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PubMedDate not supplied

Spinal reflex excitability changes after cervical and lumbar spinal manipulation: a comparative study.

BACKGROUND CONTEXT: Spinal manipulation (SM) is a commonly employed nonoperative treatment modality in the management of patients with neck, low back or pelvic pain. One basic physiologic response to SM is a transient decrease in motoneuron activity as assessed using the Hoffmann reflex (H-reflex) technique. Previous research from our laboratory indicates that both SM with a high-velocity, low-amplitude thrust and mobilization without thrust produced a profound but transient attenuation of motoneuronal activity of the lumbosacral spine in asymptomatic subjects. To date, effects of cervical SM procedures on the excitability cervical motoneuron pools are unknown. PURPOSE: The objective of this research was to a gain a more complete understanding of the physiologic effects of SM procedures on motoneuron activity, by comparing the effects of regional SM on cervical and lumbar motoneuron pool excitability. STUDY DESIGN/SETTING: Maximal H-reflex amplitudes were recorded before and after SM in both the cervical and lumbar regions of asymptomatic subjects in two successive experimental sessions. PATIENT SAMPLE: Asymptomatic, young healthy volunteers were used in this study. OUTCOME MEASURES: Changes in flexor carpi radialis and gastrocnemius H-reflex amplitudes before and after SM procedures. METHODS: H-reflexes recorded form the tibial and median nerves were evaluated before and after lumbar and cervical SM, respectively. RESULTS: Both Lumbar and cervical SM produced a transient but significant attenuation of motoneuron excitability. The attenuation of the tibial nerve H-reflex amplitude was proportionately greater than that of the median nerve, which occurred after cervical SM. CONCLUSIONS: SM procedures lead to transient suppression of motoneuron excitability, as assessed by the H-reflex technique. Lumbar spine SM appears to lead to greater attenuation of motoneuron activity compared with that of the cervical region. Thus, these two distinct regions of the spine may possess different responsiveness levels to spinal manipulative therapy.

Adult↗
PubMed2003

MK-801 inhibits the micturition reflex in chronic bladder irritation caused by crystalluria in the rat.

Urodynamic and pharmacological studies were performed to investigate the effect of crystalluria on the micturition reflex and the involvement of glutamatergic transmission. The rats, which were given LP-805 (100 mg/kg/day) orally for 12 days, voided crystalluria. The pH of these crystalluria (LP-805 urine) was the same as normal urine. The amount of crystals was 70-100/division magnified 400 x. The end of the crystals was sharp. Intravesical administration of LP-805 urine induced hyperreflexia of the micturition reflex in normal rats. When the infusion solution was changed to LP-805 urine from saline, the latency was reduced to 57.6+/-2.1% of control in single cystometrogram (CMG) or was reduced to 51.4+/-0.9% of control in continuous CMG. The voiding volume was reduced to 52.1+/-3.6% of control in single CMG or was reduced to 62.5+/-0.8% of control in continuous CMG. These parameters were recovered after LP-805 urine was removed. Intravesical administration of acetic acid did not induce hyperreflexia of the micturition reflex in LP-805-treated rats. These data suggest that the chronic irritation by aculeate crystals might induce hyperreflexia of the micturition reflex, which increase afferent neuronal activity. Intravenous administration of MK-801 (0.001 to 1 mg/kg) inhibited the micturition reflex in a dose-dependent manner. The ID50 in LP-805-treated rats (0.03 mg/kg i.v.) was lower than that in normal rats (0.56 mg/kg i.v.). After chronic irritation of the bladder epithelium, MK-801 sensitivity was enhanced for the micturition reflex. These data suggested that crystalluria elicit hyperreflexia in the micturition reflex that mediated with NMDA glutamatergic receptors.

Animals↗
PubMed1980

The stapedius reflex in idiopathic facial palsy.

Various aspects of the stapedial reflex responses and facial palsy were investigated. In the first study the initial reflex responses following facial palsy in 120 patients were compared with the outcome. In 42 patients with a present stapedial reflex, the full recovery rate was 92 per cent as compared to 78 patients with an absent stapedial reflex and a full recovery rate of 73 per cent. Twenty-five patients with facial palsy and absent stapedial reflex were followed up. In 21 patients (84 per cent) the return of a positive stapedial reflex was the first sign of recovery, and it preceded any other evidence of recovery by 6 weeks. The third study showed that the stapedial reflex does not participate in the synkinetic movement of post-paralytic patients.

Facial Paralysis↗
PubMed2001

Influence of methodological parameters on human jaw-stretch reflexes.

The influence of methodological parameters and experimental conditions on the human jaw-stretch reflex was studied in healthy subjects in order to develop a reliable tool for investigation of the excitability of motoneuron pool. Short-latency excitatory reflex responses were evoked by a custom-made stretch device with the subjects biting on a jaw-bar with their front teeth. The displacement and ramp time of the stretches were accurately controlled and automatically triggered by a computer. The reflex responses were measured in the surface electromyogram (EMG) of the masseter and anterior temporalis muscles with online monitoring of the clenching level. The peak-to-peak amplitude of the jaw-stretch reflex was shown to be proportional to the level of EMG activity during isometric contractions, to increase proportionally with increasing stretch displacement at a given ramp time, and to decrease proportionally with increasing ramp time at a given stretch displacement. There were no significant differences in the reflex amplitude between repeated recordings within one session or between different sessions. Local anesthetic around the lower incisors as well as the upper incisors had no significant influence on the reflex amplitude. However, different biting positions on the bars of the stretch device significantly influenced the amplitude of the stretch reflex.

Adult↗
PubMed1985

Grooming reflexes and Brown-Séquard epilepsy in cats with pontile lesions.

The literature on the relation between the scratch reflex and Brown-Séquard epilepsy in the guinea pig indicates that the scratch reflex is a stimulus-induced myoclonus that is the first component of a complete seizure. Cats with pontile lesions and cats with frontal neocortical lesions exhibit the scratch reflex and other grooming reflexes. The grooming reflexes in cats with pontile lesions develop over a period of a year or more into complete seizures that are similar to Brown-Séquard epilepsy as described for the guinea pig by Brown-Séquard and others. Cinematographic analyses revealed that the scratch reflex in cats with pontile lesions and in cats with frontal neocortical lesions has the same frequency and the same complex spatial and temporal pattern as normal scratching behavior. In addition, the myoclonus of the complete seizures is identified as the scratch reflex, representing a very vigorous and long-lasting afterdischarge. Reconstruction of the pontile lesions indicate that the lateral and rostral portions of the paralemniscal tegmental fields were destroyed along with portions of the pontile gray and pyramidal tract.

Animals↗
PubMed1980

Hypothetical spinal pacemaker regulating penile reflexes in rats: evidence from transection of spinal cord and dorsal penile nerves.

Male rats were given three weekly tests for penile reflexes, which were evoked from supine animals by extending, and then maintaining, the glans penis outside its sheath. Six days prior to Tests 2 and 3, five groups (n = 5--7) of males were subjected to spinal cord (SC) transection (at the ninth thoracic vertebra), dorsal penile nerve (DPN) transection, both operations (one after Test 1, the other after Test 2), or no surgery. Penile reflex potential was drastically depressed in males receiving DPN surgery after Test 1 and much enhanced in males in which the SC was cut. The depression in reflexes following DPN transection was reversed by subsequent SC transection. Conversely, SC transection prevented most of the depressive effects of subsequent DPN transection. It is inferred that (a) during the reflex latency of intact males, DPN-mediated tonic stimulation acts to reduce the suprasegmental inhibition of penile reflexes and (b) following the reduction in suprasegmental inhibition, whether functionally by DPN-mediated stimulation or surgically by spinal transection, a spinal pacemaker regulates the rate at which clusters of penile reflexes occur, irrespective of further DPN-mediated afference. The reflex pacemaker may also contribute to the pacing of the male's attempts to copulate, but the pacemaker must have considerable latitude for entrainment during copulation by stimuli extrinsic and intrinsic to the male.

Animals↗
PubMed1975

Anticipatory middle-ear reflex activity from noisy toys.

Middle-ear reflex activity was measured in 14 listeners in response to visual and acoustic exposure to each of seven noisy toys (such as a cap gun, party horn, cow bell, and so forth). Anticipatory middle-ear reflex (AMER) activity was a common occurrence. Normal middle-ear reflex generally occurred after the sound exposure. AMERs generally occurred in the two seconds prior to sound exposure but as early as 10 seconds before sound exposure. Loudness ratings and exposure SPLs were obtained. The presence of acoustically evoked middle-ear (ME) reflex activity and AMERs to the toys was generally unrelated to SPL or reflex threshold. Many reflex responses occurred in response to exposure SPLs below reflex threshold and with low anticipated loudness rating.

Auditory Perception↗
PubMed1996

Reflex responses of lip muscles in young and older women.

The perioral reflex in response to innocuous mechanical stimulation of the lip vermilion was studied in 20 young and 20 older women. Responses to stimuli at the right and left sides of both the upper and lower lips were recorded. Results show significant specificity of response, especially for upper lip sites. Reflex response at the site of stimulation was greatest in amplitude and shortest in latency, followed by response at sites ipsilateral to the site of stimulation. Younger subjects showed greater localizing tendency than older subjects. Stimulation was significantly less likely to produce a reflex response in the older group. When reflex responses did occur, they were significantly lower in amplitude and longer in latency than the responses of the younger group. Nonetheless, reflex responses were common in both groups, with responses at the site of stimulation occurring 78% of the time in older women and 90% of the time in younger women. Every participant showed at least one reflex response to lip stimulation. Results suggest decreasing complexity of synaptic drive to the perioral system in old age but also show that reflexive response does not deteriorate completely, remaining an available element for motor control in normal older women.

Adult↗
PubMed2001

Effects of heterotopic- and segmental counter-stimulation on the nociceptive withdrawal reflex in humans.

A nociceptive withdrawal reflex in 12 human volunteers was elicited by painful electrical stimulation applied to the cutaneous innervation area of the sural nerve. The evoked electromyographic reflex activities were recorded with surface electrodes placed on the short head of the biceps femoris muscle ipsi-lateral to sural nerve stimulation, before, during and after conditioning stimuli. The nociceptive withdrawal reflex was conditioned by nociceptive and non-nociceptive, heterotopic and segmental counter-stimulation. Heterotopic nociceptive counter-stimulation and segmental nociceptive counter-stimulation were induced by ice water applied to the contra-lateral hand and foot, respectively. Heterotopic nociceptive counter-stimulation produced a significant inhibition of the nociceptive withdrawal reflex and the associated pains rating to sural nerve stimulation. Segmental nociceptive counter-stimulation inhibited the pain rating and tended to inhibit the nociceptive withdrawal reflex. There was no obvious correlation between visual analogue scale (VAS) and the nociceptive withdrawal reflex elicited by sural nerve stimulation neither in the group nor in the individual subject. This suggests that the nociceptive withdrawal reflex cannot always be used as a quantitative measure of pain.

Adult↗
PubMed2000

Study of the effects of various transcutaneous electrical nerve stimulation (TENS) parameters upon the RIII nociceptive and H-reflexes in humans.

Despite over two decades of clinical use, the neurophysiological and anti-nociceptive effects of transcutaneous electrical nerve stimulation (TENS) have yet to be definitively described. The current study was designed to examine the effect of TENS on the RIII nociceptive reflex elicited in healthy human subjects; the H-reflex was measured concomitantly to monitor changes in alpha-motoneuron excitability. Following approval from the university's ethical committee, 50 healthy human volunteers (25 male and 25 female) participated in the study. The subjects ranged in age from 18 to 30 years (mean 22, SD 3). Subjects were randomly allocated equally to a control group or one of four TENS groups. In the TENS groups, stimulation was applied for a total of 15 min over the sural nerve in the left leg. Ipsilateral RIII and H-reflexes were recorded five times during the 45 min experimental period. In addition, subjects also rated pain associated with the RIII reflex using a computerized visual analogue scale (VAS). Statistical analysis using two-way repeated-measures ANOVA showed no differences between groups for H-reflex, RIII reflex nor VAS data. These results suggest that TENS does not significantly affect either of the two reflexes, at least using the parameters and application time in the current study.

Adolescent↗
PubMed1999

Modulation of jaw reflexes by remote noxious stimulation and mental state: possible association with psychological measurements of mental stress and occupation.

Combined electrophysiological and psychophysical experiments were performed on 15 human subjects to investigate the possible effects of perceived stress or mental occupation on jaw reflexes. Electromyographic recordings were made from the masseter and anterior temporalis muscles, of the series of excitatory and inhibitory reflexes evoked by tapping on an upper incisor tooth. The reflexes were modified by application of painful cold (3 degrees C) stimuli to the subject's hand (remote noxious stimulation) or by the subject undertaking mental exercises (the 17 times table). The resulting changes in the reflexes usually involved transient increases in EMG activity around the interfaces between successive inhibitory and excitatory responses. Both the remote noxious stimuli and the mental exercises usually produced increases in both stress and mental occupation as assessed using visual analogue scales. However, correlations between these psychological effects and the effects on the reflexes were generally weak or absent. We conclude that the modulation of jaw reflexes by remote noxious stimuli or mental activity is not likely to be dependent on an individual's conscious awareness of a change in mental state. On the other hand, data from a related study suggest that the effects on the reflex may be more closely related to the autonomic responses to stress.

Adult↗
PubMedDate not supplied

Acute effects of L- and T-type calcium channel antagonists on cardiovascular reflexes in conscious rabbits.

1. The effects of the relatively selective T-type voltage- operated calcium channel (VOCC) antagonist mibefradil were compared with verapamil, an L-type VOCC antagonist, on a range of autonomic reflexes in conscious rabbits. 2. Mean arterial pressure (MAP), heart rate (HR), the baroreceptor-HR reflex, postural adaptation reflex (90 degrees head-up tilt), Bezold-Jarisch-like reflex and the vasoconstrictor component of the nasopharyngeal reflex were assessed before and during i.v. infusion of vehicle (saline), mibefradil or verapamil. Doses of mibefradil that gave low (M1; 0.45 +/- 0.02 microg/mL) and high (M2; 0.93 +/- 0.05 microg/mL) plasma concentrations, or verapamil (0.059 +/- 0.004 microg/mL; n = 6 each) were chosen to mimic clinically observed therapeutic levels. 3. At steady state infusion over 30-90 min, MAP was significantly lower in M2 (- 7 mmHg) and verapamil (- 6 mm Hg) treatments, but only verapamil caused a significant tachycardia (+ 31 b.p.m.) compared with vehicle. Mibefradil (M2) and verapamil decreased the HR range of the baroreflex by 27 and 29%, respectively, but neither treatment affected the vagal or sympathetic constrictor components of the Bezold-Jarisch-like and nasopharyngeal reflexes, respectively. 4. In response to 90 degrees tilt, vehicle- and verapamil-treated rabbits responded with small rises in MAP of 4 +/- 2 and 8 +/- 2 mm Hg, respectively, 5 s into the upright posture, while M1 and M2 caused falls in MAP of 6 +/- 4 and 9 +/- 3 mm Hg, respectively, at 5 s. 5. Thus, both L- and T-type VOCC antagonists, at plasma concentrations in the clinical range, lowered MAP in the conscious rabbit, but only mibefradil caused postural hypotension. We conclude that T-type VOCC may play an important role in the venoconstrictor reflex in response to tilt in the rabbit.

Animals↗
PubMed1999

Sensorimotor transformation in cat nociceptive withdrawal reflex system.

The withdrawal reflex system of higher vertebrates has been extensively used as a model for spinal sensorimotor integration, nociceptive processing and plasticity. In the rat, the nociceptive withdrawal reflex system appears to have a modular organization. Each reflex module controls a single muscle or a few synergistic muscles, and its cutaneous receptive field corresponds to the skin area withdrawn upon contraction of the effector muscle(s) when the limb is in the standing position. This organization principle is at odds with the 'flexion reflex' concept postulated from cat studies. To assess the generality of the modular organization principle we have therefore re-examined the cutaneous input to the withdrawal reflex system of the cat. The cutaneous receptive fields of hindlimb and forelimb muscles were mapped using calibrated noxious pinch stimulation and electromyographic recording technique in barbiturate anaesthetized animals. The investigated muscles had specific cutaneous receptive fields that appeared to correspond to the area of the skin withdrawn upon contraction of the muscle when the limb is in the standing position. The spatial organization of receptive fields in the cat was similar to that in the rat. However, differences in gain properties of reflexes to some anatomically equivalent muscles in the two species were observed, possibly reflecting adaptations to the biomechanics characteristic of the digitigrade and plantigrade stance in cats and rats, respectively. Implications of the findings for the generality of the modular organization of the withdrawal reflex system and for its adaptive properties are discussed.

Animals↗
PubMed2003

Effects of ketamine on electroencephalographic and autonomic arousal and segmental reflex responses in the cat.

OBJECTIVE: To provide evidence concerning doses of ketamine that affect electroencephalographic (EEG) and autonomic signs of arousal during nociceptive stimulation. STUDY DESIGN: Prospective psychophysical test in people. Single injection or progressively increasing infusions of ketamine in cats. ANIMALS AND PEOPLE: Seven people (20-60 years old) and three cats (3-5 kg) for EEG recording and six cats for EMG recordings. METHODS: In order to define innocuous and nociceptive stimulus intensities which could be applied to cats to evaluate arousal, psychophysical evaluations of sensations elicited by compression of the skin overlying phalangeal bones of the hand were obtained from human subjects. Then, following administration of ketamine, recordings of EEG frequency and of autonomic responses (heart rate, respiratory rate and arterial blood pressure) were obtained before and during stimulation of the tails of cats at pressures identified by human observers as either innocuous or nociceptive. Observations of withdrawal reflexes of the hindlimbs following interdigital skin stimulation were interposed between recording periods. In separate sessions, stretch reflex activity was assessed during awake and anesthetic conditions by recording electromyographic activity from soleus muscles and resistive force to dorsiflexion of the tibiotarsal joint. RESULTS: There were no changes in either total EEG (0.5-30.0 Hz), low-frequency (0.6-7.5 Hz) or high-frequency (7.5-30.0 Hz) power produced by nociceptive stimulation for a period of 18-24 minutes following an intramuscular bolus dose of ketamine (33.0 mg kg-1), although withdrawal reflexes were present. Thereafter, nociceptive stimulation produced EEG arousal responses in the low-frequency and total power range and increased systolic blood pressure and respiration rate. In tests after intravenous infusion of ketamine (10.0-22.2 mg kg-1 hour-1), total and low-frequency EEG power and autonomic responses to nociceptive stimulation were eliminated. Organized motor responses were never elicited during IV infusion, but withdrawal reflexes were observed at each dosage. Also, stretch reflexes were shown by quantitative analysis to be retained at all doses of ketamine infusion. CONCLUSIONS AND CLINICAL RELEVANCE: These results show that testing of withdrawal reflexes does not reveal the adequacy of ketamine anesthesia. Segmental stretch and withdrawal reflexes are preserved and can be investigated during infusion of ketamine at doses that eliminate arousal from brief periods of nociceptive stimulation.

Adult↗
PubMed2000

Inhibition of the triceps surae stretch reflex by stimulation of the deep peroneal nerve in persons with spastic stroke.

OBJECTIVE: To reduce the triceps surae stretch reflex by electrical stimulation of the deep peroneal nerve. DESIGN: Intervention study. SETTING: Research institution. PARTICIPANTS: Sample of convenience of 10 spastic stroke individuals. INTERVENTION: After the deep peroneal nerve was stimulated between 0.9 and 4 times tibialis anterior motor threshold, the triceps surae was stretched to elicit a reflex. MAIN OUTCOME MEASURE: The triceps surae stretch reflex was quantified by the amplitude of the reflex electromyography (EMG) in soleus and medial gastrocnemius muscles and mean ankle moment. Paired t test and the Wilcoxon signed rank test (p < .05) were used to evaluate the effect of conditioning stimulation. RESULTS: The soleus stretch reflex EMG was reduced significantly (p < .001) by stimulating the deep peroneal nerve to 25%+/-6% (standard error) of the unconditioned value (relaxed triceps surae). The optimal interval between stimulation and stretch was 141+/-15 msec. The velocity threshold increased significantly (p = .006) from a median value of 8 degrees per second to 33 degrees per second and the area under the stretch velocity/stretch reflex relation decreased significantly (p < .001) (soleus EMG). CONCLUSIONS: The stretch reflex of relaxed triceps surae in persons with spastic stroke can be extensively reduced by stimulating the deep peroneal nerve at several times motor threshold of the tibialis anterior.

Aged↗
PubMed2002

Does wearing a functional knee brace affect hamstring reflex time in subjects with anterior cruciate ligament deficiency during muscle fatigue?

OBJECTIVE: To evaluate the effects of wearing a functional knee brace and muscle fatigue on hamstring reflex time in subjects with anterior cruciate ligament (ACL) deficiency. DESIGN: Repeated-measures clinical trial. SETTING: Outpatient physical therapy department. PARTICIPANTS: Sixteen subjects with ACL deficiency. INTERVENTION: Subjects tested with and without a functional knee brace before and after an exercise protocol designed to fatigue the knee muscles. MAIN OUTCOME MEASURE: Latency of hamstring reflex muscle activity after sudden perturbation of the knee. RESULTS: Wearing a knee brace shortened the hamstring reflex latency regardless of fatigue (F(1,15)=20.62, P<.001). Muscle fatigue lengthened the hamstring reflex time regardless of the bracing condition (F(1,15)=7.57, P<.015). CONCLUSION: Wearing a functional knee brace facilitated hamstring muscle reflex, but muscle fatigue lengthened the hamstring reflex latency. Subjects with ACL deficiency should not rely on the knee brace to facilitate hamstring reflex for joint protection during prolonged sporting activities when muscles are fatigued.

Achilles Tendon↗
PubMed2001

Does the absence of anal reflexes guarantee a "safe bladder" in children with spina bifida?

INTRODUCTION: Increased detrusor pressure is a risk factor for renal damage in patients with neuropathic bladder, and probably requires inappropriate contraction of the external urethral sphincter. It seems logical that the absence of sacrally-mediated anal reflexes in a child with spina bifida makes such sphincteric spasm unlikely. One report has suggested that, in such circumstances, neuropathic bladder behaviour is usually predictable and safe. This article examines the reliability of this assumption, and whether routine urodynamic studies can be, therefore, safely omitted in this group. MATERIALS AND METHODS: 76 children and adolescents (aged 3 - 18 years) with spina bifida were tested for the presence of the anocutaneous reflex immediately prior to video-urodynamic studies, on entry into a therapeutic trial. The relationship between the anal reflex status and two surrogate indicators of urethral sphincter function, namely maximal detrusor pressure (MDP) and leak point pressure (LPP), was analysed. RESULTS: Only 11 (14 %) children had a positive reflex. Their mean MDP and their mean LPP were not statistically significantly greater than those in children without an intact reflex. Indeed the reflex was absent in the only two patients with MDP, > or = 100 cm H2O, and in the only five children with LPP, > or = 60 cm H2O. CONCLUSION: The absence of anal reflexes is a poor predictor of safe bladder pressures in children with spina bifida. There is no justification for depriving such a population of routine urodynamic assessment on this basis. Our impression remains that there is probably no such entity as a predictably safe neuropathic bladder.

Adolescent↗
PubMed2006

Changes in the reflex excitability during and after a sustained, low-intensity muscle contraction.

The purpose of the study was to evaluate the soleus H-reflex amplitude during and after a low-intensity isometric contraction. Twelve healthy, untrained subjects performed a 10-minute isometric plantar flexion at 20% of their maximum voluntary contraction torque output. The electromyogram, H-reflex, and maximum M-wave (Mmax) of the soleus muscle was recorded during and 10 minutes after the end of the contraction. The results indicated that the H-reflex increased significantly (mean +/- SEM: 44.7 +/- 16.6%, p < 0.05), but when the fatigue protocol was over, the H-reflex was depressed for the first 3 minutes, relative to the H-reflex that was recorded before fatigue, when the muscle was relaxed. The Mmax did not change significantly during the whole experiment. Furthermore, the stimulation frequency (0.1 vs. 0.3 Hz) did not have any significant effect on the H-reflex modulation. The results of the current study suggest that the reflex excitability is increased as fatigue develops, whereas this increase turns to depression for the first minutes of the recovery phase. The functional significance of these changes and the neural mechanisms which might be responsible are discussed.

Adult↗