Classifications

Table 33.2. classification based on whether neurogenic

Preganglionic

parasympathetic

efferents,

vesicourethral dysfunction affects bladder, outlet (urethra,

originating in the SPN, release acetylcholine

bladder neck, external urethral sphincter), or both

which activates nicotinic receptors on ganglia in

Bladder

Outlet

the pelvic plexus or within the bladder/urethral

overactive

increased resistance

wall. Likewise, postganglionic parasympathetic

nerves release acetylcholine that via muscarinic

•  Neurogenic detrusor

•  Detrusor sphincter

receptor (M3) contract the detrusor, whereas

overactivity

dyssynergia

M2 activation turns off intracellular signaling

•  Poor compliance

•  Detrusor internal

responsible for detrusor relaxation.8 Thus anti-

muscarinics are the primary drug treatment of

•  High detrusor leak P

sphincter dyssynergia

OAB. Nitric oxide (NO) released from parasym-

•  Dysfunction voider

Underactive

reduced resistance

Preganglionic sympathetic fibers in the lower

•  Impaired contractility

•  Uninhibited sphincter

urinary tract in thoracic spinal cord segment

T11 to lumbar spinal cord segment L2. Symp-

relaxation

athetic postganglionic neurons mostly contain

•  Detrusor areflexia

•  Intrinsic sphincter

noradrenaline. Exogenous noradrenaline con-

deficiency

tracts smooth muscle by the stimulation of a1-

adrenoceptors predominately 1A in the urethra

and 1D in the bladder neck.9 Therefore, alpha

most other neurologic disorders.The International

adrenergic antagonists have

been

useful in

reducing outlet

resistance in

conditions with

Continence Society (ICS) classification is essentially

failure to empty. In contrast, activation of b3-

aurodynamicclassificationschemewhichassumes

adrenoceptors relaxes smooth muscle in the

that every patient undergoes urodynamics.

detrusor.9 Passive, elastic properties of the blad-

der body in addition to local neural networks of

Autonomic Pathways

urothelium and interstitial cells as well as neural

mechanisms are involved in accommodation of

Innervating the LUT

the bladder to large volumes during urine stor-

age (compliance). Bladder accommodation of

The parasympathetics innervating the bladder

urine and contraction is also influenced by the

and urethra originate from the sacral parasympa-

urothelium and interstitial cells although pre-

thetic nucleus (SPN) located in S2–S4 of the sacral

cise mechanisms are unclear.

spinal cord to form the pelvic nerve.Preganglionic

axons in the pelvic nerve then synapse on post-

ganglionic neurons in pelvic ganglia.

Somatic Pathways

Sensory neuron cell bodies reside in dorsal

root ganglia (DRG).Afferents in the bladder and

urethra are low threshold myelinated (Ad) and

The neurons innervating the striated muscle of

unmyelinated (C-fibers) fibers that convey

the external urethral sphincter (EUS) and the

mechanical or noxious stimuli to the dorsal

pelvic floor emerge from the anterior horn of

horn of the spinal cord via the pelvic and hypo-

S2–S4. These motoneurons originate in an area

gastric nerves. The afferents triggering micturi-

termed Onuf’s nucleus. The axons travel to the

tion travel in the pelvic nerve. Bladder afferents

EUS and the periurethral striated muscle in the

containing nitric oxide synthase, glutamate, and

pudendal nerve.

a variety of neuropeptides enter the dorsal horn

Afferents from the EUS travel in the pudendal

of the spinal cord.5-7 There, second-order neu-

nerve.Neuromodulation by stimulation of sacral

rons project rostrally to supraspinal sites includ-

nerve roots may work by somatic or non–blad-

ing the hypothalamus, thalamus, and pons. The

der afferent stimulation causing central inhibi-

hypothalamus is known to coordinate auto-

tionofmicturition(forurgeurinaryincontinence

nomic activity. The thalamus processes nocicep-

[UI]) or the EUS (for retention). The striated

tive information. The pons is specifically

muscles of the lower urinary tract are inner-

involved in micturition.

vated by somatic cholinergic nerves that arise