TROPICAL SYNAPSES
Reflections on topics including clinical neurology, recent publications in neuroscience,
philosophy of biology, "neuro-doubt" about modern media hype of new neuro-scientific procedures and methods, local oceanography, tropical horticulture, the Hawai'i health scene, and whatever else dat's da kine...
Heliconias are striking plants when in bloom. What we see most as the flowers are specially shaped and pigmented leaves, called bracts. The much smaller flowers are nestled within the brachts and may last less than 24 hours each, but they too can be striking. See the indigo flower in the pictures.
In the bioRxiv preprint here, the authors find that the type of vagus nerve stimulation used to treat intractable epilepic seizures may open the blood-brain barrier to penetration by the cerebrospinal fluid, increasing the "washing" of fluid through the cells of the brain. The cause of this effect remains unclear. The effect on CSF penetration is not likely to cause any of VNS's known effects on epilepsy. Instead, because the vagus nerve is already known to be intimately involved with such autonomic functions as the body's circulation, VNS's effects of brain fluid flows is more likely to be a consequence of vagus nerve action on the circulation of the CSF lymphatic system (the "adrenergic signaling" mentioned in the article).
Where would this effect be useful clinically? This is not clear, but the possibility of increasing the effects of intrathecal chemotherapy on certain cancers comes to mind.
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ABSTRACT
Is Vagus Nerve Stimulation Brain Washing? Kevin P. Cheng1*, Sarah K. Brodnick1*, Stephan L. Blanz1, Weifeng Zeng2, Jack Kegel1, Jane A. Pisaniello1, Jared P. Ness1, Erika Ross3, Evan N. Nicolai1,4, Megan L. Settell1,4, James K. Trevathan1,4, Samuel O. Poore1,2, Aaron J. Suminski1,5, Justin C. Williams1,5*, Kip A. Ludwig1,5* One Sentence Summary: Cervical vagus nerve stimulation using clinically derived parameters enhances movement of cerebrospinal fluid into the brain parenchyma presenting a previously unreported effect of vagus nerve stimulation with potential clinical utility. Abstract: Vagal nerve stimulation (VNS) is an FDA approved treatment method for intractable epilepsy, treatment resistant depression, cluster headaches and migraine with over 100,000 patients having received vagal nerve implants to date. Moreover, evidence in the literature has led to a growing list of possible clinical indications, with several small clinical trials applying VNS to treat conditions ranging from neurodegenerative diseases to arthritis, anxiety disorders, and obesity. Despite the growing list of therapeutic applications, the fundamental mechanisms by which VNS achieves its beneficial effects are poorly understood and an area of active research. In parallel, the glymphatic and meningeal lymphatic systems have recently been proposed and experimentally validated to explain how the brain maintains a healthy homeostasis without a traditionally defined lymphatic system. In particular, the glymphatic system relates to the interchange of cerebrospinal fluid (CSF) and interstitial fluid (ISF) whose net effect is to wash through the brain parenchyma removing metabolic waste products and misfolded proteins from the interstitium. Of note, clearance is sensitive to adrenergic signaling, and a primary driver of CSF influx into the parenchyma appears to be cerebral arterial pulsations and respiration. As VNS has well-documented effects on cardiovascular and respiratory physiology as well as brain adrenergic signaling, we hypothesized that VNS delivered at clinically derived parameters would increase CSF influx in the brain. To test this hypothesis, we injected a low molecular weight (3 kD) lysine-fixable fluorescent tracer (TxRed) into the CSF system of mice with a cervical vagus nerve cuff implant and measured the amount of CSF penetrance following VNS. We found that the clinical VNS group showed a significant increase in CSF dye penetrance as compared to the naïve control and sham groups. This study demonstrates that VNS therapeutic strategies already being applied in the clinic today may induce intended effects and/or unwanted side effects by altering CSF/ISF exchange in the brain. This may have broad ranging implications in the treatment of various CNS pathologies.
Vaccination policy by country: orange -- Mandatory vaccination blue -- Voluntary vaccination green -- Vaccination not mandatory, but proof of vaccination needed to enroll in public schools
There's been some discussion this year in the news, because of the increase in measles cases this year, about public health regulations and their relation to vaccination rates. Many countries do not require vaccination, but still have good vaccination rates. There is some tension between parental autonomy and the public health of the population, one that is solved for the most part when parents are sufficiently rational about their children's health.
Map from Wikipedia,
Apparently, Google thinks so! They memorialized Eddi Aikau gave him a doodle on the Google search home page today. Here.
