Coordination impairment between the somatic and parasympathetic nervous system divisions in the human sacral micturition centre following spinal cord injury.

Abstract

The detrusor-sphincteric dyssynergia is analyzed by comparing the natural impulse patterns of secondary muscle spindle afferents (SP2) contributing to continence (SP2 fibre activity changes are similar to detrusor pressure changes) and sphincteric motoneurons in a brain-dead human with those in patients with spinal cord injuries. In the brain-dead the sphincteric motoneurons, subserving continence, were inhibited at a time, when preganglionic parasympathetic efferents and a SP2 fibre increased their activity (physiologic). In paraplegics the sphincteric motoneurons were not inhibited (pathophysiologic). In the brain-dead, an SP2 fibre showed doublet firing (interspike interval (II) 10 to 14 ms) for low level parasympathetic activation and multi-ending regular firing for high parasympathetic activation. In one paraplegic with strong bladder dysfunction, the multi-ending regular firing was replaced by a repeated burst firing with a shortest II of 0.2 ms (transmission frequency = 5000 Hz). The pathologic firing patterns of the SP2 fibres, the detrusor-sphincteric dyscoordination, and hyperreflexia in paraplegics are most likely a result of neuronal network changes in the parasympathetic and somatic nervous system divisions of the sacral micturition center after spinal cord injury. It is discussed that urinary bladder functions can be re-learned.