Histological identification of nasopharyngeal mechanoreceptors

Neural mechanisms of respiratory interoception

Respiratory interoception is one of the internal bodily systems that is comprised of different types of somatic and visceral sensations elicited by different patterns of afferent input and respiratory motor drive mediating multiple respiratory modalities. Respiratory interoception is a complex system, having multiple afferents grouped into afferent clusters and projecting into both discriminative and affective centers that are directly related to the behavioral assessment of breathing. The multi-afferent system provides a spectrum of input that result in the ability to interpret the different types of respiratory interceptive sensations. This can result in a response, commonly reported as breathlessness or dyspnea. Dyspnea can be differentiated into specific modalities. These respiratory sensory modalities lead to a general sensation of an Urge-to-Breathe, driven by a need to compensate for the modulation of ventilation that has occurred due to factors that have affected breathing. The multiafferent system for respiratory interoception can also lead to interpretation of the sensory signals resulting in respiratory related sensory experiences, including the Urge-to-Cough and Urge-to-Swallow. These behaviors are modalities that can be driven through the differentiation and integration of multiple afferent input into the respiratory neural comparator. Respiratory sensations require neural somatic and visceral interoceptive elements that include gated attention and detection leading to respiratory modality discrimination with subsequent cognitive decision and behavioral compensation. Studies of brain areas mediating cortical and subcortical respiratory sensory pathways are summarized and used to develop a model of an integrated respiratory neural network mediating respiratory interoception.

The Feel of Speech: Multisystem and Polymodal Somatosensation in Speech Production

PURPOSE

The oral structures such as the tongue and lips have remarkable somatosensory capacities, but understanding the roles of somatosensation in speech production requires a more comprehensive knowledge of somatosensation in the speech production system in its entirety, including the respiratory, laryngeal, and supralaryngeal subsystems. This review was conducted to summarize the system-wide somatosensory information available for speech production.

METHOD

The search was conducted with PubMed/Medline and Google Scholar for articles published until November 2023. Numerous search terms were used in conducting the review, which covered the topics of psychophysics, basic and clinical behavioral research, neuroanatomy, and neuroscience.

RESULTS AND CONCLUSIONS

The current understanding of speech somatosensation rests primarily on the two pillars of psychophysics and neuroscience. The confluence of polymodal afferent streams supports the development, maintenance, and refinement of speech production. Receptors are both canonical and noncanonical, with the latter occurring especially in the muscles innervated by the facial nerve. Somatosensory representation in the cortex is disproportionately large and provides for sensory interactions. Speech somatosensory function is robust over the lifespan, with possible declines in advanced aging. The understanding of somatosensation in speech disorders is largely disconnected from research and theory on speech production. A speech somatoscape is proposed as the generalized, system-wide sensation of speech production, with implications for speech development, speech motor control, and speech disorders.

Balloon dilation for persistent unilateral chronic obstructive Eustachian tube dysfunction is effective: a prospective multicentre study

PURPOSE

Balloon dilatation of the Eustachian tube (BDET) is an option for treating chronic obstructive Eustachian tube dysfunction (COETD). In this prospective multicentric study, the main objective was to evaluate the results of BDET in unilateral COETD refractory to medical treatment.

METHODS

Adults with unilateral COETD whose Eustachian Tube Score (ETS) was less than 5 despite medical pressure therapy were included. The primary endpoint was the change in ETS measured at 2, 6, and 12 months after BDET. Secondary objectives were the evolution of clinical symptoms assessed by the Eustachian Tube Questionnaire (ETDQ-7), audiometry, tympanometry, and otoscopy changes after BDET.

RESULTS

Twenty-eight patients were included between May 2014 and December 2017 and were treated with BDET without adverse effects in three different referral centers. Population's median age was 52 (Q25; Q75: 24, 82) years. The median follow-up time was 381 (Q25; Q75: 364; 418) days. The median ETS was 2 (Q25; Q75: 1; 4) before BDET. There was a significant improvement in ETS at 2 and 6 months and 1 year after BDET (score at 1 year: 6 (Q25; Q75: 2; 8) (p < 0.0001)). There was a significant, sustained improvement in the ETDQ-7 with a score of 4.21 (Q25; Q75-3.50; 4.79) before BDET and 3.43 (Q25; Q75-2.43; 4.14) (p = 0.0012) at 1 year. There was a suggestive improvement in tympanometry results at 1 year (p = 0.025).

CONCLUSION

BDET provides an improvement in symptoms and objective measures assessed at 1 year in patients with COETD who have failed medical treatment.

TRIAL REGISTRATION

NCT02123277 (April 25, 2014).

Micromolding of Amphotericin-B-Loaded Methoxyethylene-Maleic Anhydride Copolymer Microneedles

Biocompatible and biodegradable materials have been used for fabricating polymeric microneedles to deliver therapeutic drug molecules through the skin. Microneedles have advantages over other drug delivery methods, such as low manufacturing cost, controlled drug release, and the reduction or absence of pain. The study examined the delivery of amphotericin B, an antifungal agent, using microneedles that were fabricated using a micromolding technique. The microneedle matrix was made from Gantrez^TM AN-119 BF, a benzene-free methyl vinyl ether/maleic anhydride copolymer. The Gantrez^TM AN-119 BF was mixed with water; after water evaporation, the polymer exhibited sufficient strength for microneedle fabrication. Molds cured at room temperature remained sharp and straight. SEM images showed straight and sharp needle tips; a confocal microscope was used to determine the height and tip diameter for the microneedles. Nanoindentation was used to obtain the hardness and Young’s modulus values of the polymer. Load–displacement testing was used to assess the failure force of the needles under compressive loading. These two mechanical tests confirmed the mechanical properties of the needles. In vitro studies validated the presence of amphotericin B in the needles and the antifungal properties of the needles. Amphotericin B Gantrez^TM microneedles fabricated in this study showed appropriate characteristics for clinical translation in terms of mechanical properties, sharpness, and antifungal properties.

Topography of sensory receptors within the human glenohumeral joint capsule

BACKGROUND AND HYPOTHESES

Sensory receptors in the joint capsule are critical for maintaining joint stability. However, the distribution of sensory receptors in the glenohumeral joint of the shoulder, including mechanoreceptors and free nerve endings, has not been described yet. This study aimed to describe the distributions of different sensory receptor subtypes in the glenohumeral joint capsule. Our hypotheses were as follows: (1) Sensory receptor subtypes would differ in density but follow a similar distribution pattern, and (2) the anterior capsule would have the highest density of sensory receptors.

METHODS

Six glenohumeral joint capsules were harvested from the glenoid to the humeral attachment. The capsule was divided into 4 regions of interest (anterior, posterior, superior, and inferior) and analyzed using modified gold chloride stain. Sensory receptors as well as free nerve endings were identified and counted under a light microscope from sections of each region of interest. The density of each sensory receptor subtype was calculated relative to capsule volume.

RESULTS

Sensory receptors were distributed in the glenohumeral joint capsule with free nerve endings. The anterior capsule exhibited the highest median density of all 4 sensory receptors examined, followed by the superior, inferior, and posterior capsules. The median densities of these sensory receptor subtypes also significantly differed (P = .007), with type I (Ruffini corpuscles) receptors having the highest density (2.97 U/cm³), followed by type IV (free nerve endings, 2.25 U/cm³), type II (Pacinian corpuscles, 1.40 U/cm³), and type III (Golgi corpuscles, 0.24 U/cm³) receptors.

CONCLUSION

Sensory receptor subtypes are differentially expressed in the glenohumeral joint capsule, primarily type I and IV sensory receptors. The expression of sensory receptors was dominant in the anterior capsule, stressing the important role of proprioception feedback for joint stability. The surgical procedure for shoulder instability should consider the topography of sensory receptors to preserve or restore the proprioception of the shoulder joint.

Tympanic Resonance Hypothesis

Seemingly unrelated symptoms in the head and neck region are eliminated when a patch is applied on specific locations on the Tympanic Membrane. Clinically, two distinct patient populations can be distinguished; cervical and masticatory muscle tensions are involved, and mental moods of anxiety or need. Clinical observations lead to the hypothesis of a “Tympanic Resonance Regulating System.” Its controller, the Trigeminocervical complex, integrates external auditory, somatosensory, and central impulses. It modulates auditory attention, and directs it toward unpredictable external or expected domestic and internal sounds: peripherally by shifting the resonance frequencies of the Tympanic Membrane; centrally by influencing the throughput of auditory information to the neural attention networks that toggle between scanning and focusing; and thus altering the perception of auditory information. The hypothesis leads to the assumption that the Trigeminocervical complex is composed of a dorsal component, and a ventral one which may overlap with the concept of “Trigeminovagal complex.” “Tympanic Dissonance” results in a host of local and distant symptoms, most of which can be attributed to activation of the Trigeminocervical complex. Diagnostic and therapeutic measures for this “Tympanic Dissonance Syndrome” are suggested.

Comparison of sonotubometry, impedance, tubo-tympano-aerography, and tubomanometry to test eustachian tube function

PURPOSE

There is currently no gold standard for the diagnosis of eustachian tube (ET) dysfunction. To provide an objective basis for the clinical diagnosis of ET dysfunction, we explored the characteristics of sonotubometry, impedance, tubo-tympano-aerography (TTAG), and tubomanometry (TMM) in volunteers with healthy ETs.

MATERIALS AND METHODS

Sonotubometry, impedance, TTAG, and TMM tests were performed in 110 healthy ears of 55 volunteers, and the characteristics of each ET test were compared and discussed.

RESULTS

The ET opening rate was compared between sonotubometry with dry swallowing, impedance with the Valsalva maneuver, TTAG with the Valsalva maneuver, and TMM with a nasopharyngeal pressure of 50 mbar in 100 (90.9%), 102 (92.7%), 99 (90.0%), and 104 (94.5%) ears, respectively; there was no significant difference among the four methods (P = 0.575). In sonotubometry, both dry swallowing and the Valsalva maneuver were superior to wet swallowing in terms of detecting ET opening (P = 0.000). In TMM, both the opening rate and the external auditory canal pressure were positively correlated with the nasopharyngeal pressure. Specifically, the opening rate and external auditory canal pressure increased with an increase in the nasopharyngeal pressure (r = 0.271, P = 0.000; r = 0.315, P = 0.000, respectively).

CONCLUSIONS

Sonotubometry, impedance, TTAG, and TMM have their own advantages and disadvantages. In clinical practice, the appropriate ET function test should be chosen on the basis of the patient's specific condition.

The Effects of Hypoxia on Middle Ear Pressure Regulation

Background: Middle ear (ME) pressure regulation has been suggested as a physiological mechanism that maintains pressure equilibrium between the ME and the ambient environment. This mechanism would be based on a complex sensorineural reflex loop composed of mechanoreceptors, an integrative center, and efferent neural pathways. Our aim was to demonstrate that hypoxic conditions, which would inhibit mechanoreceptors in general, similarly participate in the inhibition of the opening of the Eustachian tube (ET), and thus, to suggest that such receptors are involved in the overall regulation of ME pressure. Materials and Methods: Among 14 healthy volunteers, tubomanometry was performed in normoxia followed by hypoxia, and 3 parameters were evaluated for each ear under each condition, allowing the evaluation of the reactivity of the system: ET opening latency index (R), the Index of Velum Contraction (IVC), and the latency of pressure instauration (C2-C1). Results: Hypoxia induced a significant increase in the opening latency index of ET opening, without deleterious effects on the quality (IVC) and latency (C2-C1) of soft palate contraction. Conclusions: Our study supports the theory of a sensorineural reflex loop and provides evidence for the existence of mechanoreceptors, whose function is modified by changes in oxygen partial pressure, able to collect information on pressure variations between the ME and the external environment.

Advances in Eustachian tube function testing

Obstructive and patulous Eustachian tube dysfunction provide a significant diagnostic and management challenge. The development of new treatments such as balloon Eustachian tuboplasty has generated renewed interest in measuring Eustachian tube function, as a method of selecting appropriate patients for intervention, and measuring their treatment outcomes.

This review summarises recent findings relating to Eustachian tube function assessment. Increasingly it is recognised that patient reported outcome measures based on symptoms are highly non-specific and non-diagnostic, and clinical assessment alone may not permit the selection of individuals with abnormal Eustachian tube opening. Tests of Eustachian tube opening therefore may represent a practical and objective addition to patient assessment in clinic, allowing the identification of individuals with abnormal (patulous or obstructive) Eustachian tube function. A diagnostic pathway is described on this basis.

More work is required to validate the described Eustachian tube function tests, and there remain individuals, such as those with dysfunction limited to pressure challenges, in whom function tests have yet to fully characterise the disorder.

An Integrative Model Accounting for the Symptom Cluster Triggered After an Acoustic Shock

Acoustic shocks and traumas sometimes result in a cluster of debilitating symptoms, including tinnitus, hyperacusis, ear fullness and tension, dizziness, and pain in and outside the ear. The mechanisms underlying this large variety of symptoms remain elusive. In this article, we elaborate on the hypothesis that the tensor tympani muscle (TTM), the trigeminal nerve (TGN), and the trigeminal cervical complex (TCC) play a central role in generating these symptoms. We argue that TTM overuse (due to the acoustic shock), TTM overload (due to muscle tension), and ultimately, TTM injury (due to hypoxia and "energy crisis") lead to inflammation, thereby activating the TGN, TCC, and cortex. The TCC is a crossroad structure integrating sensory inputs coming from the head-neck complex (including the middle ear) and projecting back to it. The multimodal integration of the TCC may then account for referred pain outside the ear when the middle ear is inflamed and activates the TGN. We believe that our model proposes a synthetic and explanatory framework to explain the phenomena occurring postacoustic shock and potentially also after other nonauditory causes. Indeed, due to the bidirectional properties of the TCC, musculoskeletal disorders in the region of the head-neck complex, including neck injury due to whiplash or temporomandibular disorders, may impact the middle ear, thereby leading to otic symptoms. This previously unavailable model type is experimentally testable and must be taken as a starting point for identifying the mechanisms responsible for this particular subtype of tinnitus and its associated symptoms.

The pharyngeal recess/Eustachian tube complex forms an acoustic passageway

We propose that the complex formed by the Pharyngeal Recess and Eustachian Tube, acts as an acoustic passageway for sounds originating inside the body: sounds made by one's voice, breathing, mastication, one's heartbeats. The antagonistic effect of two sets of muscles, one innervated by the trigeminal nerve, the other by the vagal nerve and cervical plexus, enables the body to modulate transmission of sound via this passageway and hence modulate the awareness of body sounds. Impairment of this system can be due to local factors, such as adhesions over the pharyngeal recess or inflammation inside the pharyngeal recess and/or Eustachian tube; or to tensions of the muscles involved, related to other causes. Dysfunction of the system can lead to symptoms related to increased or decreased awareness of body sounds, such as autophony, hearing of pulsating sounds and clicks in the ear; sensory symptoms related to increased activation of the nerves such as fullness feeling in the ear, facial pain, burning mouth syndrome, globus pharyngeus, pharyngeal pain; and symptoms related to inappropriate muscular contraction such as masticatory and cervical muscle tensions, bruxism, and tension type headache. The functioning of this acoustic passageway is related to the concept of the Trigeminocervical complex. The concept of Vagocervical complex is proposed.

Tubotympanic system functioning

The Eustachian (auditory) tube and tympanomastoid cavities form an anatomic and functional whole that cannot easily be divided, and is therefore known as the "tubotympanic system". The system has been the focus of several studies, with complex and sometimes contradictory results, making an overview of its functioning difficult to obtain. The objective of the present article is to review the current state of knowledge, as an indispensable preliminary to understanding tubotympanic system dysfunction, and notably the development of chronic otitis. The system as a whole is covered by mucosa, which provides continuity, although with certain particularities from one area to another, and plays a primordial role. Thus, under physiological conditions, gas diffusion across the tympanomastoid mucosa largely ensures the equilibrium of pressure between the middle ear and outside environment, the tube orifice being very little involved. Under large rapid change in atmospheric pressure, the aeration function of the Eustachian tube comes into play, governed by a reflex mechanism. The system also has other functions that are essential to good middle-ear functioning: protection against nasopharyngeal secretions and pathogens and against certain physiological noises; middle-ear cavity clearance by mucociliary transport of pathogens, partly related to submucosal gland secretion; and immune defense.