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PubMedDate not supplied

Neurophysiological methods for the assessment of spasticity: the Hoffmann reflex, the tendon reflex, and the stretch reflex.

PURPOSE: To review the literature concerning neurophysiological methods to assess spasticity with respect to mechanisms and methodology, and to describe the three most commonly used methods: the Hoffmann reflex (H-reflex), the Tendon reflex (T-reflex), and the Stretch Reflex (SR). METHOD: A systematic internet database search was performed to identify neurophysiological measurement methods of spasticity. A systematic exclusion procedure resulted in 185 included references, completed by additional informal search. For this paper, information about the H-, T- and stretch reflexes was extracted from these references. RESULTS: Although the reflexes are basically monosynaptic, there are many supraspinal pathways which modulate the responses in terms of their amplitude and latency. As a consequence the methods are sensitive to a considerable number of experimental conditions and are characterized by a moderate reliability and sensitivity. Correlations with other (i.e. biomechanical, neurophysiological or clinical) spasticity assessment parameters are moderate to poor. Standardised and broadly accepted protocols are still largely lacking preventing an effective exchange of knowledge. CONCLUSIONS: The clinical and experimental use of the three methods is restricted due to moderate reliability and sensitivity. It is recommended to perform combined neurophysiological-biomechanical assessment of spasticity during active, functional movement.

Electromyography↗
PubMed1996

Ureterovesical junction inhibitory reflex and vesicoureteral junction excitatory reflex: description of two reflexes and their role in the ureteric antireflux mechanism.

The purpose of this study was to investigate the response of the ureterovesical junction (UVJ) to ureteric distension and to bladder filling with the aim of elucidating the mechanism of UVJ antireflux. The study was performed on 13 healthy volunteers [age 41.4 +/- 10.2 (SD) years; nine men, four women]. A ureteric catheter connected to a pressure transducer was introduced into the ureter proper. After recording the ureteric pressure, the catheter was withdrawn to the bladder, and the resting pressures in the UVJ and bladder were registered. The catheter was positioned in the UVJ and a 3F balloon-tipped ureteric catheter was introduced into the ureter proper and filled saline in increments of 1 ml. The pressure response of the ureter and UVJ to ureteric distension was recorded. The bladder was then filled with 400 ml saline at two rates, slow (10 ml/min) and rapid (150 ml/min), and UVJ pressure response was registered. The aforementioned tests were repeated after anesthetizing the UVJ, the bladder musculature surrounding the UVJ and the ureteric wall at the site of the ureteric distension, respectively. Ureteric distension of the lower 2-3 cm effected ureteric pressure elevation (P < 0.05) and a UVJ pressure drop (P < 0.05); no pressure response of the UVJ occurred upon ureteric distension above this level. Slow bladder filling induced an increase in the UVJ (P < 0.01) and vesical (P < 0.01) pressures only when vesical filling reached a mean of 219.6 +/- 79.4 ml and above. Upon rapid vesical filling the pressure response occurred at a smaller volume (136.6 +/- 52.3 ml). The pressure response did not occur when the UVJ was anesthetized. The study showed that lower ureteric distension was associated with a UVJ pressure drop. This reflex relationship, which we call the "ureterovesical junction inhibitory reflex," was reproducible and disappeared on anesthetizing the UVJ or ureter. Vesical filling above a certain volume induced a UVJ pressure increase which was reproducible and disappeared on anesthetizing the UVJ; we call this reflex relationship the "vesicoureteral junction excitatory reflex." These two reflexes seem to regulate the entry of urine from the ureters to the bladder and prevent ureteric reflux during bladder filling. In conclusion, two reflexes are identified that might contribute to the mechanism of UVJ antireflux.

Adult↗
PubMed1997

Pelviureteral inhibitory reflex and ureteropelvic excitatory reflex: role of the two reflexes in regulation of urine flow from the renal pelvis to the ureter.

The mechanism by which the ureteropelvic junction (UPJ) regulates the passage of urine from the renal pelvis to the ureter, and prevents urinary backflow from the the ureter to the renal pelvis, is not completely understood. The current communication studies this mechanism in 18 dogs. With the dogs under anesthesia, nephrostomy was done through which two catheters (one pressure and one balloon-tipped) were introduced into the UPJ and the renal pelvis, respectively. Renal pelvis distension with a balloon filled with 1 ml of saline effected a rise of renal pelvic pressure from a mean basal pressure of 4.8 +/- 1.2 cm H2O to 6.9 +/- 2.3 cm H2O (P < 0.05). The basal UPJ pressure of 12.6 +/- 2.7 cm H2O showed no significant change with 1 ml distention of the renal pelvic balloon (P > 0.05). Renal pelvic distension with 2, 3, and 4 ml caused a significant rise of renal pelvic pressure to 8.4 +/- 2.7 (P < 0.05), 10.6 +/- 2.2 (P < 0.01), and 11.8 +/- 1.9 (P < 0.01) cm H2O, respectively, and a significant drop of UPJ pressure to 4.8 +/- 1.2, 4.7 +/- 1.1, and 4.6 +/- 1.2 cm H2O (P < 0.01), respectively. Ureteric distension with a balloon filled with 0.5 ml of saline significantly raised the ureteric pressure from a mean basal value of 4.3 +/- 1.4 cm H2O to 14.7 +/- 3.3 cm H2O (P < 0.01) and the UPJ pressure to a mean of 20.8 +/- 3.8 (P < 0.05). Ureteric distension with 1 and 1.5 ml of saline led to an elevation of ureteric and UPJ pressure which was not significantly different from that observed with distension with 0.5 ml (P > 0.05). In contrast, the UPJ showed no significant pressure change upon distension of the locally anesthetized renal pelvis or ureter, respectively. Likewise, the locally anesthetized UPJ exhibited no significant pressure response to renal pelvic or ureteric distension. The study demonstrates that urine might have to accumulate in the renal pelvis up to a certain volume and pressure so as to effect UPJ opening, which occurs at its maximum irrespective of the distending volume. UPJ opening upon renal pelvic distension postulates a reflex relationship which we call "pelviureteral inhibitory reflex." This reflex is believed to regulate the passage of urine from the renal pelvis to the ureter. Ureteric distension closes the UPJ; we call this reflex action the "ureteropelvic excitatory reflex" as it seems to prevent reflux of urine through the UPJ and thus protects the kidney. The concept that the UPJ acts as a physiologic sphincter is put forward.

Anesthesia↗
PubMed1996

Inhibition of the soleus H-reflex during dorsiflexion is dependent on individual differences in maximal soleus H-reflex as a test reflex.

The quantitative differences among individuals in the natural reciprocal inhibition of the soleus H-reflex during dorsiflexion were examined, in conjunction with the maximal H-reflex as the test reflex size in each individual. Maximal H-reflex was expressed relative to the maximal M-response (H(max)) when compared among individuals. Analysis showed that with increases in H(max) at rest in each individual, the inhibitory effect was first enhanced, then reached a peak, and was finally alleviated. This pattern was similar to the intraindividual pattern of the inhibitory effect induced by specific conditioning stimulus as a function of the test reflex size.

Adolescent↗
PubMed2000

Anatomical evidence for two spinal 'afferent-interneuron-efferent' reflex pathways involved in micturition in the rat: a 'pelvic nerve' reflex pathway and a 'sacrolumbar intersegmental' reflex pathway.

We labeled interneurons in the L1-L2 and L6-S1 spinal cord segments of the rat that are involved in bladder innervation using transneuronal retrograde transport of pseudorabies virus (PRV) in normal animals and in animals with selected nerve transections. Preganglionic neurons were identified using antisera against choline acetyltransferase (ChAT). In some experiments we labelled parasympathetic preganglionic neurons (PPNs) in the L6-S1 spinal cord by retrograde transport of Fluorogold from the major pelvic ganglion. We identified bladder afferent terminals using the transganglionic transport of the anterograde tracer cholera toxin subunit b. We present anatomical evidence for two spinal pathways involved in innervation of the bladder. First, in the intact rat, afferent information from the bladder connects, via interneurons in L6-S1, to the PPNs that provide the efferent innervation of the bladder. The afferent terminals were located mainly in close apposition to interneurons located dorsal to the retrogradely labeled PPNs. Second, using L6-S1 ganglionectomies or L6-S1 ventral root rhizotomies we limited viral transport to the sympathetic pathways innervating the bladder. This procedure also labelled interneurons (but not PPNs) with PRV in the L6-S1 spinal cord in a location very similar to those described in the intact rat. These interneurons also receive bladder afferent terminals but we propose that they project to sympathetic preganglionic neurons, most of which are in the L1-L2 spinal segments. Based on this anatomical evidence, we propose the existence of two spinal reflex pathways involved in micturition: a pathway limited to a reflex arc in the pelvic nerve (presumably excitatory to the detrusor muscle); and a pathway involving the pelvic nerve and sympathetic nerve fibers, some of which may travel in the hypogastric (presumably inhibitory to the detrusor muscle).

Animals↗
PubMed1998

Sensitivity of H-reflexes and stretch reflexes to presynaptic inhibition in humans.

The sensitivity of soleus H-reflexes, T-reflexes, and short-latency stretch reflexes (M1) to presynaptic inhibition evoked by a weak tap applied to the biceps femoris tendon or stimulation of the common peroneal nerve (CPN) was compared in 17 healthy human subjects. The H-reflex was strongly depressed for a period lasting up to 300-400 ms (depression to 48 +/- 23%, mean +/- SD, of control at a conditioning test interval of 70 ms) by the biceps femoris tendon tap. In contrast, the short-latency soleus stretch reflex elicited by a quick passive dorsiflexion of the ankle joint was not depressed. The soleus T-reflex elicited by an Achilles tendon tap was only weakly depressed (92 +/- 8%). The H-reflex was also significantly more depressed than the T-reflex at long intervals (>15 ms) after stimulation of CPN (H-reflex 63 +/- 14%, T-reflex 91 +/- 13%; P < 0. 01). However, the short-latency (2 ms) disynaptic reciprocal Ia inhibition evoked by stimulation of CPN was equally strong for H- and T-reflexes (H-reflex 72 +/- 10%, T-reflex 67 +/- 13%; P = 0.07). Peaks in the poststimulus time histogram (PSTH) of the discharge probability of single soleus motor units (n = 53) elicited by an Achilles tendon tap had a longer duration than peaks evoked by electrical stimulation of the tibial nerve (on average 5.0 ms as compared with 2.7 ms). All parts of the electrically evoked peaks were depressed by the conditioning biceps femoris tendon tap (average depression to 55 +/- 27% of control; P < 0.001). A similar depression was observed for the initial 2 ms of the peaks evoked by the Achilles tendon tap (69 +/- 48%; P < 0.001), but the last 2 ms were not depressed. Conditioning stimulation of the CPN at long intervals (>15 ms) also depressed all parts of the electrically evoked PSTH peaks (n = 34; average 65%; P < 0.001) but had only a significant effect on the initial 2 ms of the peaks evoked by the Achilles tendon tap (85%; P < 0.001). We suggest that the different sensitivity of mechanically and electrically evoked reflexes to presynaptic inhibition is caused by a difference in the shape and composition of the excitatory postsynaptic potentials underlying the two reflexes. This difference may be explained by a different composition and/or temporal dispersion of the afferent volleys evoked by electrical and mechanical stimuli. We conclude that it is not straightforward to predict the modulation of stretch reflexes based on observations of H-reflex modulation.

Adult↗
PubMed2006

Role of reflex gain and reflex delay in spinal stability--a dynamic simulation.

The goal of this study was to investigate the role of reflex and reflex time delay in muscle recruitment and spinal stability. A dynamic biomechanical model of the musculoskeletal spine with reflex response was implemented to investigate the relationship between reflex gain, co-contraction, and stability in the spine. The first aim of the study was to investigate how reflex gain affected co-contraction predicted in the model. It was found that reflexes allowed the model to stabilize with less antagonistic co-contraction and hence lower metabolic power than when limited to intrinsic stiffness alone. In fact, without reflexes there was no feasible recruitment pattern that could maintain spinal stability when the torso was loaded with 200N external load. Reflex delay is manifest in the paraspinal muscles and represents the time from a perturbation to the onset of reflex activation. The second aim of the study was to investigate the relationship between reflex delay and the maximum tolerable reflex gain. The maximum acceptable upper bound on reflex gain decreased logarithmically with reflex delay. Thus, increased reflex delay and reduced reflex gain requires greater antagonistic co-contraction to maintain spinal stability. Results of this study may help understanding of how patients with retarded reflex delay utilize reflex for stability, and may explain why some patients preferentially recruit more intrinsic stiffness than healthy subjects.

Humans↗
PubMed2004

Determination of baroreceptor-stroke volume reflex sensitivity by power spectral analysis: a quantitative probe of baroreceptor-cardiac reflex.

Baroreceptor-cardiac reflex, which consists of baroreceptor-induced chronotropic and inotropic actions, is a very useful index of cardiac sympathovagal balance. Baroreceptor-heart rate reflex sensitivity, which reflects baroreceptor-induced chronotropic action, has been used as a marker of baroreceptor-cardiac reflex. However, it cannot be used in patients with chronotropic incompetence and/or implanted cardiac pacemaker. We hypothesized that baroreceptor-stroke volume (SV) reflex sensitivity, which reflects baroreceptor-induced inotropic action, may also be a useful method for measurement of baroreceptor-cardiac reflex, similar to the baroreceptor-heart rate reflex sensitivity. To test this hypothesis, we measured baroreceptor-SV reflex sensitivity expressed as ratio of low frequency (LF) power to total power of SV fluctuation (LF/TP(SV): %/mmHg) by spectral analysis of mean blood pressure and SV fluctuations, the gain in low-frequency band between two signals in supine and 60 degrees upright positions, and compared these values to baroreceptor-heart rate reflex sensitivity in 14 healthy subjects. Baroreceptor-SV reflex sensitivity correlated significantly with baroreceptor-heart rate reflex sensitivity (r = 0.73, p < 0.0001). In addition, baroreceptor-SV reflex sensitivity correlated significantly and positively with high frequency (HF) power (r = 0.57, p < 0.005) and negatively with LF/HF ratio (r = -0.57, p < 0.005) in power spectral analysis of R-R interval variability. Moreover, baroreceptor-SV reflex sensitivity in LF/TP(SV) correlated positively with the R-R interval (r = 0.70, p < 0.0001) and negatively with diastolic blood pressure (r = -0.50, p < 0.01). We conclude that baroreceptor-SV reflex sensitivity in LF/TP(SV) can be used as a quantitative probe of baroreceptor-cardiac reflex, similar to the baroreceptor-heart rate reflex sensitivity in healthy subjects, and it may enable us to estimate inotropic aspect in baroreceptor-cardiac reflex in patients with chronotropic incompetence and/or implanted pacemaker.

Adult↗
PubMed1999

The stretch reflex and H-reflex of the human soleus muscle during walking.

Due to the complexity of applying a well-defined stretch during human walking, most of our knowledge about the short latency stretch reflex modulation in humans is based on H-reflex studies. To illuminate the difference between the two methodologies, both types of reflexes were evoked in the same subjects, same experiment. Stretch reflexes were evoked via a stretch device capable of evoking stretch reflexes of the human soleus muscles during walking. H-reflexes were elicited by an electrical stimulation of the tibial nerve at the popliteal fossa at the knee. A significantly different modulation of the two reflexes was found in the late stance where the stretch reflex decreased in relation to the H-reflex. This was consistent with the unloading of the muscle spindles during the push-off in the late stance, suggesting a complex alpha-gamma coactivation, if any, at this time of the step. The soleus stretch reflex and H-reflex were compared during the stance phase of walking and sitting at matched soleus activity. No difference was found in the amplitude of the stretch reflex. However, there was a significant decrease of the H-reflex during the stance phase of walking, consistent with a task-specific presynaptic mediated reflex control. It is proposed that the short latency stretch reflex during walking is not sensitive to such a presynaptic inhibition.

Adult↗
PubMed1992

The relationships between the degree of grasp-reflex asymmetry, grasp-reflex strength from the right and left hands, and body weight in the male and female newborn with and without familial sinistrality.

The relation of the degree of grasp-reflex asymmetry to the strength of right- and left-hand grasp-reflex strength and body weight was studied in human newborn. In the total sample (N = 103), the right minus left (R-L) reflex strength was found to be positively linearly related to the grasp-reflex strengths from the right and left hands in FS-subjects; the correlation was higher for the right hand than the left hand. In FS+ subjects (N = 17), there was not a significant correlation between R-L and right-reflex strength; left-reflex strength was found to be negatively linearly related to the R-L reflex strength. In FS- subjects, the right- and left-reflex strengths showed a positive linear correlation with body weight. In FS+ subjects, only the left-reflex showed a positive linear correlation with body weight. The R-L reflex tended to be positively correlated with body weight in FS- subjects and negatively correlated in FS+ subjects. In females (N = 58), the relation of R-L to right and left reflex was similar to that for the total sample. There was no significant correlation between grasp reflex and body weight in FS- females. In FS+ females (N = 8), there was a positive linear correlation between the right grasp-reflex and body weight; the left grasp-reflex did not show such a significant correlation. The R-L grasp-reflex strength was not correlated with body weight in females.(ABSTRACT TRUNCATED AT 250 WORDS)

Body Weight↗
PubMed2001

Detection of red reflex asymmetry by pediatric residents using the Brückner reflex versus the MTI photoscreener.

OBJECTIVE: To compare the ability of pediatric residents to differentiate an asymmetric from a symmetric red reflex in patients with anisometropia and microstrabismus using the Brückner reflex and the Medical Technology Innovations (MTI) photoscreener. METHODS: A prospective, masked, case-control study was performed. Twelve pediatric residents evaluated 10 study patients and 6 control subjects in a masked manner in 2 separate sessions, using the Brückner reflex or the MTI photoscreener, evaluating for asymmetric (abnormal) or symmetric (normal) red reflexes between the 2 eyes. Each study patient had asymmetric red reflexes and the amblyogenic risk factor of anisometropia or microstrabismus. Each control subject had symmetric red reflexes. RESULTS: The pediatric residents had a mean correct score of 82% (69%-100%) using the MTI photoscreener versus a mean correct score of 65% (44%-81%) using the Brückner reflex (McNemar test: alpha < 0.01). The sensitivity of the MTI photoscreener evaluation was 89% in comparison to 61% for the Brückner reflex. The specificities for the MTI photoscreener versus the Brückner reflex were similar at 69% and 71%, respectively. CONCLUSIONS: Pediatric residents were better at detecting asymmetric red reflexes in patients with anisometropia and microstrabismus when evaluating MTI photoscreener photographs than when evaluating the red reflexes by the Brückner reflex. The MTI photoscreener may be a more sensitive method than the Brückner reflex to screen for the common amblyogenic risk factors of anisometropia and microstrabismus by easier detection of red reflex asymmetry.

Adult↗
PubMed2003

The effect of quadriceps-electrocutaneous stimulation on the T-reflex and the H-reflex of the soleus muscle.

OBJECTIVE: To investigate the effect of ipsilateral quadriceps-electrocutaneous stimulation on the T-reflex and the H-reflex of the soleus muscle, and to examine the interactions in human cutaneous sensation - the soleus motoneuron pathway. METHODS: The T-reflex and H-reflex tests were performed bilaterally on 50 able-bodied adults with a standardized technique using the soleus muscle. The reflexes were conditioned by electrocutaneous stimuli applied to the ipsilateral quadriceps using the optimal transcutaneous electrical nerve stimulation (TENS) machine (3 x perception, intensity 15-30 mA). The conditioning stimuli were followed by reflex tests by 30-50 ms (conditioning A) and 80-100 ms (conditioning B). The latency and amplitude of the T-reflex and H-reflex were measured before (control) and after conditioning stimuli (A and B) and at sham (placebo). RESULTS: There were no significant differences between the right and left sides and between the control and placebo in both T-reflex and H-reflex. There were significant differences in both latency and amplitude of the T-reflex only between control and conditioning A. There were no significant differences between control and conditioning tests in the H-reflex. CONCLUSIONS: The above results suggest that supraspinal center and cutaneous fusimotor reflexes, which increase the sensitivity of the soleus muscle spindle, mediate the observed motoneuron excitability changes.

Adult↗