Urethro-vesical function during spinal shock

Summary Twenty spinal shock patients were investigated with simultaneous urethrovesical, anal and rectal pressure recordings and EMG of the external urethral and anal sphincters. Dynamic and static urethral pressure profiles (UPP) were carried out with empty and full bladder. Baldder filling was accompanied by an increased resistance in the internal sphincter zone, which in turn was paralleled in the majority of cases by an elevation of pressure in the membranous urethra without concomitant increase of its EMG activity. This is suggestive of an increased sympathetic activity in the bladder neck area and in the smooth muscle component of the external urethral sphincter. Dynamic pullthrough UPP's displayed higher resistances in the membranous urethra than static interrupted UPP's pointing to the role played by the urethral muscosal receptors in eliciting artefactual results. Higher pressures were recorded in the juxtabulbar portion of the membranous urethra than in its mid portion pointing to a gradient of pressure within the external urethral sphincter itself. The amount of EMG activity recorded in the anal and urethral sphincters at rest was somewhat decreased; high pressures and distinct reflex activity were recorded in both sphincters showing that they escape spinal shock characterized primarily by areflexia. After defining spinal shock a rational explanation based upon neuroanatomical and neurophysiological findings is offered as to why somatic activity of the sacral segments escapes it as evidenced by clincial, urodynamic, and electromyographic recordings.