Domingo Sánchez y Sánchez (1860-1947): Cajal's man on the nervous system of invertebrates

Domingo Sánchez y Sánchez (1860-1947), a distinguished disciple of Santiago Ramón y Cajal, played a fundamental role in the Spanish School of Neurohistology through the meticulous use of diverse staining and microscopic techniques in the study of the histology and physiology of the invertebrate nervous system, generating valuable contributions that were recognized and cited by the scientific community. His research covered a wide range of areas: he was initially an anthropologist and zoologist, later earning a doctorate in Medicine and specializing in the neurohistology of invertebrates, including the detailed study of the retina and nerve centers of insects, and the discovery of histolysis in nerve centers of insect larvae during metamorphosis, challenging scientific paradigms of the time. Furthermore, Sánchez's work on the neurofibrils of insects was crucial in supporting Cajal's neuronal theory and refuting Bethe and Apathy's reticularist hypothesis. Additionally, he also made preliminary observations of the Golgi apparatus, the lysosomal system, the endoplasmic reticulum, and the sarcoplasmic reticulum of skeletal muscles (Cajal-Fusari network). Domingo Sánchez y Sánchez's exceptional scientific research and contributions to neurohistology in 20th century Spain continue to serve as a significant legacy.

Life science identifiers

Apis mellifera: urn:lsid:zoobank.org:act:9082C709-6347-4768-A0DC-27DC44400CB2Helix aspersa: urn:lsid:zoobank.org:act:9099927E-24DF-4F89-B352-6B7902CD4A38.

The Importance of Cajal's and Lorente de Nó's Neuroscience to the Birth of Cybernetics

The beginnings of cybernetics were marked by the publication of two papers in 1943. In the first one, Rosenblueth, Wiener, and Bigelow claimed that purposeful behavior is a circular process controlled by negative feedback. In the second seminal paper, McCulloch and Pitts proposed that neurons are interconnected working as logical operators. Both articles raised human-machine analogies and mathematically formulated cognitive mechanisms. These ideas ignited the interest of von Neumann, who was developing the first stored-program computer. Thus, after a preliminary meeting in 1945, a series of meetings were held between 1946 and 1953. The role of the Spanish neurophysiologist Rafael Lorente de Nó in the beginnings of cybernetics is attested not only by his participation in the core members of these Macy conferences but also for his previous description of reverberating circuits formed by a closed chain of internuncial neurons. This was the first neurobiologic demonstration of a feedback loop. Most researchers considered the central nervous system as a mere reflex organ until then; nevertheless, he demonstrated a self-sustained central activity in the nervous system, supporting the idea of self-regulating mechanisms as a key concept not just in machines but also in the brain.

The vestibular system: Contributions of Lorente de Nó

BACKGROUND

Rafael Lorente de Nó was a neuroscientist that worked alongside two of the giants of Medicine, the Nobel Prize winners Cajal and Bárány.

OBJECTIVE

To describe the contributions of Lorente de Nó to vestibular neuroscience.

METHODS

Detailed review of the publications of Lorente de Nó and analysis of the archives from Junta para Ampliación de Estudios e Investigaciones Científicas at Residencia de Estudiantes (Madrid, Spain), Casa de Salud Valdecilla at Hospital Universitario Marqués de Valdecilla (Santander, Spain), Becker Medical Library at Washington University (St. Louis, MO, USA), Rockefeller Archive Center (Sleepy Hollow, New York, NY, USA), Archivo Fernando de Castro (Madrid, Spain), Biblioteca Nacional de España (Madrid, Spain) and Legado Cajal at Instituto Cajal (Madrid, Spain). Most of this material is unpublished and includes over a hundred letters to or from Lorente.

RESULTS

Lorente de Nó made a substantial contribution to our understanding of the vestibular system. Amongst these, he meticulously detailed the course of the vestibular nerve and its central projections. He described the vestibulo-ocular reflex as the consequence of an integration of the various nuclei and connections across the vestibular system, rather than a simple three-neuron arc. He also highlighted the role of the reticular formation in the generation of the fast phase of the nystagmus.

CONCLUSIONS

Lorente de Nó was a pioneer of modern neuro-otology, having made outstanding contributions to vestibular neuroscience, forging novel discoveries that still burn true today.

Unification of Treatments and Interventions for Tinnitus Patients (UNITI): a study protocol for a multi-center randomized clinical trial

BACKGROUND

Tinnitus represents a relatively common condition in the global population accompanied by various comorbidities and severe burden in many cases. Nevertheless, there is currently no general treatment or cure, presumable due to the heterogeneity of tinnitus with its wide variety of etiologies and tinnitus phenotypes. Hence, most treatment studies merely demonstrated improvement in a subgroup of tinnitus patients. The majority of studies are characterized by small sample sizes, unstandardized treatments and assessments, or applications of interventions targeting only a single organ level. Combinatory treatment approaches, potentially targeting multiple systems as well as treatment personalization, might provide remedy and enhance treatment responses. The aim of the present study is to systematically examine established tinnitus therapies both alone and in combination in a large sample of tinnitus patients. Further, it wants to provide the basis for personalized treatment approaches by evaluating a specific decision support system developed as part of an EU-funded collaborative project (Unification of treatments and interventions for tinnitus patients; UNITI project).

METHODS/STUDY DESIGN

This is a multi-center parallel-arm randomized clinical trial conducted at five different clinical sites over the EU. The effect of four different tinnitus therapy approaches (sound therapy, structured counseling, hearing aids, cognitive behavioral therapy) applied over a time period of 12 weeks as a single or rather a combinatory treatment in a total number of 500 chronic tinnitus patients will be investigated. Assessments and interventions are harmonized over the involved clinical sites. The primary outcome measure focuses on the domain tinnitus distress assessed via the Tinnitus Handicap Inventory.

DISCUSSION

Results and conclusions from the current study might not only provide an essential contribution to combinatory and personalized treatment approaches in tinnitus but could also provide more profound insights in the heterogeneity of tinnitus, representing an important step towards a cure for tinnitus.

TRIAL REGISTRATION

ClinicalTrials.gov NCT04663828 . Registered on 11 December 2020.

DNA Methylation Signature in Mononuclear Cells and Proinflammatory Cytokines May Define Molecular Subtypes in Sporadic Meniere Disease

Meniere Disease (MD) is a multifactorial disorder of the inner ear characterized by vertigo attacks associated with sensorineural hearing loss and tinnitus with a significant heritability. Although MD has been associated with several genes, no epigenetic studies have been performed on MD. Here we performed whole-genome bisulfite sequencing in 14 MD patients and six healthy controls, with the aim of identifying an MD methylation signature and potential disease mechanisms. We observed a high number of differentially methylated CpGs (DMC) when comparing MD patients to controls (n= 9545), several of them in hearing loss genes, such as PCDH15, ADGRV1 and CDH23. Bioinformatic analyses of DMCs and cis-regulatory regions predicted phenotypes related to abnormal excitatory postsynaptic currents, abnormal NMDA-mediated receptor currents and abnormal glutamate-mediated receptor currents when comparing MD to controls. Moreover, we identified various DMCs in genes previously associated with cochleovestibular phenotypes in mice. We have also found 12 undermethylated regions (UMR) that were exclusive to MD, including two UMR in an inter CpG island in the PHB gene. We suggest that the DNA methylation signature allows distinguishing between MD patients and controls. The enrichment analysis confirms previous findings of a chronic inflammatory process underlying MD.

Burden of Rare Variants in the OTOG Gene in Familial Meniere's Disease

OBJECTIVES

Meniere's disease (MD) is a rare inner ear disorder characterized by sensorineural hearing loss, episodic vertigo, and tinnitus. Familial MD has been reported in 6 to 9% of sporadic cases, and few genes including FAM136A, DTNA, PRKCB, SEMA3D, and DPT have been involved in single families, suggesting genetic heterogeneity. In this study, the authors recruited 46 families with MD to search for relevant candidate genes for hearing loss in familial MD.

DESIGN

Exome sequencing data from MD patients were analyzed to search for rare variants in hearing loss genes in a case-control study. A total of 109 patients with MD (73 familial cases and 36 early-onset sporadic patients) diagnosed according to the diagnostic criteria defined by the Barany Society were recruited in 11 hospitals. The allelic frequencies of rare variants in hearing loss genes were calculated in individuals with familial MD. A single rare variant analysis and a gene burden analysis (GBA) were conducted in the dataset selecting 1 patient from each family. Allelic frequencies from European and Spanish reference datasets were used as controls.

RESULTS

A total of 5136 single-nucleotide variants in hearing loss genes were considered for single rare variant analysis in familial MD cases, but only 1 heterozygous likely pathogenic variant in the OTOG gene (rs552304627) was found in 2 unrelated families. The gene burden analysis found an enrichment of rare missense variants in the OTOG gene in familial MD. So, 15 of 46 families (33%) showed at least 1 rare missense variant in the OTOG gene, suggesting a key role in familial MD.

CONCLUSIONS

The authors found an enrichment of multiplex rare missense variants in the OTOG gene in familial MD. This finding supports OTOG as a relevant gene in familial MD and set the groundwork for genetic testing in MD.

Towards a unification of treatments and interventions for tinnitus patients: The EU research and innovation action UNITI

Tinnitus is the perception of a phantom sound and the patient's reaction to it. Although much progress has been made, tinnitus remains a scientific and clinical enigma of high prevalence and high economic burden, with an estimated prevalence of 10%-20% among the adult population. The EU is funding a new collaborative project entitled "Unification of Treatments and Interventions for Tinnitus Patients" (UNITI, grant no. 848261) under its Horizon 2020 framework. The main goal of the UNITI project is to set the ground for a predictive computational model based on existing and longitudinal data attempting to address the question of which treatment or combination of treatments is optimal for a specific patient group based on certain parameters. Clinical, epidemiological, genetic and audiological data, including signals reflecting ear-brain communication, as well as patients' medical history, will be analyzed making use of existing databases. Predictive factors for different patient groups will be extracted and their prognostic relevance validated through a Randomized Clinical Trial (RCT) in which different patient groups will undergo a combination of tinnitus therapies targeting both auditory and central nervous systems. From a scientific point of view, the UNITI project can be summarized into the following research goals: (1) Analysis of existing data: Results of existing clinical studies will be analyzed to identify subgroups of patients with specific treatment responses and to identify systematic differences between the patient groups at the participating clinical centers. (2) Genetic and blood biomarker analysis: High throughput Whole Exome Sequencing (WES) will be performed in well-characterized chronic tinnitus cases, together with Proximity Extension Assays (PEA) for the identification of blood biomarkers for tinnitus. (3) RCT: A total of 500 patients will be recruited at five clinical centers across Europe comparing single treatments against combinational treatments. The four main treatments are Cognitive Behavioral Therapy (CBT), hearing aids, sound stimulation, and structured counseling. The consortium will also make use of e/m-health applications for the treatment and assessment of tinnitus. (4) Decision Support System: An innovative Decision Support System will be implemented, integrating all available parameters (epidemiological, clinical, audiometry, genetics, socioeconomic and medical history) to suggest specific examinations and the optimal intervention strategy based on the collected data. (5) Financial estimation analysis: A cost-effectiveness analysis for the respective interventions will be calculated to investigate the economic effects of the interventions based on quality-adjusted life years. In this paper, we will present the UNITI project, the scientific questions that it aims to address, the research consortium, and the organizational structure.

Differential Proinflammatory Signature in Vestibular Migraine and Meniere Disease

Vestibular Migraine (VM) and Meniere's Disease (MD) are episodic vestibular syndromes defined by a set of associated symptoms such as tinnitus, hearing loss or migraine features during the attacks. Both conditions may show symptom overlap and there is no biological marker to distinguish them. Two subgroups of MD patients have been reported, according to their IL-1β profile. Therefore, considering the clinical similarity between VM and MD, we aimed to investigate the cytokine profile of MD and VM as a means to distinguish these patients. We have also carried out gene expression microarrays and measured the levels of 14 cytokines and 11 chemokines in 129 MD patients, 82 VM patients, and 66 healthy controls. Gene expression profile in peripheral blood mononuclear cells (PBMC) showed significant differences in MD patients with high and low basal levels of IL- 1β and VM patients. MD patients with high basal levels of IL- 1β (MDH) had overall higher levels of cytokines/chemokines when compared to the other subsets. CCL4 levels were significantly different between MDH, MD with low basal levels of IL- 1β (MDL), VM and controls. Logistic regression identified IL- 1β, CCL3, CCL22, and CXCL1 levels as capable of differentiating VM patients from MD patients (area under the curve = 0.995), suggesting a high diagnostic value in patients with symptoms overlap.

Clinical Features of Headache in Patients With Diagnosis of Definite Vestibular Migraine: The VM-Phenotypes Projects

Migraine is a common neurological disorder characterized by episodic headaches with specific features, presenting familial aggregation. Migraine is associated with episodic vertigo, named Vestibular Migraine (VM) whose diagnosis mainly rely on clinical history showing a temporary association of symptoms. Some patient refers symptoms occurring in pediatric age, defined "episodic symptoms which may be associated with migraine." The aim of this cross sectional observational study was to assess migraine-related clinical features in VM subjects. For the purpose, 279 patients were recruited in different centers in Europe; data were collected by a senior neurologist or ENT specialist through a structured questionnaire. The age of onset of migraine was 21.8 ± 9. The duration of headaches was lower than 24 h in 79.1% of cases. Symptoms accompanying migrainous headaches were, in order of frequency, nausea (79.9%), phonophobia (54.5%), photophobia (53.8%), vomiting (29%), lightheadedness (21.1%). Visual or other auras were reported by 25.4% of subjects. A familial aggregation was referred by 67.4%, while migraine precursors were reported by 52.3% of subjects. Patients reporting nausea and vomiting during headaches more frequently experienced the same symptoms during vertigo. Comparing our results in VM subjects with previously published papers in migraine sufferers, our patients presented a lower duration of headaches and a higher rate of familial aggregation; moreover some common characters were observed in headache and vertigo attacks for accompanying symptoms like nausea and vomiting and clustering of attacks.

Genetic contribution to vestibular diseases

Growing evidence supports the contribution of allelic variation to vestibular disorders. Heritability attributed to rare allelic variants is found in familial vestibular syndromes such as enlarged vestibular aqueduct syndrome or familial Meniere disease. However, the involvement of common allelic variants as key regulators of physiological processes in common and rare vestibular diseases is starting to be deciphered, including motion sickness or sporadic Meniere disease. The genetic contribution to most of the vestibular disorders is still largely unknown. This review will outline the role of common and rare variants in human genome to episodic vestibular syndromes, progressive vestibular syndrome, and hereditary sensorineural hearing loss associated with vestibular phenotype. Future genomic studies and network analyses of omic data will clarify the pathway towards a personalized stratification of treatments.

Vestibulo-ocular reflex gain values in the suppression head impulse test of healthy subjects

OBJECTIVE

To assess whether there are differences in vestibulo-ocular reflex (VOR) gain for suppression head impulse (SHIMP) and head impulse (HIMP) video head impulse test paradigms, and if so, what are their causes.

METHODS

Prospective multicenter observational double-blind nonrandomized clinical study was performed by collecting 80 healthy subjects from four reference hospitals. SHIMP data was postprocessed to eliminate impulses in which early SHIMP saccades were detected. Differences between HIMP and SHIMP VOR gain values were statistically evaluated. Head impulse maximum velocity, gender, age, direction of impulse, and hospital center were considered as possible influential factors.

RESULTS

A small significant statistical difference between HIMP and SHIMP VOR gain values was found on repeated measures analysis of variance (-0.05 ± 0.006, P < 0.001). Optimized linear model showed a significant influence of age variable on the observed differences for HIMP and SHIMP gain values and did not find influence between gain values differences and maximum head impulse velocity. Both HIMP and SHIMP VOR gain values were significant lower (-0.09, P < 0.001) when the impulses were performed to the left side.

CONCLUSION

We had observed a difference in SHIMP and HIMP gain values not adequately explained by known gain modification factors. The persistence of this slight but significant difference indicates that there are more factors causing lower SHIMP VOR gain values. This difference must to be considered in further studies as well as in the clinical SHIMP testing protocols. We hypothesized that VOR phasic response inhibition could be the underlying cause of this difference.

LEVEL OF EVIDENCE

2b. Laryngoscope, 128:2383-2389, 2018.

Extended phenotype and clinical subgroups in unilateral Meniere disease: A cross-sectional study with cluster analysis

OBJECTIVES

To define clinical subgroups by cluster analysis in patients with unilateral Meniere disease (MD) and to compare them with the clinical subgroups found in bilateral MD.

DESIGN

A cross-sectional study with a two-step cluster analysis.

SETTINGS

A tertiary referral multicenter study.

PARTICIPANTS

Nine hundred and eighty-eight adult patients with unilateral MD.

MAIN OUTCOME MEASURES

best predictors to define clinical subgroups with potential different aetiologies.

RESULTS

We established five clusters in unilateral MD. Group 1 is the most frequently found, includes 53% of patients, and it is defined as the sporadic, classic MD without migraine and without autoimmune disorder (AD). Group 2 is found in 8% of patients, and it is defined by hearing loss, which antedates the vertigo episodes by months or years (delayed MD), without migraine or AD in most of cases. Group 3 involves 13% of patients, and it is considered familial MD, while group 4, which includes 15% of patients, is linked to the presence of migraine in all cases. Group 5 is found in 11% of patients and is defined by a comorbid AD. We found significant differences in the distribution of AD in clusters 3, 4 and 5 between patients with uni- and bilateral MD.

CONCLUSIONS

Cluster analysis defines clinical subgroups in MD, and it extends the phenotype beyond audiovestibular symptoms. This classification will help to improve the phenotyping in MD and facilitate the selection of patients for randomised clinical trials.

Menière's disease

Menière's disease (MD) is a chronic multifactorial disorder of the inner ear characterized by episodic vestibular symptoms associated with sensorineural hearing loss, tinnitus, and aural pressure. Epidemiologic and genomic evidence supports a genetic susceptibility with multiple biochemical pathways involved, including the endocrine system, innate immune response, and autonomic nervous system. Allergens, infectious agents, vascular events, or genetic factors could modify inner-ear homeostasis and trigger MD. The diagnosis of MD is based on clinical criteria and requires the observation of an episodic vertigo syndrome associated with low- to medium-frequency sensorineural hearing loss and fluctuating aural symptoms (hearing loss, tinnitus, and/or fullness) in the affected ear. Headache is also found during the attacks and bilateral involvement is found in 25-40% of cases. Audiologic and vestibular assessment is recommended to monitor the clinical course. The treatment of MD is symptomatic to obtain relief of vestibular episodes and preventive to limit hearing loss progression. Treatment options include sodium restriction, betahistine, intratympanic gentamicin, or steroids and eventually surgery, such as cochlear implantation.