Neutral wrist splinting in carpal tunnel syndrome: a comparison of night-only versus full-time wear instructions

OBJECTIVE: To compare the effects of night-only to full-time splint wear instructions on symptoms, function, and impairment in carpal tunnel syndrome (CTS). DESIGN: Randomized clinical trial with 6-week follow-up. SETTING: Veterans Administration Medical Center, outpatient clinic. SUBJECTS: Outpatients with untreated CTS were consecutively recruited from our electrodiagnostics lab. Twenty-one patients (30 hands) were enrolled, and 17 patients (24 hands) completed the study. INTERVENTIONS: Thermoplastic, custom-molded, neutral wrist splints with subjects receiving either full-time or night-only wear instructions. OUTCOME MEASURES: Symptoms and functional deficits were measured by Levine's self-administered questionnaire, and physiologic impairment was measured by median nerve sensory and motor distal latency. COMPLIANCE AND CROSSOVER: Almost all (92%) of the combined sample reported frequent splint use, but their adherence to specific wearing instructions was limited. A majority (73%) of the full-time group reported splint wear less than one half of waking hours, and some (23%) of the night-only group reported occasional daytime wear. Despite this tendency for treatment crossover, the two treatment groups differed in daytime wear as intended (chi2 analysis, p = .004). RESULTS: The combined sample improved in three of four outcome measures: sensory distal latency (mean = .28msec, standard deviation [SD] = .37, p = .004), symptom severity (mean = .64, SD = .46, p = .0001), and functional deficits (mean = .49, SD = .51, p = .0001). Severity of CTS was a factor only in sensory distal latency improvement (more improvement in severe CTS). Subjects receiving full-time wear instructions showed superior distal latency improvement, both motor (.35 vs -.07msec, p = .04) and sensory (.46 vs . 13msec, p = .05) when compared with subjects receiving night-only wear instructions. CONCLUSIONS: This study provides added scientific evidence to support the efficacy of neutral wrist splints in CTS and suggests that physiologic improvement is best with full-time splint wear instructions.     

Across-tarsal-tunnel motor-nerve conduction technique.

Tarsal tunnel syndrome is a commonly considered compression of the tibial nerve and its plantar divisions as the nerve curves behind the medial malleolus underneath the flexor retinaculum. Motor, sensory, and/or mixed-nerve conduction studies are used to confirm or exclude the presence of compression of the posterior tibial nerve and its plantar divisions. In previous studies, stimulation has been done either proximal to the tunnel or distally in the sole of the feet or in the toes. Thus, differentiation between compression of the nerve within the proximal tarsal tunnel, as distinguished from compression of the plantar nerves in the distal tarsal tunnel or distal to the tunnel, has not been feasible. In addition, onset latency is frequently difficult to measure, and peak latencies have not been reported for the motor-evoked action potential. This study reports across-tarsal-tunnel latencies and amplitude decrements for both the medial and the lateral plantar nerves. For the medial plantar nerve with active electrodes placed over the medial head of the flexor pollicis brevis, the calculated mean + 2SD across tunnel onset latency is 3.2msec, peak latency is 2.9msec, and amplitude decrement is 29.3%. For the lateral plantar division, the calculated across-tunnel onset latency is 3.2msec, peak latency is 2.9msec, and amplitude decrement is 27.2%. Medial plantar nerve latency distal to the tarsal tunnel for the mean + 2SD is 5.9msec to onset and 9.5msec to peak, and the lateral plantar nerve latency is onset 5.9msec and peak 9.7msec.     

Paired study of the dorsal cutaneous ulnar and superficial radial sensory nerves

Nerve conduction studies of the dorsal cutaneous ulnar nerve (DCU) have been suggested as a useful technique for identifying distal ulnar nerve lesions. In this study a standardized method was used to establish normal conduction parameters of the DCU that were compared to conduction parameters of the superficial radial sensory nerve (SR) in the same extremity. Fifty-five extremities of 33 neurologically healthy subjects aged 22 to 69 years (mean = 37; SD = 13) were examined. Dorsal hand skin temperature of each subject was 31 to 36 C. The DCU and SR were antidromically stimulated 14cm proximal to plastic-mounted bipolar electrodes placed on the dorsum of the hand over each nerve. Latency to onset, latency to peak, and amplitude (mean +/- 2SD) for the DCU were 2.2 +/- 0.3msec, 2.8 +/- 0.5msec, and 24 +/- 17 microV; and for the SR were 2.2 +/- 0.3msec, 2.8 +/- 0.3msec, and 32 +/- 18 microV, respectively. Significant correlations (p less than 0.005) were found between the DCU and SR latencies to onset, and DCU and SR latencies to peak. These results suggest that distal sensory latencies of the DCU and SR are similar, and that a paired study of these nerves may be useful in distinguishing distal ulnar nerve entrapment syndromes when routine studies are equivocal.     

Visual function with acupuncture tested by visual evoked potential

Visual evoked potential (VEP) testing is used frequently and is an important ophthalmologic physiological test to examine visual functions objectively. The VEP is a complicated waveform consisting of negative waveform named N75 and N135, and positive waveform named P100. Delayed P100 latency and greatly attenuated amplitude on VEP are known characteristics for diagnosing optic nerve disease. Acupuncture has been used to treat wide clinical symptoms with minimal side effects. The confirmation of the efficacy of acupuncture generally relies on subjective symptoms. There is not much scientific evidence supporting the acupuncture treatments for eye diseases up to today. However, the VEP test can evaluate objectively and numerically the efficacy of the treatment by the acupuncture. We analyzed 19 healthy subjects (38 eyes). The P100 latencies in the group of less than 101.7 msec (total average) before acupuncture stimulations were not different than those after treatment (98.2 +/- 3.0 msec, 98.2 +/- 4.0 msec, respectively, p = 0.88, n = 17), but the latencies in those subjects with longer or equal to 101.7 msec were statistically different after acupuncture (104.6 +/- 2.8 msec, 101.9 +/- 3.7 msec, respectively, p = 0.006, n = 21). These results show that the acupuncture stimulation contributes to the P100 latencies of pattern reversal (PR)-VEP to some subjects who have delayed latencies, and this electrophysiological method is a valuable technique in monitoring the effectiveness of acupuncture therapy in the improvements of visual functions. The purpose of this study is to evaluate the physiological effects by acupuncture stimulations using PR-VEP in normal subjects.     

Reference values for peroneal nerve motor conduction to the tibialis anterior and for peroneal vs. tibial latencies

OBJECTIVE: To generate a large normative database for the peroneal study to the tibialis anterior and to analyze differences between the peroneal latency to the extensor digitorum brevis and the tibial latency to the abductor hallucis. DESIGN: A total of 244 asymptomatic subjects without risk factors for neuropathy were tested for latency, amplitude, area, duration, and nerve conduction velocity to the tibialis anterior. For the peroneal/tibial analysis, 221 subjects were included. Temperature control was used, and demographic characteristics were recorded. RESULTS: Latency to the tibialis anterior increased and nerve conduction velocity decreased with increasing height. Amplitudes, area, and nerve conduction velocity were lower in older persons. The upper limits of normal (97th percentile) were 4.9 msec (latency) and 15.0 msec (duration). The lower limits of normal (3rd percentile) were 1.7 mV (amplitude), 6.8 microV/sec (area), and 43 m/sec (nerve conduction velocity). The upper limits of normal side-to-side difference was 1.2 msec (latency), 6.3 msec (duration), 50% (amplitude), 47% (area), and 20% (nerve conduction velocity). The upper limits of normal drop from below- to above-fibular-head stimulation was 36% (amplitude) and 43% (area). For the peroneal/tibial comparison, the upper limits of normal latency increase of peroneal over tibial was 1.8 msec and tibial over peroneal was 1.5 msec. CONCLUSION: A large normative database was collected. Upper and lower limits of normal were calculated, and side-to-side differences were analyzed. For the peroneal/tibial comparison, an upper limits of normal difference was described.     

Nonuniformity of AH Intervals During Stimulation at Different Left Atrial Sites

Studies in humans have found left atrial stimulation via the coronary sinus (CS) to elicit significantly shorter atrium-His (AH) intervals as compared to right atrial stimulation, but whether pacing at dijferent left atrial sites (anterior vs posterior left atrium, i.e., far distal vs proximal CSJ affects the AH interval has not been studied. Hence, in 22 patients, we compared the effects of stimulation from various atriai sites, including anterior high right atrium (HRA), distal CS, mid-CS, and proximal CS, on; stimulus-atrium (SA), AH, and stimuIus-His intervals on the His bundle electrogram. Paced cycle length differed for each patient (range 900–350 msec, mean 532 ± 140 msec), but conduction intervals from different atrial sites were compared using identical cycle length in each patient. The mean SA intervals were 34 ± 10 msec, 57 ± 10 msec, 44 ± 11 msec, and 32 ± 8 msec with stimulation, respectively, from HRA, distal CS, mid-CS. and proximal CS (each significantly different except for HRA vs proximal CSJ. The mean AH intervals were 123 ± 23 msec, 104 ± 28 msec, 95 ± 15 msec, and 90 ± 18 msec with stimulation, respectively, from HRA, distal CS, mid-CS, and proximal CS (each significantly different except for mid-CS vs proximal CSJ. In 13 patients, the discrepancy in AH intervals during distal versus proximal CS stimulation was > 15 msec; in 9 patients this difference was only < 10 msec, considered within the range of measurement error. Thus, in a significant portion of patients, discrepant AH intervals were demonstrated during stimulation from the distal versus proximal CS. These previously undescribed observations suggest that electrophysiological studies on atrioventricular nodal conduction that involve left atrial stimulation must take into account actual location of the stimulation site (anterior or posterior) in order to properly interpret the findings.     

Quantitative Relationship Between Atrial Refractoriness and the Dispersion of Refractoriness in Atrial Vulnerability

We investigated the quantitative relationship between the atrial refractory period and the dispersion of refractoriness with respect to atrial vulnerability in 19 adult mongrel dogs. The atrial effective refractory period (AERP) was measured at the sinus node area (SNA), the low posterior right atrium (LRA), and the distal coronary sinus. The study was performed under the following conditions: (1) control status; (2) hypothermia (30°C); (3) vagus nerve stimulation; and (4) a combination of (2) and (3). The subjects were separated into two groups: atrial fibrillation (AF) (+) group (n = 23), which developed AF by atrial extrastimulus due to increased vulnerability, and AF (−) group (n = 39), which did not develop AF. The mean AERP was 97 ± 23 msec (mean ± SD) in the AF (+) group and 124 ± 23 msec in the AF (−) group, with a significantly shorter refractory period seen in the former (P < 0.001). The dispersion of refractoriness was 59 ± 24 msec in the AF (+) group and 29 ± 18 msec in the AF (−) group, with a significant increase noted in the former (P < 0.001), On X-Y coordinates (where X denotes the AERP, and Y denotes the dispersion of refractoriness) the data from the AF (+) group were clustered in the upper left region of the graph while the data from the AF (−) group were clustered in the lower right region. These two groups were separated by a linear equation of Y = 0.86X - 57 with a predictability of 90.3%. No difference in the time from SNA stimulation to LRA excitation was found between the groups. On the basis of these results, we suggest that increased atria) vulnerability can be predicted from an analysis of the quantitative relationship between the atrial refractory period and the dispersion of refractoriness.     

Temperature effect on antidromic and orthodromic sensory nerve action potential latency and amplitude

The measurement of sensory nerve action potential (SNAP) latency and amplitude is often necessary to accurately diagnose disorders of peripheral nerves. The sensory evoked response can be obtained using either the antidromic (AD) or orthodromic (OD) technique. In a previous study we demonstrated that in healthy subjects the AD SNAP distal latency of median and ulnar nerves at 14 cm distance is approximately 0.2 msec slower than the OD SNAP distal latency at 32C. The AD SNAP amplitude was also two times greater than the OD SNAP amplitude. In this study we observed that these differences between the AD and OD SNAP latency and amplitude varied significantly as temperature changed. The AD median nerve SNAP distal latency was delayed by .06 msec/degree with cooling. The OD median nerve SNAP distal latency was delayed by .03 msec/degree with cooling. These values represent less of a slowing per degree centigrade cooling than has been previously noted in the literature. The median nerve SNAP amplitude was found to increase with upper extremity cooling with the AD and OD technique by 3.5 microV and 0.5 microV per degree, respectively. For accurate interpretation of SNAP latency and amplitude, the electromyographer must be familiar with the technique used and the differing effect of the temperature with each technique.     

Muscle sounds from evoked twitches in the hand

Skeletal muscle emits acoustic signals during voluntary contraction and during twitches produced by electric stimulation of peripheral nerves. Supramaximal, percutaneous electric stimulation was applied to the median or ulnar nerve, while electric and sound signals were recorded from the abductor pollicis brevis or abductor digiti minimi muscles, respectively, in 27 volunteers without known disease. Reproducible waveforms were obtained with the following means and standard deviations: (1) latency from stimulus to onset of sound, median = 6.9 +/- 0.8msec, ulnar = 6.6 +/- 1.0msec; (2) latency from stimulus to peak of sound, median = 15.1 +/- 1.5msec, ulnar = 13.1 +/- 1.5msec; (3) latency from onset of surface electric to onset of sound, median = 3.6 +/- 1.0msec, ulnar = 3.9 +/- 1.1msec; (4) baseline-to-peak amplitude of sound, median = 860 +/- 270mV, ulnar = 640 +/- 230mV; and (5) baseline-to-peak amplitude of surface electric, median = 11.4 +/- 3.0mV, ulnar = 10.1 +/- 2.4mV. Stimulated muscle sounds are useful when artifacts, such as tremor, interfere with voluntary muscle sound recordings, or when quantitative information is needed to relate electric to contractile muscle activity.     

尺神经共同刺激影响腕管综合征正中神经远端潜伏期：避免误差的定量测定

目的研究尺神经-大鱼际复合肌肉动作电位(CMAP)潜伏期正常值,以定量分析尺神经共同刺激所致腕管综合征(CTS)患者正中神经-大鱼际潜伏期的误差。 方法正常组112例,记录224侧正中神经-拇短展肌（APB）和224侧尺神经-大鱼际的CMAP潜伏期和波幅。另对其中10例20侧正中神经,分别记录以正中神经-APB最大波幅之刺激强度的30%、50%、70%、100%刺激时的CMAP潜伏期和波幅。其中4例分别予以120%、150%和200%的超强刺激,记录CMAP潜伏期和波幅。CTS组16例,记录到正中神经-APB的CMAP最大波幅后,继续增大刺激强度,记录尺神经共同刺激效应后的正中神经-大鱼际CMAP。 结果①正常组：尺神经-大鱼际远端潜伏期为（3.17±0.25）ms,波幅为（6.60±1.07）mV;正中神经-APB远端潜伏期为(3.45±0.31)ms,波幅为(6.47±1.08)mV。当正中神经刺激强度从引出最大CMAP波幅之强度的30%、50%、70%增加至100%,正中神经远端潜伏期相应缩短0.1~0.3ms;达到最大波幅后继续增加刺激强度至120%、150%和200%的超强刺激,则潜伏期不再继续缩短。②CTS组：尺神经共同刺激所引起的正中神经-大鱼际CMAP潜伏期缩短范围为0.5~8.7ms,导致正中神经-APB的错误潜伏期范围为(2.9~4.1)ms。 结论CTS患者正中神经检测时,若正中神经-APB CMAP潜伏期随刺激强度增大而缩短超过0.3ms,并且达到2.9~4.1ms的范围,则提示可能发生了尺神经共同刺激。     

Median nerve determinations: analysis of two techniques

The objective of this study was to compare two techniques of obtaining median motor and sensory nerve determinants. One method utilized premeasured electrode placement, while the other used anatomic landmarks. It was postulated that increased accuracy could be achieved by more precise measuring techniques. The right median nerve in 50 able-bodied subjects was investigated. Each subject was tested by both anatomic and premeasured methods. Skin temperatures were maintained between 31C and 33C. Latencies were measured to onset and peak, and amplitudes were gauged from baseline to peak. Latency studies were evaluated. Results concluded that mean distal motor latencies, stimulating 8cm from active recording electrode, was 3.1msec +/- 0.4 and amplitude was 11.1mV +/- 3.0. Stimulating at distal wrist crease, mean latency was 2.6msec +/- 0.38 and amplitude was 11.3mV +/- 3.6. Sensory latencies to onset of response when stimulating 14cm from active ring electrode with reference 4cm distally were 2.1msec +/- 0.25. Sensory latency when stimulating at wrist crease and ring electrodes over proximal interphalangeal and distal interphalangeal joints was 2.1msec +/- 0.25 to onset and 2.8msec +/- 0.32 to peak and amplitude was 36.1 +/- 14.6. The authors concluded that there was no statistically significant difference in accuracy between the premeasured and anatomic methods.     

Electrodiagnostic values through the thoracic outlet using C8 root needle studies, F-waves, and cervical somatosensory evoked potentials

Mid-humerus cadaver determinations of ulnar F-wave, C7 spinal somatosensory evoked potential (SEP), and modified C8 root stimulation (RS) were performed bilaterally on 20 normal subjects to standardize technique and obtain normal values for the segment from mid-humerus to cervical spine. Our cadaver study shows that the best position for upper extremity measurement of mid-humerus-cervical spine distance is at 60 degrees of shoulder abduction, 45 degrees of internal rotation, and at the distance of 35cm, measured by caliper. Using this position and distance the following normal values were obtained: 1) Mid-humerus F-wave minimal, maximal, and mean latencies, and minimal nerve conduction velocity (NCV) were 21.8 +/- 1.2msec, 22.3 +/- 1.2msec, 22.3 +/- 1.1msec, and 59.7 +/- 2.4m/sec, respectively. Latency difference between minimal and maximal F-wave was 1.4 +/- 0.4msec. 2) Cervical spine SEP was 5.1 +/- 0.4msec, with left to right difference of less than 0.9msec. 3) C8 RS and mid-humerus ulnar nerve (UN) pick-up latency and NCV were 4.9 +/- 0.2msec and 71.4 +/- 2.2m/sec, whereas C8 root pick-up and mid-humerus UN stimulation latency and NCV were 5.2 +/- 0.4msec and 66.9 +/- 5.2m/sec, respectively. To evaluate proximal nerve conductivity through the thoracic outlet, the sequential use of the three modified techniques for 35cm mid-humerus-cervical spine distance is recommended.     

Palmar conduction time of median and ulnar nerves of normal subjects and patients with carpal tunnel syndrome.

The wrist-palm conduction time for the median and ulnar nerves was determined using antidromic technique in thirty normal subjects. For the median nerve, the conduction time was 1.6 msec. to initial deflection from baseline and 1.7 msec. to peak of the initial negative deflection for the mean plus 2 SD. The median wrist-palm conduction time was then compared to the difference between the median and ulnar wrist-digit conduction times (mean plus 2 SD of 0.5 msec. measured either to initial deflection or peak negative deflection) in order to determine which technique aids more in the electrodiagnosis of patients with a presumptive clinical diagnosis of carpal tunnel syndrome but which normal distal sensory latencies. It was found in ten patients that the results of these two electrodiagnostic methods paralleled each other, and neither appeared more sensitive than the other in establishing the diagnosis.     

Effects of transcutaneous electrical nerve stimulation and aspirin on late somatosensory evoked potentials in normal subjects

The effects on late somatosensory evoked potentials (SEPs) of transcutaneous nerve stimulation (TENS) and aspirin (600 mg), compared with placebo, were studied in 32 young, healthy male and female volunteers. SEPs were produced by electrical stimulation of the median nerve at moderate, non-painful, intensities. There was a reduction in the peak-to-peak amplitude of the late components N1P2 (N1 latency: 100-160 msec; P2 latency: 160-260 msec) of the SEP in all groups over time. TENS but not aspirin produced further significant changes compared with placebo, including a fall in N1P2 amplitude, an increase in N1 latency, and a decrease in the total excursion of the SEP between 25 and 450 msec after stimulus onset.     

Conduction studies of the medial cutaneous nerve of the forearm

The forearm medial cutaneous nerve is a pure sensory branch from the medial cord of the brachial plexus. Its fibers are derived from the eighth cervical and first thoracic nerves. A simple, easily reproducible antidromic technique for studying conduction of the forearm medial cutaneous nerve is described with the knowledge (obtained from cadaver dissections) of its exact topography. Sixty nerves were studied in 30 able-bodied adults, 15 women and 15 men. Surface stimulation was done over the medial aspect of the middle of the arm at a level where the nerve pierces the deep fascia. Surface recordings were made 18cm distally over the course of its volar branch. Action potentials were obtained in 100% of the subjects without electronic averaging. Mean values obtained were as follows: latency to onset 2.73 +/- 0.17 msec; latency to peak 3.31 +/- 0.19 msec; conduction velocity of the fastest fibers 65.9 +/- 4.3 m/s; amplitude 15.4 +/- 4.1 microvolts, and the mean difference in latency between the right and left nerves in the same subject was 0.1 msec. Conduction studies of this nerve should be useful in electrodiagnostic evaluation of peripheral neuropathy (particularly in below amputees), local neuropathic conditions, and entrapment syndromes involving the medial cord of the brachial plexus.     

Averaged axillary F-loop latency of median and ulnar nerves

Axillary F-loop latencies (AFLL) were measured on median and ulnar nerves of 54 normal volunteers. The median and ulnar nerves were stimulated at the wrist and at the axilla 25cm distal to the sternal notch. The compound muscle action potentials were recorded from thenar and hypothenar muscles. Averaged tracings from 32 consecutive stimuli at the wrist were obtained. The averaged F-wave latencies were measured to the peak (Fwp) of the averaged F-wave. The M-wave latencies from wrist and axilla stimulation were measured to the onset of the wave (Mw and Ma, respectively). The averaged AFLL (a-AFLL) was calculated as (Fwp + Mw)-2 Ma. The average values of a-AFLL were 14.12 +/- 0.88msec for median nerve, and 13.97 +/- 0.90msec for ulnar nerve. There was no significant difference between male and female subjects, nor between the right and left sides. Seven subjects with EMG evidence of C8 or C8 to T1 radiculopathy, although manifesting normal AFLL gauged by the regular method (ie, measured to the onset of the shortest F-wave latency among eight tracings), had significantly longer "averaged AFLL" in both median and ulnar nerves of the affected side than the a-AFLL obtained from the normal side. It is concluded that the a-AFLL is a more sensitive measure than the "regular AFLL" in the assessment of proximal nerve lesion (especially C8 or C8 to T1 radiculopathy).     

Ulnar nerve involvement in carpal tunnel syndrome

This is a retrospective study of the involvement of the ulnar nerve in patients with electrodiagnostic evidence of carpal tunnel syndrome as defined by median sensory nerve action potential (SNAP) greater than 3.6msec at the wrist and/or motor distal latency in excess of 4.3msec. The study included 248 patients, 63 (25%) with unilateral and 185 (75%) with bilateral carpal tunnel syndrome. The electrodiagnostic criteria for ulnar nerve involvement was a SNAP peak latency greater than 3.7msec and/or motor distal latency in excess of 4.2msec. One hundred fourteen patients (46%) had delayed ulnar SNAP peak at the wrist; of these, 100 cases had bilateral ulnar nerve involvement and 14 had unilateral abnormalities. Slowing of the motor nerve conduction velocity for the elbow-wrist segment was noted in 24% and 15% of the study group for the median and ulnar nerves, respectively. An incidental finding was the presence of "double crush syndrome" in 35 patients (14%). The results of this study suggest the frequent association of ulnar nerve involvement at the wrist for sensory fibers and carpal tunnel syndrome.     

Meralgia paresthetica: the diagnostic value of somatosensory evoked potentials.

Somatosensory evoked potentials elicited by stimulation of the lateral femoral cutaneous nerve were investigated in 20 able-bodied persons and 22 patients diagnosed clinically to have meralgia paresthetica. There was no statistically significant difference between the right and left sides for P0 and N1 latencies in able-bodies subjects. For all patients, abnormalities were found on the side clinically affected. The mean values were 38.11 msec for P0 and 47.49msec for N1 on the affected side and 32.62msec and 41.44msec on the unaffected side (p less than .01). The mean latency differences between the two sides P0 and N1 were 5.49msec and 6.05msec, respectively (p less than .01). Hence, this technique proved to be a useful objective diagnostic aid in meralgia paresthetica.     

Properties of the inhibitory junction potentials recorded from smooth muscle cells of the guinea-pig duodenum

Inhibitory junction potentials (IJPs) in response to single or repetitive stimulation were recorded intracellularly from smooth muscles of the guinea-pig duodenum. The amplitude of the IJP was dependent on the stimulus intensity and duration. The hyperpolarization of up to 30 mV was evoked by a single pulse. The mean values of the latency, the fall time, the rate of hyperpolarization, the half decay time and the time constant for decay of the IJPs evoked by 0.3 msec stimulation were 67 msec, 130 msec, 86 mV/sec, 156 msec and 194 msec, respectively. The latency and the half decay time were slightly decreased by changes in the stimulus intensity and duration. When repetitive stimulation was applied at low frequencies, successive IJPs were evoked but their amplitudes were decreased gradually. The maximum amplitude of the hyperpolarization was increased with increasing the frequency of stimulation over than 10 Hz. The spike activity due to rebound excitation was potentiated at high frequency. Over 90% of the cells exhibited only the IJP without atropinization. The excitatory junction potentials and the complex type in response to a brief pulse were recorded from a few cells. These results suggest the predominant nonadrenergic inhibition on the duodenal smooth muscles.     

Suprapubic reflex. Electrophysiological study in normal patients]

INTRODUCTION: In spinal cord injuries patients, tapping the suprapubic aera is a strong stimulus to ellicit detrusor contraction and can be used in the management of neurogenic bladder. This stimulation also determines a perineal muscles contraction. This striated response was mentionned in animal studies but never specifically analysed in men especially in normal subjects.AIMS OF THE STUDY: Our objective was to describe pelvic floor responses with measurement of reflex latency following suprapubic mechanical stimulation.METHODS: 21 patients without neurological disease were studied. They were 14 women and 7 men. Mean age was 51 (SD=14,2). Motor responses were recorded with a needle electrode inserted in the left bulbocavernosus muscle. Stimulation was delivered with an electromechanical hammer, tapping directly on the suprapubic aera.RESULTS: A polyphasic muscular response was always and easily elicited in all patients. Mean latency was 67,5 ms. (SD = 14,7). The reproducibility between the first and second mechanical responses was good with no statistical difference (r=0,966; p=0,0001).DISCUSSION: Our study clearly demonstrates a suprapubic bulbocavernosus reflex (SBR). Many arguments can be retained for a polysynaptic reflex (polyphasic response, habituation and short latency of the reflex, mean latency in the habitual values of R2 responses following electrical stimulation of the dorsal nerve of the penis). We hypothetize that: the true stimulus is the stimulation of the bladder wall tenso-receptors; integration level of the SBR is the sacral segments and the efferent limb the pudendal nerve; afferent pathways could be vehicled by pelvic nerve fibers.CONCLUSION: Competition between a preponderant (or exaggerated) SBR and a bladder contraction following suprapubic tapping, may constitute a real functional outlet obstruction giving incomplete or complete retention in some suprasacral bladders. In normal subjects, SBR can be considered as a continence reflex with increase of perineal tone following the stimulation of the bladder wall tenso-receptors during stress.