Sexual health in neuromuscular diseases: Neglected challenges revealed by a scoping review.

Cerebral small vessel disease (cSVD) has several radiological features, including white matter hyperintensities (WMH), lacunes, microhaemorrhages, and perivascular spaces, which may result in symptoms. cSVD contributes to substantial proportions of stroke and cognitive impairment, and cerebrovascular dysfunction appears to be an early tractable microvascular abnormality. Therefore, measuring microvascular dysfunction within the central nervous system could help us understand pathophysiological mechanisms and help identify and measure the effects of novel interventions. Cerebrovascular reactivity (CVR) to inhaled carbon dioxide (CO) reflects the chemo-regulatory function of microvessels to dilate, is related to the severity of cSVD features, may predispose to future development of brain lesions, and appears to respond to interventions targeting vascular endothelial function. CVR can be assessed using the blood oxygen level dependent magnetic resonance imaging (BOLD MRI) response to 6% inhaled CO. However, neither BOLD MRI nor conventional structural MRI are able to resolve individual microvessels at the arteriole, capillary or venule level – the epicentre of cSVD pathogenesis. Transcranial doppler ultrasound can estimate CVR as change in velocity in one large artery, usually the middle cerebral artery, but is operator-dependent, limited by acoustic window, and gives an average blood flow response for the whole arterial territory. Blood vessels of the retina are visible on ophthalmoscopy, and share embryology, anatomy and physiology with the brain vasculature. Like the cerebrovasculature, retinal microvessels serve neural tissue that is highly metabolically active and reliant on a constant supply of oxygen and glucose. This explains broad similarities in neurovascular unit structure, blood-barrier function and microvascular geometry between retina and brain, as well as similar capacities to regulate local blood flow through chemo-regulation (e.g., reactivity to CO), neurovascular coupling, and autoregulation.