A conceptual model for changes in finger photoplethysmograph signals caused by hand posture and isothermic regulation

Objective. To observe changes in baseline and pulsatile light absorbance (photoplethysmograph, PPG) in the finger-tip, by raising the hand above the horizontal plane in recumbent subjects. We applied current knowledge of the circulation to the finger-tip, particularly arteriovenous anastomoses (AVAs), and the physiology of the venous circulation. Approach. We studied healthy young volunteers in a quiet thermoneutral environment. A finger plethysmograph on the non-dominant hand recorded transmission of red and infra-red light, and the values were converted into absorbance to allow comparisons within and between subjects. Breathing movements were recorded unobtrusively to assess any effect on absorbance and the pulse amplitude of the signals. All body movements were passive: the study arm was elevated in a trough to about 40° above the horizontal plane. The following conditions were studied, each for 15 minutes, using the last 10 minutes for analysis: recumbent, study arm elevated, study arm horizontal, and both legs elevated by 40°. Main results. There was a substantial time-related effect, and considerable variation between subjects. Arm elevation reduced red light absorbance and increased the range of amplitudes of the PPG waveform: only in subjects with large absorbances, did waveform amplitude increase. The other main effect was that spontaneous, thermoregulatory decreases in absorbance were associated with decreases in waveform amplitude. Significance. Finger-tip vessels distend with blood when AVAs open. The vessels pulsate more strongly if venous collapse allows the vessels to become more compliant. The postcapillary circulation is likely to be an important source of pulsation.

Pathophysiology and surgical treatment of spinal adhesive arachnoid pathology: patient series

BACKGROUND Spinal adhesive arachnoid pathology is a rare cause of myelopathy. Because of rarity and variability, mechanisms of myelopathy are unknown. The authors retrospectively analyzed patients to understand pathophysiology and provide implications for surgical treatment. OBSERVATIONS Nineteen consecutive patients were studied. Thirteen patients had a secondary pathology due to etiological disorders such as spinal surgery or hemorrhagic events. They received arachnoid lysis (4 patients), syringo-subarachnoid (S-S) shunt (8 patients) with or without lysis, or anterior decompression. Three of them developed motor deterioration after lysis, and 6 patients needed further 8 surgeries. Another 6 patients had idiopathic pathology showing dorsal arachnoid cyst formation at the thoracic level that was surgically resected. With mean follow-up of 44.3 months, only 4 patients with the secondary pathology showed improved neurological grade, whereas all patients with idiopathic pathology showed improvement. LESSONS The idiopathic pathology was the localized dorsal arachnoid adhesion that responded to surgical treatment. The secondary pathology produced disturbed venous circulation of the spinal cord by extensive adhesions. Lysis of the thickened fibrous membrane with preservation of thin arachnoid over the spinal veins may provide safe decompression. S-S shunt was effective if the syrinx extended to the level of normal subarachnoid space.

Acquired pial arteriovenous fistula secondary to cerebral cortical vein thrombosis: A case report and review of the literature

Pial arteriovenous fistulas (AVFs) are rare neurovascular malformations. They differ from arteriovenous malformations (AVMs) in that they involve single or multiple feeding arteries, draining directly into a dilated cortical vein with no intervening nidus. Pial and dural AVFs differ in blood supply, as the first originate from pial or cortical arteries and the latter from outside the dural leaflets. Unlike dural AVFs, most of the pial AVFs are supratentorial. The vast majority are congenital, manifesting during infancy. Acquired pial AVFs are significantly rarer and occur after vasculopathy, head trauma, brain surgery, or cerebral vein thrombosis. We describe a unique case of an acquired pial AVF in a 50-year-old man secondary to a cortical vein thrombosis manifesting as a focal-onset seizure with secondary generalization. A cerebral digital subtraction angiography revealed a low-flow pial AVF fed by a postcentral branch of the left middle cerebral artery draining to the superior sagittal sinus via a cortical vein. It also showed a collateral venous circulation adjacent to the previously thrombosed left parietal vein. There was no evidence of an associated dural AVF or venous varix. Endovascular treatment was scheduled three months later, but the angiogram preceding the embolization showed spontaneous and complete closure of the malformation. To our knowledge, this is the first case illustrating acquired pure pial AVF unaccompanied by a dural component following cortical vein thrombosis, eventually resulting in an unprompted closure.

Adipose Tissue and Biological Factors. Possible Link between Lymphatic System Dysfunction and Obesity

The World Health Organization (WHO) has recognised obesity as one of the top ten threats to human health. Obesity is not only a state of abnormally increased adipose tissue in the body, but also of an increased release of biologically active metabolites. Moreover, obesity predisposes the development of metabolic syndrome and increases the incidence of type 2 diabetes (T2DM), increases the risk of developing insulin resistance, atherosclerosis, ischemic heart disease, polycystic ovary syndrome, hypertension and cancer. The lymphatic system is a one-directional network of thin-walled capillaries and larger vessels covered by a continuous layer of endothelial cells that provides a unidirectional conduit to return filtered arterial and tissue metabolites towards the venous circulation. Recent studies have shown that obesity can markedly impair lymphatic function. Conversely, dysfunction in the lymphatic system may also be involved in the pathogenesis of obesity. This review highlights the important findings regarding obesity related to lymphatic system dysfunction, including clinical implications and experimental studies. Moreover, we present the role of biological factors in the pathophysiology of the lymphatic system and we propose the possibility of a therapy supporting the function of the lymphatic system in the course of obesity.

The Rare Cases of Parotid Gland Arteriovenous Malformations

Arteriovenous malformation (AVM) results from errors in vascular development during embryogenesis; absent capillary beds lead to shunting directly from the arterial to venous circulation. Although it is common in the head and neck region, AVMs located in the parotid gland are quite rare. Here, we report two cases of arteriovenous malformation of the parotid gland that presented to our out-patient setup with swelling in the parotid region and were diagnosed as arteriovenous malformation on histopathological study after surgical resection.

Coronary venous therapy to improve microvascular dysfunction

The coronary circulation is a complex system in which vascular resistances are determined by an interplay of forces in at least three compartments: the epicardial, the microvascular, and the venous district. Cardiologists, and particularly interventional cardiologists, normallly place the focus of their attention on diseases of the epicardial coronary circulation as possible causes of coronary syndromes and neglect the importance of the other two compartments of coronary circulation. The study of the coronary microcirculation, an increasingly recognized source of ischemia, has long been disregarded, but is witnessing a revival since the (re-)introduction of diagnostic tools in the better equipped catheterization laboratories. Unfortunately, to date our understanding of coronary microvascular disease remains incomplete and the numerous proposed classifications fail to reflect its complexity. Further, no specific therapy for these disorders is available. The coronary venous circulation is an even more neglected third vascular district. Its role in regulating coronary resistances is almost completely unexplored, but inital evidence suggests that the modulation of venous pressure might help improve coronary perfusion. Coronary sinus interventions are a group of invasive techniques (both surgical and catheter-based) that are designed to treat ischaemic heart disease by increasing coronary venous pressure and therefore redistributing coronary blood flow towards the endocardium. In this review paper, we revise the role of these interventions with particular focus on acute and chronic coronary microvascular disease.

Aberrant Neurogliovascular Unit Dynamics in Cerebral Small Vessel Disease: A Rheological Clue to Vascular Parkinsonism

The distinctive anatomical assemble and functionally discrete multicellular cerebrovasculature dynamics confer varying rheological and blood–brain barrier permeabilities to preserve the integrity of cerebral white matter and its neural microenvironment. This homeostasis intricately involves the glymphatic system that manages the flow of interstitial solutes, metabolic waste, and clearance through the venous circulation. As a physiologically integrated neurogliovascular unit (NGVU) serving a particularly vulnerable cerebral white matter (from hypoxia, metabolic insults, infection, and inflammation), a likely insidious process over a lifetime could inflict microenvironment damages that may lead to pathological conditions. Two such conditions, cerebral small vessel disease (CSVD) and vascular parkinsonism (VaP), with poorly understood pathomechanisms, are frequently linked to this brain-wide NGVU. VaP is widely regarded as an atypical parkinsonism, described by cardinal motor manifestations and the presence of cerebrovascular disease, particularly white matter hyperintensities (WMHs) in the basal ganglia and subcortical region. WMHs, in turn, are a recognised imaging spectrum of CSVD manifestations, and in relation to disrupted NGVU, also include enlarged perivascular spaces. Here, in this narrative review, we present and discuss on recent findings that argue for plausible clues between CSVD and VaP by focusing on aberrant multicellular dynamics of a unique integrated NGVU—a crossroad of the immune–vascular–nervous system—which may also extend fresher insights into the elusive interplay between cerebral microvasculature and neurodegeneration, and the potential therapeutic targets.

A subset of arachnoid granulations in humans drain to the venous circulation via intradural lymphatic vascular channels

OBJECTIVE The discovery of dural lymphatics has spurred interest in the mechanisms of drainage of interstitial fluid from the CNS, the anatomical components involved in clearance of macromolecules from the brain, mechanisms of entry and exit of immune components, and how these pathways may be involved in neurodegenerative diseases and cancer metastasis. In this study the authors describe connections between a subset of arachnoid granulations (AGs) and the venous circulation via intradural vascular channels (IVCs), which stain positively with established lymphatic markers. The authors postulate that the AGs may serve as a component of the human brain’s lymphatic system. METHODS AGs and IVCs were examined by high-resolution dissection under stereoscope bilaterally in 8 fresh and formalin-fixed human cadaveric heads. The superior sagittal sinus (SSS) and adjacent dura mater were immunostained with antibodies against Lyve-1 (lymphatic marker), podoplanin (lymphatic marker), CD45 (panhematopoietic marker), and DAPI (nuclear marker). RESULTS AGs can be classified as intradural or interdural, depending on their location and site of drainage. Interdural AGs are distinct from the dura, adhere to arachnoid membranes, and occasionally open directly in the inferolateral wall or floor of the SSS, although some cross the infradural folds of the dura’s inner layer to meet with intradural AGs and IVCs. Intradural AGs are located within the leaflets of the dura. The total number of openings from the AGs, lateral lacunae, and cortical veins into the SSS was 45 ± 5.62 per head. On average each cadaveric head contained 6 ± 1.30 intradural AGs. Some intradural AGs do not directly open into the SSS and use IVCs to connect to the venous circulation. Using immunostaining methods, the authors demonstrate that these tubular channels stain positively with vascular and lymphatic markers (Lyve-1, podoplanin). CONCLUSIONS AGs consist of two subtypes with differing modes of drainage into the SSS. A subset of AGs located intradurally use tubular channels, which stain positively with vascular and lymphatic markers to connect to the venous lacunae and ultimately to the SSS. The present study suggests that AGs may function as a component of brain lymphatics. This finding has important clinical implications for cancer metastasis to and from the CNS and may shed light on mechanisms of altered clearance of macromolecules in the setting of neurodegenerative diseases.