Inhibitory Reflex Research Articles

Impact of bispectral index monitoring on critical incidents rate in high-risk patients: a randomised controlled trial

Background. The likelihood of intraoperative critical incidents depends largely on reflex control of the cardiorespiratory system that is often susceptible to chronic pathology. The reflex suppression may link to the depth of anaesthesia, making the latter monitoring particularly important at higher hypotension risks and their patient predisposition.Objectives. A study of the effect of bispectral index anaesthesia monitoring on critical incidents (CIs) rate in high-risk abdominal surgery patients.Methods. A randomised controlled trial enrolled 80 high-risk and 80 low-risk patients. Each cohort randomly allocated patients between subcohorts (by 40 people): 1 — anaesthesia rendered to maintain a 40–60 bispectral index (treatment cohort), 2 — by clinical values and anaesthetic level control in exhaled gas (control cohort), intraoperative control of anaesthetic requirement, bispectral index and critical incidents.Results. A critical incidents rate analysis in high-risk patients showed a lower rate in the bispectral index anaesthesia control cohort. Total 127 critical incidents were registered in 53 patients. The analysis revealed fewer CIs for objective sedation depth monitoring, 45% patients of treatment cohort vs. 87.5% in control. Significantly fewer (by half) patients exhibited hypotension in the treatment cohort, with lower (4-fold) rates of arrhythmia, bradycardia and general respiratory CIs. Anaesthetic doses and bispectral indices at anaesthesia stages were significantly lower in the treatment cohort as well.Conclusion. Objective anaesthesia depth monitoring in high-risk patients reduces the rates of haemodynamic incidents during anaesthesia maintenance and respiratory incidents at arousal due to prevention of excessive anaesthetic depth.

Early investigations into improving bowel and bladder function in fetal ovine myelomeningocele repair

IntroductionFetal myelomeningocele (MMC) repair improves lower extremity motor function. We have previously demonstrated that augmentation of fetal MMC repair with placental mesenchymal stromal cells (PMSCs) seeded on extracellular matrix (PMSC-ECM) further improves motor function in the ovine model. However, little progress has been made in improving bowel and bladder function, with many patients suffering from neurogenic bowel and bladder. We hypothesized that fetal MMC repair with PMSC-ECM would also improve bowel and bladder function. MethodsMMC defects were surgically created in twelve ovine fetuses at median gestational age (GA) 73 days, followed by defect repair at GA101 with PMSC-ECM. Fetuses were delivered at GA141. Primary bladder function outcomes were voiding posture and void volumes. Primary bowel function outcome was anorectal manometry findings including resting anal pressure and presence of rectoanal inhibitory reflex (RAIR). Secondary outcomes were anorectal and bladder detrusor muscle thickness. PMSC-ECM lambs were compared to normal lambs (n = 3). ResultsEighty percent of PMSC-ECM lambs displayed normal voiding posture compared to 100% of normal lambs (p = 1). Void volumes were similar (PMSC-ECM 6.1 ml/kg vs. normal 8.8 ml/kg, p = 0.4). Resting mean anal pressures were similar between cohorts (27.0 mmHg PMSC-ECM vs. normal 23.5 mmHg, p = 0.57). RAIR was present in 3/5 PMSC-ECM lambs that underwent anorectal manometry and all normal lambs (p = 0.46). Thicknesses of anal sphincter complex, rectal wall muscles, and bladder detrusor muscles were similar between cohorts. ConclusionOvine fetal MMC repair augmented with PMSC-ECM results in near-normal bowel and bladder function. Further work is needed to evaluate these outcomes in human patients.

Oxygen Therapy in Cluster Headache, Migraine, and Other Headache Disorders

Oxygen therapy (OT) can relieve head pain in certain primary headache disorders, including cluster headache (CH). The exact underlying mechanism is currently uncertain, but suggested mechanisms include inhibition of the trigeminoautonomic reflex, modulation of neurotransmitters, and cerebral vasoconstriction. OT is the standard for acute treatment of CH, but patients with CH often experience considerable difficulties accessing home OT due to problems with insurance coverage. Inhalation of 100% oxygen at 6–12 L/min for 15–30 min using a non-rebreather face mask is one of the most effective acute therapies for CH, but several trials have indicated the superiority of higher oxygen flow rates of up to 15 L/min and/or using a demand-valve oxygen mask that can produce very high flow rates. Two randomized controlled trials have demonstrated the efficacy of OT in migraine, but obtaining reliable evidence is considered difficult because of different inhalation protocols, varying outcome measures, and small samples. There are some reports on the efficacy of OT as an adjuvant therapy in hypnic headache, primary headache in the emergency department, and even postdural puncture headache. The goal of this review article is to expand the knowledge regarding the use of oxygen in the treatment of headache disorders.

Comparison of clinical outcome and anal manometry following laparoscopic-assisted anorectoplasty and posterior sagittal anorectoplasty in patients with high and intermediate anorectal malformation: A randomised controlled trial.

Introduction:High and intermediate types of anorectal malformations (ARMs) may be managed by either open posterior sagittal anorectoplasty (PSARP) or by laparoscopic-assisted anorectoplasty (LAARP). Most of the literature favours one approach over the other based on retrospective analysis. We performed this study with the aim to compare the short-term outcomes of both procedures.Materials and Methods:All paediatric patients with high and intermediate ARM were enrolled and randomised into two groups: open PSARP group and LAARP group. Outcome parameters such as faecal continence using Kelly's scoring system, anal manometric parameters and post-operative complications were compared between the groups.Results:A total of 16 patients were included with equal distribution in the open PSARP and LAARP group. Patient's variables were comparable in both the groups. Five patients developed immediate post-operative complications, three in the LAARP and two in the open group. The mean Kelly's score was 3.63 ± 1.6 versus 2.57 ± 1.9 (P = 0.132) for LAARP and PSARP group, respectively. The mean resting pressure was 34.71 ± 6.26 cm of H2O and 35 ± 6.16 cm of H2O (P = 0.384) in LAARP and open group, respectively. Rectoanal inhibitory reflex was demonstrated in 6/7 patients in LAARP group and 5/7 patients in open group.Conclusion:Faecal continence in patients undergoing either of the procedure is comparable. However, wound-related complications are lesser in LAARP procedure.

Absence of a significant interaction of two common NOS1 and 5-HTT polymorphisms on sensorimotor gating in humans.

The neurotransmitter serotonin has been critically implicated in the pathogenesis of several mental disorders. The serotonin transporter (5-HTT) is a key regulator of serotonergic neurotransmission and its genetic variability is associated with increased risk of psychopathology. One well known polymorphic locus in the 5-HTT gene affecting its expression is a tandem repeat in the promoter region (5-HTTLPR). It has been reported that 5-HTT is functionally coupled with the neuronal nitric oxide synthase (NOS1 or nNOS), an enzyme catalyzing the production of nitric oxide (NO). We have previously demonstrated that a tandem repeat polymorphism in the promoter of NOS1 exon 1f (Ex1f-VNTR) is associated with sensorimotor gating, a marker of inhibitory processing and a well established endophenotype of several neuropsychiatric disorders. Here we investigated the combined genetic effects of NOS1 Ex1f-VNTR and 5-HTTLPR on sensorimotor gating, measured by prepulse inhibition (PPI) of the acoustic startle reflex, in 164 healthy adults. We found no evidence for the interaction between NOS1 Ex1f-VNTR and 5-HTTLPR on PPI. PPI was associated with NOS1 Ex1f-VNTR, but not 5-HTTLPR. Our data suggest that while NOS1 plays a role in sensorimotor gating, the nitrergic pathway of gating regulation does not involve the action of 5-HTT.

Electrophysiological assessment of the cranial reflexes

Electrophysiological assessment methods play a key role in the diagnosis of various neurological disorders. Electrophysiological evaluation of cranial reflexes is particularly valuable for neurologists. This article provides an overview of electrophysiological evaluation methods for cranial reflexes, which are most commonly used in clinical practice. They provide objective assessment of the functional integrity of nervous system structures that make up the cranial reflex arc, identify the level and, in some cases, the nature of disease, as well as pathophysiological mechanisms of central and peripheral nervous system disorders. We describe the instruments and main approaches to analysing the results for the standard blink reflex, blink reflex with prepulse inhibition, blink reflex with paired stimuli and recovery curve evaluation, reflex inhibition of the levator palpebrae superioris, jaw jerk reflex, and reflex inhibition (cutaneous silent period) of the masseter muscle.

Voluntary suppression of neck reflexes during passive head-on-trunk rotations: reflex gain control versus proprioceptive feedback.

Normal subjects can completely eliminate resistance upon imposed head-on-trunk rotations when they are asked to relax. It is not, however, clear how neck reflexes to stretch can be voluntarily suppressed. Reflexive responses might be modified by adjusting the gain of the reflex loop through descending control. Theoretically, necessary corrections upon interfering disturbances during coordinated motor performance requiring the interplay of relaxation/activation may be missing if muscle relaxation is taking place exclusively by this mechanism. It has been alternatively proposed that sensory information from the periphery may be allowed to "neutralize" neck reflexes if it is fed back with opposite sign to the structures driving the reflexes. Six healthy subjects were asked to relax while subjected to head-on-trunk rotations generated by a head motor. After any initial resistance had completely subsided, the head was unexpectedly exposed to "ramp-and-hold" perturbations of up to 2° amplitude and 0.7 s duration. Resistance to stretch consistently reappeared thereupon, suggesting that stretch reflex gain had not been set to zero during the previously achieved complete relaxation. Resistance to perturbations under these circumstances was compared with the forces generated when the same ramp-and-hold displacements were delivered unpredictably to the head held stationary. A quantitative model of neck proprioceptive reflexes suppression has been thus constructed. Gain scheduling or "motor set" cannot sufficiently account for the voluntary reflex suppression during slow passive head rotations. Instead, we propose as underlying mechanism, the "neutralization" of the controlling servo by means of continuous feedback tracking displacement and force signals from the periphery.NEW & NOTEWORTHY Head stabilizing neck reflexes can be voluntarily suppressed or activated depending on the task at hand. By applying brief perturbations unexpectedly, both during passive head-on-trunk movements and at rest, we investigated the mechanism of voluntary suppression of resistance to stretch. A physiologically plausible, neuromechanical model of voluntary/reflexive interactions was constructed favoring feedback over reflex gain adjustments. Accordingly, muscle relaxation during imposed head movements is based on sensory feedback similarly to muscle contractions during purposeful movements.

Adolescent THC Treatment Does Not Potentiate the Behavioral Effects in Adulthood of Maternal Immune Activation.

Both in utero exposure to maternal immune activation and cannabis use during adolescence have been associated with increased risk for the development of schizophrenia; however, whether these exposures exert synergistic effects on brain function is not known. In the present study, mild maternal immune activation (MIA) was elicited in mice with prenatal exposure to polyinosinic-polycytidylic acid (poly(I:C)), and ∆9-tetrahydrocannabinol (THC) was provided throughout adolescence in cereal (3 mg/kg/day for 5 days). Neither THC nor MIA pretreatments altered activity in assays used to characterize hyperdopaminergic states in adulthood: amphetamine hyperlocomotion and prepulse inhibition of the acoustic startle reflex. Adolescent THC treatment elicited deficits in spatial memory and enhanced spatial reversal learning in adult female mice in the Morris water maze, while exposure to MIA elicited female-specific deficits in fear extinction learning in adulthood. There were no effects in these assays in adult males, nor were there interactions between THC and MIA in adult females. While doses of poly(I:C) and THC were sufficient to elicit behavioral effects, particularly relating to cognitive performance in females, there was no evidence that adolescent THC exposure synergized with the risk imposed by MIA to worsen behavioral outcomes in adult mice of either sex.

P024 Anorectal Manometry in Patients with Fecal Incontinence After Ileal Pouch-Anal Anastomosis for Inflammatory Bowel Disease: A Cohort Study.

Fecal incontinence (FI) affects up to 1 in 4 patients with inflammatory bowel disease (IBD) and is associated with inflammation, surgeries, and altered rectal sensitivity. Ileal pouch-anal anastomosis (IPAA) is a surgical intervention for select IBD patients to avoid a permanent stoma. High-resolution anorectal manometry (HRAM) studies in IBD patients with FI demonstrate lower resting pressures and rectal sensory dysfunction. However, HRAM data in IBD patients with FI post-IPAA remains limited. We hypothesized patients with FI would have lower resting and squeeze pressures and rectal hypersensitivity compared to healthy controls and that these changes would be similar after IPAA. Retrospective review of prospectively collected data was conducted on patients undergoing HRAM from 2017-2021 at a single urban academic medical center. Patient characteristics (age, gender, BMI, stool frequency, diabetes, pregnancy history) and surgical history (prior perianal surgery, index vs. re-do IPAA) were obtained. HRAM variables included rectoanal inhibitory reflex (RAIR), sphincter length, resting, squeeze, cough, and push pressures, sensation thresholds (first sensation, constant sensation, desire to defecate, urgency to defecate, max tolerable volume), and balloon expulsion test (BET). HRAM outcomes in IPAA patients with FI (IPAA-FI) were compared to non-IBD patients with FI (non-IBD-FI). HRAM data for both patient cohorts were also compared to existing normative data of healthy controls. Non-IBD patients with constipation and FI were excluded from analysis. An independent samples t-test was performed (p < 0.05) for continuous variables, and chi-square test was used for categorical variables. Fifty-six patients (66% female) were in the non-IBD-FI group. Eighteen patients (67% female) were in the IPAA-FI group. Average age in the IPAA-FI cohort was 44.8 ± 13.6 vs. 66.3 ± 14.4 in the non-IBD-FI group (p< 0.01). Sphincter length in the IPAA-FI group was 2.7 ± 1.1cm vs. 3.2 ± 0.6cm in the non-IBD-FI group (p=0.03). There was no significant difference in sensation thresholds or resting, squeeze, cough, and push pressures between the two groups. Urinary incontinence was observed in 5.6% of IPAA-FI patients vs. 44.6% of non-IBD-FI patients (p < 0.01). RAIR was present in 38.5% of IPAA-FI patients vs. 100% of non-IBD-FI patients (p < 0.01). Both patient cohorts had significantly shorter sphincter length, lower squeeze and push pressures, and lower sensation thresholds compared to normative data. Resting pressures for the IPAA-FI group was not significantly different compared to healthy controls. Overall, anorectal pressures and sensation are similar between IPAA-FI and non-IBD-FI patients. However, the underlying FI mechanism seems to differ. Higher rates of urinary incontinence in the non-IBD-FI cohort suggests global pelvic floor dysfunction compared to IPAA-FI patients who are younger and have post-operative neuromuscular dysfunction, as evidenced by shorter sphincter length and absent RAIR. Though rectal hypersensitivity and lower squeeze/push pressures are observed in both patient groups compared to healthy controls, normal resting pressure in IPAA-FI suggests that potentially different normative ranges are needed for this cohort to accurately assess post-surgical changes and guide pre-operative counseling.

Hirschsprung Disease.

Hirschsprung Disease.

High-Resolution Anorectal Manometry-A Prospective Cohort Study in Healthy Infants.

Functional gastrointestinal disorders (FGD) are common during early childhood. In severe defecation disorders, anorectal manometry (AM) is done to exclude aganglionosis. High-resolution anorectal manometry (HRAM) can probably improve diagnostics but normative data in infants are scarce. This study aims to provide HRAM data in healthy infants overall and in subgroups of infants with FGD, defined as functional constipation (FC), infant colic (IC), and infant dyschezia (ID) (ROME 3 criteria). This prospective observational cohort study enrolled healthy term infants, having HRAM at 2 and 6 months, using a water-perfused pediatric anorectal silicone catheter. Data were provided for presence of anorectal waves and recto anal inhibitory reflex (RAIR), volume needed to elicit RAIR and anal resting pressure (ARP). Questionnaires at 2 and 6 months identified subjects with FC, IC, and ID. A total of 187 HRAM investigations were done in 107 infants, without any complications. Normal RAIR was found in all, at least on one occasion. Mean ARP increased between 2- and 6-month investigations in infants without FGD. No other differences in HRAM data could be seen between infants with or without an FGD. At 2 months FC, IC, and ID were seen (2%, 4%, and 17%), whereas at 6 months only FC and ID were seen (7% and 1%). We can provide data on HRAM in infants at 2 and 6 months of age. When performing repeated HRAM in healthy infants, RAIR was found in all subjects. HRAM is safe, easy tolerable, and can be recommended in infants with or without FGD.

Central Ocular Motor Disorders: Clinical and Topographic Anatomical Diagnosis, Syndromes and Underlying Diseases.

The key to the diagnosis of ocular motor disorders is a systematic clinical examination of the different types of eye movements, including eye position, spontaneous nystagmus, range of eye movements, smooth pursuit, saccades, gaze-holding function, vergence, optokinetic nystagmus, as well as testing of the function of the vestibulo-ocular reflex (VOR) and visual fixation suppression of the VOR. This is like a window which allows you to look into the brain stem and cerebellum even if imaging is normal. Relevant anatomical structures are the midbrain, pons, medulla, cerebellum and rarely the cortex. There is a simple clinical rule: vertical and torsional eye movements are generated in the midbrain, horizontal eye movements in the pons. For example, isolated dysfunction of vertical eye movements is due to a midbrain lesion affecting the rostral interstitial nucleus of the medial longitudinal fasciculus (riMLF), with impaired vertical saccades only or vertical gaze-evoked nystagmus due to dysfunction of the Interstitial nucleus of Cajal (INC). Lesions of the lateral medulla oblongata (Wallenberg syndrome) lead to typical findings: ocular tilt reaction, central fixation nystagmus and dysmetric saccades. The cerebellum is relevant for almost all types of eye movements; typical pathological findings are saccadic smooth pursuit, gaze-evoked nystagmus or dysmetric saccades. The time course of the development of symptoms and signs is important for the diagnosis of underlying diseases: acute: most likely stroke; subacute: inflammatory diseases, metabolic diseases like thiamine deficiencies; chronic progressive: inherited diseases like Niemann-Pick type C with typically initially vertical and then horizontal saccade palsy or degenerative diseases like progressive supranuclear palsy. Treatment depends on the underlying disease. In this article, we deal with central ocular motor disorders. In a second article, we focus on clinically relevant types of nystagmus such as downbeat, upbeat, fixation pendular, gaze-evoked, infantile or periodic alternating nystagmus. Therefore, these types of nystagmus will not be described here in detail.

The role of enteric inhibitory neurons in intestinal motility.

The enteric nervous system controls much of the mixing and propulsion of nutrients along the digestive tract. Enteric neural circuits involve intrinsic sensory neurons, interneurons and motor neurons. While the role of the excitatory motor neurons is well established, the role of the enteric inhibitory motor neurons (IMNs) is less clear. The discovery of inhibitory transmission in the intestine in the 1960's in the laboratory of Geoff Burnstock triggered the search for the unknown neurotransmitter. It has since emerged that most neurons including the IMNs contain and may utilise more than one transmitter substances; for IMNs these include ATP, the neuropeptide VIP/PACAP and nitric oxide. This review distinguishes the enteric neural pathways underlying the 'standing reflexes' from the pathways operating physiologically during propulsive and non-propulsive movements. Morphological evidence in small laboratory animals indicates that the IMNs are located in the myenteric plexus and project aborally to the circular muscle, where they act by relaxing the muscle. There is ongoing 'tonic' activity of these IMNs to keep the intestinal muscle relaxed. Accommodatory responses to content further activate enteric pathways that involve the IMNs as the final neural element. IMNs are activated by mechanical and chemical stimulation induced by luminal contents, which activate intrinsic sensory enteric neurons and the polarised interneuronal ascending excitatory and descending inhibitory reflex pathways. The latter relaxes the muscle ahead of the advancing bolus, thus facilitating propulsion.

Epidemiology and pathophysiology of low anterior resection syndrome

Low anterior resection syndrome (LARS) is a constellation of symptoms that includes incontinence to flatus and/or feces, urgency, and frequency. LARS affects up to 80% of patients after low anterior resection. The pathophysiology of LARS is complex, and a variety of mechanisms have been proposed. These mechanisms include disruption of autonomic innervation and the rectoanal inhibitory reflex, internal anal sphincter dysfunction, decreased anal canal sensation, and decreased capacity and compliance of the neorectum. As the management of colorectal diseases such as rectal cancer continues to improve, there is a concomitant increase in organ preservation, survivorship, and attention to quality of life. Therefore, recognition and understanding of LARS is key to the diagnosis and treatment of this debilitating disease process.

Effects of sagittal split osteotomy on brainstem reflexes.

This prospective study was designed to assess whether patients with skeletal deformities show characteristic masseter inhibitory reflex (MIR) and blink reflex (BR) patterns. A secondary aim was to investigate whether these reflexes change following bilateral sagittal split osteotomy (BSSO). Fourteen consecutive patients who underwent single-jaw BSSO and 14classI subjects who constituted the control group were enrolled into the study. MIR and BR, obtained by the stimulation of supraorbital (SBR) and mental nerves (MBR), were electrophysiologically recorded. Sensory impairment in the mental nerve distribution was clinically tested. Three evaluation periods were specified as immediately before (T0), 1month (T1) and 6months (T2) after surgery. MIR early silent period duration was significantly shorter in the patients at T0 (p < 0.001). Sensory deficits developed on 23sides after BSSO, of which, 17recovered after 6months. At T1, MBR was inelicitable bilaterally in 3patients and unilaterally in 2patients. These responses were still unrecordable bilaterally in 1patient, and unilaterally in 4patients at T2. MIR were unrecordable on 18sides at T1 and recovered on 11sides at T2. There were no parallels between the clinical sensory deficits and the abnormal results of the reflexes. Shorter MIR in patients with dentofacial abnormalities may be areflection of an adapted trigeminal reflex mechanism. Although MBR and MIR abnormalities do not develop parallel to the clinical sensory deficits, their course might provide insights into the disturbed trigeminal reflex pathways.

Involvement of anti-inflammatory, antioxidant, and BDNF up-regulating properties in the antipsychotic-like effect of the essential oil of Alpinia zerumbet in mice: a comparative study with olanzapine.

The current drug therapy for schizophrenia effectively treats acute psychosis and its recurrence; however, this mental disorder's cognitive and negative symptoms are still poorly controlled. Antipsychotics present important side effects, such as weight gain and extrapyramidal effects. The essential oil of Alpinia zerumbet (EOAZ) leaves presents potential antipsychotic properties that need further preclinical investigation. Here, we determined EAOZ effects in preventing and reversing schizophrenia-like symptoms (positive, negative, and cognitive) induced by ketamine (KET) repeated administration in mice and putative neurobiological mechanisms related to this effect. We conducted the behavioral evaluations of prepulse inhibition of the startle reflex (PPI), social interaction, and working memory (Y-maze task), and verified antioxidant (GSH, nitrite levels), anti-inflammatory [interleukin (IL)-6], and neurotrophic [brain-derived neurotrophic factor (BDNF)] effects of this oil in hippocampal tissue. The atypical antipsychotic olanzapine (OLZ) was used as standard drug therapy. EOAZ, similarly to OLZ, prevented and reversed most KET-induced schizophrenia-like behavioral alterations, i.e., sensorimotor gating deficits and social impairment. EOAZ had a modest effect on the prevention of KET-associated working memory deficit. Compared to OLZ, EOAZ showed a more favorable side effects profile, inducing less cataleptic and weight gain changes. EOAZ efficiently protected the hippocampus against KET-induced oxidative imbalance, IL-6 increments, and BDNF impairment. In conclusion, our data add more mechanistic evidence for the anti-schizophrenia effects of EOAZ, based on its antioxidant, anti-inflammatory, and BDNF up-regulating actions. The absence of significant side effects observed in current antipsychotic drug therapy seems to be an essential benefit of the oil.

Anti Zic4 Paraneoplastic Neurological Syndrome Presenting as Oscillopsia.

Anti Zic4 Paraneoplastic Neurological Syndrome Presenting as Oscillopsia.

Distal Colon Motor Coordination: The Role of the Coloanal Reflex and the Rectoanal Inhibitory Reflex in Sampling, Flatulence, and Defecation.

Distal Colon Motor Coordination: The Role of the Coloanal Reflex and the Rectoanal Inhibitory Reflex in Sampling, Flatulence, and Defecation.

Can Propofol Be Used to Assess the Presence of the Rectoanal Inhibitory Reflex During Anorectal Manometry Studies?

To study changes in intra-anal pressure (IAP) and characteristics of the rectoanal inhibitory reflex (RAIR) during anorectal manometry (ARM) in patients undergoing anesthesia induction with propofol. Prospective study in which ARM was performed at baseline while patients were awake and repeated after propofol-induced anesthesia. We studied IAP and the presence and characteristics of the RAIR before and after propofol. A total of 27 patients were included (63% male; 9.2 years). Three patients had obstructive symptoms after Hirschsprung disease repair (HSCR), and 24 had intractable constipation. At baseline, the RAIR was present on 21 of 27 patients and absent on 6 of 27. Of the six patients with an absent RAIR, it remained absent in four of six (three known HSCR, and one new diagnosis of IAS achalasia), and two of six had a normal RAIR during propofol. Therefore, RAIR was present in all patients with constipation. The mean resting IAP was significantly lower after propofol. The percentage of IAS relaxation after lower balloon volume inflations was significantly higher during propofol (P < 0.05). No difference was observed over the latency time or the total relaxation time after propofol. Propofol can be used to assess the presence of the RAIR during ARM in children who are uncooperative and undergoing other procedures under anesthesia. On the other hand, propofol significantly reduces the resting IAP and increases the percentage of internal anal sphincter relaxation after balloon distention. These findings may impact the interpretation to decide if an intervention is needed, or if there is a possible spinal neuropathy.

Salicylate-Induced Changes in Hearing Thresholds in Mongolian Gerbils Are Correlated With Tinnitus Frequency but Not With Tinnitus Strength.

Tinnitus is an auditory phantom percept without external sound sources. Despite the high prevalence and tinnitus-associated distress of affected patients, the pathophysiology of tinnitus remains largely unknown, making prevention and treatments difficult to develop. In order to elucidate the pathophysiology of tinnitus, animal models are used where tinnitus is induced either permanently by noise trauma or transiently by the application of salicylate. In a model of trauma-induced tinnitus, we have suggested a central origin of tinnitus-related development of neuronal hyperactivity based on stochastic resonance (SR). SR refers to the physiological phenomenon that weak subthreshold signals for given sensors (or synapses) can still be detected and transmitted if appropriate noise is added to the input of the sensor. The main objective of this study was to characterize the neurophysiological and behavioral effects during salicylate-induced tinnitus and compare these to the conditions within the trauma model. Our data show, in line with the pharmacokinetics, that hearing thresholds generally increase 2 h after salicylate injections. This increase was significantly stronger within the region of best hearing compared to other frequencies. Furthermore, animals showed behavioral signs of tinnitus during that time window and frequency range as assessed by gap prepulse inhibition of the acoustic startle reflex (GPIAS). In contrast to animals with noise trauma-induced tinnitus, salicylate-induced tinnitus animals showed no correlation between hearing thresholds and behavioral signs of tinnitus, indicating that the development of tinnitus after salicylate injection is not based on SR as proposed for the trauma model. In other words, salicylate-induced tinnitus and noise trauma-induced tinnitus are not based on the same neurophysiological mechanism.