Difference between revisions of "7° Clinical case: Brainstem neoplasm in Orofacial pain"

== Abstract ==

[[File:Capsaicina.jpg|left|300x300px]]

=== Introduction ===

The brain stem is the caudal portion of the brain that connects the diencephalon to the spinal cord and cerebellum.<ref>Hurley RA, Flashman LA, Chow TW, Taber KH. The brainstem: anatomy, assessment, and clinical syndromes. J Neuropsychiatry Clin Neurosci. 2010;22(1):iv. doi: 10.1176/jnp.2010.22.1.iv. </ref> The brainstem mediates the sensory and motor pathways between the spinal cord and the brain and contains the nuclei of the cranial nerves, the ascending reticular activating system (ARAS), and the autonomic nuclei. It controls brainstem reflexes and the sleep-wake cycle and is responsible for autonomous control of the cardiovascular, respiratory, digestive and immune systems. Brainstem dysfunction can result from various acute or chronic insults, including stroke, infectious, cancer, inflammatory, and neurodegenerative diseases. In the context of critical illness, the brain stem can be susceptible to various insults that can be classified as structural and non-structural in origin. Brainstem dysfunction can therefore contribute to impaired consciousness, cardiocirculatory and respiratory insufficiency and therefore to increased mortality <ref>Annane D, Trabold F, Sharshar T, Jarrin I, Blanc AS, Raphael JC, et al. Inappropriate sympathetic activation at onset of septic shock: a spectral analysis approach. Am J Respir Crit Care Med août. 1999;160(2):458–465. doi: 10.1164/ajrccm.160.2.9810073.</ref><ref>Sharshar T, Porcher R, Siami S, Rohaut B, Bailly-Salin J, Hopkinson NS, et al. Brainstem responses can predict death and delirium in sedated patients in intensive care unit. Crit Care Med août. 2011;39(8):1960–1967. doi: 10.1097/CCM.0b013e31821b843b.</ref><ref>Sharshar T, Gray F, Lorin de la Grandmaison G, Hopkinson NS, Ross E, Dorandeu A, et al. Apoptosis of neurons in cardiovascular autonomic centres triggered by inducible nitric oxide synthase after death from septic shock. Lancet Lond Engl. 2003;362(9398):1799–1805. doi: 10.1016/S0140-6736(03)14899-4. </ref><ref>Mazeraud A, Pascal Q, Verdonk F, Heming N, Chrétien F, Sharshar T. Neuroanatomy and physiology of brain dysfunction in sepsis. Clin Chest Med. 2016;37(2):333–345. doi: 10.1016/j.ccm.2016.01.013.</ref> and especially manifest as orofacial pain (OP).[https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6945639/ Brainstem dysfunction in critically ill patients]:

<blockquote>These important premises extracted from an interesting article by Sarah Benghanem<ref>Benghanem S, Mazeraud A, Azabou E, Chhor V, Shinotsuka CR, Claassen J, Rohaut B, Sharshar T. Brainstem dysfunction in critically ill patients. Crit Care. 2020 Jan 6;24(1):5. doi: 10.1186/s13054-019-2718-9.PMID: 31907011</ref> are essential details, expression of a clinical experience which led the author of the chapter to scientific and epistemological reflections on the typology of language to be used in the creation of diagnostic models. and consequently to found Masticationpedia. One cannot, personal and responsible assertion of the author of the chapters, slavishly follow an axiom, a protocol such as the DRC or whatever and risk an error of differential diagnosis which can cost the life of a human being. If there is a gap in the model, which we will demonstrate during the implementation of Masticationpedia, then it should be noted as an anomaly, analyzed and eliminated or at least modified otherwise it is not a question of paradigmatic progress but only of intensive progress. </blockquote>

It was the year 1995 when the 60-year-old female patient, who we will call with a fancy name 'Capsaicin' (we will understand the reason below) presented herself to our observation reporting bilateral diffuse orofacial pain in the temporal muscles region and in the occipital region , in addition, to the presence of burning mouth (BMS), for more than 10 years. The pain lasted for hours especially at night and did not occur cyclically. The patient was the bearer of a long-standing upper and lower ceramic fixed prosthetic rehabilitation with various fractures of the ceramic structure and wear veneers on the remaining natural teeth. However, no occlusal discrepancies were found in the prosthetic rehabilitation, but a release plate was performed by other health professionals to be used at night. The patient reported pain even with the plate inserted and was initially considered to be affected by Atypical Orofacial Pain (AOP) with a strong psychosomatic component and subsequently, according to the RDC protocol, affected by 'Temporomandibular Disorders'.

Having come to our observation, as per the Masticationpedia protocol, the main gnathological tests were performed, such as paraocclusal axiography of the condylar tracings and an interferential EMG of the masseter muscles. In this case, an ATM CT was not requested, much less an MR. We present in a schematic and representative way reporting some paragraphs exposed in the previous chapters the Masticationpedia protocol in its schematization as: assertions in the dental, neurological context and finally the diagnostic conclusion through the 'Demarcator <math>\tau</math>':

For the ''dental context'' we will have the following sentences and statements to which we give a numerical value to facilitate the treatment and that is <math>\delta_n=[0|1]</math> where <math>\delta_n=0</math> indicates 'normality' and <math>\delta_n=1</math> 'abnormality and therefore positivity of the report:

File:Immagine5.bmp.png|'''Figura 6:''' <math>\gamma_1=</math> Mechanical silent period recorded on masseter muscles right (top black corresponds to mean) left (bottom black corresponds to mean)  

</gallery>

{{Q2|In this scenario both the statements <math>\Im_o </math> and <math>\Im_n </math> are compatible, consistent and therefore true until a 'Consistency Demarcator 'τ' is found which highlights the greater weight in terms of clinical severity.

}}

The <math>\tau</math>is a representative clinical specific weight, complex to research and develop because it varies from discipline to discipline and for pathologies, essential for not colliding logical assertions <math>\Im_o</math> and <math>\Im_n</math> in diagnostic procedures and fundamental for initializing the decryption of the machine code. Basically it allows to confirm the coherence of one union <math>\Im\cup\{\delta_1,\delta_2.....\delta_n\}</math> with respect to another <math>\Im\cup\{\gamma_1,\gamma_2.....\gamma_n\}</math> and vice versa, giving greater weight to the seriousness of the assertions and of the report in the appropriate context. Sometimes the doctor is faced with a series of positive reports to which he must give the right weight, he must consider the positivity of a report which highlights, for example, an osteoarticular renewal of the TMJ cannot have the same weight as a positivity of a report confirming latency delay of a trigeminal reflex. The demarcation <math>\tau</math> weight, therefore, gives more significance to the more serious assertions in the clinical context from which they derive and therefore beyond the positivity of the assertions <math>\delta_n=1</math> or which <math>\gamma_n=1</math> in any case are always verified and respected, these must be multiplied by a <math>\tau=[0|1]</math> where <math>\tau=0</math> indicates 'Low seriousness ' while <math>\tau=1</math> 'Severe Gravity'.  

{{Q2|Unfortunately, the patient died a few years later of trochoencephalic neuroma.|.......leaving a doubt, that of the correlation between pain and capsaicin as reported by the patient on the occasion of a spicy diet.}}

The mammalian gustatory system is made up of taste buds, which are clusters of 50-100 taste cells found throughout the oral cavity. On the tongue, which is the central topic of the case report 'Capsaicin', the taste buds are located on circumvallate, foliate and fungiform papillae. Taste cells synapse with afferent fibers from branches of the cranial facial (CN VII), glossopharyngeal (CN IX) and vagus (CN X) nerves which, in turn, transmit information to the central nervous system (CNS) about gustatory attributes , intensity and hedonic nature. <ref>Gutierrez, R., and S.A. Simon. 2011. Chemosensory processing in the taste-reward pathway. Flavour Fragr J, 26(4): 231–238.</ref><ref>Carleton, A., R. Accolla, and S.A. Simon. 2010. Coding in the mammalian gustatory system. Trends Neurosci, 33(7): 326–334.</ref><ref>Vincis, R. and A. Fontanini. 2016. A gustocentric perspective to understanding primary sensory cortices. Curr Opin Neurobiol, 40: 118–124</ref> The taste buds are embedded in a stratified squamous epithelium, which contains somatosensory branches of the trigeminal (CN V), glossopharyngeal (CN IX), and vagus (CN X) cranial nerves. Information from these general sensory nerves provides information to the central nervous system about mechanical, thermal, and pain stimuli.<ref name=":1" /><ref>Kaneko, Y., and A. Szallasi. 2014. Transient receptor potential (TRP) channels: A clinical perspective. Br J Pharmacol, 171(10): 2474–2507. </ref> Painful stimuli can result from strong or sharp mechanical stimuli, abnormally high or low temperatures, or chemical stimuli such as capsaicin, which is found in hot peppers and causes a burning taste sensation through the intervention of Transient Receptor Potentials (TRPs).<ref name=":0" /> These TRPs are divided into six subfamilies including TRPV1, which we are interested in to hypothesize the phenomenon of pain exacerbation of the patient 'Capsaicin' in spicy diet. [[File:Trpv1 pip2 bilayer.png|thumb|'''Figura 9:''' TRPV1, VR1, transient receptor potential cation channel subfamily V member 1. [[wikipedia:TRPV1|Wikipedia]]]]

TRPV1s constitute a distinct subset of non-selective cation channels (Transient Receptor Potential) responsible for many cellular responses. They are activated by various stimuli such as acids, extracellular protons, high temperatures, plant toxins and vanilloid agonists. The TRPV1s present in mammals can be considered as sensors of chemical substances (capsaicin), thermal substances (heat) and/or harmful stimuli. The activation of TRPV1 leads to the depolarization necessary for the propagation of action potentials along the axons of the dorsal root ganglia (DRG) of neurons that project to the spinal cord and consequently also to the nociceptive trigeminal nuclei. What makes TRPV1 so critical for pain signaling is undeniably its ability to transduce inflammatory signals into electrical signals with the activation of both voltage-gated sodium and calcium channels located at the nociceptor level.<ref>Bourinet E, Altier C, Hildebrand M E, Trang T, Salter MW, Zamponi GW. Calcium permeable ion channels in pain signaling. Physiol Rev 2014; 94: 81–140.</ref> The implication of TRPV1 in pathological pain prompted a careful study of these proteins. The limiting element in pharmacological research at the application level was the peculiarity of the TRPV1 channel, i.e. its polymodal mechanism of activation (heat, capsaicin, pH), which led to a high level of complexity in the design of a specific modality inhibitor.  

The interaction between neurons and immune cells is a well-known phenomenon.<ref>Jacobson A, Yang D, Vella M, Chiu IM (May 2021). "The intestinal neuro-immune axis: crosstalk between neurons, immune cells, and microbes". ''Mucosal Immunology''. '''14''' (3): 555–565. doi:10.1038/s41385-020-00368-1. PMC 8075967. <nowiki>PMID 33542493</nowiki>.</ref> TRPV1 plays its role, too, in neuroinflammation by being expressed in both neurons and immune cells. Significant importance should be given to the confirmed expression of TRPV1 in microglia and astrocytes, cells found in the vicinity of neurons. The neuro-immune axis is the site of production of neuroinflammatory molecules and receptors that interact between the two systems and ensure a complex response to external stimuli (or to the body's own pathologies). TRPV1 is said to contribute to microglia autophagy through its Ca²⁺ signaling, which leads to mitochondria-induced cell death. Basically, TRPV1 is a pro-apoptotic element.  

Antagonists block the ''activity of TRPV1'', thereby reducing pain. Antagonists identified include the [[wikipedia:Receptor_antagonist#Competitive|competitive antagonist capsazepine and the non-competitive antagonist]] [[wikipedia:Ruthenium_red|ruthenium red]]. These agents could be beneficial if applied systematically.<ref>Khairatkar-Joshi N, Szallasi A (January 2009). "TRPV1 antagonists: the challenges for therapeutic targeting". ''Trends in Molecular Medicine''. '''15''' (1): 14–22. doi:10.1016/j.molmed.2008.11.004. <nowiki>PMID 19097938</nowiki>.</ref> TRPV1 antagonists have shown efficacy in reducing nociception from inflammatory and neuropathic pain models in rats.<ref>Jhaveri MD, Elmes SJ, Kendall DA, Chapman V (July 2005). "Inhibition of peripheral vanilloid TRPV1 receptors reduces noxious heat-evoked responses of dorsal horn neurons in naïve, carrageenan-inflamed and neuropathic rats". ''The European Journal of Neuroscience''. '''22''' (2): 361–370. doi:10.1111/j.1460-9568.2005.04227.x. <nowiki>PMID 16045489</nowiki>. S2CID 24664751.</ref> This provides evidence that TRPV1 is the sole receptor for [[wikipedia:Capsaicin|capsaicin]].<ref>Story GM, Crus-Orengo L (2008). "Feel the Burn". ''American Scientist''. '''95''' (4): 326–333. doi:10.1511/2007.66.326. ISSN 0003-0996. Archived from the original on January 19, 2008.</ref> In humans, drugs that target TRPV1 receptors could be used to treat neuropathic pain associated with multiple sclerosis, chemotherapy, or amputation, as well as pain associated with the inflammatory response of damaged tissue, such as in osteoarthritis.<ref>Gunthorpe MJ, Szallasi A (2008). "Peripheral TRPV1 receptors as targets for drug development: new molecules and mechanisms". ''Current Pharmaceutical Design''. '''14''' (1): 32–41. doi:10.2174/138161208783330754. <nowiki>PMID 18220816</nowiki>.</ref>

TRPV1 is activated by several agonists of natural origin.<ref>Boonen, Brett; Startek, Justyna B.; Talavera, Karel (2016-01-01). Chemical Activation of Sensory TRP Channels. Topics in Medicinal Chemistry. Springer Berlin Heidelberg. pp. 1–41. [1]doi:10.1007/7355_2015_98.</ref> Agonists such as capsaicin and resiniferatoxin activate TRPV1 and, after prolonged application, cause the decrease of TRPV1 activity (desensitization), leading to pain relief through the subsequent decrease of the TRPV1-mediated release of inflammatory molecules upon exposure to noxious stimuli.  

These results demonstrate the importance of chloride homeostasis in the regulation of the excitability of the neuronal DRGs, i.e. of the dorsal root ganglia and obviously of the trigeminal somatosensory nuclei and in the pain phenomenon as a whole; one of the new approaches, therefore, where to intervene to mitigate painful hypersensitivity and neurogenic inflammation.

</ref> Burning mouth syndrome (BMS) is often an idiopathic, chronic intractable pain condition, affecting 1.5-5.5% of middle-aged and older women. We investigated heat and capsaicin receptor TRPV1, and its regulatory nerve growth factor (NGF), in BMS. BMS patients (n=10) and controls (n=10) were evaluated for baseline and post-topical capsaicin pain scores, and their tongue biopsies were immunostained for TRPV1, NGF, and neurofilament structural nerve markers and periphery. Nerve fibers penetrating the epithelium were less abundant in the BMS (p<0.0001), indicating ''small fiber neuropathy''. TRPV1-positive fibers were overall significantly increased in BMS (p=0.0011), as were NGF fibers (p<0.0001) and NGF staining of basal epithelial cells (p<0.0147). There was a significant correlation between baseline pain score and TRPV1 (p=0.0143) and NGF (p=0.0252) fibers. A significant correlation was observed between baseline and post-capsaicin pain (p=0.0006).

{{Q2|We are sure we know everything|}}{{bib}}