anti-migraine compounds are believed to have actions that include peripheral inhibition of calcitonin gene-related peptide (CGRP) release from trigeminal neurones, or preventing dural vessel dilation, or both. CGRP antagonists can block both neurogenic and CGRP-induced dural vessel dilation. Nitric oxide (NO) can induce headache in migraine patients and often triggers a delayed migraine. The initial headache is thought to be caused via a direct action of the NO–cGMP pathway that causes vasodilation by vascular smooth muscle relaxation, while the delayed headache is likely to be a result of triggering trigeminovascular activation. Nitric oxide synthase (NOS) inhibitors are effective in the treatment of acute migraine. The present studies used intravital microscopy to examine the effects of specific NOS inhibitors on neurogenic dural vasodilation (NDV) and CGRP-induced dilation. The non-specific and neuronal NOS (nNOS) inhibitors were able to partially inhibit NDV, while the non-specific and endothelial NOS (eNOS) inhibitors were able to partially inhibit the CGRP induced dilation. There was no effect of the inducible NOS (iNOS) inhibitor. The data suggest that the delayed headache response triggered by NO donors in humans may be due, in part, to increased nNOS activity in the trigeminal system that causes CGRP release and dural vessel dilation. Further, eNOS activity in the endothelium causes NO production and smooth muscle relaxation by direct activation of the NO–cGMP pathway, and may be involved in the initial headache response. Keywords: Migraine, nitric oxide, calcitonin gene related peptide, trigeminovascular system, middle meningeal artery, intravital microscopy Introduction The detailed pathophysiology of migraine is beginning to be understood and is likely to be related to activation of trigeminovascular afferents (Goadsby, 2001). There are sensory fibres within the trigeminal Nerve that innervate the cranial blood vessels and contain the vasodilator neuropeptides calcitonin gene-related peptide (CGRP) and substance P (Edvinsson et al., 1987; Jansen et al., 1991). These trigeminal sensory fibres become active during the migraine and their activation results in the release of CGRP (Gallai et al., 1995; Goadsby et al., 1990). The increased level of CGRP is reversed with sumatriptan (Goadsby & Edvinsson, 1993), which is an extremely effective treatment for acute migraine (Ferrari et al., 2001). The most reliable human experimental model for migraine induction (Edvinsson, 1999) is achieved with administration of nitric oxide (NO) donors to migraineurs (Thomsen et al., 1994). The mechanism of this response and its interaction with CGRP-induced changes in the dural circulation are, therefore, of considerable interest. The successful clinical action of acute specific anti-migraine drugs, ergot derivatives and triptans-5-HT1B/1D receptor agonists, is likely to relate their ability to inhibit release of neuropeptides from trigeminal sensory Nerve fibres (Goadsby, 2000). When the dura mater is electrically stimulated in rats it causes the dilation of dural blood vessels (Williamson et al., 1997b). This is likely to be caused by CGRP release from trigeminal sensory Nerves that innervate the cranial blood vessels since the effect is abolished by the CGRP receptor antagonist hCGRP(8-37) (Williamson et al., 1997a). Significant attenuation of the neurogenic meningeal vasodilator response is similarly seen with triptans, such as sumatriptan (Williamson et al., 1997b) and rizatriptan (Williamson et al., 1997c). Intravenous administration of CGRP also causes dural blood vessel dilation that is similarly abolished by the CGRP antagonist hCGRP(8-37), although it was not abolished by sumatriptan, indicating that it is likely the triptans act prejunctionally to prevent CGRP release (Williamson et al., 1997a, b). Nitric oxide (NO) is a potent endogenous vasodilator with an impressive array of biological actions (Moncada et al., 1991). NO causes an immediate headache in migraine sufferers and less often in control subjects, and in migraineurs triggers a delayed headache several hours after a NO infusion has ceased that fulfils the International Headache Society criteria (Headache Classification Committee of The International Headache Society, 1988) for migraine (Iversen et al., 1989; Olesen et al., 1993; 1994). This is also seen when NO is given exogenously (Krabbe & Olesen, 1980; Lassen et al., 1995), and is likely to be related to endothelial activation (Jansen Olesen et al., 1997). In experimental animals NO is also able to cause meningeal vessel dilation when given intravenously (Akerman et al., 2001). Although the immediate headache caused by NO can be attributed to a direct action on blood vessels, and a possible role in the NO–cyclic guanosine monophosphate (NO–cGMP) pathway, a direct action is unlikely to explain the delayed headache response (Olesen et al., 1995). It seems possible that NO might act on the trigeminovascular system, including trigeminal neurons, to trigger the delayed headache response. Glyceryl trinitrate (GTN) when infused through the intra-carotid artery was able to sensitize and increase the discharge rate of trigeminovascular neurons which have received inputs from the superior sagittal sinus immediately and also beyond the time of infusion of GTN (Lambert et al., 2000). Fos expression in the trigeminal nucleus caudalis is affected by NO (Hoskin et al., 1999; Jones et al., 2001; Tassorelli et al., 1997; 2000; Tassorelli & Joseph, 1995). It would seem likely that the activation of the trigeminovascular system by NO might involve an interaction with calcitonin gene-related peptide (CGRP) to cause the dural blood vessel dilation during migraine. There is evidence that a relationship between NO and CGRP does exist. Indeed CGRP and NOS seem to coexist in trigeminal ganglion cells, although it was found that L-nitroarginine methylester (L-NAME), a nitric oxide synthase inhibitor (NOS) had no effect on cortical blood flow following Nasociliary Nerve stimulation while the hCGRP8-37 reduced the blood flow (Edvinsson et al., 1998). The effectiveness of NOS inhibitors as a potential migraine treatment has been examined in a single small study. The authors demonstrated, using a non-specific NOS NG-methyl-L-arginine (L-NMMA), that it was possible to provide relief to patients experiencing headache (Lassen et al., 1997). A side effect of using a non-specific NOS inhibitor were the changes in blood pressure and heart rate over time that would limit the usefulness of this compound in the clinic. It is remarkable that the same NOS inhibitor could reduce pain in patients with Chronic Tension-Type Headache (Ashina et al., 1999). In this series of experiments we sought first, to determine if a non-specific NOS inhibitor was able to interact with CGRP in the trigeminovascular system by observing its effects on both the neurogenically mediated dural blood vessel dilation and also on CGRP-induced dilation. Secondly, we administered specific inhibitors to endothelial NOS (eNOS), neuronal NOS (nNOS) and inducible NOS (iNOS) to determine which is likely to be involved in trigeminovascular transmission, and therefore be a potential therapeutic target.
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Calcitonin gene-related peptide and nitric oxide in the trigeminal ganglion: cerebral vasodilatation from trigeminal Nerve stimulation involves mainly calcitonin gene-related peptide.
Journal of the autonomic nervous system, 1998Co-Authors: L Edvinsson, Peter J. Goadsby, H Mulder, R UddmanAbstract:Nitric oxide (NO) is a novel neurotransmitter candidate to which a large number of physiological roles has been ascribed. In the present study, immunocytochemistry was used to demonstrate NO synthase (NOS) and to investigate possible co-localization with other neurotransmitters. In the trigeminal ganglion of the cat, a moderate number of NOS immunoreactive Nerve cell bodies was seen, of which the major part also expressed calcitonin gene-related peptide (CGRP). The Nerve cell bodies expressing NOS in the trigeminal ganglion were predominantly of small to medium size; while numerous cell bodies of varying size contained CGRP. With in situ hybridization using oligonucleotide probes, CGRP mRNA was demonstrated in almost all trigeminal neurons of the cat. Stimulation of the Nasociliary Nerve resulted in a frequency-dependent increase in ipsilateral local cortical blood flow by 30 +/- 6%. Administration of the NOS inhibitor NG-nitro-L-arginine-methylester (L-NAME) did not significantly alter this response when applied intravenously or on the cortical surface. Local cortical administration of the CGRP blocker h-CGRP (8-37) did not alter the cerebral vasodilator response to hypercapnia or resting flow. However, the Nasociliary Nerve response was reduced by 50% after h-CGRP (8-37), with a general shift to the right of the frequency-response curve. These data suggest that although NOS is seen in several trigeminal ganglion cells and coexists with CGRP in a subpopulation of the sensory neurons, its role in trigeminally mediated vasodilatation was not significant.
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Inhibition of calcitonin gene-related peptide by h-CGRP(8-37) antagonizes the cerebral dilator response from Nasociliary Nerve stimulation in the cat.
Neuroscience letters, 1993Co-Authors: Peter J. GoadsbyAbstract:The head is innervated by neurons with cell bodies in the trigeminal ganglion that contain both calcitonin gene-related peptide (CGRP) and substance P. The CGRP-containing neurons preferentially innervate the cerebral vessels and when activated produce both an increase in blood flow and local release of CGRP. In this study, the CGRP antagonist h-CGRP(8-37) was examined for its ability to interfere with trigeminal-evoked cerebral vasodilator responses in the alpha-chloralose anaesthetised cat. Nasociliary Nerve stimulation produced a characteristic frequency-dependent increase in cerebral cortical blood flow with a mean maximum of 35 +/- 7% at 20 Hz. Following administration of h-CGRP(8-37), this response was reduced by half with a general shift to the right of the frequency-response curve. These data further support the view that CGRP is an important transmitter agent in the trigeminovascular system that is responsible for a great part of the vasodilator capacity of trigeminal neurons.
Nyall R London - One of the best experts on this subject based on the ideXlab platform.
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expanded exposure and detailed anatomic analysis of the superior orbital fissure implications for endonasal and transorbital approaches
Head and Neck-journal for The Sciences and Specialties of The Head and Neck, 2020Co-Authors: Nyall R London, Daniel M Prevedello, Lifeng Li, Xiaohong Chen, Ricardo L CarrauAbstract:This study aimed to ascertain the maximal exposure of the superior orbital fissure (SOF) afforded by combining endonasal and transorbital endoscopic approaches. Six cadaveric specimens (12 sides) were dissected using endonasal and transorbital endoscopic approaches to access the SOF. The order of the approaches was alternated in each specimen (eg, starting with an endonasal approach in one side followed by a transorbital exposure and reversing the order on the contralateral side). Maximal exposure of the SOF and its contents for individual and combined approaches were explored. The endonasal corridor provided adequate access to the inferomedial 1/3 of the SOF and including the proximal segments of cranial Nerves (CN) III, V1 and VI. A transorbital approach was superior accessing the superolateral 2/3's of the SOF, including the superior ophthalmic vein, lacrimal Nerve, and distal segment of the CN VI at the lateral aspect; the Nasociliary Nerve and divisions of CN III centrally; and the frontal Nerve and CN IV at the dorsal aspect of levator palpebrae superioris. This study suggests that a combined endonasal and transorbital exposure of the SOF may be advantageous to address lesions in this challenging region.
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Transnasal prelacrimal approach to the inferior intraconal space: a feasibility study.
International forum of allergy & rhinology, 2019Co-Authors: Nyall R London, Daniel M Prevedello, Samuel Silva, Ricardo L CarrauAbstract:BACKGROUND Endonasal access to the inferomedial and inferolateral intraconal space via the orbital floor has not been reported. The primary purpose of this study was to assess the feasibility of accessing the inferior intraconal space through the orbital floor via a transnasal prelacrimal approach. Secondarily, it aims to highlight anatomical relationships of neurovascular structures in this space, as a requirement to prevent complications. METHODS Six cadaveric heads (12 sides) were dissected using a transnasal prelacrimal approach. The orbital floor, medial to the infraorbital canal, was removed and the periorbita opened to expose the inferior rectus muscle. The inferomedial and inferolateral intraconal space was accessed alongside the medial and lateral border of inferior rectus muscle, respectively. Various anatomical relationships of adjacent neurovascular structures were recorded, and the distances among the recti muscles and optic Nerve were also measured. RESULTS The infraorbital Nerve is located at the inferolateral aspect of inferior rectus muscle. In the inferomedial intraconal space, we identified the inferomedial muscular trunk of the ophthalmic artery, optic Nerve, and branches of the oculomotor Nerve; whereas the inferolateral intraconal space contained the inferolateral muscular trunk of ophthalmic artery, branches of the oculomotor and Nasociliary Nerve, and abducens Nerve. Distances from the medial, inferior, and lateral recti muscles to the optic Nerve were (mean ± standard deviation) 4.70 ± 1.18 mm, 5.60 ± 0.93 mm, and 7.98 ± 1.99 mm, respectively. Distances from the inferior rectus muscle to the inferior borders of medial and lateral recti muscles were 4.45 ± 1.23 mm and 8.77 ± 1.80 mm. CONCLUSION It is feasible to access the inferior intraconal space through the orbital floor via a transnasal prelacrimal approach. The access may be subdivided into inferomedial and inferolateral corridors according to the entry point at the medial or lateral border of the inferior rectus muscle. Neurovascular structures in the inferior intraconal space are visualized directly, which should enhance their preservation.
Ricardo L Carrau - One of the best experts on this subject based on the ideXlab platform.
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expanded exposure and detailed anatomic analysis of the superior orbital fissure implications for endonasal and transorbital approaches
Head and Neck-journal for The Sciences and Specialties of The Head and Neck, 2020Co-Authors: Nyall R London, Daniel M Prevedello, Lifeng Li, Xiaohong Chen, Ricardo L CarrauAbstract:This study aimed to ascertain the maximal exposure of the superior orbital fissure (SOF) afforded by combining endonasal and transorbital endoscopic approaches. Six cadaveric specimens (12 sides) were dissected using endonasal and transorbital endoscopic approaches to access the SOF. The order of the approaches was alternated in each specimen (eg, starting with an endonasal approach in one side followed by a transorbital exposure and reversing the order on the contralateral side). Maximal exposure of the SOF and its contents for individual and combined approaches were explored. The endonasal corridor provided adequate access to the inferomedial 1/3 of the SOF and including the proximal segments of cranial Nerves (CN) III, V1 and VI. A transorbital approach was superior accessing the superolateral 2/3's of the SOF, including the superior ophthalmic vein, lacrimal Nerve, and distal segment of the CN VI at the lateral aspect; the Nasociliary Nerve and divisions of CN III centrally; and the frontal Nerve and CN IV at the dorsal aspect of levator palpebrae superioris. This study suggests that a combined endonasal and transorbital exposure of the SOF may be advantageous to address lesions in this challenging region.
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Transnasal prelacrimal approach to the inferior intraconal space: a feasibility study.
International forum of allergy & rhinology, 2019Co-Authors: Nyall R London, Daniel M Prevedello, Samuel Silva, Ricardo L CarrauAbstract:BACKGROUND Endonasal access to the inferomedial and inferolateral intraconal space via the orbital floor has not been reported. The primary purpose of this study was to assess the feasibility of accessing the inferior intraconal space through the orbital floor via a transnasal prelacrimal approach. Secondarily, it aims to highlight anatomical relationships of neurovascular structures in this space, as a requirement to prevent complications. METHODS Six cadaveric heads (12 sides) were dissected using a transnasal prelacrimal approach. The orbital floor, medial to the infraorbital canal, was removed and the periorbita opened to expose the inferior rectus muscle. The inferomedial and inferolateral intraconal space was accessed alongside the medial and lateral border of inferior rectus muscle, respectively. Various anatomical relationships of adjacent neurovascular structures were recorded, and the distances among the recti muscles and optic Nerve were also measured. RESULTS The infraorbital Nerve is located at the inferolateral aspect of inferior rectus muscle. In the inferomedial intraconal space, we identified the inferomedial muscular trunk of the ophthalmic artery, optic Nerve, and branches of the oculomotor Nerve; whereas the inferolateral intraconal space contained the inferolateral muscular trunk of ophthalmic artery, branches of the oculomotor and Nasociliary Nerve, and abducens Nerve. Distances from the medial, inferior, and lateral recti muscles to the optic Nerve were (mean ± standard deviation) 4.70 ± 1.18 mm, 5.60 ± 0.93 mm, and 7.98 ± 1.99 mm, respectively. Distances from the inferior rectus muscle to the inferior borders of medial and lateral recti muscles were 4.45 ± 1.23 mm and 8.77 ± 1.80 mm. CONCLUSION It is feasible to access the inferior intraconal space through the orbital floor via a transnasal prelacrimal approach. The access may be subdivided into inferomedial and inferolateral corridors according to the entry point at the medial or lateral border of the inferior rectus muscle. Neurovascular structures in the inferior intraconal space are visualized directly, which should enhance their preservation.
