The vagus nerve somatosensory evoked potential in the intact brain: state-of-evidence and some representative vignettes.

OBJECTIVE: Scalp-recorded evoked potentials elicited by applying afferent electrical stimulation at the tragus region of the human external ear have shown inconsistent results. We aim to disentangle discrepant findings and interpretations, and put forward novel physiological explanations on the origin of the vagus nerve somatosensory evoked potentials (VSEP). METHODS: We systematically search and critically appraise in PubMed, Web of Science, and Scielo databases the scientific reports publishing VSEP findings elicited by afferent electrical stimulation at the tragus region from individuals without brain disorders. Eligible studies published from January 2000 to April 2020 were extracted. The following information was identified from each article: number of participants; age; gender; stimulating/recording and grounding electrodes as well as stimulus side, intensity, duration, frequency, and polarity. Information about physiological parameters and neurobiological variables was also extracted. Representative vignettes with novel scalp responses induced by stimulating the tragus were also included to add support to our conclusions. RESULTS: 140 healthy participants were identified from six selected reports. Mean age ranged from 24.3 to 61.5 years. Stimulating and recording aspects were miscellaneous among studies. Scalp responses marked as the VSEP were recorded in 76% of participants, and showed high variability, low validity and poor reproducibility. Age correlated with response latencies. There were not gender differences in scalp response parameters. Cardiovascular function was unaltered by tragus stimulation. Vignettes showed that the VSEP was scalp muscle responses. CONCLUSION: VSEP did not fulfil evoked potential guidelines. VSEP corresponded to volume conduction propagating from muscles surrounding scalp recording sites.

[Neurorehabilitation: from a rigid past to a plastic future]. / Neurorrehabilitación: de un pasado rígido a un futuro plástico.

Since ancient times, several cultures including those from China, Egypt, India and Rome gave rigid solutions to improve physical problems of affected people by several neurological disorders. These measures were applied, at that time, by individuals prepared for doing such task. It evolved throughout the years supported by the discovery and comprehension of the so-called neural plasticity as well as the current evidences that the nervous system is able of remodelating itself even in adult times. It is known today that synaptic modulation is the base of neurorehabilitation improved by use and application of specific protocols to each neurological disorder. Among these, we have to consider not only all of the already known on rehabilitation measures but also on neurorobotic, neurorestauration, neuromodulation, neurostimulation as well as virtual reality, among others interventions. Neurorehabilitation has been able to put together modern science with ancient manual therapies helping to change, in a positive way, the attitude toward people with disabilities in the twenty one century; likewise, it offers new hopes for functional recovery where before was nothing. Further, it gives opportunities to get a better quality of life to affected people and its corresponding families. It is very interesting to know that the modern concepts of neurorehabilitation performed in a multidisciplinary approach are very useful for humans on the Earth and people interested in conquer Space.

Incomplete facial nerve palsy: new lessons from activated orbicularis oculi muscles.

Motor nerve conduction studies (MNCS) and blink reflexes (BR) were done on a 42-year-old female patient who presented with peripheral facial nerve palsy (PFNP); these investigations were done while she had her facial muscles relaxed ("A"), and contracted ("B"). While in the "A" state, MNCS of the facial nerves had prolonged latency and low amplitude and R3 of the blink reflex was absent in the affected side; an early contralateral R1 response was recorded on the unaffected side. In state "B," the third silent period was "prolonged" on the affected side and absent on the unaffected one. This is an illustrative case of a variant of facial nerve palsy in humans.

Territorial and Extraterritorial Trigeminocardiac Reflex: A Review for the Neurosurgeon and a Type IV Reflex Vignette.

The trigeminocardiac reflex (TCR) is a complex and, sometimes, fatal event triggered by overstimulation of the trigeminal nerve (TN) and its territorial and spinal cord branches. We reviewed and compiled for the neurosurgeon key aspects of the TCR that include a novel and straightforward classification, as well as morphophysiology, pathophysiology, neuromonitoring and neuromodulation features. Further, we present intraoperative data from a patient who developed extraterritorial, or type IV, TCR while undergoing a cervical surgery. TCR complexity, severity and unwanted outcomes indicate that this event should not be underestimated or overlooked in the surgical room. Timely TCR recognition in surgical settings is valuable for applying effective intraoperative management to prevent catastrophic outcomes.

Smell status in functional movement disorders: New clues for diagnosis and underlying mechanisms.

OBJECTIVE: Functional movement disorders (FMDs) mimic a range of movements, neuropsychiatric and neurodegenerative disorders known to have smell dysfunction, which has been neglected in terms of its application to FMD. We aim to determine the smell status in FMD patients tested by a non-invasive, reliable and validated olfactory test. PATIENTS AND METHODS: We quantitatively assessed in thirty-five FMD patients their smell status and compared it to that of healthy age- and sex-matched controls, and of patients with Parkinson's disease (PD). All participants were administered the Brief Smell Identification Test (B-SIT), a standardized short version of the University of Pennsylvania Smell Identification Test (UPSIT). The Picture Identification Test (PIT), a visual test analogous in content and form to the UPSIT designed to control for non-olfactory cognitive confounds, was also administered. RESULTS: The B-SIT scores of the FMD patients were higher than those from PD patients [respective means (standard deviations: SDs) = FMD, 9.54 (1.57); PD, 4.64 (1.05), p < 0.01)] but similar to the smell scores from healthy controls [9.97 (1.77), p = 0.35]. Gender, age, time of disease onset, smoking status, and phenotypic expression did not influence the test scores. Fourteen FMD patients who mentioned having olfactory dysfunction before smell testing have their test results within normal range. PIT scores from patients and healthy controls were within normal range. CONCLUSIONS: These findings indicate that FMD patients have normal olfactory function. Olfactory testing may be helpful in identifying and differentiating FMD from other movement, neurodegenerative and neuropsychiatric diseases for which smell function is altered.

[Functional neurology of blepharospasm]. / Neurología funcional del blefaroespasmo.

Benign essential blepharospasm is characterized by abnormal repetitive movements of lid closure and spasm of the orbiculari oculi muscles. Modern theories postulate that this movement disorder originates by abnormal processing of afferent information with further disintegration of the sensorimotor neural program at central levels of the nervous system all of which is seen as dystonic movements in genetically susceptible people. Different investigations including neuroimagin, genetic and neurophysiological studies have discovered new findings on what structures are involved and how this abnormal movement is generated. Among these research is noteworthy the study of electrically elicited blink reflex. It consists of three responses called non-nociceptive (R1), nociceptive (R2) and ultranociceptive (R3). Such blink reflexes, mostly the ultranociceptive response (R3), seem to be very useful to understand more deeply the pathophysiology of this focal dystonia, to perform the functional endophenotyping and to do a more appropriate follow-up of this complex neurological problem.

[Hemiplegia with two Babinski's sign]. / Hemiplejía con dos signos de Babinski.

Neurological signs and symptoms are very important to establish a correct neurological diagnosis. We present here a Colombian female patient, 60 years-old, who had ischaemic stroke in the left cerebral media artery. It produced right hemiplegia, motor aphasia, "central" facial palsy and atrophy of right platysma muscle. This latter finding, described originally by Joseph Babinski as "The Babinski Sign" was observed only two years and seven months after the ictus even when she had, previously, been evaluated by several neurologists. The underdiagnosis of clinical signs like the one described here may lead to erroneous diagnosis that will, ultimately, affect neurorehabilitation measures.

[Concepts, confusions and contradictions on the impact factor in Colombia]. / Concepciones, confusiones y contradicciones del factor de impacto en Colombia.

Latin American scientists are making tremendous efforts to conduct good-quality research worthy of being published internationally. However, Colciencias, an entity created to support this research in Colombia, introduced scienciometric evaluations which had been re-evaluated elsewhere some time ago, based on measurements of aspects such as the ill-termed "impact factor". Even more serious is that the aforementioned government office is unaware that measures are based on debated mathematical principles, placing Colombian science at imminent risk of suffering from an academic yatrogeny of irreparable consequences. Therefore, an urgent restructuring of the way in which Colombia's scientific production is to be evaluated is thus mandatory before these measures have a negative impact thereon.

Capsaicin effects on blinking.

Blinking is a normal human phenomenon involving trigeminal and facial pathways. To gain understanding on the neurobiology of blinking, five normal subjects were investigated before and after application of transdermal capsaicin at the forehead for two weeks. No effects of topical capsaicin were detected in eye blink rates. However, when capsaicin was applied to a female subject with blepharospasm, she showed a dramatic restoration of her vision subsequent to blinking modification. Deactivation of abnormal A-to-C fibers cross talks at the trigeminal-facial pathways seems to be the most likely mechanism of such improvement.

[Colciencias and disdain for Colombian scientists: from the Stone Age to the impact factor]. / Colciencias e inconciencias con los científicos Colombianos: de la edad de piedra al factor de impacto.

Writing has dramatically evolved in the world; however, qualification of scientific production in Colombia has not, including the improper use of decree 1444/93 and 1279/02. The last of these decrees authorized Colciencias, the Colombian government institute created to support scientific research in Colombia, to establish rules for its implementation. Colciencias decided to evaluate scientific papers produced in Colombia based on the non-scientific method of the "impact factor", and considered that citations in MEDLINE/PubMed and PsylNFO were second line publications thus violating Colombian law. This affects not only the progress of scientific research in Colombia but also researchers' income and puts Colombia's scientific journals and publications at great disadvantage. Scientific papers indexed in qualified databases such as MEDLINE/PubMed must be judged according to law in order to prevent further injuries to the developing Colombian scientific production.

Trypanosoma cruzi-associated cerebrovascular disease: a case-control study in Eastern Colombia.

Trypanosoma cruzi infection is a common cause of cardiopathy in South America leading it eventually to an established stroke; however, the association between T. cruzi infection itself and cerebrovascular disease is still unknown. We did a case-control study at Eastern Colombia and found that T. cruzi infection was more frequent and statistically significant in stroke cases (24.4%) than controls (1.9%), (Chi square: 21.72; OR: 16.13; 95% confidence interval (CI): 3.64-71.4; p<0.00001). After removing the seropositive patients with cardiological abnormalities, the significance still remained by multivariate analysis (p<0.05). This is the first case-control study that demonstrated a significant link between this infection and symptomatic cerebrovascular disease, mainly ischemic, regardless of cardiac abnormalities. Therefore, we recommend that patients with stroke must be screened for T. cruzi infection if they currently live or have lived in places where this parasite is considered endemic.

[Neurological effects of American trypanosomyiasis: clinical aspects]. / Neurotripanosomiasis americana: aspectos clínicos de un problema básico.

Trypanosoma cruzi, causative agent of Chagas disease, affects not only cardiac and intestinal structures but also neurological structures. A high prevalence of T. cruzi infection occurs in Colombia, prompting the present study. First, a qualitative metaanalysis was undertaken using the PubMed database, the electronic internet engine Altavista, Colombian journals indexed by Colciencias, and three relevant textbooks. The following key words were used: Trypanosoma, Chagas disease, nervous system, spinal cord, central nervous system, peripheral nervous system, neuromuscular junction, autonomic nervous system, muscle, muscle disorders, neuromuscular disease, neuromuscular disorders, synapticopathies and dysautonomia. The documents analyzed numbered 116 and included original papers, reviews, case reports, editorials, brief communications, conferences and book chapters. At minimum, each document included data involving ELISA testing, indirect immunofluorescense, or parasitemia levels in the clinical, serological or histopathological studies. Polymerase chain reaction (PCR) studies were not included because of the recent introduction of PCR as a confirmatory technique for Chagas disease in Colombia. Chagas disease affects the central, the peripheral and the autonomic nervous system in humans, although its effects on the antonomic system is most commonly investigated in Colombia. Neurological lesions must be evaluated carefully, because patients may be misdiagnosed and treated as carriers of 'idiopathic' diseases. Neurological pathologies poses a serious threat in Colombia due to the prevalence of Chagas disease.

Chemosensory rehabilitation and malnutrition in the newborn: how far, how close?

Olfaction is critical to the hedonic appreciation of foods, caloric regulation of food intake, quality of life and taste preferences since birth. However, malnutrition in newborns down-regulates chemosensory function. Thus, olfactory measures might be used as early markers of chemosensory dysfunction in malnutrition, and may also be useful in assessing feeding adjustments during nutritional rehabilitation. Olfactory anomalies originated by malnutrition would be reversed by nutritional rehabilitation following flavor-enhancing odorants.

Novel mechanisms underlying inhibitory and facilitatory transcranial magnetic stimulation abnormalities in Parkinson's disease.

BACKGROUND AND AIMS: The motor-evoked potential (MEP) induced by transcranial magnetic stimulation (TMS), its recruitment and the conditioning effects of weak stimuli in Parkinson's disease (PD) have shown contradictory results. The aim of this study is to definitively establish the influences of PD on the TMS-evoked MEP. METHODS: We investigated resting and active motor thresholds, resting and active recruitment curves, and short interval intracortical inhibition (ICI) and facilitation (ICF) in 39 PD patients and 40 age-matched healthy controls. The Unified Parkinson's Disease Rating Scale (UPDRS) motor score was used as a clinical measure. RESULTS: MEPs to single pulses were slightly, but significantly, larger in the PD patients at rest, but increased much less than controls with voluntary muscle activation. PD patients also showed clearly and consistently less ICI and ICF by the conditioning pulse. Both ICI and ICF correlated with MEP threshold in healthy subjects, but not in PD patients. None of the TMS measures correlated with the UPDRS. CONCLUSIONS: This study strongly supports the view that PD-related MEPs reflect a disturbed signal-noise ratio of pyramidal neuron responses. Such disturbance may be due to a complex combination of altered presynaptic and surround inhibition that results in unbalanced excitatory/inhibitory input at the brain motor cortex level.

Profound olfactory dysfunction in myasthenia gravis.

In this study we demonstrate that myasthenia gravis, an autoimmune disease strongly identified with deficient acetylcholine receptor transmission at the post-synaptic neuromuscular junction, is accompanied by a profound loss of olfactory function. Twenty-seven MG patients, 27 matched healthy controls, and 11 patients with polymiositis, a disease with peripheral neuromuscular symptoms analogous to myasthenia gravis with no known central nervous system involvement, were tested. All were administered the University of Pennsylvania Smell Identification Test (UPSIT) and the Picture Identification Test (PIT), a test analogous in content and form to the UPSIT designed to control for non-olfactory cognitive confounds. The UPSIT scores of the myasthenia gravis patients were markedly lower than those of the age- and sex-matched normal controls [respective means (SDs) =20.15 (6.40) & 35.67 (4.95); p<0.0001], as well as those of the polymiositis patients who scored slightly below the normal range [33.30 (1.42); p<0.0001]. The latter finding, along with direct monitoring of the inhalation of the patients during testing, implies that the MG-related olfactory deficit is unlikely due to difficulties sniffing, per se. All PIT scores were within or near the normal range, although subtle deficits were apparent in both the MG and PM patients, conceivably reflecting influences of mild cognitive impairment. No relationships between performance on the UPSIT and thymectomy, time since diagnosis, type of treatment regimen, or the presence or absence of serum anti-nicotinic or muscarinic antibodies were apparent. Our findings suggest that MG influences olfactory function to the same degree as observed in a number of neurodegenerative diseases in which central nervous system cholinergic dysfunction has been documented.

WITHDRAWN: Mechanisms Underlying Inhibitory and Facilitatory Transcranial Magnetic Stimulation Abnormalities in a Large Sample of Patients with Parkinson's Disease.

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