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Reflex and Electromyographic Abnormalities Associated with Fecal Incontinence
Vol. 53, No.1 Printed in U.S.A.
GASTROENTEROLOGY
Copyright© 1967 by The Williams & Wilkins Co.
REFLEX AND ELECTROMYOGRAPHIC ABNORMALITIES ASSOCIATED WITH FECAL INCONTINENCE JuAN ALvA, M.D., ALBERT I. MENDELOFF, M.D., AND MARVIN M. ScHUSTER, M.D. The Department of Medicine, The Baltimore City Hospitals and The Johns Hopkins University School of Medicine, Baltimore, Maryland
Fecal incontinence can result from disorders of the anal sphincters in the absence of other rectal or colonic abnormalities. The present studies were designed to assess rectosphincteric reflexes in incontinent patients and to determine whether there is selective impairment of either the autonomic reflexes of the internal sphincter or the somatic reflexes of the external sphincter.
Materials aud Methods Twenty-five normal subjects were studied and compared to 12 patients with gross fecal incontinence (Table 1). Five of these patients had intact musculature but disrupted innervation due to either complete transection of the lumbar spinal cord or partial transection as a result of spinal cord tumors. Two patients had intact innervation but had primary muscle disease and 5 patients had injury to anal musculature secondary to surgical trauma. With subjects in the left lateral decubitus position, simultaneous pressure recordings were obtained separately from the internal and external anal sphincters, and electromyographic recordings were obtained from the external sphincter. The pressure-sensing device consisted of a hollow steel cylinder around which Received November 30, 1966. Accepted February 23, 1967. This paper was read at the Meeting of the American Gastroenterological Association, May 1965.
Address requests for reprints to: Dr. Marvin Schuster, Baltimore City Hospitals, 4940 Eastern Avenue, Baltimore, Maryland 21224. This investigation was supported by Research Grant AM 07862 from the National Institute of Arthritis and Metabolic Diseases. The authors wish to thank Miss Johanna Bengel for her able technical assistance, and Drs. Robert Teasdall and Richard Johns for their helpful advice.
a molded double balloon was tied, creating two compartments, each of which communicated via polyethylene tubing to pressure transducers (Sanborn Model 267 B) and a direct writing recorder' (Sanborn Model 964). This device was placed within the anal canal so that when each balloon was inflated with 10 ml of air the cephalad balloon was surrounded by the internal sphincter and the caudad balloon by the subcutaneous bundle of the external sphincter (fig. 1). A concentric needle electrode was inserted into the external sphincter for · electromyographic recording of spike potentials. This needle was inserted to an approximate depth of 1 em and its location monitored by the burst of activity heard on the loud speaker and visualized on the oscilloscopic screen of the electromyograph. A Miller Abbott balloon was inserted into the rectum through the hollow core of the cylinder. Anal reflexes were stimulated by rapid momentary distension of this balloon with 50 ml of air. The pressure tracings were recorded on two channels of a direct writing recorder at a speed of 1 mm per sec. The mean voltage of electromyographic spike potentials was recorded on a third channel, as well as on the rapid moving paper of the electromyograph (at 5 em per sec). The mean voltage is a linear tracing which represents the mean of the amplitude and frequency of spike potentials as analyzed electronically by the recorder (fig. 2). Spike potentials were also recorded on the electromyograph as a continuous record at 5 em per sec or as individual potentials at a sweep speed of 2.5 msec per em.
Results
M.
In all of the normal subjects the response to rectal distension consisted of relaxation of the internal sphincter and contraction of the external sphincter {fig. 3). The electromyograph showed continuous minimal electrical activity even in the resting state. Rectal distension produced a tran101
102
Vol. 53, No.1
A LVA E'l' AL . T ABLE
1. Incontinent patien/.s N o. of patients
Spinal cord lesions Spinal cord tumor post resection. Tra umatic spi nal cord t ransection . Anal sphincter injuries H emorrhoidectomy .. Lace ration during childbir t h . :\Iyopathy Dermatomyosit is . .... ... . .. . . .. ... . . Ocula r myopathy.
3 2
4 1
sient burst of increased activity beyond t hat seen in the resting muscle (figs. 3 and 4).
The degree of internal sphincter relaxation and external sphincter contraction was directly proportional to t he degree of rectal distension, with no relaxation appearing when less than 10 ml of air was inflated into t he distending balloon. The last level at which a response was obtained is referred t o as t he t hreshold. A greater degree of distension was generally re-
EXT.
BALLOON
TO ELECTROMYOGRAPH
Fra. 1. Schematic representation of recording t echnique. Transient distension of rectal balloon pr ovides stimulus for reflex responses from internal and external sphincters. Separate pressures are obtained from internal and external balloons and electromyographic tracing from concentric needle electrode in subcutaneous bundle of external sphincter.
103
ABNOR!VIALITIES ·wiTH FECAL INCONTINENCE
quired for the external sphincter response than for the internal sphincter (fig. 5). In 11 of the 12 patients with fecal incontinence rectal distension produced nor-
NORMAL ELECTROMYOGRAM
1 so J.IV
J
I--.._.._.-.j~~m""11~w~~~utaUII-I•,,...,......... A
ELECTROMYOGRAM
l \,II
B
0
2 Time in seconds
__________. / \
A
I
50 J.IV - v - - - -
\j~
Mean
Voltage
0 0
B
2 Time in seconds
FIG. 2. Mean voltage recording. Upper tracing shows routine recording of electromyographic spike potentials. Lower tracing shows mean voltage obtained by instantaneous electronic integration of the mean of amplitude and frequency of spike potentials from the npper tracing.
+--+---
.02 .04 0 .02 Time in seconds
.04
FrG. 4. Electromyogram at slow and fast speeds. The upper tracing shows spike potentials at slow speed during rest (A) and during rectal distension (B) indicated by arrows. Electrical activity is present during rest, and increases abruptly with rectal distension. Two tracings below show individual spike potentials taken at high speed during rest (A) and during stimulation (B).
NORMAL
~rv- Int. sphincter
1
+
-10
-20 0> § -30 Q)
.<: (.)
-A....----- Mean voltage
0
20
40
Time in seconds FIG. 3. Normal response to rectal distension. Pressure decrease indicates reflex relaxation of internal sphincter (upper line) and pressure increase signals reflex contraction of external sphincter (middle line). Increase in electrical activity appears in the contracting external sphincter (bottom line). Arrows indicate rapid inflation and deflation of the rectal balloon.
mal internal sphincter relaxation but no external sphincter contraction as measured manometrically, and the electromyograph disclosed no burst of electrical activity (fig. 6). Resting electrical activity was either absent or markedly diminished (fig. 7). One patient had reflex contraction of the external sphincter, although the contraction was extremely weak. In patients with myopathy, electrical activity was diminished at rest and there was no increase in activity with rectal distension (fig. 8). Analysis of individual action potentials demonstrated features characteristic of myopathy; that is, there was a decrease in duration of spike potentials as compared to the normal, as well as a decrease in voltage. The average duration in patients with myopathy was 1.8 msec compared to the normal of 3.42 msec. Discussion
The maintenance of fecal continence is a complex affair depending upon many factors. This study concerns itself specifically with the relative importance of
104
Vol. 53, No.1
ALVA ET AL .
REFLEX THRESHOLD +30 +20 +10
"'
"'z "
0
r;1t1
INT. SPHINCT.
+10] 0
-__,.-......__~~~-~--~ EXT.SPHINCT. 50cc.
2.5cc.
n
0
20
1~ 40
60
15cc.
IOcc.
1~
5cc.
1~
80 100 120 140 TIME IN SECONDS
160
1~ 180
200
FIG. 5. Threshold for rectosphincteric reflexes. Decreasing responses are seen in internal and external sphincters with decreasing volume of rectal distension (volume indicated at bottom of figure) until no response is obtained. In this particular patient internal sphincter threshold is 10 ml, and external sphincter threshold is 25 mi. NORMAL
v
FECAL INCONT.
+ 0 IOj¥
Int . sphincter
-10 ~ -20 0
.c
-30
u
"'
t+20lL +15
+10 +5 0
- - - - - E x t . sphincter
distension produces reflex relaxation of the smooth muscle (internal sphincter) at the same time that it induces reflex contraction of the striated muscle (external sphincter). Moreover, previous work has shown that the internal sphincter exercises constant tonus in the resting state.1 • 2 The present work demonstrates, in addition, that there is constant electrical activity of the external sphincter at rest, indicating that it, too, maintains constant tonus. This observation is consistent with results reported by others in animals 3 and man. 4 To date
- - - - - M e a n voltage
0
20 40
FECAL INCONT. 0
20
40
ELECTROMYOGRAM
Time in seconds
Fw. 6. Response to rectal distension of normal subjects (left) and incontinent patients (1ight). Normal relaxation of internal sphincter is seen in incontinent patients (upper line, 1ight), but with rectal distension external sphincter does not contract (middle line) and there is no increase in electrical activity in the external sphincter (bottom line ).
A
50 JJV
I~~---......--------0
2 Time in seconds
50JJV
two rectosphincteric reflexes and the roles of each of the two sphincter components in the preservation of continence. This problem is of particular interest, since the two muscle components respond to the same stimulus in opposite directions. Rectal
B
I 0
A
.02
B
.04
0
.02
.04
Time in seconds
FIG. 7. Electromyographic tracing of external sphincter in incontinent patients. There is no burst of electrical activity with rectal distension.
July 1967
105
ABNORMALITIES WITH FECAL I NCONTINENCE
no stimulus has been found which can induce reflex contraction of the internal sphincter. The only response normally available to this mmcle is relaxation. This suggests that, in the resting state, the internal sphincter is contracted at maximal or near maximal levels. On the other hand , the extern al sphincter, although tonically contracted, can respond to rectal distension by further contraction, and, therefore, is not maximally contracted in the resting state. In patients who were incontinent, regardless of whether incontinence was on the basis of neurological or muscular abnormality, the internal sphincter response \Yas present but the external sphincter response was not. It can therefore be concluded that, of the two sphincter components, it is the voluntary external sphincter which plays the major role in maintenance of sphincteric continence. Since gross fecal incontinence was present in the patients studied, it is possible that the internal sphincter, which is normally in a state of tonic contraction, may play a role in the maintenance of continence when fecal material is presented to the rectum in amounts insufficient to distend it and thus insufficient to induce relaxation of the internal sphincter. Other work 5 similarly suggests that the tonically contracted internal sphincter plays a role in maintaining continence specifi cally of liquid feces and flatus. There is evidence which tends to corroborate this point, since the threshold for t he external sphincter response is generally higher than for the internal sphincter (fig. 5). In other words, the smallest volume of rectal distension which elicits an internal sphincter response does not produce reflex external sphincter contraction, which implies that the tonically contracted internal sphincter can present an adequate barrier to small volumes of colonic contents. The relaxation which appears in the internal sphincter with adequate rectal distension would not be expected fo facilitate continence, but might prepare for defecation. By contrast the external sphincter is normally in a state of minimal tonus and promptly contracts when the rectum is
ELECTROMYOGRAM NORMAL
l
1
50
~vI__ ,.~ji.UJilllJ../.
r
MYOPATHY
2
0 Time in seconds
FIG. 8. Electromyogram in incont inent patients with myopathy (lo wer line ) compared with normal subjects (upp er line). Although resting electrical activity is present in myopathy as in normal subj ect, no reflex increase in activity is seen in myopathy with rectal distension.
sufficiently distended. This could facilitate continence. Moreover, the present study shows a correlation between impairment of external sphincter response and incontinence regardless of underlying cause. In addition to reflex control, the voluntary control of fecal continence is directly dependent upon the external anal sphincter. Even though this muscle can remain fully contracted voluntarily for only 1 min before beginning to fatigue, 6 this is apparently sufficient under normal conditions to allow for rectal adaptation to occur to prevent fecal incontinence until voluntary defecation takes place. The concentric needle electrode is capable of recording only from striat ed muscle and cannot pick up electrical potentials from smooth muscle. Therefore the information obtained from the electromyographic studies confirms the manometric observation that the external sphincter contracts with rectal distension and provides the additional information that this sphincter is in a state of tonic contraction. Electromyography can also demonstrate, as it did in these studies, a pattern characteristic of myopathy, which the mano-
106
ALVA ET ilL.
metric technique cannot, and it can therefore show whether the anal sphincter is involved in myopathy affecting other muscles, as well as help to separate muscle disorders from neurological disorders. Summary
A technique is described for obtaining simultaneous manometric recordings of reflex responses from the internal and external anal sphincters along with electromyographic activity from the external sphincter. This combined technique demonstrates that, in the normal resting state, the internal sphincter is strongly contracted and the external sphincter minimally contracted. Patients were studied with fecal incontinence on the basis of neurological impairment, myopathy, and anal muscle injury. Normal internal sphincter reflexes were present, but external sphincter reflexes were absent in incontinence regardless of underlying cause, indicating that, of the two muscle components, the external sphincter plays the major role in the preservation of continence. Myopathy was demonstrated elec-
Vol. 5S, No . 1
tromyographically in the external sphincter of patients who had incontinence associated with myop athy of other muscles. REFERENCES 1. Schuster, M. M., P. Hookman, T. R. Hendrix, and A. I. Mendeloff. 1965. Simultaneous manometric recording of internal and external anal sphincteri c reflexes. Bull. Hopkins Hosp. 116 : 79--88. 2. Schuster, M. M., T. R. Hendrix, and A. I. M endeloff. 1963. The internal anal sphincter response: M anometric studies on its normal physiology, neural pathways, and alteration in bowel disorders. J. Clin. Invest. 42 : 196-207. 3. Bishop, B. 1959. Reflex activity of the external anal sphincter of cat. J. Physiol. (London) 137 : 679-692. 4. Porter, N. H. 1962. A physiologic study of the pelvic floor and rectal prolapse. Ann. Ro~·. Coli. Surg. Eng. 31: 379--404. 5. Bennett, R. C., and G . L. Duthie. 1964. The functional importance of the internal anal sphincter. Brit. J. Surg. 51: 355-357. 6. Gaston, E. A. 1948. Fecal continence follow ing resection of various portions of the rectum with preservation of the anal sphincters. Surg. Gynec. Obstet. 87 : 669-678.
GASTROENTEROLOGY
Copyright© 1967 by The Williams & Wilkins Co.
REFLEX AND ELECTROMYOGRAPHIC ABNORMALITIES ASSOCIATED WITH FECAL INCONTINENCE JuAN ALvA, M.D., ALBERT I. MENDELOFF, M.D., AND MARVIN M. ScHUSTER, M.D. The Department of Medicine, The Baltimore City Hospitals and The Johns Hopkins University School of Medicine, Baltimore, Maryland
Fecal incontinence can result from disorders of the anal sphincters in the absence of other rectal or colonic abnormalities. The present studies were designed to assess rectosphincteric reflexes in incontinent patients and to determine whether there is selective impairment of either the autonomic reflexes of the internal sphincter or the somatic reflexes of the external sphincter.
Materials aud Methods Twenty-five normal subjects were studied and compared to 12 patients with gross fecal incontinence (Table 1). Five of these patients had intact musculature but disrupted innervation due to either complete transection of the lumbar spinal cord or partial transection as a result of spinal cord tumors. Two patients had intact innervation but had primary muscle disease and 5 patients had injury to anal musculature secondary to surgical trauma. With subjects in the left lateral decubitus position, simultaneous pressure recordings were obtained separately from the internal and external anal sphincters, and electromyographic recordings were obtained from the external sphincter. The pressure-sensing device consisted of a hollow steel cylinder around which Received November 30, 1966. Accepted February 23, 1967. This paper was read at the Meeting of the American Gastroenterological Association, May 1965.
Address requests for reprints to: Dr. Marvin Schuster, Baltimore City Hospitals, 4940 Eastern Avenue, Baltimore, Maryland 21224. This investigation was supported by Research Grant AM 07862 from the National Institute of Arthritis and Metabolic Diseases. The authors wish to thank Miss Johanna Bengel for her able technical assistance, and Drs. Robert Teasdall and Richard Johns for their helpful advice.
a molded double balloon was tied, creating two compartments, each of which communicated via polyethylene tubing to pressure transducers (Sanborn Model 267 B) and a direct writing recorder' (Sanborn Model 964). This device was placed within the anal canal so that when each balloon was inflated with 10 ml of air the cephalad balloon was surrounded by the internal sphincter and the caudad balloon by the subcutaneous bundle of the external sphincter (fig. 1). A concentric needle electrode was inserted into the external sphincter for · electromyographic recording of spike potentials. This needle was inserted to an approximate depth of 1 em and its location monitored by the burst of activity heard on the loud speaker and visualized on the oscilloscopic screen of the electromyograph. A Miller Abbott balloon was inserted into the rectum through the hollow core of the cylinder. Anal reflexes were stimulated by rapid momentary distension of this balloon with 50 ml of air. The pressure tracings were recorded on two channels of a direct writing recorder at a speed of 1 mm per sec. The mean voltage of electromyographic spike potentials was recorded on a third channel, as well as on the rapid moving paper of the electromyograph (at 5 em per sec). The mean voltage is a linear tracing which represents the mean of the amplitude and frequency of spike potentials as analyzed electronically by the recorder (fig. 2). Spike potentials were also recorded on the electromyograph as a continuous record at 5 em per sec or as individual potentials at a sweep speed of 2.5 msec per em.
Results
M.
In all of the normal subjects the response to rectal distension consisted of relaxation of the internal sphincter and contraction of the external sphincter {fig. 3). The electromyograph showed continuous minimal electrical activity even in the resting state. Rectal distension produced a tran101
102
Vol. 53, No.1
A LVA E'l' AL . T ABLE
1. Incontinent patien/.s N o. of patients
Spinal cord lesions Spinal cord tumor post resection. Tra umatic spi nal cord t ransection . Anal sphincter injuries H emorrhoidectomy .. Lace ration during childbir t h . :\Iyopathy Dermatomyosit is . .... ... . .. . . .. ... . . Ocula r myopathy.
3 2
4 1
sient burst of increased activity beyond t hat seen in the resting muscle (figs. 3 and 4).
The degree of internal sphincter relaxation and external sphincter contraction was directly proportional to t he degree of rectal distension, with no relaxation appearing when less than 10 ml of air was inflated into t he distending balloon. The last level at which a response was obtained is referred t o as t he t hreshold. A greater degree of distension was generally re-
EXT.
BALLOON
TO ELECTROMYOGRAPH
Fra. 1. Schematic representation of recording t echnique. Transient distension of rectal balloon pr ovides stimulus for reflex responses from internal and external sphincters. Separate pressures are obtained from internal and external balloons and electromyographic tracing from concentric needle electrode in subcutaneous bundle of external sphincter.
103
ABNOR!VIALITIES ·wiTH FECAL INCONTINENCE
quired for the external sphincter response than for the internal sphincter (fig. 5). In 11 of the 12 patients with fecal incontinence rectal distension produced nor-
NORMAL ELECTROMYOGRAM
1 so J.IV
J
I--.._.._.-.j~~m""11~w~~~utaUII-I•,,...,......... A
ELECTROMYOGRAM
l \,II
B
0
2 Time in seconds
__________. / \
A
I
50 J.IV - v - - - -
\j~
Mean
Voltage
0 0
B
2 Time in seconds
FIG. 2. Mean voltage recording. Upper tracing shows routine recording of electromyographic spike potentials. Lower tracing shows mean voltage obtained by instantaneous electronic integration of the mean of amplitude and frequency of spike potentials from the npper tracing.
+--+---
.02 .04 0 .02 Time in seconds
.04
FrG. 4. Electromyogram at slow and fast speeds. The upper tracing shows spike potentials at slow speed during rest (A) and during rectal distension (B) indicated by arrows. Electrical activity is present during rest, and increases abruptly with rectal distension. Two tracings below show individual spike potentials taken at high speed during rest (A) and during stimulation (B).
NORMAL
~rv- Int. sphincter
1
+
-10
-20 0> § -30 Q)
.<: (.)
-A....----- Mean voltage
0
20
40
Time in seconds FIG. 3. Normal response to rectal distension. Pressure decrease indicates reflex relaxation of internal sphincter (upper line) and pressure increase signals reflex contraction of external sphincter (middle line). Increase in electrical activity appears in the contracting external sphincter (bottom line). Arrows indicate rapid inflation and deflation of the rectal balloon.
mal internal sphincter relaxation but no external sphincter contraction as measured manometrically, and the electromyograph disclosed no burst of electrical activity (fig. 6). Resting electrical activity was either absent or markedly diminished (fig. 7). One patient had reflex contraction of the external sphincter, although the contraction was extremely weak. In patients with myopathy, electrical activity was diminished at rest and there was no increase in activity with rectal distension (fig. 8). Analysis of individual action potentials demonstrated features characteristic of myopathy; that is, there was a decrease in duration of spike potentials as compared to the normal, as well as a decrease in voltage. The average duration in patients with myopathy was 1.8 msec compared to the normal of 3.42 msec. Discussion
The maintenance of fecal continence is a complex affair depending upon many factors. This study concerns itself specifically with the relative importance of
104
Vol. 53, No.1
ALVA ET AL .
REFLEX THRESHOLD +30 +20 +10
"'
"'z "
0
r;1t1
INT. SPHINCT.
+10] 0
-__,.-......__~~~-~--~ EXT.SPHINCT. 50cc.
2.5cc.
n
0
20
1~ 40
60
15cc.
IOcc.
1~
5cc.
1~
80 100 120 140 TIME IN SECONDS
160
1~ 180
200
FIG. 5. Threshold for rectosphincteric reflexes. Decreasing responses are seen in internal and external sphincters with decreasing volume of rectal distension (volume indicated at bottom of figure) until no response is obtained. In this particular patient internal sphincter threshold is 10 ml, and external sphincter threshold is 25 mi. NORMAL
v
FECAL INCONT.
+ 0 IOj¥
Int . sphincter
-10 ~ -20 0
.c
-30
u
"'
t+20lL +15
+10 +5 0
- - - - - E x t . sphincter
distension produces reflex relaxation of the smooth muscle (internal sphincter) at the same time that it induces reflex contraction of the striated muscle (external sphincter). Moreover, previous work has shown that the internal sphincter exercises constant tonus in the resting state.1 • 2 The present work demonstrates, in addition, that there is constant electrical activity of the external sphincter at rest, indicating that it, too, maintains constant tonus. This observation is consistent with results reported by others in animals 3 and man. 4 To date
- - - - - M e a n voltage
0
20 40
FECAL INCONT. 0
20
40
ELECTROMYOGRAM
Time in seconds
Fw. 6. Response to rectal distension of normal subjects (left) and incontinent patients (1ight). Normal relaxation of internal sphincter is seen in incontinent patients (upper line, 1ight), but with rectal distension external sphincter does not contract (middle line) and there is no increase in electrical activity in the external sphincter (bottom line ).
A
50 JJV
I~~---......--------0
2 Time in seconds
50JJV
two rectosphincteric reflexes and the roles of each of the two sphincter components in the preservation of continence. This problem is of particular interest, since the two muscle components respond to the same stimulus in opposite directions. Rectal
B
I 0
A
.02
B
.04
0
.02
.04
Time in seconds
FIG. 7. Electromyographic tracing of external sphincter in incontinent patients. There is no burst of electrical activity with rectal distension.
July 1967
105
ABNORMALITIES WITH FECAL I NCONTINENCE
no stimulus has been found which can induce reflex contraction of the internal sphincter. The only response normally available to this mmcle is relaxation. This suggests that, in the resting state, the internal sphincter is contracted at maximal or near maximal levels. On the other hand , the extern al sphincter, although tonically contracted, can respond to rectal distension by further contraction, and, therefore, is not maximally contracted in the resting state. In patients who were incontinent, regardless of whether incontinence was on the basis of neurological or muscular abnormality, the internal sphincter response \Yas present but the external sphincter response was not. It can therefore be concluded that, of the two sphincter components, it is the voluntary external sphincter which plays the major role in maintenance of sphincteric continence. Since gross fecal incontinence was present in the patients studied, it is possible that the internal sphincter, which is normally in a state of tonic contraction, may play a role in the maintenance of continence when fecal material is presented to the rectum in amounts insufficient to distend it and thus insufficient to induce relaxation of the internal sphincter. Other work 5 similarly suggests that the tonically contracted internal sphincter plays a role in maintaining continence specifi cally of liquid feces and flatus. There is evidence which tends to corroborate this point, since the threshold for t he external sphincter response is generally higher than for the internal sphincter (fig. 5). In other words, the smallest volume of rectal distension which elicits an internal sphincter response does not produce reflex external sphincter contraction, which implies that the tonically contracted internal sphincter can present an adequate barrier to small volumes of colonic contents. The relaxation which appears in the internal sphincter with adequate rectal distension would not be expected fo facilitate continence, but might prepare for defecation. By contrast the external sphincter is normally in a state of minimal tonus and promptly contracts when the rectum is
ELECTROMYOGRAM NORMAL
l
1
50
~vI__ ,.~ji.UJilllJ../.
r
MYOPATHY
2
0 Time in seconds
FIG. 8. Electromyogram in incont inent patients with myopathy (lo wer line ) compared with normal subjects (upp er line). Although resting electrical activity is present in myopathy as in normal subj ect, no reflex increase in activity is seen in myopathy with rectal distension.
sufficiently distended. This could facilitate continence. Moreover, the present study shows a correlation between impairment of external sphincter response and incontinence regardless of underlying cause. In addition to reflex control, the voluntary control of fecal continence is directly dependent upon the external anal sphincter. Even though this muscle can remain fully contracted voluntarily for only 1 min before beginning to fatigue, 6 this is apparently sufficient under normal conditions to allow for rectal adaptation to occur to prevent fecal incontinence until voluntary defecation takes place. The concentric needle electrode is capable of recording only from striat ed muscle and cannot pick up electrical potentials from smooth muscle. Therefore the information obtained from the electromyographic studies confirms the manometric observation that the external sphincter contracts with rectal distension and provides the additional information that this sphincter is in a state of tonic contraction. Electromyography can also demonstrate, as it did in these studies, a pattern characteristic of myopathy, which the mano-
106
ALVA ET ilL.
metric technique cannot, and it can therefore show whether the anal sphincter is involved in myopathy affecting other muscles, as well as help to separate muscle disorders from neurological disorders. Summary
A technique is described for obtaining simultaneous manometric recordings of reflex responses from the internal and external anal sphincters along with electromyographic activity from the external sphincter. This combined technique demonstrates that, in the normal resting state, the internal sphincter is strongly contracted and the external sphincter minimally contracted. Patients were studied with fecal incontinence on the basis of neurological impairment, myopathy, and anal muscle injury. Normal internal sphincter reflexes were present, but external sphincter reflexes were absent in incontinence regardless of underlying cause, indicating that, of the two muscle components, the external sphincter plays the major role in the preservation of continence. Myopathy was demonstrated elec-
Vol. 5S, No . 1
tromyographically in the external sphincter of patients who had incontinence associated with myop athy of other muscles. REFERENCES 1. Schuster, M. M., P. Hookman, T. R. Hendrix, and A. I. Mendeloff. 1965. Simultaneous manometric recording of internal and external anal sphincteri c reflexes. Bull. Hopkins Hosp. 116 : 79--88. 2. Schuster, M. M., T. R. Hendrix, and A. I. M endeloff. 1963. The internal anal sphincter response: M anometric studies on its normal physiology, neural pathways, and alteration in bowel disorders. J. Clin. Invest. 42 : 196-207. 3. Bishop, B. 1959. Reflex activity of the external anal sphincter of cat. J. Physiol. (London) 137 : 679-692. 4. Porter, N. H. 1962. A physiologic study of the pelvic floor and rectal prolapse. Ann. Ro~·. Coli. Surg. Eng. 31: 379--404. 5. Bennett, R. C., and G . L. Duthie. 1964. The functional importance of the internal anal sphincter. Brit. J. Surg. 51: 355-357. 6. Gaston, E. A. 1948. Fecal continence follow ing resection of various portions of the rectum with preservation of the anal sphincters. Surg. Gynec. Obstet. 87 : 669-678.