SciCombinator

Discover the most talked about and latest scientific content & concepts.

Concept: Carotid sinus

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Objective. Hypertension is the largest threat to patient health and a burden to health care systems. Despite various options, 30% of patients do not respond sufficiently to medical treatment. Mechanoreceptors in the aortic arch relay blood pressure (BP) levels through vagal nerve (VN) fibers to the brainstem and trigger the baroreflex, lowering the BP. Selective electrical stimulation of these nerve fibers reduced BP in rats. However, there is no technique described to localize and stimulate these fibers inside the VN without inadvertent stimulation of non-baroreceptive fibers causing side effects like bradycardia and bradypnea. Approach. We present a novel method for selective VN stimulation to reduce BP without the aforementioned side effects. Baroreceptor compound activity of rat VN (n = 5) was localized using a multichannel cuff electrode, true tripolar recording and a coherent averaging algorithm triggered by BP or electrocardiogram. Main results. Tripolar stimulation over electrodes near the barofibers reduced the BP without triggering significant bradycardia and bradypnea. The BP drop was adjusted to 60% of the initial value by varying the stimulation pulse width and duration, and lasted up to five times longer than the stimulation. Significance. The presented method is robust to impedance changes, independent of the electrode’s relative position, does not compromise the nerve and can run on implantable, ultra-low power signal processors.

Concepts: Medicine, Electrochemistry, Vagus nerve, Carotid sinus, Vagus nerve stimulation, Electrochemical cell, Hypotension, Baroreflex

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The anterior clinoid process (ACP) is critically related to the clinoidal portion of the internal carotid artery (ICA). The deep location of the ACP makes treatment of vascular and neoplastic lesions related to the ACP challenging. Removal of the ACP is advocated to facilitate treatment of such lesions. However injury to the clinoidal ICA remains a potential and dreadful complication of ACP removal. The aim of this study was to demonstrate an endoscopic assisted technique to perform intradural removal of the ACP via a pterional approach with continuous visualization of the clinoidal ICA.

Concepts: Internal carotid artery, Common carotid artery, External carotid artery, Carotid sinus, Internal jugular vein, Anterior clinoid process

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We report the case of a 40-year-old woman with a severe factor XI (FXI) deficiency who died from a stroke due to bilateral internal carotid arteries occlusion after a laparoscopic gastric bypass (bariatric surgery). This stroke was probably secondary to a pulmonary embolism with a paradoxical embolism through a previously unknown foramen ovale. This woman who had one severe episode of bleeding before the bypass received for the intervention a single infusion of 27 U/kg of FXI concentrate. A careful evaluation of the bleeding and thrombotic risk was performed before surgery, and despite all preventive measures, this tragic event occurred. The aim of this report is to alert medical teams to carefully balance the benefit-risk of such an intervention in a patient with a severe FXI deficiency.

Concepts: Obesity, Internal carotid artery, Common carotid artery, External carotid artery, Carotid sinus, Internal jugular vein, Factor XI, Embolism

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: During evaluation for monocular visual loss, a 48-year-old woman was found to have a posttraumatic paraophthalmic internal carotid artery (ICA) pseudoaneurysm. She underwent reconstruction of the ophthalmic segment of the right ICA with a Pipeline embolization device but her vision did not return.

Concepts: Internal carotid artery, Common carotid artery, External carotid artery, Ophthalmology, Carotid sinus, Internal jugular vein, Ophthalmic artery, Amaurosis fugax

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OBJECTIVE: Differentiation between an occluded and a patent extracranial internal carotid artery (ICA) is crucial in the diagnostic workup of patients with acute ischemic stroke; particularly in patients eligible for endovascular treatment. We report neurological and radiological findings of cases in which CTA in the acute phase incorrectly revealed an occlusion of the ICA. METHODS: In our image data base of 54 patients with acute ischemic stroke eligible for endovascular treatment, we searched for patients with an occluded extracranial ICA on CTA whereas DSA proved that this artery was patent. Of these patients, all available images were re-examined to investigate possible causes of these so-called pseudo-occlusions. RESULTS: We detected 6 patients (11%) with a pseudo-occlusion. The pseudo-occlusions on CTA were associated with reduced flow due to carotid T-occlusions (4 cases) or a combination of a high degree stenosis of the extracranial ICA and MCA occlusion (2 cases). CONCLUSION: CTA in the acute phase of ischemic stroke needs to be interpreted with severe caution, and in endovascular treatment decisions we should be aware that an extracranial ICA occlusion may be a false positive finding.

Concepts: Atherosclerosis, Stroke, Middle cerebral artery, Internal carotid artery, Common carotid artery, External carotid artery, Carotid sinus, Internal jugular vein

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It has been established that vagal nerve stimulation (VNS) benefits patients and/or animals with heart failure. However, the impact of VNS on sympathetic nerve activity (SNA) remains unknown. In this study, we investigated how vagal afferent stimulation (AVNS) impacts baroreflex control of SNA. In 12 anesthetized Sprague-Dawley rats, we controlled the pressure in isolated bilateral carotid sinuses (CSP), and measured splanchnic SNA and arterial pressure (AP). Under a constant CSP, increasing the voltage of AVNS dose dependently decreased SNA and AP. The averaged maximal inhibition of SNA was -28.0 ± 10.3%. To evaluate the dynamic impacts of AVNS on SNA, we performed random AVNS using binary white noise sequences, and identified the transfer function from AVNS to SNA and that from SNA to AP. We also identified transfer functions of the native baroreflex from CSP to SNA (neural arc) and from SNA to AP (peripheral arc). The transfer function from AVNS to SNA strikingly resembled the baroreflex neural arc and the transfer functions of SNA to AP were indistinguishable whether we perturbed ANVS or CSP, indicating that they likely share common central and peripheral neural mechanisms. To examine the impact of AVNS on baroreflex, we changed CSP stepwise and measured SNA and AP responses with or without AVNS. AVNS resets the sigmoidal neural arc downward, but did not affect the linear peripheral arc. In conclusion, AVNS resets the baroreflex neural arc and induces sympathoinhibition in the same manner as the control of SNA and AP by the native baroreflex.

Concepts: Myocardial infarction, Vagus nerve, Control theory, Carotid sinus, Autonomic nervous system, Vagus nerve stimulation, Parasympathetic nervous system, Transfer function

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Implanted vagus nerve stimulation (VNS) has been used to treat seizures and depression. In this study, we explore the mechanism of action of non-invasive vagus nerve stimulation (nVNS) for the treatment of trigeminal allodynia. Rats were repeatedly infused with inflammatory mediators directly onto the dura, which leads to chronic trigeminal allodynia. nVNS for 2min decreases periorbital sensitivity in rats with periorbital trigeminal allodynia for up to 3.5hr after stimulation. Using microdialysis, we quantified levels of extracellular neurotransmitters in the trigeminal nucleus caudalis (TNC). Allodynic rats showed a 7.7±0.9 fold increase in extracellular glutamate in the TNC following i.p. administration of the chemical headache trigger, glyceryl trinitrate (GTN; 0.1mg/kg). Allodynic rats, which received nVNS, had only a 2.3±0.4 fold increase in extracellular glutamate following GTN similar to the response in control naive rats. When nVNS was delayed until 120min after GTN treatment, the high levels of glutamate in the TNC were reversed following nVNS. The nVNS stimulation parameters used in this study did not produce significant changes in blood pressure or heart rate. These data suggest that nVNS may be used to treat trigeminal allodynia.

Concepts: Inflammation, Nervous system, Vagus nerve, Cranial nerves, Acetylcholine, Carotid sinus, Vagus nerve stimulation, Vagus

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Randomized trials support carotid endarterectomy (CEA) in asymptomatic patients with ≥60% internal carotid artery (ICA) stenosis. The widely referenced Society for Radiologists in Ultrasound Consensus Statement on carotid duplex ultrasound (CDUS) imaging indicates that an ICA peak systolic velocity (PSV) ≥230 cm/s corresponds to a ≥70% ICA stenosis, leading to the potential conclusion that asymptomatic patients with an ICA PSV ≥230 cm/s would benefit from CEA. Our goal was to determine the natural history stroke risk of asymptomatic patients who might have undergone CEA based on consensus statement PSV of ≥230 cm/s but instead were treated medically based on more conservative CDUS imaging criteria.

Concepts: Atherosclerosis, Medical imaging, Internal carotid artery, Common carotid artery, External carotid artery, Medical ultrasonography, Carotid sinus, Internal jugular vein

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