DETRUSOR-SPHINCTERIC DYSSYNERGIA IN PARAPLEGICS COMPARED WITH THE SYNERGIA IN A BRAIN-DEAD HUMAN BY USING THE SINGLE-FIBER ACTION-POTENTIALRECORDING METHOD

(1) Humans with spinal cord lesions often show detrusor-sphincteric dy ssynergia of the urinary bladder which is reflected urodynamically in the detrusor pressure and a simultaneous increase in electromyographic pelvic floor activity. (2) The time-course of the increase in the sec ondary muscle spindle afferent activity, induced by the parasympatheti c nervous system in muscle spindles contributing to continence, is ver y similar to that of detrusor pressure. The detrusor-sphincteric dyssy nergia is therefore analysed by comparing the natural impulse patterns of secondary muscle spindle afferents (SP2) and sphincteric motoneuro ns in a brain-dead human with those in patients with spinal cord lesio n. The parasympathetic nervous system was activated by painful bladder catheter pulling. (3) In a brain-dead human the sphinteric motoneuron s subserving continence were inhibited at a time, when preganglionic p arasympathetic efferents increased their activity for 10 s and an SP2 fibre increased its activity for several minutes. In a paraplegic with a strong bladder dysfunction, the SP2 fibre activity increased, due t o parasympathetic activation, lasted for approx. 1 min, showed undulat ions and its amplitude was smaller than that measured in a brain-dead human. The sphincteric motoneurons were not inhibited. (4) In the brai n-dead human, an SP2 fibre showed doublet firing with interspike inter vals (IIs) of a duration between 10 and 14 ms for low level parasympat hetic activation. For high level parasympathetic activation this singl e parent spindle afferent fibre showed multi-ending regular firing of up to 6 endings with IIs of a duration of predominantly 15 to 25 ms. I n one paraplegic with a strong bladder dysfunction the doublet firing was less regular, even though two II peaks at 10.2 and 11.2 ms occurre d in a II distribution similar to the brain-dead human. The multi-endi ng regular firing was replaced by a repeated burst firing. In a second paraplegic with strong detrusor-sphincteric dyssynergia the burst fir ing consisted of up to 6 impulses with increasing IIs and a first II o f approx. 0.2 ms (transmission frequency 5000 Hz). In a third parapleg ic with a lesser dysfunction of the bladder a highly activated SP2 fib re showed an activity pattern intermediate to those of multi-ending re gular firing and burst firing. (5) The time constant for the activity decrease of a spindle afferent fibre following parasympathetic activat ion was to 31 s in a paraplegic and approx. 40 s in a brain-dead human . It is concluded that the muscle spindles are unchanged following spi nal cord lesion. The pathologic firing patterns of the SP2 fibres are thus a result of neuronal network changes in the parasympathetic nervo us system of the sacral micturition center. (6) Differences in axon me mbrane properties between animals and humans, simultaneous action of t he somatic and the parasympathetic divisions, the detrusor-sphincteric coordination, hyperreflexia and clinical implications are discussed.