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Electrodiagnosis of Striated Urethral Sphincter Dysfunction
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0022-5347/79/1223-0361$02.00/0 THE JOURNAL OF UROLOGY Copyright© 1979 by The Williams & Wilkins Co.
Vol. 122, September Printed in U.S.A.
ELECTRODIAGNOSIS o~:[~!~~~o~RETHRAL SPHINCTER
;~~:
t~'';_,
MARGARETE DIBENEDETTO
AND
SUBBARAO V. YALLA *
From the Department of Physical Medicine and Rehabilitation, Division of Urology, Surgical Service, Veterans Administration Hospital, West Roxbury and the Harvard Program in Urology (Longwood Area), Boston, Massachusetts
ABSTRACT
In many centers urethral striated sphincter electromyography has become an essential component of urodynamic testing. The urologist who uses this modality of investigation in an attempt to understand the pathophysiology of striated sphincter dysfunction must have some basic knowledge of electromyography. Attempts have been made to provide such basic information, especially relating to the methods of evaluation and interpretation. We also have incorporated our own views based on our experience with more than 200 subjects with neuropathic vesicourethral dysfunctions. The most common clinical problems necessitating sphincter evaluation are neurological disorders resulting in urinary obstructions and/or incontinence, myelodysplasia, multiple sclerosis, diabetes mellitus, peripheral neuropathy involving pelvic floor and perineal musculature, sexual dysfunctions, spinal cord injuries and tumors, and conditions with unexplained urodynamic abnormalities. The electrodiagnosis of striated urethral dysfunction is comprised of sphincter electromyography to evaluate the intrinsic activity at rest, appraisal of action potential parameters on volition and quantification of recruitment on maximal effort. In addition, kinesiological assessment may be performed synchronously with urodynamic evaluation. 1 In our studies on >200 subjects we elicited, in addition to the record of the sphincter activity at rest, during bladder filling and voiding, its reflex responses to mechanical bulbocavernosus stimulation. Electrobulbocavernosus stimulation was introduced recently to quantitate the stimulus and to record sacral cord reflex transit time. 2 Sphincter activity also is monitored during various bladder rehabilitative maneuvers. 3 We herein review the literature on sphincter electromyography and submit our views on methods of evaluation and interpretation of various neuropathic sphincter dysfunctions. MATERIAL, METHOD AND INTERPRETATION
The transperineal route is used in all of our studies in which a coaxial needle electrode is used. t The needle is introduced through the perineum in the midline and the tip is guided to the level of the apex of the prostate while a finger is in the rectum to palpate the prostate. In female patients the electrode needle is introduced either transvaginally or at a site lateral to the urethral meatus. The needle is introduced paraurethrally 1 to 1.5 cm. deep towards the mid urethral segment. Fluoroscopic observation of the tip of the electrode needle in relation to the urethral catheter and anatomic landmarks of symphysis pubis will assist in the accurate placement of the electrode into the periurethral striated musculature. Oscilloscopic and audio findings will establish the correct placement of the needle electrode. In subjects with complete, long-standing lower motor neuron sphincter lesions complete electric silence will make the investigator rely only upon fluoroscopic observations. We advocate the aforementioned techniques and find them useful in our evaluations. Other electromyographic techniques also have been described. 4 Instead of a coaxial type, monopolar needles may be used, placing a superficial reference electrode on the Accepted for publication September 29, 1978. * Requests for reprints: Veterans Administration Hospital, 1400 VFW Parkway, West Roxbury, Massachusetts 02132. t DISA Electronics, 779 Susquehanna Ave., Franklin Lakes, New Jersey 07417.
thigh. Wire electrodes can be placed on either side of the sphincter because they have the advantage of not being displaced in studies of long duration. Some workers use bipolar surface electrodes mounted on an anal plug to record the combined activity of the external anal sphincter. 5 We have used coaxial needle electrodes introduced at the anal mucocutaneous junction. We also record the anal sphincter activity with synchronous monitoring of the urethral sphincter activity. We realize that disassociation may be demonstrated by both sphincters, especially in incomplete neurological lesions and in patients who earlier had an anal operation. Extrapolation of the anal sphincter activity with the striated urethral sphincter function could, therefore, lead to erroneous impressions. Paper readout interpretation of the electromyographic activity must be done with caution, especially when recording is done with pen recording systems. Blaivas and associates reemphasized the importance of oscilloscopic observations for more accurate analysis. 6 The slow paper speed (0.5 to 10 mm. per second) causes artifacts such as 60 cycle interference or base line shifts to appear as changes in sphincter activity and induces much error in the analysis. Unless the oscilloscope is observed at the same time and note is made of what really represents electromyographic signals, wrong interpretation may be made. Optimal paper speed to observe action potential parameters is 25 to 35 cm. per second and for kinesiological observations the speed of the paper can be 5 to 10 cm. per second. Basic electromyographic parameters. At rest: The urethral and anal sphincters almost always show continuous low frequency activity (fig. 1). The firing of action potentials range between 1 and 4 per second. These tonic contractions of the sphincter muscles are believed to arise from slow twitch (red) muscle fibers, while rapid response sphincter activity appears to be owing to the function of white or fast twitch fibers. 5 The amplitude of these potentials is 50 to 300 µv. and 3 to 5 msec. in duration. Chantraine reports never to have seen complete relaxation of a sphincter unless the patient was attempting micturition or defecation. 7 He believes that appearance of electrical silence during a rest period indicates displacement of the needle to the pelvic floor muscles, which do show silence at rest. In our experience, however, we have seen occasionally silence at rest in the anal sphincter. Displacement of the needle electrode will be entertained only when the muscle spike activity is not demonstrated on reflex maneuvers. This silence was observed after prolonged examination. It is important to point out also that even in healthy subjects the anal sphincter frequently shows less activity than the urethral sphincter without any apparent abnormality in this muscle.
361
362
DIBENEDETTO AND YALLA
Volitional: Action potentials recruited on volition show a mean amplitude of 500 /LV. but may reach 2 or even 3 mv. The mean duration for adults is 5.5 msec. in the urethral sphincter and 5.6 msec. in the anal sphincter, while in children it is 4.2 msec. in the urethral sphincter and 4.5 msec. in the anal sphincter. 7 As in skeletal muscles 7 to 10 per cent polyphasics are to be considered within the norm. Maximal effort: On maximal effort, which can be produced by volitional effort or by reflex maneuvers, a complete interference pattern can be observed. According to W aylonis and Aseff children do not reach the normal adult pattern until they are 70 weeks old and a steady increase of recruitment is noted. 8 From birth to about 6 months a pattern of 2 + out of a scale of 5 may be observed; from 6 to about 16 months a pattern of 3 + is observed and from 19 to 30 months a pattern of 4 + may be seen. It should be noted that testing for the mere presence of anal sphincter activity in infants born with an imperforated anus is of extreme importance before operation to assure proper results. 9 Lower motor neuron lesions. Spontaneous potentials, mainly fibrillations, are observed after denervation. Since the sphincter muscles are small fibrosis sets in quite early and no electrical activity can be identified in a long-standing complete lesion. Ingberg and Johnson report electromyographic findings in infants with myelodysplasia. 10 They found evidence of small fibrillation type continuous potentials of 30 to 50 /LV. in amplitude and a mean duration of 1 msec. preoperatively. Postoperatively, spontaneous potentials showed different parameters (60 to 90 /LV. and an average duration of 1.5 msec.). Whether this finding indicated normal fibrillations (owing to lack of nervous system maturation) in the preoperative phase, as reported in other muscles in the neonatal period, while the postoperative spontaneous potentials represent evidence of definite new denervation, cannot be said at this point. Ingberg also considers the presence of insertional activity in the myelodysplasia in
L.J
IOms FIG. 1. Top line shows striated urethral sphincter base line activity. Second line shows dissociated, low frequency activity of anal sphincter.
children as a favorable sign for later appearance of action potentials. Fibrillation potentials are seen much more frequently than positive sharp waves. It must be noted that in complete sphincter denervation of recent onset recognition of spontaneous potentials does not represent a problem. However, in partial lesions it is quite difficult to delineate spontaneous potentials from action potentials recruited during rest periods. The parameters are frequently the same. We have found the audio information often more helpful than the visual display. We also have observed complete or partial denervation of one of the sphincters with the other sphincter being normal or partially denervated or demonstrating even upper motor neuron findings (fig. 2). This fact reveals the necessity to examine the urethral and the anal sphincters for the sake of accuracy, although anal sphincter recordings in these lesions may not help in the understanding of striated urethral sphincter dysfunction. Volitional: In adults there is marked variation in the amplitude of the observed potentials normally and especially in lower motor neuron lesions. It is possible to find reduced amplitude potentials or action potentials of up to 2 or 3 mv. amplitude. We have found in patients with spinal cord lesions usually a reduced amplitude, while in patients with peripheral nerve lesions amplitudes appear to be increased. Duration usually is increased slightly but not as marked as observed in skeletal muscles. Polyphasia may be 90 to 100 per cent or as little as 10 per cent (fig. 3, A). In children with myelodysplasia Ingberg and Johnson report amplitudes of first recruited action potentials from 100 to 500 /LV. (mean /Lv.) and durations from 4 to 15 msec. in comparison to the normal range they observed from 100 to 1,500 /LV. (mean 500 /LV.) and durations from 2 to 10 msec. 10 High frequency bizarre discharges also can be encountered in sphincters of a small number of patients. In 5 subjects we have observed actually myotonic type discharges presenting the typical waxing and waning characteristics of myotonia (fig. 3, B). Chantraine and associates report bizarre discharges in a small number of patients with myelodysplasia. 11 The myotonic or high frequency bizarre discharges may occur in either one or both sphincters and we have observed these in lower motor neuron as well as in upper motor neuron lesions. One of these patients had a sphincterotomy and the histologic examination of the striated sphincter showed muscle degeneration and fibrosis, which may or may not be related to the observed phenomena. Further investigations are needed in this direction. Maximal effort: As in skeletal muscle lower motor neuron lesions of the sphincters show reduced recruitment in proportion to the amount of denervation present. The aforementioned pathological phenomena can be observed readily in the urethral and anal sphincters. The importance is in the recognition of patients needing this type of examination. This is especially true in children with spina bifida or in adults who do not have
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20ms FIG. 2. Top line shows urethral sphincter (upper motor neuron lesion)-motor units can be identified. Second line represents activity of anal sphincter (lower neuron lesion)-no motor units seen.
ELECTRODIAGNOSIS OF STRIATED URETHRAL SPHINCTER DYSFUNCTION
other objective neurological signs causing suspicion of such involvement. 12 The study on patients with enuresis has shown varied results. Some groups report as much as 60 per cent of the patients showing some form of neurological abnormality, while others report much lower incidences. In postoperative incontinence (post-prostatectomy or radical hysterectomy) varying experiences have been reported. To help distinguish a peripheral nerve involvement from an anterior horn cell lesion pudenda! nerve conduction studies may be performed or the sacral somatic reflex arc can be studied by penile or clitoral stimulation. Kinesiological assessment. This evaluation consists of electromyography of the urethral and anal sphincters during bladder filling, observation of reflex activity during voiding and voluntary depression of reflex activity or volitional-induced voiding. The tests are performed in conjunction with cystometry, allowing investigation of time relationships between detrusor reflex and striated sphincter activity and also the recognition of relationships between increased or decreased bladder or urethral pressures to the pelvic floor muscle activation. Normal bladder-sphincter relationships. At rest with an empty bladder there is minimal electrical activity observed in the urethral and anal sphincters. With increased bladder filling there is a gradual increase in motor unit activity as to the amplitude, the number and the rate of firing. Just before, at
A 100-'fvl '-v-'
IOms B
IOO'fv~
'--v-'
20ms FIG. 3. A, striated urethral sphincter shows polyphasic activity. Patient has alcoholic peripheral neuropathy. B, striated urethral sphincter shows myotonic type activity (with characteristic waxing and waning dive-bomber sound); 17-year-old girl with Ll spinal cord injury lesion.
363
the onset or shortly after voiding there is complete electrical silence. The normal individual can recruit the complete interference pattern immediately on command to stop voiding, which then is followed in 2 to 3 seconds by cessation of urinary flow. Upper motor neuron lesions (reflex or automatic bladder). In contrast to skeletal muscles spontaneous potentials cannot be observed and action potentials are of normal parameters with complete interference patterns on maximal effort. The deviation from the norm is discussed under kinesiological assessment since the study involves measurement of recruitment at different intervals in relation to other observed phenomena. The patient cannot perceive bladder filling or fullness and cannot voluntarily initiate voiding. Micturition is reflex in nature and involuntary. At rest there may be more marked sphincter activity than normal, although at times activity also decreases to a low rate when observed for several hours. There also is increased activity during bladder filling but when voiding starts instead of relaxation further increase in striated sphincter activity is observed (bladder-sphincter dyssynergia). The most common causes for reflex bladder are 1) cord lesion above the conus, 2) massive brain trauma, 3) suprasacral spinal cord tumor, 4) syringomyelia and 5) multiple sclerosis. Lower motor neuron lesion (autonomous bladder). This is a result of loss of sensory or sensory and motor limb of the reflex arc. The patient cannot perceive bladder fullness or voluntarily initiate voiding. However, this can be accomplished by the Crede maneuver. At rest: In complete early lesions, starting 2 to 4 weeks after onset, there are fibrillations. Occasional positive sharp waves also have been reported. In partial lesions resting activity is either diminished or normal. On bladder filling there is less activation of motor units and on voluntary contraction a diminished response never reaching a full interference pattern can be observed. Most common causes for this form of bladder are injuries to the sacral spinal cord or after a radical pelvic operation. While a bladder in spinal shock may have similar responses it must be noted that our observation of the urethral and anal sphincters in patients as early as 24 hours after complete spinal cord injury above the conus have shown good interference patterns (fig. 4). These patients, indeed, were in spinal shock with absence of tendon reflexes and detrusor areflexia. This is opposite to the observations of Melzak and Porter, who saw completely inactive sphincters during spinal shock before the reflex activity recovered. 13 Mixed neurogenic bladder. Patients with this form of abnormality seem to have a combination of upper motor neuron and incomplete lower motor neuron lesions to the external sphincters. Resting motor unit activity may be either normal, decreased or increased. Activation also may fall in any one of these categories. There may be a marked difference in anal and urethral sphincters or even between the different quadrants. Responses in sphincter or other pelvic floor muscles also may
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20ms FIG. 4. Top line shows urethral striated sphincter with motor units and interference pattern; 22-year-old man 3 days after complete C4 spinal cord injury lesion shows motor units.
364
DIBENEDETTO AND Y ALLA
vary. 14 The most common cause for this type of bladder is myelodysplasia or myelomalacia of vascular origin (infarct in the territory of the artery of Adamkiewicz) or compression fractures of Ll. Uninhibited bladder. This type of bladder can occur without any evidence of neurological deficit and consists of the symptomatology of urinary urgency, frequency and incontinence. The vesical reflex arc is intact and functional but the inhibitory fibers from the higher centers are non-functional. The sphincter electromyography shows normal reflex activity but inability or, at least, difficulty for the patient to recruit voluntarily a full pattern to interrupt the voiding stream or voluntarily relax the pelvic floor for initiation of voiding. Recording of reflex activity. The bulbocavernosus reflex is elicited by pinching the glans penis or clitoris, causing reflex contraction of pelvic floor musculature (fig. 5). Clinically, this often is difficult to evaluate especially in normal individuals because of volitional inhibitory influences. Electromyography of the sphincters enhances the ability to recognize the presence or absence of this phenomenon. It is an S2 to S4 integrated spinal cord reflex. Absence suggests a lesion at that level. Increase of abdominal pressure, as in the V alsalva maneuver, coughing or sobbing causes a sudden burst of electrical activity in both sphincters. This response cannot be observed in low sacral lesions or in involvement of lower thoracic and upper lumbar segments supplying the musculature effecting the intraabdominal pressure. Digital-rectal stimulation causes an increase of electrical activity followed by relaxation. However, one can observe in some patients immediate cessation of electrical activity on digital stimulation, indicating pelvic floor relaxation. These phenomena can be seen as long as the lower sacral segments are intact. Electrical-evoked reflex response. Bradley and associates reported a technique of stimulating the bladder mucosa and recording from the anal sphincter, which they called detrusor and urethral electromyelography. 10 Latencies recorded were 50 to 70 msec. They believe this is a measurement of the anatomic integrity of segmental innervation of the detrusor muscle and periurethral striated muscles as well as the corticoregulatory tracts. They observed abolition of response on conscious effort to relax the pelvic floor. Dick and associates studied pudendal sexual reflexes and reported stimulation of the dorsal nerves of the penis with recording from bulbocavernosus and ischiocavernosus muscles. 16 Their latency is 34 to 40 msec. Stimulation from the prostatic urethra evokes a response in 60 msec., while from the distal 2 cm. of the urethra a mean latency of 30 msec. was observed. This was believed to be caused by the fact that the prostatic urethra receives its sensory innervation from autonomic fibers, which have slower conduction than the somatic fibers. In our own laboratory we use stimulation of the dorsal nerve of the penis or clitoris with ring electrodes around the penis or clamped-on disk electrodes on the clitoris and record from the urethral and anal sphincters. Latencies also are 25 to 40 msec. Threshold response is observed usually at about
20ms FIG. 6. Top line shows urethral striated sphincter. Bottom line shows anal sphincter. Evoked responses by electrostimulation of dorsal nerve of penis and normal latency are shown.
75 to 100 volts and 0.1 to 0.2 msec. stimulus duration at about 200 volts. Amplitude of this response usually is 600 to 800 µv. Mean duration is 35 msec. (fig. 6). When the frequency of stimuli is increased from 10 to 20 per second, lower voltage (30 to 40) was required to produce sphincter contractions. Conduction velocities of the efferent somatic nerve (pudendal nerve) have been described by Chantraine and associates. 17 Stimulation is done with needle stimulating electrodes near the sciatic spine where the pudendal nerve is adjacent to the pudendal artery. Stimulation at this area causes a response in normal individuals, with a mean latency of 5.1 msec. ± 0.16 in the urethral sphincter and 5.5 msec. ± 0.25 in the anal sphincter. A second point of stimulation that is more difficult to reach is the area where the pudendal nerve is in the lesser sciatic notch. A distance between the 2 points of stimulation usually is about 5.5 to 7.8 cm. A needle 70 mm. long has to be used to reach deep enough to excite the nerve properly. A mean conduction velocity for normal subjects is reported to be 57.8 ± 3.9 meters per second for the urethral branch and 56.3 ± 2.8 meters per second for the anal branch. In patients with cauda equina syndromes or peripheral neuropathies these values are decreased. As it may be noted through the different types of conduction studies any aspect of the reflex arc may be investigated separately or combined, which may help in the differential diagnosis of a questionable peripheral lesion. In conclusion, electrodiagnostic evaluation using the aforementioned techniques could be useful in the understanding of difficult urodynamic problems that are not solved otherwise by conventional urodynamic testing. REFERENCES 1. Yalla, S. V., Rossier, A. B. and Fam, B.: Vesicourethral pressure
2. 3.
4.
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5.
20ms
6.
FIG. 5. Top line shows urethral striated sphincter. Bottom line shows anal sphincter. Bulbocavernosus stimulation produced bursts of activities in both sphincters.
7.
recordings in the assessment of neurogenic bladder functions in spinal cord injury patients. Urol. Int., 32: 161, 1977. Yalla, S. V., DiBenedetto, M., Blunt, K. J., Sethi, J.M. and Fam, B. A.: Urethral striated sphincter responses to electrobulbocavernosus stimulation. J. Urol., 119: 406, 1978. Yalla, S. V., Rossier, A. B. and Fam, B. A.: Dyssynergic vesicourethral responses during bladder rehabilitation in spinal cord injury patients: effects of suprapubic percussion, Crede and bethanechol chloride. J. Urol., 115: 575, 1976. Goodgold, J. and Eberstein, A.: Instrumentation for electromyography; electrical safety. In: Electrodiagnosis of Neuromuscular Diseases, 2nd ed. Edited by J. Goodgold and A. Eberstein. Baltimore: The Williams & Wilkins Co., chapt. 4, pp. 43-61, 1977. Bradley, W. E., Scott, F. B. and Timm, G. W.: Sphincter electromyography. Urol. Clin. N. Amer., 1: 69, 1974. Blaivas, J. G., Labib, K. L., Bauer, S. B. and Retik, A. B.: A new approach to electromyography of the external urethral sphincter. J. Urol., 117: 773, 1977. Chantraine, A.: EMG examination of anal and urethral sphincter.
ELECTRODIAGNOSIS OF STRIATED URETHRAL SPHINCTER DYSFUNCTION
In: New Developments in Electromyography and Clinical Neurophysiology. Edited by J.E. Desmedt. Basel: Karger, vol. 2, pp. 421-432, 1973.
8. Waylonis, G. W. and Aseff, J. N.: Anal sphincter electromyography in the first two years of life. Arch. Phys. Med. Rehab., 54: 525, 1973.
9. Archibald, K. C. and Goldsmith, E. I.: Sphincteric electromyography. Arch. Phys. Med. Rehab., 48: 387, 1967. 10. Ingberg, H. 0. and Johnson, A. W.: Electromyographic evaluation of infants with lumbar meningomyelocele. Arch. Phys. Med. Rehab., 44: 86, 1963. 11. Chantraine, A., Lloyd, K. and Swinyard, C. A.: The sphincter ani externus in spina bifida and myelomeningocele. J. Urol., 95: 250, 1966. 12. Dorfman, L. E., Bailey, J. and Smith, J.P.: Subclinical neurogenic bladder in children. J. Urol., 101: 48, 1968. 13. Melzak, J. and Porter, N. H.: Studies of the reflex activities of the external sphincter ani in spinal man. Paraplegia, 1: 277, 1964. 14. Vereecken, R. L. and Verduyn, H.: The electrical activity of the
paraurethral and perinea! muscles in normal and pathological conditions. Brit. J. Urol., 42: 457, 1970. 15. Bradley, W. E., Timm, G. W., Rockswold, G. L. and Scott, F. B.: Detrusor and urethral electromyelography. J. Urol., 114: 891, 1975. 16. Dick, H. C., Bradley, W. E., Scott, F. B. and Timm, G. W.: Pudenda! sexual reflexes. Electrophysiologic investigations. Urology, 3: 376, 1974. 17. Chantraine, A., DeLeval, J. and Onkelinx, A.: Motor conduction
velocity in the internal pudenda! nerves. In: New Development in Electromyography and Clinical Neurophysiology. Edited by J. E. Desmedt. Basel: Karger, pp. 433-438, 1973. EDITORIAL COMMENT This is a valuable contribution. It is timely inasmuch as it expresses the increasing interest in electromyography. I would like to emphasize
the difficulty in obtaining reliable and meaningful electromyographic tracings of the urinary voluntary sphincter. Our experience shows that surface electrodes are worthless. Accurate placement of needles in the urinary sphincter is extremely difficult, yet important if one has to rely on the recorded activity. Most of the time but not always anal sphincter activity reflects activity of the urethral sphincter. Artifacts are common and can lead to misinterpretation. I agree with the basic observations mentioned in this paper, which reinforce the known physiologic fact that there is a constant low frequency activity of the resting sphincter. This activity becomes silent during voiding (or usually a few seconds before), then sharply increases at the end of voiding and finally returns to a low level as the resting phase begins. It also is known that the voluntary sphincter does not use all its potential capacity: recruitment of more action potential is always available to the voluntary sphincter, either voluntarily or reflexly, in association with other movements. Our observations also confirm the authors' statement that in upper motor neuron lesions voluntary sphincter activity is recovered almost immediately. Actually, we did record it in
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0022-5347/79/1223-0361$02.00/0 THE JOURNAL OF UROLOGY Copyright© 1979 by The Williams & Wilkins Co.
Vol. 122, September Printed in U.S.A.
ELECTRODIAGNOSIS o~:[~!~~~o~RETHRAL SPHINCTER
;~~:
t~'';_,
MARGARETE DIBENEDETTO
AND
SUBBARAO V. YALLA *
From the Department of Physical Medicine and Rehabilitation, Division of Urology, Surgical Service, Veterans Administration Hospital, West Roxbury and the Harvard Program in Urology (Longwood Area), Boston, Massachusetts
ABSTRACT
In many centers urethral striated sphincter electromyography has become an essential component of urodynamic testing. The urologist who uses this modality of investigation in an attempt to understand the pathophysiology of striated sphincter dysfunction must have some basic knowledge of electromyography. Attempts have been made to provide such basic information, especially relating to the methods of evaluation and interpretation. We also have incorporated our own views based on our experience with more than 200 subjects with neuropathic vesicourethral dysfunctions. The most common clinical problems necessitating sphincter evaluation are neurological disorders resulting in urinary obstructions and/or incontinence, myelodysplasia, multiple sclerosis, diabetes mellitus, peripheral neuropathy involving pelvic floor and perineal musculature, sexual dysfunctions, spinal cord injuries and tumors, and conditions with unexplained urodynamic abnormalities. The electrodiagnosis of striated urethral dysfunction is comprised of sphincter electromyography to evaluate the intrinsic activity at rest, appraisal of action potential parameters on volition and quantification of recruitment on maximal effort. In addition, kinesiological assessment may be performed synchronously with urodynamic evaluation. 1 In our studies on >200 subjects we elicited, in addition to the record of the sphincter activity at rest, during bladder filling and voiding, its reflex responses to mechanical bulbocavernosus stimulation. Electrobulbocavernosus stimulation was introduced recently to quantitate the stimulus and to record sacral cord reflex transit time. 2 Sphincter activity also is monitored during various bladder rehabilitative maneuvers. 3 We herein review the literature on sphincter electromyography and submit our views on methods of evaluation and interpretation of various neuropathic sphincter dysfunctions. MATERIAL, METHOD AND INTERPRETATION
The transperineal route is used in all of our studies in which a coaxial needle electrode is used. t The needle is introduced through the perineum in the midline and the tip is guided to the level of the apex of the prostate while a finger is in the rectum to palpate the prostate. In female patients the electrode needle is introduced either transvaginally or at a site lateral to the urethral meatus. The needle is introduced paraurethrally 1 to 1.5 cm. deep towards the mid urethral segment. Fluoroscopic observation of the tip of the electrode needle in relation to the urethral catheter and anatomic landmarks of symphysis pubis will assist in the accurate placement of the electrode into the periurethral striated musculature. Oscilloscopic and audio findings will establish the correct placement of the needle electrode. In subjects with complete, long-standing lower motor neuron sphincter lesions complete electric silence will make the investigator rely only upon fluoroscopic observations. We advocate the aforementioned techniques and find them useful in our evaluations. Other electromyographic techniques also have been described. 4 Instead of a coaxial type, monopolar needles may be used, placing a superficial reference electrode on the Accepted for publication September 29, 1978. * Requests for reprints: Veterans Administration Hospital, 1400 VFW Parkway, West Roxbury, Massachusetts 02132. t DISA Electronics, 779 Susquehanna Ave., Franklin Lakes, New Jersey 07417.
thigh. Wire electrodes can be placed on either side of the sphincter because they have the advantage of not being displaced in studies of long duration. Some workers use bipolar surface electrodes mounted on an anal plug to record the combined activity of the external anal sphincter. 5 We have used coaxial needle electrodes introduced at the anal mucocutaneous junction. We also record the anal sphincter activity with synchronous monitoring of the urethral sphincter activity. We realize that disassociation may be demonstrated by both sphincters, especially in incomplete neurological lesions and in patients who earlier had an anal operation. Extrapolation of the anal sphincter activity with the striated urethral sphincter function could, therefore, lead to erroneous impressions. Paper readout interpretation of the electromyographic activity must be done with caution, especially when recording is done with pen recording systems. Blaivas and associates reemphasized the importance of oscilloscopic observations for more accurate analysis. 6 The slow paper speed (0.5 to 10 mm. per second) causes artifacts such as 60 cycle interference or base line shifts to appear as changes in sphincter activity and induces much error in the analysis. Unless the oscilloscope is observed at the same time and note is made of what really represents electromyographic signals, wrong interpretation may be made. Optimal paper speed to observe action potential parameters is 25 to 35 cm. per second and for kinesiological observations the speed of the paper can be 5 to 10 cm. per second. Basic electromyographic parameters. At rest: The urethral and anal sphincters almost always show continuous low frequency activity (fig. 1). The firing of action potentials range between 1 and 4 per second. These tonic contractions of the sphincter muscles are believed to arise from slow twitch (red) muscle fibers, while rapid response sphincter activity appears to be owing to the function of white or fast twitch fibers. 5 The amplitude of these potentials is 50 to 300 µv. and 3 to 5 msec. in duration. Chantraine reports never to have seen complete relaxation of a sphincter unless the patient was attempting micturition or defecation. 7 He believes that appearance of electrical silence during a rest period indicates displacement of the needle to the pelvic floor muscles, which do show silence at rest. In our experience, however, we have seen occasionally silence at rest in the anal sphincter. Displacement of the needle electrode will be entertained only when the muscle spike activity is not demonstrated on reflex maneuvers. This silence was observed after prolonged examination. It is important to point out also that even in healthy subjects the anal sphincter frequently shows less activity than the urethral sphincter without any apparent abnormality in this muscle.
361
362
DIBENEDETTO AND YALLA
Volitional: Action potentials recruited on volition show a mean amplitude of 500 /LV. but may reach 2 or even 3 mv. The mean duration for adults is 5.5 msec. in the urethral sphincter and 5.6 msec. in the anal sphincter, while in children it is 4.2 msec. in the urethral sphincter and 4.5 msec. in the anal sphincter. 7 As in skeletal muscles 7 to 10 per cent polyphasics are to be considered within the norm. Maximal effort: On maximal effort, which can be produced by volitional effort or by reflex maneuvers, a complete interference pattern can be observed. According to W aylonis and Aseff children do not reach the normal adult pattern until they are 70 weeks old and a steady increase of recruitment is noted. 8 From birth to about 6 months a pattern of 2 + out of a scale of 5 may be observed; from 6 to about 16 months a pattern of 3 + is observed and from 19 to 30 months a pattern of 4 + may be seen. It should be noted that testing for the mere presence of anal sphincter activity in infants born with an imperforated anus is of extreme importance before operation to assure proper results. 9 Lower motor neuron lesions. Spontaneous potentials, mainly fibrillations, are observed after denervation. Since the sphincter muscles are small fibrosis sets in quite early and no electrical activity can be identified in a long-standing complete lesion. Ingberg and Johnson report electromyographic findings in infants with myelodysplasia. 10 They found evidence of small fibrillation type continuous potentials of 30 to 50 /LV. in amplitude and a mean duration of 1 msec. preoperatively. Postoperatively, spontaneous potentials showed different parameters (60 to 90 /LV. and an average duration of 1.5 msec.). Whether this finding indicated normal fibrillations (owing to lack of nervous system maturation) in the preoperative phase, as reported in other muscles in the neonatal period, while the postoperative spontaneous potentials represent evidence of definite new denervation, cannot be said at this point. Ingberg also considers the presence of insertional activity in the myelodysplasia in
L.J
IOms FIG. 1. Top line shows striated urethral sphincter base line activity. Second line shows dissociated, low frequency activity of anal sphincter.
children as a favorable sign for later appearance of action potentials. Fibrillation potentials are seen much more frequently than positive sharp waves. It must be noted that in complete sphincter denervation of recent onset recognition of spontaneous potentials does not represent a problem. However, in partial lesions it is quite difficult to delineate spontaneous potentials from action potentials recruited during rest periods. The parameters are frequently the same. We have found the audio information often more helpful than the visual display. We also have observed complete or partial denervation of one of the sphincters with the other sphincter being normal or partially denervated or demonstrating even upper motor neuron findings (fig. 2). This fact reveals the necessity to examine the urethral and the anal sphincters for the sake of accuracy, although anal sphincter recordings in these lesions may not help in the understanding of striated urethral sphincter dysfunction. Volitional: In adults there is marked variation in the amplitude of the observed potentials normally and especially in lower motor neuron lesions. It is possible to find reduced amplitude potentials or action potentials of up to 2 or 3 mv. amplitude. We have found in patients with spinal cord lesions usually a reduced amplitude, while in patients with peripheral nerve lesions amplitudes appear to be increased. Duration usually is increased slightly but not as marked as observed in skeletal muscles. Polyphasia may be 90 to 100 per cent or as little as 10 per cent (fig. 3, A). In children with myelodysplasia Ingberg and Johnson report amplitudes of first recruited action potentials from 100 to 500 /LV. (mean /Lv.) and durations from 4 to 15 msec. in comparison to the normal range they observed from 100 to 1,500 /LV. (mean 500 /LV.) and durations from 2 to 10 msec. 10 High frequency bizarre discharges also can be encountered in sphincters of a small number of patients. In 5 subjects we have observed actually myotonic type discharges presenting the typical waxing and waning characteristics of myotonia (fig. 3, B). Chantraine and associates report bizarre discharges in a small number of patients with myelodysplasia. 11 The myotonic or high frequency bizarre discharges may occur in either one or both sphincters and we have observed these in lower motor neuron as well as in upper motor neuron lesions. One of these patients had a sphincterotomy and the histologic examination of the striated sphincter showed muscle degeneration and fibrosis, which may or may not be related to the observed phenomena. Further investigations are needed in this direction. Maximal effort: As in skeletal muscle lower motor neuron lesions of the sphincters show reduced recruitment in proportion to the amount of denervation present. The aforementioned pathological phenomena can be observed readily in the urethral and anal sphincters. The importance is in the recognition of patients needing this type of examination. This is especially true in children with spina bifida or in adults who do not have
'---v--J
20ms FIG. 2. Top line shows urethral sphincter (upper motor neuron lesion)-motor units can be identified. Second line represents activity of anal sphincter (lower neuron lesion)-no motor units seen.
ELECTRODIAGNOSIS OF STRIATED URETHRAL SPHINCTER DYSFUNCTION
other objective neurological signs causing suspicion of such involvement. 12 The study on patients with enuresis has shown varied results. Some groups report as much as 60 per cent of the patients showing some form of neurological abnormality, while others report much lower incidences. In postoperative incontinence (post-prostatectomy or radical hysterectomy) varying experiences have been reported. To help distinguish a peripheral nerve involvement from an anterior horn cell lesion pudenda! nerve conduction studies may be performed or the sacral somatic reflex arc can be studied by penile or clitoral stimulation. Kinesiological assessment. This evaluation consists of electromyography of the urethral and anal sphincters during bladder filling, observation of reflex activity during voiding and voluntary depression of reflex activity or volitional-induced voiding. The tests are performed in conjunction with cystometry, allowing investigation of time relationships between detrusor reflex and striated sphincter activity and also the recognition of relationships between increased or decreased bladder or urethral pressures to the pelvic floor muscle activation. Normal bladder-sphincter relationships. At rest with an empty bladder there is minimal electrical activity observed in the urethral and anal sphincters. With increased bladder filling there is a gradual increase in motor unit activity as to the amplitude, the number and the rate of firing. Just before, at
A 100-'fvl '-v-'
IOms B
IOO'fv~
'--v-'
20ms FIG. 3. A, striated urethral sphincter shows polyphasic activity. Patient has alcoholic peripheral neuropathy. B, striated urethral sphincter shows myotonic type activity (with characteristic waxing and waning dive-bomber sound); 17-year-old girl with Ll spinal cord injury lesion.
363
the onset or shortly after voiding there is complete electrical silence. The normal individual can recruit the complete interference pattern immediately on command to stop voiding, which then is followed in 2 to 3 seconds by cessation of urinary flow. Upper motor neuron lesions (reflex or automatic bladder). In contrast to skeletal muscles spontaneous potentials cannot be observed and action potentials are of normal parameters with complete interference patterns on maximal effort. The deviation from the norm is discussed under kinesiological assessment since the study involves measurement of recruitment at different intervals in relation to other observed phenomena. The patient cannot perceive bladder filling or fullness and cannot voluntarily initiate voiding. Micturition is reflex in nature and involuntary. At rest there may be more marked sphincter activity than normal, although at times activity also decreases to a low rate when observed for several hours. There also is increased activity during bladder filling but when voiding starts instead of relaxation further increase in striated sphincter activity is observed (bladder-sphincter dyssynergia). The most common causes for reflex bladder are 1) cord lesion above the conus, 2) massive brain trauma, 3) suprasacral spinal cord tumor, 4) syringomyelia and 5) multiple sclerosis. Lower motor neuron lesion (autonomous bladder). This is a result of loss of sensory or sensory and motor limb of the reflex arc. The patient cannot perceive bladder fullness or voluntarily initiate voiding. However, this can be accomplished by the Crede maneuver. At rest: In complete early lesions, starting 2 to 4 weeks after onset, there are fibrillations. Occasional positive sharp waves also have been reported. In partial lesions resting activity is either diminished or normal. On bladder filling there is less activation of motor units and on voluntary contraction a diminished response never reaching a full interference pattern can be observed. Most common causes for this form of bladder are injuries to the sacral spinal cord or after a radical pelvic operation. While a bladder in spinal shock may have similar responses it must be noted that our observation of the urethral and anal sphincters in patients as early as 24 hours after complete spinal cord injury above the conus have shown good interference patterns (fig. 4). These patients, indeed, were in spinal shock with absence of tendon reflexes and detrusor areflexia. This is opposite to the observations of Melzak and Porter, who saw completely inactive sphincters during spinal shock before the reflex activity recovered. 13 Mixed neurogenic bladder. Patients with this form of abnormality seem to have a combination of upper motor neuron and incomplete lower motor neuron lesions to the external sphincters. Resting motor unit activity may be either normal, decreased or increased. Activation also may fall in any one of these categories. There may be a marked difference in anal and urethral sphincters or even between the different quadrants. Responses in sphincter or other pelvic floor muscles also may
'-v--J
20ms FIG. 4. Top line shows urethral striated sphincter with motor units and interference pattern; 22-year-old man 3 days after complete C4 spinal cord injury lesion shows motor units.
364
DIBENEDETTO AND Y ALLA
vary. 14 The most common cause for this type of bladder is myelodysplasia or myelomalacia of vascular origin (infarct in the territory of the artery of Adamkiewicz) or compression fractures of Ll. Uninhibited bladder. This type of bladder can occur without any evidence of neurological deficit and consists of the symptomatology of urinary urgency, frequency and incontinence. The vesical reflex arc is intact and functional but the inhibitory fibers from the higher centers are non-functional. The sphincter electromyography shows normal reflex activity but inability or, at least, difficulty for the patient to recruit voluntarily a full pattern to interrupt the voiding stream or voluntarily relax the pelvic floor for initiation of voiding. Recording of reflex activity. The bulbocavernosus reflex is elicited by pinching the glans penis or clitoris, causing reflex contraction of pelvic floor musculature (fig. 5). Clinically, this often is difficult to evaluate especially in normal individuals because of volitional inhibitory influences. Electromyography of the sphincters enhances the ability to recognize the presence or absence of this phenomenon. It is an S2 to S4 integrated spinal cord reflex. Absence suggests a lesion at that level. Increase of abdominal pressure, as in the V alsalva maneuver, coughing or sobbing causes a sudden burst of electrical activity in both sphincters. This response cannot be observed in low sacral lesions or in involvement of lower thoracic and upper lumbar segments supplying the musculature effecting the intraabdominal pressure. Digital-rectal stimulation causes an increase of electrical activity followed by relaxation. However, one can observe in some patients immediate cessation of electrical activity on digital stimulation, indicating pelvic floor relaxation. These phenomena can be seen as long as the lower sacral segments are intact. Electrical-evoked reflex response. Bradley and associates reported a technique of stimulating the bladder mucosa and recording from the anal sphincter, which they called detrusor and urethral electromyelography. 10 Latencies recorded were 50 to 70 msec. They believe this is a measurement of the anatomic integrity of segmental innervation of the detrusor muscle and periurethral striated muscles as well as the corticoregulatory tracts. They observed abolition of response on conscious effort to relax the pelvic floor. Dick and associates studied pudendal sexual reflexes and reported stimulation of the dorsal nerves of the penis with recording from bulbocavernosus and ischiocavernosus muscles. 16 Their latency is 34 to 40 msec. Stimulation from the prostatic urethra evokes a response in 60 msec., while from the distal 2 cm. of the urethra a mean latency of 30 msec. was observed. This was believed to be caused by the fact that the prostatic urethra receives its sensory innervation from autonomic fibers, which have slower conduction than the somatic fibers. In our own laboratory we use stimulation of the dorsal nerve of the penis or clitoris with ring electrodes around the penis or clamped-on disk electrodes on the clitoris and record from the urethral and anal sphincters. Latencies also are 25 to 40 msec. Threshold response is observed usually at about
20ms FIG. 6. Top line shows urethral striated sphincter. Bottom line shows anal sphincter. Evoked responses by electrostimulation of dorsal nerve of penis and normal latency are shown.
75 to 100 volts and 0.1 to 0.2 msec. stimulus duration at about 200 volts. Amplitude of this response usually is 600 to 800 µv. Mean duration is 35 msec. (fig. 6). When the frequency of stimuli is increased from 10 to 20 per second, lower voltage (30 to 40) was required to produce sphincter contractions. Conduction velocities of the efferent somatic nerve (pudendal nerve) have been described by Chantraine and associates. 17 Stimulation is done with needle stimulating electrodes near the sciatic spine where the pudendal nerve is adjacent to the pudendal artery. Stimulation at this area causes a response in normal individuals, with a mean latency of 5.1 msec. ± 0.16 in the urethral sphincter and 5.5 msec. ± 0.25 in the anal sphincter. A second point of stimulation that is more difficult to reach is the area where the pudendal nerve is in the lesser sciatic notch. A distance between the 2 points of stimulation usually is about 5.5 to 7.8 cm. A needle 70 mm. long has to be used to reach deep enough to excite the nerve properly. A mean conduction velocity for normal subjects is reported to be 57.8 ± 3.9 meters per second for the urethral branch and 56.3 ± 2.8 meters per second for the anal branch. In patients with cauda equina syndromes or peripheral neuropathies these values are decreased. As it may be noted through the different types of conduction studies any aspect of the reflex arc may be investigated separately or combined, which may help in the differential diagnosis of a questionable peripheral lesion. In conclusion, electrodiagnostic evaluation using the aforementioned techniques could be useful in the understanding of difficult urodynamic problems that are not solved otherwise by conventional urodynamic testing. REFERENCES 1. Yalla, S. V., Rossier, A. B. and Fam, B.: Vesicourethral pressure
2. 3.
4.
'-y--)
5.
20ms
6.
FIG. 5. Top line shows urethral striated sphincter. Bottom line shows anal sphincter. Bulbocavernosus stimulation produced bursts of activities in both sphincters.
7.
recordings in the assessment of neurogenic bladder functions in spinal cord injury patients. Urol. Int., 32: 161, 1977. Yalla, S. V., DiBenedetto, M., Blunt, K. J., Sethi, J.M. and Fam, B. A.: Urethral striated sphincter responses to electrobulbocavernosus stimulation. J. Urol., 119: 406, 1978. Yalla, S. V., Rossier, A. B. and Fam, B. A.: Dyssynergic vesicourethral responses during bladder rehabilitation in spinal cord injury patients: effects of suprapubic percussion, Crede and bethanechol chloride. J. Urol., 115: 575, 1976. Goodgold, J. and Eberstein, A.: Instrumentation for electromyography; electrical safety. In: Electrodiagnosis of Neuromuscular Diseases, 2nd ed. Edited by J. Goodgold and A. Eberstein. Baltimore: The Williams & Wilkins Co., chapt. 4, pp. 43-61, 1977. Bradley, W. E., Scott, F. B. and Timm, G. W.: Sphincter electromyography. Urol. Clin. N. Amer., 1: 69, 1974. Blaivas, J. G., Labib, K. L., Bauer, S. B. and Retik, A. B.: A new approach to electromyography of the external urethral sphincter. J. Urol., 117: 773, 1977. Chantraine, A.: EMG examination of anal and urethral sphincter.
ELECTRODIAGNOSIS OF STRIATED URETHRAL SPHINCTER DYSFUNCTION
In: New Developments in Electromyography and Clinical Neurophysiology. Edited by J.E. Desmedt. Basel: Karger, vol. 2, pp. 421-432, 1973.
8. Waylonis, G. W. and Aseff, J. N.: Anal sphincter electromyography in the first two years of life. Arch. Phys. Med. Rehab., 54: 525, 1973.
9. Archibald, K. C. and Goldsmith, E. I.: Sphincteric electromyography. Arch. Phys. Med. Rehab., 48: 387, 1967. 10. Ingberg, H. 0. and Johnson, A. W.: Electromyographic evaluation of infants with lumbar meningomyelocele. Arch. Phys. Med. Rehab., 44: 86, 1963. 11. Chantraine, A., Lloyd, K. and Swinyard, C. A.: The sphincter ani externus in spina bifida and myelomeningocele. J. Urol., 95: 250, 1966. 12. Dorfman, L. E., Bailey, J. and Smith, J.P.: Subclinical neurogenic bladder in children. J. Urol., 101: 48, 1968. 13. Melzak, J. and Porter, N. H.: Studies of the reflex activities of the external sphincter ani in spinal man. Paraplegia, 1: 277, 1964. 14. Vereecken, R. L. and Verduyn, H.: The electrical activity of the
paraurethral and perinea! muscles in normal and pathological conditions. Brit. J. Urol., 42: 457, 1970. 15. Bradley, W. E., Timm, G. W., Rockswold, G. L. and Scott, F. B.: Detrusor and urethral electromyelography. J. Urol., 114: 891, 1975. 16. Dick, H. C., Bradley, W. E., Scott, F. B. and Timm, G. W.: Pudenda! sexual reflexes. Electrophysiologic investigations. Urology, 3: 376, 1974. 17. Chantraine, A., DeLeval, J. and Onkelinx, A.: Motor conduction
velocity in the internal pudenda! nerves. In: New Development in Electromyography and Clinical Neurophysiology. Edited by J. E. Desmedt. Basel: Karger, pp. 433-438, 1973. EDITORIAL COMMENT This is a valuable contribution. It is timely inasmuch as it expresses the increasing interest in electromyography. I would like to emphasize
the difficulty in obtaining reliable and meaningful electromyographic tracings of the urinary voluntary sphincter. Our experience shows that surface electrodes are worthless. Accurate placement of needles in the urinary sphincter is extremely difficult, yet important if one has to rely on the recorded activity. Most of the time but not always anal sphincter activity reflects activity of the urethral sphincter. Artifacts are common and can lead to misinterpretation. I agree with the basic observations mentioned in this paper, which reinforce the known physiologic fact that there is a constant low frequency activity of the resting sphincter. This activity becomes silent during voiding (or usually a few seconds before), then sharply increases at the end of voiding and finally returns to a low level as the resting phase begins. It also is known that the voluntary sphincter does not use all its potential capacity: recruitment of more action potential is always available to the voluntary sphincter, either voluntarily or reflexly, in association with other movements. Our observations also confirm the authors' statement that in upper motor neuron lesions voluntary sphincter activity is recovered almost immediately. Actually, we did record it in