1. Both the detrusor and the sphincter are overactive due to lack of control and descending inhibition from the pons and cortex, and both the sphincter and detrusor muscles contract reflexively when stretched.
2. The detrusor reflexively contracts at small volumes, and contracts against an overactive sphincter, causing high pressures in the bladder.
Detrusor Areflexia (Flaccid Bladder)
1. Flaccid bladder results from injury to the sacral cord or cauda equina giving a lower motor neuron lesion and evidenced by an areflexic detrusor muscle.
2. The external sphincter tone tends to be flaccid, causing incontinence.
3. Internal sphincter tone may be intact due to the higher origin of the sympathetic innervation, in this case complete emptying, even with externally applied suprapubic pressure, may be difficult.
Figure 11. 2=normal function; 1=reduced or altered neurological function; 0=complete loss of control; NT=unable to assess due to preexisting or concomitant problems.