F- CLINICAL ASPECTS OF SPINAL CORD INJURIES
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bladder and abrupt closing of the vesical neck. Burgheli & Ichim (1970) stimulated
electrically the motor nerves of the bladder, following introduction of a cold-light
cystoscope through an opening above the posterior border of the trigone and filling the
bladder with saline. From that position, the function of the bladder could be observed
and registered by endovesical cinematography. Following stimulation of the nervi pelvici
through double electrodes the pressure produced by detrusor contractions overcomes the
resistance of the tone of the sphincter system and voiding occurs. However, 10-15
seconds later the stimulating effect on the sympathetic fibres in the plexus pelvicus, where
both parasympathetic and sympathetic fibres are mixed, evokes contraction of the
smooth sphincter and the bladder emptying is stopped. This is accomplished by the
longer latent period of sympathetic stimulation. From these observations, the authors
assume, as already mentioned above, the existence of a smooth internal sphincter which
plays a part in the closing mechanism of the bladder.
Although modern anatomical research (Krantz, 1951; Woodburne, 1960, 1967)
is in accordance with the views of previous authors (Le Gros Clark, 1883; Griffiths,
1895) that anatomically there is a continuation of bladder and urethra and that the
detrusor muscle fibres open mechanically the proximal part of the vesical neck, there is no
doubt about the reciprocity between the expulsive action of the detrusor and the inhibi
tory action of the vesical neck. The response of the vesical neck (internal sphincter
complex) is like that of the external urethral sphincter opposite to that of the detrusor
muscle. Denny-Brown & Robertson (1933), recording simultaneously vesical, urethral,
rectal, perineal and abdominal wall pressure, found reflex relaxation of the detrusor when
the sphincters contracted and vice versa. However, in normal conditions, the inhibitory
function of the vesical neck complex is less essential during micturition than during sexual
function, where contraction of the smooth muscle bundles of the vesical neck is important
and acts like a trap-door in preventing regurgitation of the ejaculate into the bladder
during orgasm. It is well known that, following prostatectomy, this trap-door action is
abolished and regurgitation of the ejaculate into the bladder during orgasm occurs as a
result of the destruction of the prostatic and membranous structures of the urethra. The
disturbed balanced reciprocity between the forces of expulsion and the inhibitory
function of the vesical neck complex is the primary cause of bladder dysfunction in
lesions of the central nervous system. This will be discussed later.
Desire
to rnicturate
is precipitated primarily by increased bladder volume
initiating reflex detrusor contraction followed by relaxation of the sphincter complex.
The relationship between bladder volume and the first desire to void varies individually.
Best & Taylor (1935) found first desire to void at about half the volume of the bladder
content required to cause irresistible urgency of micturition. During sleep in the adult,
when conscious awareness of bladder distension is eliminated, afferent impulses emanat
ing from the distended viscus may be strong enough to interrupt the sleep, thus restoring
desire to void and promoting volitional voiding. In very young children who have not
full control, these afferent impulses may initiate voiding without arousing consciousness
and bed wetting is the result.
The reflex action of the bladder is also subject to volitional and emotional impulses
which in certain extrinsic (for instance cold) or intrinsic conditions may facilitate micturi-
