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At least 775 records · Page 43Linked to original sources
PubMed1993

Bilateral asymmetries in the jaw-jerk reflex activity in man.

In order to investigate whether there are bilateral differences in the sensitivity of the mandibular stretch (jaw-jerk) reflex between patients with a myogenous craniomandibular dysfunction (CMD) and healthy controls free from signs and symptoms of CMD, jaw-jerk reflexes were elicited under standardized conditions in two groups of 10 gender- and age-matched subjects. The reflexes were recorded bilaterally from the masseter and the anterior temporal muscles by means of bipolar surface electromyogram (EMG). Reflex amplitudes at a mandibular displacement of exactly 80 microns and at a background muscle activity of exactly 12% maximum voluntary contraction were determined from relations between reflex amplitude and jaw displacement. These were obtained at a visually controlled, constant clenching level. For both groups, comparisons were made between reflex amplitudes from the right- and the left-hand side. In CMD patients with predominantly unilateral jaw muscle pain, comparisons were also made between the pain and non-pain sides. Although significant side asymmetries were found in many individuals, no significant differences were found among bilateral asymmetries in reflex sensitivity between patients and controls. No influence of pain side on the asymmetries was found. It was concluded that neuromuscular factors do not cause significant bilateral differences in the sensitivity of the jaw-jerk reflex between patients with myogenous CMD and controls. In a control experiment, in which eight healthy control subjects participated, the influence of a possible asymmetry in jaw displacement on the reflex sensitivity was evaluated. To achieve this, reflexes were elicited not only by means of a bilaterally imposed mandibular load, but also by means of loading via a unilateral bite-fork, so that an equal, constant jaw displacement could be imposed successively on both sides of the mandible. As no significant differences were found in bilateral asymmetries in reflex sensitivity between unilateral and bilateral mandibular loading, the influence of a possible asymmetrical jaw displacement on side asymmetries in the jaw-jerk reflex sensitivity is negligible in our experimental model.

Adult↗
PubMed1996

Sensitivity of the jaw-jerk reflex in patients with myogenous temporomandibular disorder.

Changes in the activity of human jaw-elevator muscles related to the mandibular stretch (jaw-jerk) reflex could be involved in the aetiology of temporomandibular disorders (TMD). In order to investigate whether there are differences in the sensitivity of the jaw-jerk reflex between myogenous TMD patients (n = 10) and gender- and age-matched controls (n = 10), jaw-jerk reflexes were elicited under standardized conditions. By measuring the reflex with bipolar surface electromyography (EMG), reflex sensitivity was determined from relations between reflex amplitude and jaw displacement from the masseter and the anterior temporalis muscles. Reflex amplitude and background EMG activity were normalized with respect to the maximal voluntary contraction (MVC) to correct for differences in the thickness of soft tissues overlying the muscle or in electrode placement. In addition to normalization with respect to MVC, for the patients, normalization was also applied with respect to a MVC that was scaled by multiplying values by the ratio of the mean MVC of controls to the mean MVC of patients. At a constant level of background EMG activity, the reflex sensitivity can be determined from the slope (reflex gain) and x-intercept (reflex threshold) of the reflex amplitude-jaw displacement relation. No significant differences between patients and controls were found for the gain or threshold values of either the masseter or the anterior temporalis muscles with a univariate analysis of variance. It is concluded that jaw-jerk reflex sensitivity is not significantly changed in myogenous TMD patients. Therefore, the fusimotor system probably does not play a part in the perpetuating myogenous TMD.

Action Potentials↗
PubMed1993

Variations in soleus H-reflexes as a function of plantarflexion torque in man.

The purpose of this study was to evaluate the effects of the levels of voluntary isometric contraction on the Hoffman reflex in human soleus and medial gastrocnemius (MG) muscles. H-reflexes were recorded in sixteen healthy adults at each of 16 isometric plantarflexion (pf) torque levels ranging from 0-100% of their maximum voluntary isometric contraction (MVC) and were elicited at two intensities of stimulation: (i) supramaximal for M-response and (ii) a submaximal stimulus that produced an H-reflex in soleus that was 50% of maximum H-reflex at rest. The H-reflex peak-to-peak amplitudes were linearly related to pf torque levels ranging from 0 to 50% MVC at both supramaximal and submaximal stimulus intensities. The slope of this relationship was higher for the submaximal stimulation. Beyond 60% of MVC, the soleus H-reflex amplitude showed no further increase with increasing pf torque for both stimulus intensities. Thus, beyond 50-60% of MVC the soleus H-reflex does not provide an accurate measure of soleus motor neuron pool excitability. Further experimental results showed that the H-reflex amplitude at a given torque level depended on whether torque was increasing or decreasing. When torque was increasing, the amplitude of the H-reflex was larger than when the same torque was maintained at a constant level. In contrast, if the torque was decreasing, amplitude of the reflex was lower than when torque was increasing. Therefore, variations in H-reflex amplitudes at a given torque level may be more closely correlated to the direction of the ongoing contraction than to the actual muscle force being produced at the time the H-reflex is elicited.

Adult↗
PubMed1994

Somato-sympathetic reflex transmission in the ventrolateral medulla oblongata: spatial organization and receptor types.

Tonic sympathetic activity in vivo is continuously modulated by inhibitory and excitatory reflex mechanisms. We studied the properties of somato-sympathetic excitatory reflex transmission in the rostral ventrolateral medulla (RVLM) of baroreceptor-denervated and vagotomized chloralose-anesthetized cats. Electrical stimulation of the left intercostal nerve of the 4th thoracic segment (IC-T4) elicited an early spinal and a late supraspinal reflex in the ipsilateral white ramus T3 from which recordings were made. Bilateral cooling of the ventral surface of the RVLM reversibly reduced the supraspinal reflex amplitude to 18.0 +/- 3.1% of control (100%). The spinally evoked reflex was enhanced to maximally 154.7 +/- 5.3%. Cooling of only the ipsilateral side of the RVLM was nearly equieffective in both, suppressing the supraspinal and enhancing the spinal reflex component. In contrast, cooling of the contralateral side had no significant effects on supraspinal reflex transmission but caused slight increases of the spinal reflex amplitudes. Similar effects were obtained by microinjection (RVLM) of the glutamate antagonist kynurenic acid (5 x 10(-3) M, n = 7) and the specific non-NMDA receptor antagonist CNQX (4 x 10(-3) M, n = 4) which, however, blocked the supraspinal reflex less effectively. These results demonstrate that the RVLM represents an essential relay in the transmission of both somatosympathetic reflex components. The experiments further suggest an almost completely ipsilateral neuronal pathway for the supraspinal reflex component which projects from the RVLM to the intermediolateral cell column (IML). The descending inhibition of the spinal reflex, however, receives neuronal inputs from the contralateral side.

6-Cyano-7-nitroquinoxaline-2,3-dione↗
PubMed2006

Up-regulation of 5-HT2 receptors is involved in the increased H-reflex amplitude after contusive spinal cord injury.

The amplitude of the H-reflex increases chronically after incomplete SCI and is associated with the development of exaggerated hindlimb reflexes. Although the mechanism for this increased H-reflex is not clear, previous studies have shown that pharmacological activation of the 5-HT2 receptors (5-HT2R) can potentiate the monosynaptic reflex. This study tested the hypothesis that increased expression of 5-HT2R on motoneurons is involved in increased H-reflex amplitude after a standardized clinically relevant contusive SCI. Adult female rats were subjected to contusion, complete surgical transection, or a T8 laminectomy only. At 4 weeks after surgery, H-reflex recordings from the hindpaw plantar muscles of contused rats showed twice the amplitude of that in laminectomy controls or transected rats. To probe the role of 5-HT2R in this increased amplitude, dose-response studies were done with the selective antagonists mianserin or LY53857 and the 5-HT2R agonist (+/-)-1-(2,5-Dimethoxy-4-iodophenyl)-2-aminopropane hydrochloride (DOI). The drugs were intrathecally infused into the lumbar cord while recording the H-reflex. Mianserin did not have any significant effects on the H-reflex after transection, consistent with the loss of distal serotonergic innervation. After contusion, both 5-HT2R antagonists reduced the H-reflex reflex amplitude with a significantly higher ID50 compared to the uninjured controls. The 5-HT2R agonist DOI significantly increased reflex amplitude in contused but not control rats. Furthermore, while 5-HT immunoreactivity was similar, contused rats displayed increased 5-HT2AR immunoreactivity in plantar muscle motoneurons compared to uninjured controls. We conclude that increased expression of 5-HT2R is likely to be involved in the enhanced H-reflex that develops after contusive SCI.

Amphetamines↗
PubMed2005

The lower limb flexion reflex in humans.

The flexion or flexor reflex (FR) recorded in the lower limbs in humans (LLFR) is a widely investigated neurophysiological tool. It is a polysynaptic and multisegmental spinal response that produces a withdrawal of the stimulated limb and resembles (having several features in common) the hind-paw FR in animals. The FR, in both animals and humans, is mediated by a complex circuitry modulated at spinal and supraspinal level. At rest, the LLFR (usually obtained by stimulating the sural/tibial nerve and by recording from the biceps femoris/tibial anterior muscle) appears as a double burst composed of an early, inconstantly present component, called the RII reflex, and a late, larger and stable component, called the RIII reflex. Numerous studies have shown that the afferents mediating the RII reflex are conveyed by large-diameter, low-threshold, non-nociceptive A-beta fibers, and those mediating the RIII reflex by small-diameter, high-threshold nociceptive A-delta fibers. However, several afferents, including nociceptive and non-nociceptive fibers from skin and muscles, have been found to contribute to LLFR activation. Since the threshold of the RIII reflex has been shown to correspond to the pain threshold and the size of the reflex to be related to the level of pain perception, it has been suggested that the RIII reflex might constitute a useful tool to investigate pain processing at spinal and supraspinal level, pharmacological modulation and pathological pain conditions. As stated in EFNS guidelines, the RIII reflex is the most widely used of all the nociceptive reflexes, and appears to be the most reliable in the assessment of treatment efficacy. However, the RIII reflex use in the clinical evaluation of neuropathic pain is still limited. In addition to its nocifensive function, the LLFR seems to be linked to posture and locomotion. This may be explained by the fact that its neuronal circuitry, made up of a complex pool of interneurons, is interposed in motor control and, during movements, receives both peripheral afferents (flexion reflex afferents, FRAs) and descending commands, forming a multisensorial feedback mechanism and projecting the output to motoneurons. LLFR excitability, mediated by this complex circuitry, is finely modulated in a state- and phase-dependent manner, rather as we observe in the FR in animal models. Several studies have demonstrated that LLFR excitability may be influenced by numerous physiological conditions (menstrual cycle, stress, attention, sleep and so on) and pathological states (spinal lesions, spasticity, Wallenberg's syndrome, fibromyalgia, headaches and so on). Finally, the LLFR is modulated by several drugs and neurotransmitters. In summary, study of the LLFR in humans has proved to be an interesting functional window onto the spinal and supraspinal mechanisms of pain processing and onto the spinal neural control mechanisms operating during posture and locomotion.

Electric Stimulation↗
PubMed2000

Stretch reflex adaptation in elbow flexors during repeated passive movements in unilateral brain-injured patients.

OBJECTIVE: To evaluate the effects of repeated, externally imposed, flexion-extension movements of the elbow on the resulting stretch reflex response in hemiparetic spastic brain-injured patients. These effects were compared within a recording session and across sessions for the same subject to determine the impact of movement history on the quantification of spastic hypertonia using the stretch reflex response. DESIGN: Twenty to 30 sequential, constant velocity flexion-extension movements were applied to the impaired elbow of our cohort, with a 10-second hold interposed between flexion and extension. Movements were applied regularly at 1-minute intervals. Changes in stretch reflex responses were monitored during the applied movements. PARTICIPANTS: We examined a convenience sample of seven hemiparetic brain-injured subjects between the ages of 26 and 60 yrs, with moderate-to-severe spastic hypertonia of elbow muscles (Ashworth score 2-4/4). Subjects participated in 2 to 9 sessions. MEASURES: Elbow torque, position, velocity, and electromyograms of the biceps, brachioradialis, and triceps muscles were recorded for each flexion and extension movement. Stretch reflex torque was calculated by subtracting passive torque from total elbow torque, recorded over large amplitude movements. A linear regression analysis quantified both the initial torque response of the stretch reflex and the ensuing adaptation of the stretch reflex during sequential movements. Intersession variability was characterized both for spastic hypertonia measures and for stretch reflex adaptation. RESULTS: Repeated, externally imposed, sequential flexion-extension movements of the elbow decreased the elbow flexor stretch reflex in six of seven subjects. The mean reduction in reflex torque after 30 movements was 50% of the initial torque values (p = .001, t test vs. 0% change). Intersession stretch reflex responses for each subject were found to vary greatly (SDs of reflex torque ranged from 0.1 to 4.0 Nm), and there were also significant variations in the degree of adaptation between subjects. CONCLUSIONS: Stretch reflex adaptation must be taken into consideration when spastic hypertonia is quantified using repeated joint motion, as is often the case. The magnitude of intersession variation in spastic hypertonia measures suggests that ideally, such measurements should be made across multiple sessions before conclusions are made regarding the efficacy of spastic hypertonia interventions. This study provides quantitative evidence that repeated joint movements may have a significant short-term beneficial effect on spastic hypertonia.

Adaptation, Physiological↗
PubMed1981

The bulbocavernosus reflex in urology: a prospective study of 299 patients.

Bulbocavernosus reflex was evaluated clinically in 299 patients during a routine urodynamic evaluation and compared to the electromyographic demonstration of the reflex. The findings were correlated with the neurologic status of the patients. There were 127 patients who were normal neurologically, and 98 per cent of the male and 81 per cent of the female patients in this group had a normal bulbocavernosus reflex clinically. All of the male and 92 per cent of the female patients had a bulbocavernosus reflex demonstrated by electromyography. There were 73 patients with neurologic lesions involving the sacral spinal cord. All patients with a complete lesion had absent bulbocavernosus reflexes clinically and on electromyography, while 44 per cent of the patients with incomplete sacral lesions had an intact bulbocavernosus reflex clinically and 78 per cent had reflex demonstrated by electromyography. There were 99 patients with neurologic lesions of the spinal cord above the sacral outflow, and 90 per cent of this group had demonstrable bulbocavernosus reflexes clinically and 93 per cent had the reflex demonstrated by electromyography. It is concluded that the absence of a bulbocavernosus reflex in a male patient is indicative of a neurologic lesion involving the sacral spinal cord and is highly suggestive of such a lesion in a female patient. The presence of a normal bulbocavernosus reflex in either sex does not rule out the possibility of a significant lesion. The electromyographic demonstration of the bulbocavernosus reflex is more sensitive than the clinical one.

Adolescent↗
PubMedDate not supplied

Reflex responses associated with activator treatment.

BACKGROUND: Previous studies have demonstrated the existence era reflex response, measurable by surface electromyography (sEMG), after manually delivered spinal manipulative therapy (SMT). This reflex response has been characterized as consistent, reproducible within individual subjects, and nonlocal because it extends beyond the site of manipulation. However, the nature and magnitude of possible reflex responses in the paraspinal and proximal limb muscles elicited by nonmanual SMT, such as with an adjusting instrument, remain unknown. OBJECTIVE: To characterize the reflex responses associated with SMT by using sEMG to record the responses of 16 muscles before, during, and after treatment. STUDY DESIGN: The eleetromyographic responses of 16 para-spinal and proximal limb muscles in 9 healthy, asymptomatic male volunteers were measured simultaneously by sEMG before, during, and after chiropractic SMT. METHODS: SMT thrusts were delivered to 9 asymptomatic volunteers at 6 bilateral sites (C3/4, T2/3, T6/8, T11/12, L2-4, and s1). Reflex responses were measured from 16 muscles with bipolar sEMG electrodes and collected at 2000 Hz per channel with data acquisition software. RESULTS: Approximately 68% of the SMT thrusts resulted in a detectable reflex response. The cervical spine resulted in a detectable response of 50%, thoracic spine 59%, lumbar spine 83%, and sacroiliac joints 94%. Treatments delivered to the thoracic spine elicited the largest peak-to-peak amplitude sEMG responses, whereas the lumbar spine demonstrated the most heterogeneous responses. When a reflex response was observed, it always occurred close to the treatment site ipsilaterally and was detected in muscles that had either their origin or insertion at the vertebral level that was adjusted. CONCLUSIONS: Based on the local nature, magnitude, and characteristic shape of all reflex responses observed, we hypothesized that they were likely generated by a single proprioceptor. Furthermore, the temporal properties of this reflex response suggest that they originated from the muscle spindles. In contrast to previous observations on reflex responses after manual SMT, these treatments elicited reflex responses that varied between subjects but were consistent within an individual and were local in nature. We conclude that SMT delivered in this manner results in a reflex response that is both quantitatively and qualitatively different from a manual SMT.

Adult↗
PubMed1997

Enhancement and depression of spinal reflexes by 8-hydroxy-2-(di-n-propylamino)tetralin in the decerebrated and spinalized rabbit: involvement of 5-HT1A- and non-5-HT1A-receptors.

1. In decerebrated, spinalized and paralyzed rabbits, intravenous administration of the 5-HT1A-receptor agonists (+/-)-8-hydroxy-2-(di-n-propylamino)tetralin (8-OH-DPAT, 3-300 nmol kg(-1), cumulative) and flesinoxan (22-2200 nmol kg(-1), cumulative) significantly increased the short latency reflex evoked in gastrocnemius medialis motoneurones by electrical stimulation of all myelinated afferents (Abeta and Adelta fibres) of the sural nerve. Reflexes increased to median values of 198% (inter-quartile range (IQR) 148-473%) and 296% (IQR 254-522%) of pre-drug values with the highest doses of 8-OH-DPAT and flesinoxan, respectively. The enhancement of reflexes induced by 5-HT1A-receptor agonists was not reversed by the selective 5-HT1A-receptor antagonist (S)WAY-100135 (2.05 micromol kg[-1]). 2. The effects of 8-OH-DPAT were tested after pretreatment with (S)WAY-100135 (2.05 micromol kg[-1]), its more potent analogue WAY-100635 (185 nmol kg[-1]), and the 5-HT2/5-HT1D-/5-HT7-receptor ligand ritanserin (1.67 micromol kg[-1]). 8-OH-DPAT (300 nmol kg(-1) single dose) significantly increased gastrocnemius reflex responses in the presence of (S)WAY-100135 and WAY-100635, to median values of 260% (IQR 171-295%) and 165% (IQR 136-170%) of pre-drug levels, respectively. These values were not significantly different from each other, or from the effects of 8-OH-DPAT given alone. When 8-OH-DPAT was given after ritanserin, reflexes were a median of 102% (IQR 76-148%) of pre-drug values: i.e. there was no significant increase in responses. Neither WAY-100635 nor ritanserin had any effects on reflexes per se. 3. WAY-100635 (185 nmol kg[-1]) and ritanserin (1.67 micromol kg[-1]) were given after 8-OH-DPAT (300 nmol kg[-1]). The agonist increased reflexes to a median value of 184% (IQR 135-289%), after which WAY-100635 significantly reduced responses to 165% (IQR 130-254%) and ritanserin further decreased reflexes to a median of 107% (IQR 100-154%) of pre-drug levels, i.e. not significantly different from controls. 4. Previous studies have shown that reflexes evoked by large myelinated axons tend to be suppressed, rather than enhanced, by 5-HT1A-receptor agonists. When tested against reflexes evoked by stimulation of the sural nerve at strengths between 1.5 and 2.5 times threshold, 8-OH-DPAT (3-300 nmol kg(-1), cumulative) and flesinoxan (22-2200 nmol kg(-1), cumulative) significantly reduced gastrocnemius responses to median values of 36% (IQR 15-75%) and 17% (IQR 12-38%) of pre-drug levels, respectively. This inhibition was fully reversed by (S)WAY-100135 (2.05 micromol kg[-1]). 5. These data show that drugs that are agonists at 5-HT1A-receptors increase polysynaptic spinal reflexes evoked by moderate to high stimulus intensities and depress responses to very low intensity stimuli. The inhibitory effects of these drugs were mediated through 5-HT1A-receptors as they were abolished by a selective antagonist for these sites. However, the facilitatory effects of 8-OH-DPAT could be completely blocked only by a combination of ritanserin, which has no significant affinity for 5-HT1A-receptors, with WAY-100635. It appears that the enhancement of reflexes by 8-OH-DPAT arises from a combined action at 5-HT1A-receptors and other, ritanserin-sensitive, sites which could be 5-HT1D- or 5-HT7-receptors.

8-Hydroxy-2-(di-n-propylamino)tetralin↗
PubMed2001

Neural control: novel evaluation of stretch reflex sensitivity.

We evaluated the stretch reflex activities of the elbow flexor and extensor muscles considering the relationship between the reflex electromyographic (EMG) responses and their corresponding standardized muscle stretch velocities. Specifically, muscular stretch velocity was estimated by using ultrasonograms. Stretch reflex EMG responses were elicited in the biceps brachii, brachioradialis and triceps brachii with a ramp-and-hold rotation at the elbow joint, which consisted of various angular velocities for the extension- or flexion-direction. The whole muscle stretch velocity induced by each ramp-and-hold rotation was calculated on the basis of fibre length changes associated with the elbow joint angle. A linear regression equation was fitted to the relation between the whole muscle stretch velocity and the reflex EMG responses, and the variables from the equation were used to quantify sensitivity of each reflex EMG component. The reflex EMG responses were increased as the ramp-and-hold rotational velocity increased. There were no significant differences in the recorded magnitudes of reflex EMG responses with equivalent joint rotational velocity between the brachioradialis and the triceps brachii medial head. These muscles showed the highest reflex responses in the flexor and extensor muscles, respectively. To the contrary, the reflex EMG response elicited by the standardized muscle stretches was significantly greater in the extensor muscles, indicating a higher reflex sensitivity. This was because of the lower muscle stretch velocity of the triceps brachii with an equivalent elbow joint rotation. The stretch reflex sensitivity in both the elbow flexor and extensor muscles might be regulated so as to make the reflex responses the same when the equivalent joint rotational velocity is applied to these muscles.

Elbow Joint↗
PubMed2003

The role of the brachioradialis H reflex in the management and prognosis of obstetrical brachial plexus palsy.

The H reflex was investigated to determine if it can be useful in the prognosis of obstetrical brachial plexus palsies. The H reflex is an electrically stimulated monosynaptic or oligosynaptic response which can be recorded in peripheral nerves in all muscles of infants up to approximately two years of age. It is essentially the electrophysiologic counterpart of the deep tendon reflex, and its presence indicates intact afferent and efferent axons at the particular spinal segment. Our objectives were to document the Brachioradialis H (Br H) reflex latency and amplitude in normal upper extremities of infants, to evaluate the presence or absence of the Br H reflex in obstetrical palsy neonates and infants between one and seven months of age and to determine if this test was a valid predictor of final clinical outcome. A prospective study of 109 patients was performed to measure the Br H reflex in the affected and the contralateral normal limb. The results from the abnormal limb were compared to the final clinical decision made by nine months for or against surgical intervention. In the normal limbs, a Br H latency of 10.7 +/- 0.8 msec was determined with an amplitude of 1.2 +/- 1.2 mV. The chi 2 analysis in infants from one month to seven months old revealed a strong relationship between an absent Br H reflex and little or no clinical improvement (p < 0.0001), with a sensitivity for predicting poor outcome of 85.7%. The odds ratio (with a 95% confidence interval) of a child with an absent Br H reflex not significantly improving by nine months was 8.4 times higher than if the Br H reflex was present. The false positive rate was 42% however, indicating that a significant number of patients improved clinically, despite having a nonrecordable Br H reflex at age seven months or less. The low false negative rate of 14.3% suggested that in the presence of a Br H reflex, the majority of patients recover. Therefore, the presence of the Br H reflex is a helpful test in the prognostication of good recovery in obstetrical upper plexus palsy patients.

Birth Injuries↗
PubMed1979

Effects of brain-stem and thalamic lesions on the corneal reflex: an electrophysiological and anatomical study.

In 9 patients with Wallenberg's lateral medullary syndrome, one patient with a midbrain lesion involving the right side of the tegmentum, and 2 patients with a thalamic lesion, corneal reflexes were investigated by a new electromyographic technique. The electrophysical results were compared with the results obtained by clinical observation. In the lateral medullary lesions the electrophysiologically obtained reflex responses showed four types of abnormality. Type A consisted of a bilateral delay and type B a bilateral absence of the corneal reflex response to stimulation on the affected side in combination with a normal reflex response on both sides when the cornea on the normal side was stimulated. Type C, which was present in one case, and type D which was seen in 3 cases, consisted of a bilateral absence of the corneal reflex upon stimulation on the affected side; stimulation on the unaffected side produced a normal reflex response on the intact side in combination with, respectively, a delay or absence of the corneal reflex response on the affected side. Comparison of the clinical observations with the electrophysiological findings revealed minor discrepancies in type A and B abnormalities. However, the electrophysiological type C and D abnormalities were not detected by clinical observation. These findings demonstrate that electrophysiological recording of the corneal reflex may reveal clinically undetectable abnormalities. From the electrophysiological findings it is concluded that the corneal reflex is conducted along medullary pathways running both ipsilaterally and contralaterally from the stimulated side before connecting, respectively, with the ipsilateral and contralateral facial nucleus. From the anatomical findings it is suggested that the ascending pathways from the spinal fifth nerve complex to the facial nuclei are located in the lateral reticular formation of the lower brain-stem. The normal corneal reflex responses in the presence of thalamic and midbrain lesions involving nociceptive fibres in the trigeminothalamic tract do not support a previously postulated long-loop reflex arc passing through this tract. The suprabulbar influence upon the corneal reflex is discussed.

Brain Diseases↗
PubMed1978

Primitive reflex profile. A pilot study.

Seven primitive reflexes used by physical and occupational therapists in evaluating children with cerebral palsy were each graded on a 0 to 4+ scale to constitute a Primitive Reflex Profile. The reflexes studied were the asymmetrical tonic neck reflex, the symmetrical tonic neck reflex, the tonic labyrinthine reflex, the positive support reflex, the derotational righting reflex, the Moro reflex, and the Galant reflex. The Primitive Reflex Profile was studied in 53 cerebral palsied patients to assess both the feasibility of its administration and its usefulness in discriminating functional levels of ambulation. The Primitive Reflex Profile was administered by at least two members of a team consisting of four pediatric developmentalists and two physical therapists. In using this instrument, the extreme functional groups were clearly defined and showed the expected overlap with the intermediate classification.

Adolescent↗
PubMed2001

Estimating the acoustic reflex threshold from wideband measures of reflectance, admittance, and power.

OBJECTIVE: A method was developed to estimate the contralateral acoustic reflex threshold using shifts in wideband energy reflectance, admittance magnitude and power. DESIGN: In the first experiment contralateral reflex thresholds for a noise activator were estimated on three adult participants using reflectance, admittance and power measurements at frequencies from 250 to 8000 Hz. The reflex threshold was defined using a magnitude and a correlation technique, both having the property of examining the pattern of the reflex-induced shift across a fairly broad frequency range (250 to 2000 Hz). In the second experiment, the magnitude method was modified to include an F test for the comparison of the magnitude of reflex-induced shifts in reflectance, admittance and power relative to response differences in a no-activator baseline condition. Data from four additional participants then were analyzed across a broader frequency range using a method that combined magnitude and correlation methods of estimating reflex thresholds. RESULTS: Acoustic reflex thresholds were obtained using reflectance, admittance and power-level measures in all subjects in both experiments. Individual reflex threshold estimates were as much as 24 dB lower than with the clinical system, with an average of approximately 14 dB lower for the three participants in the first experiment, and approximately 18 dB lower for the four participants in the second experiment. CONCLUSIONS: Wideband measures of reflectance, admittance and power were successfully used to estimate acoustic reflex thresholds in seven participants. A reflex threshold test was devised based on the magnitude of the response shift in the presence of a contralateral activator, and the similarity of the response shift spectra across frequency between successive activator levels. Across all participants in the study, the new test yielded a more sensitive measure of the acoustic reflex threshold than the clinical method. This finding has both clinical and theoretical implications for the study of the acoustic reflex.

Acoustic Impedance Tests↗
PubMed2006

Reflex sympathetic dystrophy in hemiplegia.

There is a high incidence of reflex sympathetic dystrophy of the upper limbs in patients with hemiplegia, and its painful and functional consequences present a problem to specialists in physical medicine and rehabilitation. This study was designed to assess the role of several factors in the occurrence of reflex sympathetic dystrophy in patients with hemiplegia. Ninety-five consecutive stroke patients (63 male and 32 female, mean age 59+/-12 years) admitted to our hospital were evaluated. Of the study group, 29 patients (30.5%) were found to develop reflex sympathetic dystrophy. There were no significant differences between the hemiplegic patient groups with or without reflex sympathetic dystrophy regarding age, gender, etiology, side of involvement, disease duration and the presence of comorbidities. The recovery stages of hemiplegia, as shown by Brunnstrom functional classification, were significantly different between the two groups; patients in lower recovery stages tended to develop reflex sympathetic dystrophy more frequently (P<0.01). Additionally, the presence of flaccidity was also a significant factor in the development of reflex sympathetic dystrophy. Glenohumeral subluxation was present in 37 patients (38.9%) in our study group and the presence of this complication was related to the occurrence of reflex sympathetic dystrophy. The presence of glenohumeral subluxation was significantly higher in patients with reflex sympathetic dystrophy (21/29, 72.4%) when compared to the patients without reflex sympathetic dystrophy (16/66, 24.2%) (P<0.001). Also, hemiplegic patients with more severe shoulder subluxation were significantly more likely to develop reflex sympathetic dystrophy. These results suggest that lower recovery stages, reduced tonus and glenohumeral subluxation significantly contribute to the occurrence of reflex sympathetic dystrophy in the hemiplegic patient. We believe that preventive and treatment measures should consider these factors as they seem to have in common a higher risk of traumatizing the paralyzed upper limb and causing reflex sympathetic dystrophy.

Aged↗
PubMed1976

Stretch reflex and servo action in a variety of human muscles.

1. In the long flexor of the thumb the latency of the stretch reflex and of other manifestations of servo action is some 45 msec, roughly double the latency of a finger jerk. 2. Tendon jerks are feeble or absent in the long flexor of the thumb even in subjects with brisk long-latency stretch reflexes in this muscle. This, and other facts, suggests that the nervous mechanism of the tendon jerk is different from that of the stretch reflex. 3. A muscle that has feeble tendon jerks may show a late component in the response to a tendon tap, with a latency similar to that of the long-latency stretch reflex. 4. On the hypothesis that the excess latency of the stretch reflex over that of a tendon jerk is because the stretch reflex employs a cortical rather than a spinal arc, the excess would be expected to be larger in magnitude for the long flexor of the big toe and smaller for the jaw closing muscles. This is confirmed, 5. An alternative hypothesis that the long latency of stretch reflexes in thumb and toe is because they are excited by slow-conducting afferents is made improbable by the finding that stretch reflexes with an equal or greater excess latency are also found in proximal arm muscles. 6. The long-latency stretch reflex in proximal muscles was seen most distinctly in a healthy subject who happened to have feeble or absent tendon jerks. In ordinary subjects there is often a large, short-latency, presumably spinal component of the stretch reflex in proximal muscles; and short-latency responses to halt and release are also seen, The significance of this spinal latency servo action in proximal muscles remains to be explored. 7. The Discussion argues that the available data on conduction time to and from the cerebral cortex are compatible with the hypothesis that the long-latency component of the stretch reflex uses a transcortical reflex arc, and that none of the experiments described in the present paper are inimical to this view.

Biomechanical Phenomena↗
PubMed1996

Postnatal development of the nociceptive withdrawal reflexes in the rat: a behavioural and electromyographic study.

1. The postnatal development of nociceptive withdrawal reflexes was studied. In awake intact rats, forelimb, hindlimb and tail reflexes were recorded on videotape. In decerebrate spinal rats, electromyography (EMG) was used to record nociceptive withdrawal reflexes in musculi extensor digitorum longus (EDL), peronei, gastrocnemius-soleus (G-S) and biceps posterior-semitendinosus (BP-ST). Thermal (short-lasting CO2 laser pulses) and mechanical stimulation were used. 2. In adults, nociceptive withdrawal reflexes were typically well directed and reflex pathways to single hindlimb muscles had functionally adapted receptive fields. By contrast, at postnatal day (P) 1-7, the nociceptive withdrawal reflexes were often inappropriate, sometimes producing movements towards the stimulation, and EMG recordings revealed unadapted variable receptive fields. With increasing age, the nociceptive withdrawal reflexes progressively became well directed, thus producing localized withdrawal. Both withdrawal movements and spatial organization of the receptive fields were adult-like at P20-25. 3. Up to P25, reflex thresholds were more or less constant in both intact awake rats and spinal decerebrate rats, except in G-S in which no nociceptive withdrawal reflexes were evoked from P20 on. After P25, mechanical, but not thermal, thresholds increased dramatically. 4. EMG recordings revealed that during the first three postnatal weeks, the latency of the CO2 laser-evoked nociceptive withdrawal reflexes decreased significantly in peronei and BP-ST, but not in EDL, and thereafter increased significantly in peronei, BP-ST and EDL. The magnitude of the nociceptive withdrawal reflexes in these muscles increased markedly between P7 and P20 and showed little change thereafter. 5. Possible mechanisms underlying the postnatal tuning of the nociceptive withdrawal reflexes are discussed.

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