Brainstem lesions influencing bladder function As discussed earlier, a role for pontine centers in human micturition has been inferred from animal experiments. The existence of a well-delineated pontine nucleus for micturition is controversial (Barrington nucleus). MRI studies by Sakakibara and colleagues have documented isolated pontine lesions as a cause of several different types of micturition difficulties.
Therapy of Disordered Micturition
Several drugs have been used in the management of flaccid and spastic disturbances of bladder function. In the case of a flaccid paralysis, bethanechol (Urecholine) produces contraction of the detrusor by direct stimulation of its muscarinic cholinergic receptors. In spastic paralysis, the detrusor can be relaxed by propantheline (Pro-Banthine, 15 to 30 mg tid), which acts as a muscarinic antagonist, and by oxybutynin (Ditropan, 5 mg bid or tid), which acts directly on the smooth muscle and also has a muscarinic antagonist action. Atropine, which is mainly a muscarinic antagonist, only partially inhibits detrusor contraction.
More recently, alpha1-sympathomimetic–blocking drugs such as terazosin, doxazosin, and tamsulosin have been used to relax the urinary sphincter and facilitate voiding. Their widest use has been in men with prostatic hypertrophy, but they may be beneficial in patients with dyssynergia of the sphincter (failure of the sphincter to open when the detrusor contracts) from neurologic disease. Several other drugs may be useful in the treatment of neurogenic bladder but can be used rationally only on the basis of sophisticated urodynamic investigations (Krane and Siroky).
Often the patient must resort to intermittent self- catheterization, which can be safely carried out with scrupulous attention to sterile technique (washing hands, disposable catheter, etc.). Some forms of chronic antibiotic therapy and acidification of urine with vitamin C (1,000 g/d) are practical aids, but their use has gone through cycles of popularity based on various studies with differing results. In selected paraplegic patients, the implantation of a sacral anterior root stimulator may prove to be helpful in emptying the bladder and achieving continence (Brindley et al).
Disturbances of Bowel Function
Ileus from spinal shock, reflex neurogenic colon, and sensory and motor paralysis are all recognized clinical entities. The colon, stomach, and small intestine may be hypotonic and distended and the anal sphincters lax, either from deafferentation, deefferentation, or both. The anal and, in the male, the bulbocavernosus reflex may be abolished. Defecation may be urgent and precipitant with higher spinal and cerebral lesions. Because the same spinal segments and nearly the same spinal tracts subserve bladder and bowel function, meningomyeloceles and other cauda equina and spinal cord diseases often cause so-called double incontinence. Fecal incontinence is less frequent than urinary incontinence, however, because the bowel is less-often filled and its content is usually solid.
Bowel dysmotility, mainly by way of ileus may be a prominent feature of immune neuropathies such as