A 64-year-old woman is evaluated for episodic urinary incontinence. Urodynamic studies reveal an overactive bladder. Symptoms persist after behavioral interventions, and the patient is unable to tolerate medical treatment. Low-amplitude electrical stimulation therapy that helps modulate neural control of the urinary bladder muscle, urethral sphincter, and pelvic muscles is planned. A stimulating electrode is most likely to be placed close to which of the following structures during this procedure?

Question

A 64-year-old woman is evaluated for episodic urinary incontinence.  Urodynamic studies reveal an overactive bladder.  Symptoms persist after behavioral interventions, and the patient is unable to tolerate medical treatment.  Low-amplitude electrical stimulation therapy that helps modulate neural control of the urinary bladder muscle, urethral sphincter, and pelvic muscles is planned.  A stimulating electrode is most likely to be placed close to which of the following structures during this procedure?

Quizplus · Accepted Answer

11ec160b_35ce_81b3_9249_792a84a208af_MD0001_00 This patient has urge incontinence due to an overactive bladder. In patients unresponsive to behavioral therapy and unable to take medications, a bladder stimulator is sometimes used. Neural stimulation is used to augment neural signals to the pelvic floor muscles and urinary sphincter, which are innervated from nerves derived from the S2-S4 nerve roots: Somatic innervation of the pelvic floor muscles helps to maintain continence because these muscles stabilize the urethra against the anterior vaginal wall. This contraction decreases the angle between the bladder neck and the urethra (ie, urethrovesical angle), thereby compressing the urethra, stopping urine flow, and maintaining continence. Therefore, increasing the strength of the pelvic floor muscles (either through physical therapy or neuromodulatory stimulation) promotes continence. The external urethral sphincter (EUS) is also under somatic control via the pudendal nerve (S2-S4); therefore, stimulation of these nerve roots will increase EUS tone to help improve urinary continence. Although the pelvic splanchnic nerves, derived from S2-S4, are classically described as providing parasympathetic input to the bladder and urethral sphincter (which promotes bladder contraction and may worsen incontinence), they are also involved in the bladder stretch-contraction reflex. Neural stimulation seems to inhibit this reflex to improve continence. (Choice A) The nucleus accumbens is part of the basal ganglia that mediates reward and pleasure. Transcranial magnetic stimulation targeting this area has been used to treat addiction, but it plays no role in urinary continence. (Choice B) Deep brain stimulation of the subthalamic nucleus has been used to treat the rigidity of Parkinson disease, but it is not involved in urinary continence. (Choice C) The vagus nerve (CN X) is involved in regulating the gastrointestinal system (eg, parasympathetic innervation stimulates gastric muscle contraction and intestinal motility); stimulation is occasionally used to improve gastric motility. However, the vagus nerve does not play a role in micturition or urinary continence. (Choice D) The T6 nerve root contributes to the greater splanchnic nerve (T5-T10), which provides sympathetic innervation to the foregut to slow peristalsis. However, sympathetic stimulation of the bladder, which inhibits detrusor contraction, originates lower, from about T10-L2. (Choice E) The L5 nerve root contributes somatic innervation to many muscles of the lower limb (eg, gluteal muscles, tibialis muscles, extensor hallucis longus) but does not innervate the pelvic floor, bladder, or urethral sphincters. Educational objective: Urge incontinence can be treated with neuromodulation directed toward the S2-S4 nerve roots, which improves pelvic floor muscle strength and contraction of the external urethral sphincter; it may also impact the bladder stretch-contraction reflex.

A 64-Year-Old Woman Is Evaluated for Episodic Urinary Incontinence