Influence of oral motor tasks on postural muscle activity during dynamic reactive balance

BACKGROUND

Jaw clenching improves dynamic reactive balance on an oscillating platform during forward acceleration and is associated with decreased mean sway speed of different body regions.

OBJECTIVE

It is suggested that jaw clenching as a concurrent muscle activity facilitates human motor excitability, increasing the neural drive to distal muscles. The underlying mechanism behind this phenomenon was studied based on leg and trunk muscle activity (iEMG) and co-contraction ratio (CCR).

METHODS

Forty-eight physically active and healthy adults were assigned to three groups, performing three oral motor tasks (jaw clenching, tongue pressing against the palate or habitual lower jaw position) during a dynamic one-legged stance reactive balance task on an oscillating platform. The iEMG and CCR of posture-relevant muscles and muscle pairs were analysed during platform forward acceleration.

RESULTS

Tongue pressing caused an adjustment of co-contraction patterns of distal muscle groups based on changes in biomechanical coupling between the head and trunk during static balancing at the beginning of the experiment. Neither iEMG nor CCR measurement helped detect a general neuromuscular effect of jaw clenching on the dynamic reactive balance.

CONCLUSION

The findings might indicate the existence of robust fixed patterns of rapid postural responses during the important initial phases of balance recovery.

Ocular surface lesions in clinical grades of Bell's phenomenon

Background

Bell's phenomenon, also known as the palpebral oculogyric reflex, is a critical reflex that protects the cornea. We developed an innovative, simple, and practical grading scale for Bell's phenomenon that includes the inverse Bell's phenomenon. Using this scale, we investigated the characteristics of Bell's phenomenon among asymptomatic individuals in different age groups and examined the frequency of ocular surface lesions in asymptomatic and symptomatic participants with different grades.

Methods

In this cross-sectional study, we randomly included 330 eyes of 165 asymptomatic, healthy, White Turkish individuals who attended the outpatient eye clinic, with a male-to-female ratio of 1:1.4, in the control group. These were categorized into four age groups: 4 - 20 years, 21 - 40 years, 41 - 60 years, and > 60 years. Eighty eyes from 40 patients with ocular surface lesions and absence of grade + 2 Bell's phenomenon were included in the symptomatic group. Bell's phenomenon was classified into five grades: grade + 2 (strong positive), grade + 1 (weak positive), grade 0 (no Bell's phenomenon, no eye movement), grade -1 (weak inverse), and grade -2 (strong inverse).

Results

We detected higher frequencies of grade + 2, + 1, and 0 in individuals aged 4 - 40, 41 - 60, and > 60 years, respectively. There was a significant difference between age groups in the frequencies of different grades (P < 0.001). Pairwise analysis revealed a significantly lower frequency of grade + 2 in the age group > 60 years compared with the 4 - 20 and 21 - 40 year groups (both P < 0.05). Grade + 2 was the most frequent in both sexes. We detected grade 0 in 27.1% of men and 22.1% of women in the control group, with no significant difference in the frequencies of different grades between sexes (P > 0.05). We observed significant differences between grades with respect to the frequency of ocular surface lesions (P < 0.001). Pairwise analysis revealed a significantly higher frequency of ocular surface lesions in asymptomatic individuals with grade 0 and all four other grades (all P < 0.001). However, the frequency of ocular surface lesions was comparable between sexes (P > 0.05). Of the 40 symptomatic individuals, 28 (70%), 5 (12.5%), 4 (10%), and 3 (7.5%) had grade 0, + 1, -1, and -2, respectively. The number of symptomatic patients was higher in grade 0 (n = 28) than in other grades (grade + 1, -1, and -2: n = 12 patients), and these individuals had a higher frequency of ocular surface lesions (n = 38 lesions) than others (grade + 1, -1, and -2: 7 lesions).

Conclusions

Using a simple, practical grading scale for Bell's phenomenon that includes inverse Bell's phenomenon, we observed that inverse Bell's phenomenon is a reflex that may be present in healthy individuals and could have a protective effect on the eye, although not to such a degree as a strong Bell's phenomenon. Our observations imply that bilateral conjunctival calcifications/Vogt's limbal girdle may be associated with grades 0 and + 1 Bell's phenomenon. Further large-scale studies are needed to determine the frequency of Bell's phenomenon in the general population using this innovative, simple, practical grading scale, and to identify the protective or injurious effect of each grade on the ocular surface.

Activated Human Adipose Tissue Transplantation Promotes Sensorimotor Recovery after Acute Spinal Cord Contusion in Rats

Traumatic spinal cord injuries (SCIs) often result in sensory, motor, and vegetative function loss below the injury site. Although preclinical results have been promising, significant solutions for SCI patients have not been achieved through translating repair strategies to clinical trials. In this study, we investigated the effective potential of mechanically activated lipoaspirated adipose tissue when transplanted into the epicenter of a thoracic spinal contusion. Male Sprague Dawley rats were divided into three experimental groups: SHAM (uninjured and untreated), NaCl (spinal cord contusion with NaCl application), and AF (spinal cord contusion with transplanted activated human fat). Pro-inflammatory cytokines (IL-1β, IL-6, TNF-α) were measured to assess endogenous inflammation levels 14 days after injury. Sensorimotor recovery was monitored weekly for 12 weeks, and gait and electrophysiological analyses were performed at the end of this observational period. The results indicated that AF reduced endogenous inflammation post-SCI and there was a significant improvement in sensorimotor recovery. Moreover, activated adipose tissue also reinstated the segmental sensorimotor loop and the communication between supra- and sub-lesional spinal cord regions. This investigation highlights the efficacy of activated adipose tissue grafting in acute SCI, suggesting it is a promising therapeutic approach for spinal cord repair after traumatic contusion in humans.

The Rate of Asystolic Reflex Syncope Is Not Influenced by Age

BACKGROUND

The head-up tilt test (HUT) and other evidence suggest that the vagal effect on the heart decreases with age.

OBJECTIVES

The main aim of the study was to assess whether this age effect also affects the rate of asystole in spontaneous reflex syncope (RS).

METHOD

We performed an analysis of pooled individual data from 4 studies that recruited patients ≥40 years of age affected by certain or suspected RS who received an implantable loop recorder (ILR) and reported follow-up data on syncope recurrence. We assessed the presence of asystolic syncope of >3 seconds or nonsyncopal asystole of >6 seconds recorded by ILR and compared the findings to tilt test results on the same patients.

RESULTS

A total of 1,046 patients received ILR because of unexplained syncope. Of these, 201 (19.2%) had a documentation of an asystolic event of 10-second (Q1-Q3: 6- to 15-second) duration. They were subdivided in 3 age tertiles: ≤60 years (n = 64), 61 to 72 years (n = 72), and ≥73 years (n = 65). The rate of asystolic events was similar in the 3 subgroups (50.1%, 50.1%, and 49.2%, respectively; P = 0.99). Conversely, the rate of asystolic syncope induced during HUT (performed in 169 of 201) was greatly age dependent (31.0%, 12.1%, and 11.1% in increasing age tertiles, respectively; P = 0.009).

CONCLUSIONS

The rate of the spontaneous asystolic form of RS documented by ILR is constant at any age >40 years. Conversely, the rate of asystolic syncope induced by HUT is higher in younger patients and decreases with age. The contrasting results between spontaneous and tilt-induced events cast doubt on the concept that asystole in RS is less common in older patients.

A novel GABRG2 variant in Sunflower syndrome: A case report and video EEG monitoring

OBJECTIVE

Sunflower syndrome is a unique photosensitive epilepsy, characterized by heliotropism and stereotyped seizures associated with handwaving. These handwaving events (HWE) are thought to be an ictal phenomenon, although current data are contrasting. Photosensitive epilepsy occurs in 2%-5% of the epilepsy forms and several pathogenic gene variants have been associated with photosensitive epilepsy. However, the genetic etiology of Sunflower syndrome remains unknown. Antiseizure medications (ASM) efficacious in treating photosensitive epilepsy are valproic acid (VPA) and levetiracetam (LEV) although some forms, such as Sunflower syndrome, can be drug-resistant.

METHODS AND RESULTS

Here, we report an 8-year-old boy with an early onset of episodes of HWE that was initially categorized as behavioral problems for which risperidone was started. However, the medical history was suggestive of Sunflower syndrome, and subsequent video EEG showed focal mostly temporal and frontotemporal (right and left) epileptiform activity and confirmed the epileptic nature of the HWE. Thus, VPA was started and initially led to seizure frequency reduction. Molecular analyses showed a pathogenic variant in GABRG2 (c.1287G>A p.(Trp429Ter)), which has been associated with photosensitive and generalized epilepsy.

SIGNIFICANCE

Overall, clinicians worldwide should be cautious by interpreting HWE and/or other tic-like movements, since an epileptic origin cannot be ruled out. A prompt and correct diagnosis can be made by performing a video EEG early on in the diagnostic process when epileptic seizures are part of the differential diagnosis. Even though the genetic etiology of Sunflower syndrome remains poorly understood, this constellation supports further genetic testing since the detection of a pathogenic variant can help in making correct decisions regarding ASM management.

Modulation of reflex responses of the anterior and posterior bellies of the digastric muscle in freely moving rats

BACKGROUND

Chewing and licking are primarily activated by central pattern generator (CPG) neuronal circuits in the brainstem and when activated trigger repetitive rhythmic orofacial movements such as chewing, licking and swallowing. These CPGs are reported to modulate orofacial reflex responses in functions such as chewing.

OBJECTIVE

This study explored the modulation of reflex responses in the anterior and posterior bellies (ant-Dig and post-Dig, respectively) of the digastric muscle evoked by low-intensity trigeminal stimulation in conscious rats.

METHODS

The ant-Dig and post-Dig reflexes were evoked by using low-intensity electrical stimulation applied to either the right or left inferior alveolar nerve. Peak-to-peak amplitudes and onset latencies were measured.

RESULTS

No difference was observed between threshold and onset latency for evoking ant-Dig and post-Dig reflexes, suggesting that the latter was also evoked disynaptically. The peak-to-peak amplitude of both reflexes was significantly reduced during chewing, licking and swallowing as compared to resting period and was lowest during the jaw-closing phase of chewing and licking. Onset latency was significantly largest during the jaw-closing phase. Inhibitory level was similar between the ant-Dig and post-Dig reflex responses and between the ipsilateral and contralateral sides.

CONCLUSION

These results suggest that both the ant-Dig and post-Dig reflex responses were significantly inhibited, probably due to CPG activation during feeding behaviours to maintain coordination of jaw and hyoid movements and hence ensure smooth feeding mechanics.

Investigating the Blink Reflex Abnormality in Dry Eye Patients

Introduction Dry eye is an ocular surface disorder caused by increased evaporation, decreased tear production, or mixed form. Tears are secreted by the lacrimal gland after lacrimal nerve stimulation connected to the facial nerve. In nerve damage, tear secretion decreases, and dry eye develops. Our aim is to investigate the presence of pathology in the facial trigeminal nerve and neuronal pathways that provide reflex connections between these nerves by measuring the blink reflex in patients with dry eyes. Methods Schirmer test and tear breakup time were performed. Tear breakup time measurement was repeated three times, and the average of three was accepted. Tear breakup time <10 seconds and Schirmer test <10 mm without local anesthesia were accepted as dry eye. Patients having traumatic corneal pathology, ectatic corneal disease, inflammatory and microbial keratitis, previous ocular surgery, glaucoma, diabetic retinopathy, and chronic neurological diseases were excluded. The control group was randomly formed from 42 eyes of 21 healthy volunteers. Blink reflex was measured in both groups, and the R1 and R2 responses of the two groups were compared. Written consent was obtained from the patient (or legal guardian) so that her medical data could be published. Results There was no significant difference between the two groups in R1 and R2 responses in both eyes. There was no significant difference in terms of gender between the two groups (p=0.100). The mean age in the patient group was significantly higher than in the control group (p<0.000). The mean Schirmer test in the patient group was 8.6±1.1 mm in the right eye and 8.97±1.0 mm in the left eye. Conclusion There was no central pathology observed in terms of reflex blinking in dry eye disease. However, in future studies, brainstem fiesta sequence magnetic resonance imaging (MRI) can be planned to evaluate central pathologies in more detail.

Heating the skin on the foot sole enhances cutaneous reflexes in the lower limb

Cutaneous input is important in postural control and balance. Aging and diabetes impair skin sensitivity and motor control. Heat application can improve skin sensation, but its influence on motor control remains unknown. This study investigated the effects of heating the skin of the foot sole on lower limb cutaneous reflexes. Reflexes were evoked in the tibialis anterior muscle of 20 young, healthy adults before and after heating the foot sole to a maximum of 42°C. While holding a 15% maximum root mean square EMG generated during maximum isometric dorsiflexion, a filtered white noise (0-50 Hz) vibration at 10 times the perceptual threshold was applied to the heel to stimulate cutaneous mechanoreceptors. Reflexes were analyzed in both the time (cumulant density) and frequency (coherence, gain) domains. Heat increased foot skin temperature ∼15.4°C (P < 0.001). Cumulant density peak to peak amplitude significantly increased by 44% after heating (P = 0.01) while latencies did not vary (P = 0.46). Coherence and gain were significantly greater in the 30- to 40-Hz range following heating (P = 0.048; P = 0.02). Heating significantly enhances lower limb cutaneous reflexes. This may be due to the increased ability of cutaneous mechanoreceptors to encode in the 30- to 40-Hz range.NEW & NOTEWORTHY Cutaneous input is a known modulator of muscle activity. Targeting skin to intentionally enhance motor output has received little attention. We explored local skin heating to enhance skin sensitivity and found a significant increase in the amplitude, coherence, and gain of cutaneous reflexes in the tibialis anterior. Our current findings provide the first support for the use of heat as a viable and easily integrated modality in rehabilitation technology to improve balance and postural control.

Reflex Hepatitis C Virus Viral Load Testing Following an Initial Positive Hepatitis C Virus Antibody Test: A Global Systematic Review and Meta-analysis

BACKGROUND

Many people who have a positive hepatitis C virus (HCV) antibody (Ab) test never receive a confirmatory HCV RNA viral load (VL) test. Reflex VL testing may help address this problem. We undertook a systematic review to evaluate the effectiveness of reflex VL testing compared with standard nonreflex approaches on outcomes across the HCV care cascade.

METHODS

We searched 4 databases for studies that examined laboratory-based reflex or clinic-based reflex VL testing approaches, with or without a nonreflex comparator, and had data on the uptake of HCV RNA VL test and treatment initiation and turnaround time between Ab and VL testing. Both laboratory- and clinic-based reflex VL testing involve only a single clinic visit. Summary estimates were calculated using random-effects meta-analyses.

RESULTS

Fifty-one studies were included (32 laboratory-based and 19 clinic-based reflex VL testing). Laboratory-based reflex VL testing increased HCV VL test uptake versus nonreflex testing (RR: 1.35; 95% CI: 1.16-1.58) and may improve linkage to care among people with a positive HCV RNA test (RR: 1.47; 95% CI: .81-2.67) and HCV treatment initiation (RR: 1.03; 95% CI: .46-2.32). The median time between Ab and VL test was <1 day for all laboratory-based reflex studies and 0-5 days for 13 clinic-based reflex testing.

CONCLUSIONS

Laboratory-based and clinic-based HCV reflex VL testing increased uptake and reduced time to HCV VL testing and may increase HCV linkage to care. The World Health Organization now recommends reflex VL testing as an additional strategy to promote access to HCV VL testing and treatment.

CLINICAL TRIALS REGISTRATION

PROSPERO CRD42021283822.

Treatment and Response Factors in Muscle Activation during Spinal Manipulation

The forces applied during a spinal manipulation produce a neuromuscular response in the paraspinal muscles. A systematic evaluation of the factors involved in producing this muscle activity provides a clinical insight. The purpose of this study is to quantify the effect of treatment factors (manipulation sequence and manipulation site) and response factors (muscle layer, muscle location, and muscle side) on the neuromuscular response to spinal manipulation. The surface and indwelling electromyographies of 8 muscle sites were recorded during lumbar side-lying manipulations in 20 asymptomatic participants. The effects of the factors on the number of muscle responses and the muscle activity onset delays were compared using mixed-model linear regressions, effect sizes, and equivalence testing. The treatment factors did not reveal statistical differences between the manipulation sequences (first or second) or manipulation sites (L3 or SI) in the number of muscle responses (p = 0.11, p = 0.28, respectively), or in muscle activity onset delays (p = 0.35 p = 0.35, respectively). There were significantly shorter muscle activity onset delays in the multifidi compared to the superficial muscles (p = 0.02). A small effect size of side (d = 0.44) was observed with significantly greater number of responses (p = 0.02) and shorter muscle activity onset delays (p < 0.001) in the muscles on the left side compared to the right. The location, layer, and side of the neuromuscular responses revealed trends of decreasing muscle response rates and increasing muscle activity onset delays as the distance from the manipulation site increased. These results build on the body of work suggesting that the specificity of manipulation site may not play a role in the neuromuscular response to spinal manipulation-at least within the lumbar spine. In addition, these results demonstrate that multiple manipulations performed in similar areas (L3 and S1) do not change the response significantly, as well as contribute to the clinical understanding that the muscle response rate is higher and with a shorter delay, the closer it is to the manipulation.

Judokas Exhibit Short Response Latency Even to Non-Judo-Specific External Perturbation: Insights Into the Involuntary Postural Control Ability in Humans

Humans experience unanticipated external postural perturbations and recover their posture faster via involuntary responses than voluntary responses. Previous cross-sectional comparisons between athletes and untrained populations have suggested that daily motor experiences can lead to adaptations in the reflex system, but the temporal aspect of this adaptation has been unclear. Here we show that judokas have an earlier muscle activation response to even non-judo-specific external perturbations compared with an untrained population. The response latency to a backward push-and-release type postural perturbation was compared between male judokas (n = 7, career >13 years, ranging from world champions to prefectural competitors) and untrained nonjudokas (n = 7). Latency was defined as the instant of tibialis anterior muscle activity onset. Judokas exhibited shorter latency (20.6 ± 7.1 ms) than nonjudokas (28.3 ± 8.9 ms). The rank order of latency in judokas did not correlate with their competition performance. We suggest that daily training in responding to perturbations might improve some parts of the sensorimotor pathway relating to postural response latency, and that this excellence in involuntary response is independent of athletic performance. The findings provide a novel perspective for understanding postural control ability in humans.

Locomotor-related propriospinal V3 neurons produce primary afferent depolarization and modulate sensory transmission to motoneurons

When a muscle is stretched, sensory feedback not only causes reflexes but also leads to a depolarization of sensory afferents throughout the spinal cord (primary afferent depolarization, PAD), readying the whole limb for further disturbances. This sensory-evoked PAD is thought to be mediated by a trisynaptic circuit, where sensory input activates first-order excitatory neurons that activate GABAergic neurons that in turn activate GABAA receptors on afferents to cause PAD, though the identity of these first-order neurons is unclear. Here, we show that these first-order neurons include propriospinal V3 neurons, as they receive extensive sensory input and in turn innervate GABAergic neurons that cause PAD, because optogenetic activation or inhibition of V3 neurons in mice mimics or inhibits sensory-evoked PAD, respectively. Furthermore, persistent inward sodium currents intrinsic to V3 neurons prolong their activity, explaining the prolonged duration of PAD. Also, local optogenetic activation of V3 neurons at one segment causes PAD in other segments, due to the long propriospinal tracts of these neurons, helping to explain the radiating nature of PAD. This in turn facilitates monosynaptic reflex transmission to motoneurons across the spinal cord. In addition, V3 neurons directly innervate proprioceptive afferents (including Ia), causing a glutamate receptor-mediated PAD (glutamate PAD). Finally, increasing the spinal cord excitability with either GABAA receptor blockers or chronic spinal cord injury causes an increase in the glutamate PAD. Overall, we show the V3 neuron has a prominent role in modulating sensory transmission, in addition to its previously described role in locomotion.NEW & NOTEWORTHY Locomotor-related propriospinal neurons depolarize sensory axons throughout the spinal cord by either direct glutamatergic axoaxonic contacts or indirect innervation of GABAergic neurons that themselves form axoaxonic contacts on sensory axons. This depolarization (PAD) increases sensory transmission to motoneurons throughout the spinal cord, readying the sensorimotor system for external disturbances. The glutamate-mediated PAD is particularly adaptable, increasing with either an acute block of GABA receptors or chronic spinal cord injury, suggesting a role in motor recovery.

Neuromechanical Strategies for Obstacle Negotiation during Overground Locomotion following Incomplete Spinal Cord Injury in Adult Cats

Following incomplete spinal cord injury in animals, including humans, substantial locomotor recovery can occur. However, functional aspects of locomotion, such as negotiating obstacles, remains challenging. We collected kinematic and electromyography data in 10 adult cats (5 males, 5 females) before and at weeks 1-2 and 7-8 after a lateral mid-thoracic hemisection on the right side of the cord while they negotiated obstacles of three different heights. Intact cats always cleared obstacles without contact. At weeks 1-2 after hemisection, the ipsilesional right hindlimb contacted obstacles in ∼50% of trials, triggering a stumbling corrective reaction or absent responses, which we termed Other. When complete clearance occurred, we observed exaggerated ipsilesional hindlimb flexion when crossing the obstacle with contralesional Left limbs leading. At weeks 7-8 after hemisection, the proportion of complete clearance increased, Other responses decreased, and stumbling corrective reactions remained relatively unchanged. We found redistribution of weight support after hemisection, with reduced diagonal supports and increased homolateral supports, particularly on the left contralesional side. The main neural strategy for complete clearance in intact cats consisted of increased knee flexor activation. After hemisection, ipsilesional knee flexor activation remained, but it was insufficient or more variable as the limb approached the obstacle. Intact cats also increased their speed when stepping over an obstacle, an increase that disappeared after hemisection. The increase in complete clearance over time after hemisection paralleled the recovery of muscle activation patterns or new strategies. Our results suggest partial recovery of anticipatory control through neuroplastic changes in the locomotor control system.SIGNIFICANCE STATEMENT Most spinal cord injuries (SCIs) are incomplete and people can recover some walking functions. However, the main challenge for people with SCIs that do recover a high level of function is to produce a gait that can adjust to everyday occurrences, such as turning, stepping over an obstacle, etc. Here, we use the cat model to answer two basic questions: How does an animal negotiate an obstacle after an incomplete SCI and why does it fail to safely clear it? We show that the inability to clear an obstacle is because of improper activation of muscles that flex the knee. Animals recover a certain amount of function thanks to new strategies and changes within the nervous system.

Multiple sensor theory in airway mechanosensory units

Two conventional doctrines govern airway mechanosensory interpretation: One-Sensor Theory (OST) and Line-Labeled Theory (LLT). In OST, one afferent fiber connects to a single sensor. In LLT, a different type of sensor sends signals via its specific line to a particular brain region to evoke its reflex. Thus, airway slowly adapting receptors (SARs) inhibit breathing and rapidly adapting receptors (RARs) stimulate breathing. However, recent studies show many different mechanosensors connect to a single afferent fiber (Multiple-Sensor Theory, MST). That is, SARs and RARs may send different types of information through the same afferent pathway, indicating different information has been integrated at the sensory unit level. Thus, a sensory unit is not merely a transducer (textbook concept), but also a processor. MST is a conceptual shift. Data generated over last eight decades under OST require re-interpretation.

Effect of Cyclooxygenase Inhibition on Peripheral Venous Distension Reflex in Healthy Humans

BACKGROUND

Peripheral venous distension evokes a pressor reflex (venous distension reflex). Afferent group III and IV nerves innervating veins are suggested as the afferent arm of the venous distension reflex. Prostaglandins stimulate/sensitize group III/IV nerves. We hypothesized that inhibition of prostaglandin synthesis by local cyclooxygenase blockade would attenuate the muscle sympathetic nerve activity (MSNA) and blood pressure responses to venous distension.

METHODS

Nineteen healthy volunteers (age, 27±5 years) participated in the study with 2 visits. To induce venous distension, a volume of solution (saline alone or 9 mg ketorolac tromethamine in saline) was infused into the vein in the antecubital fossa of an arterially occluded forearm. During the procedure, beat-by-beat heart rate, blood pressure and MSNA were recorded simultaneously. The vein size was measured with ultrasound.

RESULTS

In both visits, the venous distension procedure significantly increased blood pressure, heart rate, and MSNA (all, P<0.05). The increase in mean arterial pressure and MSNA in the ketorolac visit was significantly lower than in the control visit (∆ mean arterial pressure, 7.0±6.2 versus 13.8±7.7 mm Hg; ∆MSNA, 6.0±7.1 versus 14.8±7.7 bursts/min; both, P<0.05). The increase in vein size induced by the infusion was not different between visits.

CONCLUSIONS

The presented data show that cyclooxygenase blockade attenuates the responses in MSNA and blood pressure to peripheral venous distension reflex. The results suggest that cyclooxygenase products play a key role in evoking afferent activation responsible for the venous distension reflex.

Differences in rectoanal inhibitory reflex duration between patients with refractory functional constipationand myelomeningocele

Introduction. Usually, during anorectal manometry, only the presence or absence of rectoanal inhibitory reflex (RAIR) is investigated. Studies have reported that a detailed analysis may provide data of interest. Our hypothesis is that RAIR measurement may provide information to detect organic causes (tethered cord, lipoma, etc.) in patients in whom a functional cause had been previously considered. Objectives. To compare RAIR duration in anorectal manometry between patients with refractory functional constipation (RFC) and myelomeningocele (MMC). Population and methods. Observational, analytical, cross-sectional study (2004-2019). Patients with chronic constipation and functional and organic fecal incontinence (myelomeningocele). The anorectal manometry was performed with a water-perfused system, and the duration of RAIR was measured with different volumes (20, 40, and 60 cc). Group 1 (G1): 81 RFC. Group 2 (G2): 54 MMC. Patients with developmental delay, compliant anal sphincter, sacral agenesis and non-cooperative patients were excluded. Results. A total of 135 individuals were included (62 were male). Their median age was 9.57 years in G1 and 9.63 years in G2. Average duration in G1 versus G2 with 20 cc: 8.89 versus 15.21 seconds; 40 cc: 11.41 versus 21.12 seconds; 60 cc: 14.15 versus 26.02 seconds. The difference in RAIR duration with the varying volumes was statistically significant (p = 0.0001). Conclusion. RAIR duration was longer with increasing balloon inflation volumes in both populations. RAIR duration was longer in patients with MMC than in those with RFC. Spinal injury should be ruled out in patients with prolonged RAIR.

Short-latency stretch reflexes depend on the balance of activity in agonist and antagonist muscles during ballistic elbow movements

The spinal stretch reflex is a fundamental building block of motor function, with a sensitivity that varies continuously during movement and when changing between movement and posture. Many have investigated task-dependent reflex sensitivity, but few have provided simple, quantitative analyses of the relationship between the volitional control and stretch reflex sensitivity throughout tasks that require coordinated activity of several muscles. Here, we develop such an analysis and use it to test the hypothesis that modulation of reflex sensitivity during movement can be explained by the balance of activity within agonist and antagonist muscles better than by activity only in the muscle homonymous with the reflex. Subjects completed hundreds of flexion and extension movements as small, pseudorandom perturbations of elbow angle were applied to obtain estimates of stretch reflex amplitude throughout the movement. A subset of subjects performed a postural control task with muscle activities matched to those during movement. We found that reflex modulation during movement can be described by background activity in antagonist muscles about the elbow much better than by activity only in the muscle homonymous to the reflex (P < 0.001). Agonist muscle activity enhanced reflex sensitivity, whereas antagonist activity suppressed it. Surprisingly, the magnitude of these effects was similar, suggesting a balance of control between agonists and antagonists very different from the dominance of sensitivity to homonymous activity during posture. This balance is due to a large decrease in sensitivity to homonymous muscle activity during movement rather than substantial changes in the influence of antagonistic muscle activity.NEW & NOTEWORTHY This study examined the sensitivity of the stretch reflexes elicited in elbow muscles to the background activity in these same muscles during movement and postural tasks. We found a heightened reciprocal control of reflex sensitivity during movement that was not present during maintenance of posture. These results help explain previous discrepancies in reflex sensitivity measured during movement and posture and provide a simple model for assessing their contributions to muscle activity in both tasks.

Inspiratory muscle reflex control after incomplete cervical spinal cord injury

In healthy individuals, loading inspiratory muscles by brief inspiratory occlusion produces a short-latency inhibitory reflex (IR) in the electromyographic (EMG) activity of scalene and diaphragm muscles. This IR may play a protective role to prevent aspiration and airway collapse during sleep. In people with motor and sensory complete cervical spinal cord injury (cSCI), who were able to breathe independently, this IR was predominantly absent. Here, we investigated the reflex response to brief airway occlusion in 16 participants with sensory incomplete cSCI [American spinal injury association impairment scale (AIS) score B or C]. Surface EMG was recorded from scalene muscles and the lateral chest wall (overlying diaphragm). The airway occlusion evoked a small change in mouth pressure resembling a physiological occlusion. The short-latency IR was present in 10 (63%) sensory incomplete cSCI participants; significantly higher than the IR incidence observed in complete cSCI participants in our previous study (14%; P = 0.003). When present, mean IR latency across all muscles was 58 ms (range 29-79 ms), and mean rectified EMG amplitude decreased to 37% preocclusion levels. Participants without an IR had untreated severe obstructive sleep apnea (OSA), in contrast to those with an IR, who had either had no, mild, or treated OSA (P = 0.002). Insufficient power did not allow statistical comparison between IR presence or absence and participant clinical characteristics. In conclusion, spared sensory connections or intersegmental connections may be necessary to generate the IR. Future studies to establish whether IR presence is related to respiratory morbidity in the tetraplegic population are required.NEW & NOTEWORTHY Individuals with incomplete cSCI were tested for the presence of a short latency reflex inhibition of inspiratory muscles, by brief airway occlusion. The reflex was 4.5 times more prevalent in this group compared with those with complete cSCI and is similar to the incidence in able-bodied people. Participants without this reflex all had untreated severe OSA, in contrast to those with an IR, who either had no, mild, or treated OSA. This work reveals novel differences in the reflex control of inspiratory muscles across the cSCI population.

Continuous intraoperative neuromonitoring of the recurrent laryngeal nerve by eliciting the laryngeal adductor reflex (LAR-CIONM)

The laryngeal adductor reflex (LAR) is a life-sustaining airway protective mechanism that serves to shield the lower airways from inhaled foreign bodies. Over the past half century, the LAR has been extensively investigated and its dysfunction has been linked to far-ranging pathologies, from dysphagia to sudden infant death syndrome. Over the past 6 years, specific electromyographic waves in the LAR response have been used to devise a methodology for monitoring the vagus and recurrently laryngeal nerves during surgical procedures. This methodology involves continuous intraoperative neuromonitoring of the laryngeal adductor reflex and isthus termed 'LAR-CIONM'. In this review paper, the physiology of the LAR will be summarized as it relates to LAR-CIONM and the technique of LAR-CIONM will be described. Applications of this technique and published outcomes of LAR-CIONM will be highlighted.

Transient asystole during balloon dilation of the Eustachian tube: A case report

RATIONALE

Neurally mediated reflexes can induce cardiac arrest during head and neck surgery through mechanisms including direct vagal stimulation, trigeminocardiac reflex, and baroreceptor reflex. Balloon dilation of the Eustachian tube (BDET) is a safe procedure without serious complications, including cardiac arrest.

PATIENT CONCERNS

Transient asystole developed during BDET under general anesthesia in a 33-year-old woman as soon as the balloon in the Eustachian tube (ET) was inflated.

DIAGNOSES

Monitoring records were reviewed. The asystolic period was recorded on the patient monitor as an event, which we recalled and printed. The asystole lasted for 13 seconds.

INTERVENTIONS

The patient recovered sinus rhythm spontaneously after the balloon was deflated before resuscitation. The BDET was successfully performed after prophylaxis with vagolytic drugs.

OUTCOMES

The patient recovered uneventfully after anesthesia.

LESSONS

BDET, previously known to be a relatively safe procedure, induces asystole via balloon dilation. It is thought to be a neurally mediated vagal reflex, and both anesthesiologists and otologic physicians should pay proper attention to monitoring during the procedure.

Reflex of the Gracilis in Brain Death

In patients with brain death, reflex movements originating from spinal reflexes are observed intermittently. Generally, they can occur under hypoxic stimuli such as when the ventilator is removed, under physical stimuli such as bending the neck, or under hypotension. Finger- and toe-jerk responses are commonly observed reflex movements that can occur in patients with brain death. In addition, the Lazarus sign, known as the most dramatic reflex movement, appears mainly in the upper extremities (e.g., the hands and arms) and in the distal lower extremities (e.g., the soles and toes). This case showed a reflex movement that was triggered by the contraction of the gracilis, a proximal muscle in the lower extremities, with only a gentle stimulus on the sole.

The early history of the knee-jerk reflex in neurology

Medical interest in the knee-jerk reflex began in about 1875 with simultaneous and independent publications by Wilhelm Heinrich Erb (1840-1921) and Carl Friedrich Otto Westphal (1833-1890) contending that the knee jerk was absent (and the ankle clonus was present) in all clear cases of locomotor ataxia (tabes dorsalis). Physicians in the medical communities of Europe, Great Britain, and North America responded with case and large group studies that tested this contention. These studies revealed the usefulness of the knee jerk and other myotatic reflexes, but also unexpected characteristics. The knee jerk, apparently so simple, proved to be a complex phenomenon depending the strength of the strike on the patella, induced muscle tension, and inhibition from the brain. Was it a reflex with afferent and efferent nerves and an intervening process in the spinal cord, or was it a local phenomenon confined to the muscle itself? Experimental studies directed at the reflex issue investigated latencies from patella strike to leg extension or muscle contraction and compared them with latencies from direct muscle strikes and theoretical calculations based on reflex components. Such studies were unable to resolve the reflex issue during the nineteenth century. The physicians were shown to be limited, like all scientific explorers of the unknown, by their knowledge, methodology, and technology.

Divergent splanchnic sympathetic efferent nerve pathways regulate interleukin-10 and tumour necrosis factor-α responses to endotoxaemia

The efferent branches of the splanchnic sympathetic nerves that enhance interleukin-10 (IL-10) and suppress tumour necrosis factor-α (TNF) levels in the reflex response to systemic immune challenge were investigated in anaesthetized, ventilated rats. Plasma levels of TNF and IL-10 were measured 90 min after intravenous lipopolysaccharide (LPS, 60 µg/kg). Splanchnic nerve section, ganglionic blockade with pentolinium tartrate or β₂ adrenoreceptor antagonism with ICI 118551 all blocked IL-10 responses. Restoring plasma adrenaline after splanchnic denervation rescued IL-10 responses. TNF responses were disinhibited by splanchnic denervation or pentolinium treatment, but not by ICI 118551. Splanchnic nerve branches were cut individually or in combination in vagotomized rats, ruling out any vagal influence on results. Distal splanchnic denervation, sparing the adrenal nerves, disinhibited TNF but did not reduce IL-10 responses. Selective adrenal denervation depressed IL-10 but did not disinhibit TNF responses. Selective denervation of either spleen or liver did not affect IL-10 or TNF responses, but combined splenic and adrenal denervation did so. Finally, combined section of the cervical and lumbar sympathetic nerves did not affect cytokine responses to LPS. Together, these results show that the endogenous anti-inflammatory reflex is mediated by sympathetic efferent fibres that run in the splanchnic, but not other sympathetic nerves, nor the vagus. Within the splanchnic nerves, divergent pathways control these two cytokine responses: neurally driven adrenaline, acting via β₂ adrenoreceptors, regulates IL-10, while TNF is restrained by sympathetic nerves to abdominal organs including the spleen, where non-β₂ adrenoreceptor mechanisms are dominant. KEY POINTS: An endogenous neural reflex, mediated by the splanchnic, but not other sympathetic nerves, moderates the cytokine response to systemic inflammatory challenge. This reflex suppresses the pro-inflammatory cytokine tumour necrosis factor-α (TNF), while enhancing levels of the anti-inflammatory cytokine interleukin-10 (IL-10). The reflex enhancement of IL-10 depends on the splanchnic nerve supply to the adrenal gland and on β₂ adrenoreceptors, consistent with mediation by circulating adrenaline. After splanchnic nerve section it can be rescued by restoring circulating adrenaline. The reflex suppression of TNF depends on splanchnic nerve branches that innervate abdominal tissues including, but not restricted to, spleen: it is not blocked by adrenal denervation or β₂ adrenoreceptor antagonism. Distinct sympathetic efferent pathways are thus responsible for pro- and anti-inflammatory cytokine components of the reflex regulating inflammation.

Stop routine microscopic urinalysis in hospitalized patients with dipstick abnormalities?

BACKGROUND

Restricting the performance of microscopic urinalyses only to patients in whom it was specifically requested has been shown to reduce their number in laboratories servicing both inpatients and outpatients.

OBJECTIVE

To determine the effect of such restriction solely in in-patients in a 400-bed regional hospital.

METHODS

In 2017, we discontinued routine ('reflex') microscopic urinalysis for all positive dipstick results, and restricted such testing to in-patients in whom it was specifically requested by a doctor. We compared the numbers of patients in three internal medicine departments who had a urinalysis over 2-year periods before and after 2017, and reviewed doctors' complaints.

RESULTS

Before 2017, more than 80% of all dipstick tested samples had one or more abnormalities that led to a microscopic examination. Discontinuation of reflex microscopy reduced microscopic urinalysis to less than 10% of all patients with dipsticks on admission. Requests for repeat urinalysis decreased from 4.3% to 2.5% and there were no complaints after the change in policy.

CONCLUSIONS

Discontinuation of a 'reflex' microscopic urinalysis in patients with abnormal dipstick results did not increase repeat urine testing. Doctors apparently felt that the microscopic urinalysis does not have clinical utility in the vast majority of hospitalized adult patients.

Monosynaptic facilitation of motoneurons innervating intrinsic hand muscles mediated by group Ia afferents from the extensor carpi radialis in humans

The projection pattern of low-threshold afferents from the extensor carpi radialis (ECR) to motoneurons supplying intrinsic hand muscles was investigated using the post-stimulus time-histogram (PSTH) and electromyogram-averaging (EMG-A) methods. Electrical conditioning stimulation was applied to the radial nerve branch innervating the ECR. In the PSTH study, changes in the firing probability of single motor units following the stimulation were examined. An early and significant peak (facilitation) was induced in the motoneurons innervating the muscles, but the facilitation was induced infrequently. The central latency of the facilitation was equivalent to that of homonymous facilitation through monosynaptic path in the spinal cord. In the EMG-A study, changes in the rectified and averaged electromyograms following the conditioning stimulation were examined. An early and significant peak (facilitation) was also induced. The facilitation disappeared after withdrawal of the vibration to the ECR muscle belly. Cutaneous nerve stimulation overlaying ECR never induced such facilitation in the PSTH and EMG-A studies. These findings suggest that monosynaptic facilitation mediated by group Ia afferents of ECR to the motoneurons supplying intrinsic hand muscles exists in humans, but the connection seems to be weak. This weakness might allow manipulatory movements of the hand.

Modified defense reaction reduces biomechanical and myoelectrical ACL injury risk factors in elite Judo

In judo, an anterior cruciate ligament (ACL) injury is the most severe injury an athlete could experience. Most ACL ruptures occur when defending against an osoto-gari attack. This study aims to identify ACL risk factors during osoto-gari defence and implement a modified osoto-gari defence reaction, which is assumed to improve myoelectric patterns and ameliorate critical biomechanical risk factors for ACL injuries. Twenty-six elite judokas were enrolled in the cross-over trial (female: 6; male: 20). 3D kinematics and force dynamometrics were combined with electromyographical recordings to assess the effects of the common and the modified osoto-gari defence reaction. Compared to the common osoto-gari defence reaction (maximal knee flexion: 29 ± 12°; maximal valgus: 10 ± 5°; maximal valgus moment: 58 ± 17 Nm; peak internal rotation: 9 ± 5°), the modified osoto-gari defence reaction showed significantly reduced knee angles (31 ± 10° p < 0.05; 1 ± 0° p < 0.05; 31 ± 9 Nm p < 0.05; 3 ± 0° p < 0.05). The myoelectric activity of the hamstring increased (+5±% to +27±%, p < 0.05) in the modified compared to common defence reaction. The modified osoto-gari defence reaction reduced critical biomechanical risk factors and increased hamstring myoelectric activity. We recommend the implementation of the modified osoto-gari defence reaction in judo practice and seek to evaluate its long-term effectiveness in decreasing ACL injury incidences in elite judo.

Aortic Body Chemoreceptors Regulate Coronary Blood Flow in Conscious Control and Hypertensive Sheep

BACKGROUND

Peripheral arterial chemoreceptors monitor the chemical composition of arterial blood and include both the carotid and aortic bodies (ABs). While the role of the carotid bodies has been extensively studied, the physiological role of the ABs remains relatively under-studied, and its role in hypertension is unexplored. We hypothesized that activation of the ABs would increase coronary blood flow in the normotensive state and that this would be mediated by the parasympathetic nerves to the heart. In addition, we determined whether the coronary blood flow response to stimulation of the ABs was altered in an ovine model of renovascular hypertension.

METHODS

Experiments were conducted in conscious and anesthetized ewes instrumented to record arterial pressure, coronary blood flow, and cardiac output. Two groups of animals were studied, one made hypertensive using a 2 kidney one clip model (n=6) and a sham-clipped normotensive group (n=6).

RESULTS

Activation of the ABs in the normotensive animals resulted in a significant increase in coronary blood flow, mediated, in part by a cholinergic mechanism since it was attenuated by atropine infusion. Activation of the ABs in the hypertensive animals also increased coronary blood flow (P<0.05), which was not different from the normotensive group. Interestingly, the coronary vasodilation in the hypertensive animals was not altered by blockade of muscarinic receptors but was attenuated after propranolol infusion.

CONCLUSIONS

Taken together, these data suggest that the ABs play an important role in modulating coronary blood flow and that their effector mechanism is altered in hypertension.

Visual photosensitivity threshold and objective photosensitivity luminance in healthy human eyes assessed using an automated ocular photosensitivity analyser: a step towards translation of a clinical tool for assessing photophobia

PURPOSE

To evaluate the visual photosensitivity threshold and objective photosensitivity luminance in healthy eyes, thereby providing a normative dataset that will lead to a better understanding of diseases causing photophobia.

METHODS

This was a prospective cross-sectional study. Emmetropes whose visual acuity was better than 0.18 logMAR (6/9) with no other ocular abnormality were included. Headache Impact Test-6 and visual light sensitivity questionnaires were administered. Visual photosensitivity threshold was measured subjectively using the ocular photosensitivity analyser. Objective photosensitivity luminance was assessed manually by evaluating videos recorded using an infrared camera and noting the intensity of light at the first squeezing reflex.

RESULTS

Seventy five normal subjects (age range, 7-71 years) were included. Median age was 32.7 years (inter-quartile range, 20.3-47.9 years). Forty (53.3%) were males. Median Headache Impact Test score was 38 (inter-quartile range, 36-42) and visual light sensitivity questionnaire score was 11 (inter-quartile range, 8-15). Mean (standard deviation) right eye, left eye and binocular visual photosensitivity threshold was 3.34 (0.78), 3.33 (0.81) and 3.37 (0.78) loglux, respectively. There was a significant negative correlation of visual light sensitivity questionnaire scores with right eye, left eye and binocular visual photosensitivity thresholds, and positive correlation of age with binocular visual photosensitivity thresholds. Mean (standard deviation) right eye, left eye and binocular objective photosensitivity luminance was 3.25 (0.55), 3.35 (0.47) and 3.15 (0.52) loglux, respectively. Age was only positively correlated with binocular objective photosensitivity luminance, and there was no correlation between age and right eye or left eye objective photosensitivity luminance.

CONCLUSIONS

The study characterised, for the first time, objective photosensitivity luminance and established normative data for both visual photosensitivity threshold and objective photosensitivity luminance. The data will help in understanding the pathophysiology of diseases causing photophobia, monitoring the disease progression and evaluating treatment modalities.

Monitoring the depth of palliative sedation by video-pupillometry: A case report

BACKGROUND

Palliative sedation is sometimes interrupted by undesired arousals. Pupillometry has been used in anesthesiology to monitor pain and sedation but has never been used during palliative sedation.

ACTUAL CASE

A 48 years-old patient, with multi-metastatic cancer, underwent palliative sedation to manage global suffering. On the second day, the patient experienced arousal which required medication adjustments to ensure pain relief and increased sedation.

POSSIBLE COURSE OF ACTION

Depth of sedation is monitored with clinical scales, such as the Richmond Agitation-Sedation Scale. But these scales do not measure brain stem activity and are poor at predicting arousal.

FORMULATION OF A PLAN

During palliative sedation, an infrared pupillometer was used to monitor pupil size and pupillary reactivity (Neurolight^®, IDMed^®, Marseille, France).

OUTCOME

The pupillary light reflex was depressed during deep sedation. In our case, we observed a low-normal reflex along with dilated pupil before arousal.

LESSONS FROM THE CASE

Our case suggests that reflex intensity and pupil size might predict arousals during palliative sedation.

VIEW ON RESEARCH PROBLEMS, OBJECTIVES, OR QUESTIONS GENERATED BY THE CASE

Prospective studies are needed to confirm our findings. Pupillometry's acceptability should also be questioned from patient's, families', and caregivers' perspectives.

Effect of Yogasanas Versus Gaze Stability and Habituation Exercises on Dizziness in Vestibular Dysfunction

Background

Dizziness is a typical manifestation of vestibular pathologies. Clinical studies have shown that it affects 1.82% of young adults to more than 30% older adults. Habituation and compensation are some traditional rehabilitation protocols.

Objective

Yoga is also known to have a significant effect on vestibulopathy. Hence, a need arises to compare the above two maneuvers.

Materials and Methods

Participants were recruited (n = 32) after screening using the Dix-Hallpike and head impulse test. They were then divided into two groups (n = 16). The first one, Group A, received yogasanas, and the second one, Group B, received gaze stabilization and habituation exercises for 4 days a week for 3 weeks. Pre- and post intervention outcome measures were taken using the motion sensitivity quotient (MSQ) score and Dizziness Handicap Inventory (DHI) scale.

Results

In reducing symptoms of dizziness, the between-group comparison shows that Group A has shown greater improvement (12.37% ±1.43%) in MSQ and Group B has shown greater improvement (16.12 ± 3.56) in DHI. Within-group comparison shows that both the interventions are effective in reducing symptoms of dizziness (P < 0.05).

Conclusion

Both gaze stabilization along with habituation exercises and yogasanas are effective in improving the symptoms of dizziness in patients with peripheral vestibular dysfunction. When compared between the groups, yogasanas had a superior hand in the MSQ score, whereas gaze stabilization and habituation exercises had a superior hand in the DHI scale.

Utility of Cough Provocation Tests in Chronic Cough and Respiratory Diseases: A Comprehensive Review and Introduction of New Reference Ranges for the Capsaicin Test

Cough provocation tests (CPTs) are an objective measurement of the sensitivity of the cough reflex arc. However, they are not established in clinical practice because a large variability of response in healthy subjects limits their diagnostic value. There is a paucity of studies that have investigated CPT reference ranges in healthy subjects. This systematic review describes the variability of the responses to CPTs in healthy subjects and factors that influence it. A new analysis of 134 healthy subjects was conducted to create reference ranges for single-breath capsaicin CPT by calculating the interquartile ranges for the provocative concentration of capsaicin to induce 2 and 5 coughs. Female subjects had a more sensitive cough reflex than male counterparts. The ability of CPTs to distinguish various respiratory diseases from healthy subjects was also reviewed. Cough sensitivity was consistently heightened in the following groups: unselected patients with chronic, refractory, or recurrent cough, unexplained chronic cough, gastro-esophageal reflux-associated cough, cough-variant asthma, lower airway symptoms induced by chemical irritants, and fibrotic interstitial lung diseases. In the following groups, hypersensitivity of the cough reflex was present in those individuals whose symptom profile was predominated by cough: asthma, chronic obstructive pulmonary disease (COPD), bronchiectasis, and sarcoidosis. In the following conditions, patients usually cough in order to expectorate mucus from their airways, not because of a hypersensitive cough reflex arc: productive cough, asthma, upper airway cough syndrome, COPD, bronchiectasis, cystic fibrosis, and chronic respiratory infections. CPTs have the potential to identify patients with chronic respiratory symptoms due to cough reflex hypersensitivity, thereby providing a targeted approach for therapy.

Trunk Angle Modulates Feedforward and Feedback Control during Single-Limb Squatting

Trunk positioning and unexpected perturbations are high-risk conditions at the time of anterior cruciate ligament injury. The influence of trunk positioning on motor control responses to perturbation during dynamic performance is not known. We tested the influence of trunk position on feedforward and feedback control during unexpected perturbations while performing a novel single-limb squatting task. We also assessed the degree that feedforward control was predictive of feedback responses. In the flexed trunk condition, there were increased quadriceps (p < 0.026) and gluteus medius long-latency reflexes (p < 0.001) and greater quadriceps-to-hamstrings co-contraction during feedforward (p = 0.017) and feedback (p = 0.007) time bins. Soleus long-latency reflexes increased more than 100% from feedforward muscle activity regardless of trunk condition. Feedforward muscle activity differentially predicted long-latency reflex responses depending on the muscle (R²: 0.47-0.97). These findings support the concept that trunk positioning influences motor control responses to perturbation and that feedback responses may be invariant to the feedforward control strategy.

Duodenal and proximal jejunal motility inhibition associated with bisacodyl-induced colonic high-amplitude propagating contractions

Bisacodyl is a stimulant laxative often used in manometric studies of pediatric constipation to determine if it can initiate propulsive high-amplitude propagating contractions (HAPCs). Whereas the effects of bisacodyl infusion on colonic motility are well described, the effects of the drug on other regions of the gut after colonic infusion are not known. The aim of the present study was to characterize the effects of bisacodyl on both colonic and small bowel motility. Twenty-seven children (9.3 ± 1.2 yr) undergoing simultaneous high-resolution antroduodenal and colonic manometry were included. Small bowel and colonic motor patterns were assessed before and after colonic infusion of bisacodyl. Patients were divided into two groups: responders and nonresponders based on the presence of high-amplitude propagating contractions (HAPCs) after bisacodyl infusion. Nineteen patients were responders. A total of 188 postbisacodyl HAPCs was identified with a mean count of 10.4 ± 5.5 (range, 3-22), at a frequency of 0.6 ± 0.2/min and mean amplitude of 119.8 ± 23.6 mmHg. No motor patterns were induced in the small bowel. However, in the 19 responders the onset of HAPCs was associated with a significant decrease in small bowel contractile activity. In the nonresponders, there was no detectable change in small bowel motility after bisacodyl infusion. Bisacodyl-induced HAPCs are associated with a significant reduction in small bowel motility probably mediated by extrinsic sympathetic reflex pathways. This inhibition is potentially related to rectal distension, caused by the HAPC anal propulsion of colonic content.NEW & NOTEWORTHY The present study has shown, for the first time, that the presence of high-amplitude propagating contractions induced by bisacodyl is associated with a significant reduction in small bowel motility. These findings support of possible existence of a reflex pathway that causes inhibition of small bowel motility in response to rectal distension.

Implementation of SARS-CoV2 Screening in K-12 Schools Using In-School Pooled Molecular Testing and Deconvolution by Rapid Antigen Test

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV2) testing is one component of a multilayered mitigation strategy to enable safe in-person school attendance for the K-12 school population. However, costs, logistics, and uncertainty about effectiveness are potential barriers to implementation. We assessed early data from the Massachusetts K-12 public school pooled SARS-CoV2 testing program, which incorporates two novel design elements: in-school "pod pooling" for assembling pools of dry anterior nasal swabs from 5 to 10 individuals and positive pool deconvolution using the BinaxNOW antigen rapid diagnostic test (Ag RDT), to assess the operational and analytical feasibility of this approach. Over 3 months, 187,597 individual swabs were tested across 39,297 pools from 738 schools. The pool positivity rate was 0.8%; 98.2% of pools tested negative and 0.2% inconclusive, and 0.8% of pools submitted could not be tested. Of 310 positive pools, 70.6% had an N1 or N2 probe cycle threshold (C_T) value of ≤30. In reflex testing (performed on specimens newly collected from members of the positive pool), 92.5% of fully deconvoluted pools with an N1 or N2 target C_T of ≤30 identified a positive individual using the BinaxNOW test performed 1 to 3 days later. However, of 124 positive pools with full reflex testing data available for analysis, 32 (25.8%) of BinaxNOW pool deconvolution testing attempts did not identify a positive individual, requiring additional reflex testing. With sufficient staffing support and low pool positivity rates, pooled sample collection and reflex testing were feasible for schools. These early program findings confirm that screening for K-12 students and staff is achievable at scale with a scheme that incorporates in-school pooling, primary testing by reverse transcription-PCR (RT-PCR), and Ag RDT reflex/deconvolution testing.

Altered Vestibular Balance Function in Combat Sport Athletes

Combat sports pose a risk for accumulative injuries to the nervous system, yet fighters have remained an understudied population. Here, our purpose was to determine whether repetitive blows to the head have an effect on vestibular balance reflexes in combat sports athletes. We compared lower-limb muscle responses evoked with electrical vestibular stimuluation (EVS) between fighters (boxing/muay thai) and non-fighter controls. Each participant received stochastic vestibular stimulation (0-25 Hz, ±3 mA) over their mastoid processes while they stood relaxed with their head to the left or right. Surface electromyography was recorded from the medial gastrocnemius and soleus muscles bilaterally. Short and medium latency response (SLR/MLR) peaks were significantly delayed in the fighter group compared to controls. SLR and MLR peak amplitudes were also significantly lower in fighters. Fighter-estimated cumulative repetitive head impact (RHI) events demonstrated strong positive correlations with the timing of SLR and MLR peaks. Cumulative RHI events also negatively correlated with peak MLR amplitude and response gain at frequencies above 5 Hz. Our results provide evidence of a progressive vestibular impairment in combat sports athletes, potentially resulting from blows to the head accumulated in sparring practice and competitive bouts throughout their careers. Taken together, EVS-based vestibular assessments may provide a valuable clinical diagnostic tool and help better inform "return-to-play" and career-length decisions for not only combat sports athletes, but potentially other populations at risk of RHIs.

Reflex Epilepsy

Reflex seizures (RS) are epileptic events that are objectively and consistently elicited in response to a specific afferent stimulus or by an activity of the patient. The specific stimulus can be a variety of heterogenous intrinsic or extrinsic factors, ranging from the simple to the complex, such as flashing lights or reading a book. These seizures can take a variety of forms, comprising either general or focal onset, with or without secondary generalization. Reflex epilepsies (RE) are classified as a specific syndrome in which all epileptic seizures are precipitated by sensory stimuli. The few designated RE include idiopathic photosensitive occipital lobe epilepsy, other visual sensitive epilepsies, primary reading epilepsy, and startle epilepsy. RS that occurs within other focal or generalized epilepsy syndromes that are associated with distinct spontaneous seizures are classified by the overarching seizure type. Most patients experience spontaneous seizures along with their provoked events. RS originate from stimulation of functional anatomic networks normally functioning for physiological activities, that overlap or coincide with regions of cortical hyperexcitability. Generalized RS typically occur within the setting of IGEs and should be considered as focal seizures with quick secondary generalization via cortico-cortical or cortico-reticular pathways. In aggregate, activation of a critical neuronal mass, supported and sustained by cortico-subcortical and thalamocortical pathways eventually result in a seizure. Treatment includes antiseizure medication, commonly valproate or levetiracetam, along with lifestyle modifications, and when amenable, surgical intervention. High clinical suspicion and careful history taking must be employed in all epilepsy patients to identify reflex triggers.

Selectivity and excitability of upper-limb muscle activation during cervical transcutaneous spinal cord stimulation in humans

Cervical transcutaneous spinal cord stimulation (tSCS) efficacy for rehabilitation of upper-limb motor function was suggested to depend on recruitment of Ia afferents. However, selectivity and excitability of motor activation with different electrode configurations remain unclear. In this study, activation of upper-limb motor pools was examined with different cathode and anode configurations during cervical tSCS in 10 able-bodied individuals. Muscle responses were measured from six upper-limb muscles simultaneously. First, postactivation depression was confirmed with tSCS paired pulses (50-ms interval) for each cathode configuration (C6, C7, and T1 vertebral levels), with anode on the anterior neck. Selectivity and excitability of activation of the upper-limb motor pools were examined by comparing the recruitment curves (10-100 mA) of first evoked responses across muscles and cathode configurations. Our results showed that hand muscles were preferentially activated when the cathode was placed over T1 compared with the other vertebral levels, whereas there was no selectivity for proximal arm muscles. Furthermore, higher stimulation intensities were required to activate distal hand muscles than proximal arm muscles, suggesting different excitability thresholds between muscles. In a separate protocol, responses were compared between anode configurations (anterior neck, shoulders, iliac crests, and back), with one selected cathode configuration. The level of discomfort was also assessed. Largest muscle responses were elicited with the anode configuration over the anterior neck, whereas there were no differences in the discomfort. Our results therefore inform methodological considerations for electrode configuration to help optimize recruitment of Ia afferents during cervical tSCS.NEW & NOTEWORTHY We examined selectivity and excitability of motor activation in multiple upper-limb muscles during cervical transcutaneous spinal cord stimulation with different cathode and anode configurations. Hand muscles were more activated when the cathode was configured over the T1 vertebra compared with C6 and C7 locations. Higher stimulation intensities were required to activate distal hand muscles than proximal arm muscles. Finally, configuration of anode over anterior neck elicited larger responses compared with other configurations.

Potential Pain in Fish and Decapods: Similar Experimental Approaches and Similar Results

I review studies that examined the possibility of pain experience in fish and note how they provided guidance on general methods that could be applied to other animals such as decapod crustaceans. The fish studies initially reported the occurrence of prolonged rocking movements in trout and rubbing of their lips if they were injected with acetic acid. Subsequent studies examined the role of morphine in reducing these activities and examined shifts in attention when responding to noxious stimuli. Various studies take up these themes in decapods. The results reported for the two taxonomic groups are remarkably similar and indicate that responses of both go beyond those expected of mere nociceptive reflex. Thus, the idea of pain cannot be dismissed by the argument that fish and decapods respond only by reflex. The responses of both clearly involve central processing, and pain experience, although not proven for either, is a distinct possibility. These studies have been the subjects of highly critical opinion pieces and these are examined and rebutted. The conclusion is that both fish and decapods should be awarded consideration for their welfare.

A direct injection technique for investigation of lung sensory properties and reflex functions

NEW FINDINGS

This article reviews a unique direct injection technique that complements the more conventional right atrial injection and aerosol delivery methods to study sensory and reflex effects of the lung sensors. Used in combination with other methods, this technique should contribute to the pulmonary sensory research.

ABSTRACT

The lungs house sensory receptors (sensors) that mediate a variety of sensory and reflex responses to mechanical or chemical changes. These reflexes are mainly carried through pulmonary sympathetic and vagal afferent pathways. The chemosensors in the lung periphery are especially important in pulmonary diseases and their reflex responses have traditionally been studied either by aerosol delivery, which also activates receptors in the central airways, or by right atrial injection, which also activates receptors lying outside the lung. Thus, these techniques may confound the interpretation of sensory function. Our laboratory has developed a direct injection technique to deliver agents into the lung parenchyma, which complements the conventional techniques with some important advantages. This article reviews the technique.

A Smart Tendon Hammer System for Remote Neurological Examination

The deep tendon reflex exam is an important part of neurological assessment of patients consisting of two components, reflex elicitation and reflex grading. While this exam has traditionally been performed in person, with trained clinicians both eliciting and grading the reflex, this work seeks to enable the exam by novices. The COVID-19 pandemic has motivated greater utilization of telemedicine and other remote healthcare delivery tools. A smart tendon hammer capable of streaming acceleration measurements wirelessly allows differentiation of correct and incorrect tapping locations with 91.5% accuracy to provide feedback to users about the appropriateness of stimulation, enabling reflex elicitation by laypeople, while survey results demonstrate that novices are reasonably able to grade reflex responses. Novice reflex grading demonstrates adequate performance with a mean error of 0.2 points on a five point scale. This work shows that by assisting in the reflex elicitation component of the reflex exam via a smart hammer and feedback application, novices should be able to complete the reflex exam remotely, filling a critical gap in neurological care during the COVID-19 pandemic.

Stepping onto the unknown: reflexes of the foot and ankle while stepping with perturbed perceptions of terrain

Unanticipated variations in terrain can destabilize the body. The foot is the primary interface with the ground and we know that cutaneous reflexes provide important sensory feedback. However, little is known about the contribution of stretch reflexes from the muscles within the foot to upright stability. We used intramuscular electromyography measurements of the foot muscles flexor digitorum brevis (FDB) and abductor hallucis (AH) to show for the first time how their short-latency stretch reflex response (SLR) may play an important role in responding to stepping perturbations. The SLR of FDB and AH was highest for downwards steps and lowest for upwards steps, with the response amplitude for level and compliant steps in between. When the type of terrain was unknown or unexpected to the participant, the SLR of AH and the ankle muscle soleus tended to decrease. We found significant relationships between the contact kinematics and forces of the leg and the SLR, but a person's expectation still had significant effects even after accounting for these relationships. Motor control models of short-latency body stabilization should not only include local muscle dynamics, but also predictions of terrain based on higher level information such as from vision or memory.

Spinal stretch reflexes support efficient control of reaching

Efficiently controlling the movement of our hand requires coordinating the motion of multiple joints of the arm. Although it is widely assumed that this type of efficient control is implemented by processing that occurs in the cerebral cortex and brainstem, recent work has shown that spinal circuits can generate efficient motor output that supports keeping the hand in a static location. Here, we show that a spinal pathway can also efficiently control the hand during reaching. In our first experiment, we applied multijoint mechanical perturbations to participants' elbow and wrist as they began reaching toward a target. We found that spinal stretch reflexes evoked in elbow muscles were not proportional to how much the elbow muscles were stretched but instead were dependent on the hand's location relative to the target. In our second experiment, we applied the same elbow and wrist perturbations but had participants change how they grasped the manipulandum, diametrically altering how the same wrist perturbation moved the hand relative to the reach target. We found that changing the arm's orientation diametrically altered how spinal reflexes in the elbow muscles were evoked, and in such a way that were again dependent on the hand's location relative to the target. These findings demonstrate that spinal circuits can help efficiently control the hand during dynamic reaching actions and show that efficient and flexible motor control is not exclusively dependent on processing that occurs within supraspinal regions of the nervous system.NEW & NOTEWORTHY We have previously shown that spinal circuits can rapidly generate reflex responses that efficiently engage multiple joints to support postural hand control of the upper limb. Here, we show that spinal circuits can also rapidly generate such efficient responses during reaching actions.

Characteristics of the severely impaired hand in survivors of stroke with chronic impairments

Background: Diminished sensorimotor control of the hand is one of the most common outcomes following stroke. This hand impairment substantially impacts overall function and quality of life; standard therapy often results in limited improvement. Mechanisms of dysfunction of the severely impaired post-stroke hand are still incompletely understood, thereby impeding the development of new targeted treatments.Objective: To identify and determine potential relationships among the mechanisms responsible for hand impairment following strokeMethods: This cohort study observed stroke survivors (n = 95) with severe, chronic hand impairment (Chedoke-McMaster Hand score = 2-3). Custom instrumentation created precise perturbations and measured kinematic responses. Muscle activation was recorded through electromyography. Strength, spasticity, muscle relaxation time, and muscle coactivation were quantified.Results: Maximum grip strength in the paretic hand was only 12% of that achieved by the nonparetic hand, and only 6 of 95 participants were able to produce any net extension force. Despite force deficits, spastic reflex response of the finger flexor evoked by imposed stretch averaged 90.1 ± 26.8% of maximum voluntary activation, relaxation time averaged 3.8 ± 0.8 seconds, and coactivation during voluntary extension exceeded 30% of maximum contraction, thereby resulting in substantial net flexion. Surprisingly, these hypertonicity measures were not significantly correlated with each other.Conclusions: Survivors of severe, chronic hemiparetic stroke experience profound weakness of both flexion and extension that arises from increased involuntary antagonist activation and decreased voluntary activation. The lack of correlation amongst hypertonicity measures suggests that these phenomena may arise from multiple, potentially independent mechanisms that could require different treatments.

Inhibition and facilitation of nociceptively evoked muscular activity by fentanyl or dexmedetomidine in isoflurane-anaesthetized pigs

OBJECTIVE

To investigate motor and cardiovascular responses to dexmedetomidine or fentanyl in isoflurane-anaesthetized pigs.

STUDY DESIGN

Experimental, balanced, block randomized, two-group design.

ANIMALS

A group of 16 crossbred pigs, 55 ± 8 days (mean ± standard deviation) old.

METHODS

Deltoid electromyography (EMG) was recorded during isoflurane anaesthesia. Electrical stimulation using 5, 10, 20 and 40 mA of the distal right thoracic limb elicited a nociceptive withdrawal reflex (NWR), quantified by the area under the curve (AUC) for the simulation intensity versus EMG amplitude response curve. Latency to movement evoked by clamping a claw for maximum 60 seconds was noted. Arterial blood pressure and pulse rate were recorded. Data were sampled at baseline and during dexmedetomidine 0.25, 0.5, 1.0, 2.0, 4.0 and 8.0 μg kg^-1 hour^-1 or fentanyl 5, 10, 20, 40, 80 and 160 μg kg^-1 hour^-1 infusions. The influence of infusion rate on NWR AUC and spontaneous EMG was analysed using a mixed model, with p < 5%.

RESULTS

NWR AUC increased at fentanyl 5 μg kg^-1 hour^-1 but decreased at fentanyl 40, 80 and 160 μg kg^-1 hour^-1 and dexmedetomidine 4.0 and 8.0 μg kg^-1 hour^-1. All pigs at fentanyl 80 μg kg^-1 hour^-1, and three pigs at dexmedetomidine 8.0 μg kg^-1 hour^-1 had mechanical latencies greater than 60 seconds. Spontaneous EMG activity increased accompanied by visually evident 'shivering' at fentanyl 5, 10 and 20 μg kg^-1 hour^-1 but decreased at dexmedetomidine 2, 4 and 8 μg kg^-1 hour^-1. Clinically relevant effects of increasing infusion rates on blood pressure or pulse rate were not observed.

CONCLUSION AND CLINICAL RELEVANCE

If anaesthetic plane or antinociception is evaluated in pigs, response to claw clamping and NWR will not necessarily give uniform results when comparing drugs. If only one method is used, results should be interpreted cautiously.

Conditioned Variation in Heart Rate During Static Breath-Holds in the Bottlenose Dolphin (Tursiops truncatus)

Previous reports suggested the existence of direct somatic motor control over heart rate (f H) responses during diving in some marine mammals, as the result of a cognitive and/or learning process rather than being a reflexive response. This would be beneficial for O2 storage management, but would also allow ventilation-perfusion matching for selective gas exchange, where O2 and CO2 can be exchanged with minimal exchange of N2. Such a mechanism explains how air breathing marine vertebrates avoid diving related gas bubble formation during repeated dives, and how stress could interrupt this mechanism and cause excessive N2 exchange. To investigate the conditioned response, we measured the f H-response before and during static breath-holds in three bottlenose dolphins (Tursiops truncatus) when shown a visual symbol to perform either a long (LONG) or short (SHORT) breath-hold, or during a spontaneous breath-hold without a symbol (NS). The average f H (if Hstart), and the rate of change in f H (dif H/dt) during the first 20 s of the breath-hold differed between breath-hold types. In addition, the minimum instantaneous f H (if Hmin), and the average instantaneous f H during the last 10 s (if Hend) also differed between breath-hold types. The dif H/dt was greater, and the if Hstart, if Hmin, and if Hend were lower during a LONG as compared with either a SHORT, or an NS breath-hold (P < 0.05). Even though the NS breath-hold dives were longer in duration as compared with SHORT breath-hold dives, the dif H/dt was greater and the if Hstart, if Hmin, and if Hend were lower during the latter (P < 0.05). In addition, when the dolphin determined the breath-hold duration (NS), the f H was more variable within and between individuals and trials, suggesting a conditioned capacity to adjust the f H-response. These results suggest that dolphins have the capacity to selectively alter the f H-response during diving and provide evidence for significant cardiovascular plasticity in dolphins.

Time-of-Day-Dependent Gating of the Liver-Spinal Axis Initiates an Anti-Inflammatory Reflex in the Rat

The autonomic nervous system (ANS) modulates the immune response through the engagement of an anti-inflammatory reflex. There is controversy regarding which efferent branch of the ANS, sympathetic or parasympathetic, downregulates the intensity of the inflammatory response. Furthermore, how information about the immune status of the body reaches the CNS to engage this reflex remains unclear. The present study demonstrates the existence of a liver-spinal axis that conveys early circulating inflammatory information to the CNS in response to lipopolysaccharide (LPS) and serves as the afferent arm of a sympathetic anti-inflammatory reflex. Furthermore, brainstem and spinal cord visceral sensory neurons show a time-of-day-dependent sensitivity to the incoming inflammatory information, in particular, prostaglandins (PG). Consequentially, the liver-spinal axis promotes the retention of tumor necrosis factor α (TNFα) in the liver and spleen during the resting period, resulting in low plasmatic TNFα levels. Consistently, low sensitivity for LPS during the active period promotes the release of TNFα from the organs into the circulation, resulting in high plasmatic TNFα levels. The present novel findings illustrate how the time-of-day-dependent activation of the liver-spinal axis contributes to the daily fluctuations of the inflammatory response.

Air Pollution-Induced Autonomic Modulation

Air pollutants pose a serious worldwide health hazard, causing respiratory and cardiovascular morbidity and mortality. Pollutants perturb the autonomic nervous system, whose function is critical to cardiopulmonary homeostasis. Recent studies suggest that pollutants can stimulate defensive sensory nerves within the cardiopulmonary system, thus providing a possible mechanism for pollutant-induced autonomic dysfunction. A better understanding of the mechanisms involved would likely improve the management and treatment of pollution-related disease.

EMG-Free Monitorization of the Acoustic Startle Reflex with a Mobile Phone: Implications of Sound Parameters with Posture Related Responses

(1) Background: Acute acoustic (sound) stimulus prompts a state of defensive motivation in which unconscious muscle responses are markedly enhanced in humans. The orbicularis oculi (OO) of the eye is an easily accessed muscle common for acoustic startle reaction/response/reflex (ASR) investigations and is the muscle of interest in this study. Although the ASR can provide insights about numerous clinical conditions, existing methodologies (Electromyogram, EMG) limit the usability of the method in real clinical conditions. (2) Objective: With EMG-free muscle recording in mind, our primary aim was to identify and investigate potential correlations in the responses of individual and cooperative OO muscles to various acoustic stimuli using a mobile and wire-free system. Our secondary aim was to investigate potential altered responses to high and also relatively low intensity acoustics at different frequencies in both sitting and standing positions through the use of biaural sound induction and video diagnostic techniques and software. (3) Methods: This study used a mobile-phone acoustic startle response monitoring system application to collect blink amplitude and velocity data on healthy males, aged 18–28 community cohorts during (n = 30) in both sitting and standing postures. The iPhone X application delivers specific sound parameters and detects blinking responses to acoustic stimulus (in millisecond resolution) to study the responses of the blinking reflex to acoustic sounds in standing and sitting positions by using multiple acoustic test sets of different frequencies and amplitudes introduced as acute sound stimuli (<0.5 s). The single acoustic battery of 15 pure-square wave sounds consisted of frequencies and amplitudes between 500, 1000, 2000, 3000, and 4000 Hz scales using 65, 90, and 105 dB (e.g., 3000 Hz_90 dB). (4) Results: Results show that there was a synchronization of amplitude and velocity between both eyes to all acoustic startles. Significant differences (p = 0.01) in blinking reaction time between sitting vs. standing at the high intensity (105 dB) 500 Hz acoustic test set was discovered. Interestingly, a highly significant difference (p < 0.001) in response times between test sets 500 Hz_105 dB and 4000 Hz_105 dB was identified. (5) Conclusions: To our knowledge, this is the first mobile phone-based acoustic battery used to detect and report significant ASR responses to specific frequencies and amplitudes of sound stimulus with corresponding sitting and standing conditions. The results from this experiment indicate the potential significance of using the specific frequency, amplitude, and postural conditions (as never before identified) which can open new horizons for ASR to be used for diagnosis and monitoring in numerous clinical and remote or isolated conditions.