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Sacral neuromodulation for the treatment of bladder dysfunction.

S3 nerve root neuromodulation is becoming an accepted therapy for individuals afflicted with lower urinary tract symptoms, such as idiopathic urinary urge incontinence, frequency, urgency, and urinary retention, who fail current standard therapies. This patient population is difficult to treat, and this therapy offers an option that can restore quality of life to these individuals. While the precise pathophysiologic mechanisms underlying these voiding symptoms is unknown based on the physiology of bladder function, it is logical to conclude that they relate to some aberration of the neuromuscular apparatus of the bladder and/or its outlet (the urethra). These pathophysiologic defects are not overtly manifested outside the lower urinary tract because these patients routinely do not have any apparent neurologic deficits. The fact that S3 neuromodulation can clinically improve these lower urinary tract symptoms would support the notion that the neural regulation of the bladder is somehow altered in these patients. This paper presents a review of the current knowledge regarding sacral neuromodulation in treatment of non-neurogenic voiding dysfunction.

Electric Stimulation Therapy↗

Update on sacral neuromodulation: indications and outcomes.

Tanagho and Schmidt first introduced sacral nerve neuromodulation in 1981. Since then, it has become increasingly popular and the indications for this procedure are growing. The purpose of this article is to discuss the established indications for sacral nerve stimulation (SNS). The outcomes of the most recent studies and trials dealing with SNS are presented. An overview of the most recent techniques used for neuromodulation is detailed.

Adult↗

[Chronic sacral bilateral neuromodulation. Using a minimal invasive implantation technique in patients with disorders of bladder function].

The implantable neuromodulation system described by Tanagho and Schmidt enables unilateral sacral nerve stimulation. Reports have been made on sacral neuromodulation failures of up to 50% in patients undergoing this procedure. We chose the bilateral electrode implantation and a minimal invasive laminectomy to ensure a more effective modulation and better placement and fixation of the electrodes. After successful assessment using a peripheral nerve evaluation test, 20 patients (14 with detrusor instability, 6 with hypocontractile detrusor) underwent minimally invasive laminectomy and bilateral electrode placement. In the patients with detrusor instability, the incontinence episodes were reduced from 7.2 to 1 per day and the bladder capacity improved from 198 to 352 ml. In patients with hypocontractile detrusor, the initial residual urine level of 450 ml dropped to 108 ml. Maximum detrusor pressure during micturition rose from 12 cmH2O initially to 34 cmH2O. The average follow up period was 17.5 months. There was no sign of deterioration in the modulation effect in any of the patients. Bilateral electrode implantation and the new sacral approach allow optimal neuromodulation in patients with bladder dysfunction. Laminectomy enables optimum electrode placement and fixation with minimal trauma.

Electric Stimulation Therapy↗

Effects of total and partial spinal transections on the pudendal nerve-evoked response in rat lumbar axial muscle.

The pudendal nerve-evoked activity in lumbar axial muscle nerves 24-48 h following spinal transections was studied in order to examine the supraspinal control of the pudendal nerve-evoked response (PNER). After total transections of the spinal cord in the thoracic region the overall activity in the muscle nerves was much reduced; the evoked responses consisted only of a single peak in activity 19.8 ms (+/- 1.4 ms) following the last shock of a 3-shock pudendal nerve stimulus demonstrating that some of the earliest responses previously described for the PNER are segmental in origin. To help identify supraspinal inputs to the PNER a series of partial transections were made to cut selectively different fiber columns within the cord. Four different surgical procedures were performed: transections of the entire dorsal half of the cord; ablations of all of the medial columns; combined lesions of the dorsal half and medial columns, sparing the tracts within the ventrolateral columns and bilateral transections of the lateral columns. Following all partial transections except those of the lateral columns, the PNER was similar to that seen in intact animals. After lateral column transections however, the responses were like those seen in the totally transected animals. The combined results suggest that supraspinal influences upon the PNER are conveyed primarily via the ventrolateral columns of the spinal cord. Bilateral convergence of afferent information was evident in the totally transected animals, indicating that such convergence can occur at segmental levels. The lesions which substantially altered the PNER closely paralleled those which eliminated lordotic responsiveness in behaving female rats.

Animals↗

Response patterns of human lumbo-sacral motoneurone pools to distant somatosensory stimuli.

The response of human lumbo-sacral motoneurones to electrical stimuli applied to the trunk, the face and the arms was evaluated by means of H reflex testing in extensors and averaging the rectified tonic EMG recorded from extensors as well as flexors. In extensor and flexor muscles, the reflex pattern consisted of a non-reciprocal inhibition-facilitation, occurring with latencies of about 60 and 80 msec, respectively. With reflex testing, only facilitation was observed in extensors, beginning after a conditioning-test interval of about 40 msec and peaking at about 80 msec. This discrepancy was interpreted to indicate excitation supraliminal in a facilitatory and subliminal in an inhibitory pathway, the latter requiring an additional input to impinge on motoneurones. Afferents responsible for the described reflex actions were identified as belonging mainly to low-threshold skin nerve fibres, conducting with a maximum velocity of about 45--50 m/sec. However, medium threshold skin afferents as well as muscle and joint afferents may also play a role. Stimulation of C5 and T10 skin areas close to the neuraxis revealed similar effects, the latencies being shorter or equal with T10 compared with C5 stimulation. The possibility of a directly descending propriospinal pathway is discussed, mediating the inhibitory as well as the excitatory reflex actions described.

Adolescent↗

Restoration of micturition using microelectric current in experimentally induced spastic urinary bladder in rabbits.

The 29 rabbits used in this study were divided into three groups, A (A1 and A2), B, and C. In subgroup A1, 4 animals were used in order to verify whether the contact of an electrode to the sacral nerves results in some abnormality of voiding reflex. In subgroups A1 and A2 (4 animals each) we further studied the micturition function using three parameters: (i) urinary bladder fluoroscopy and radiography, (ii) cystomanometry, and (iii) electromyography of the pelvic floor muscles (external sphinter). In group B (9 rabbits) spastic paraplegia and micturition disturbances resulted from spinal cord compression that was induced by inserting a balloon catheter into the T11-T12 intervertebral foramen. In this group the parameters studied revealed a spastic urinary bladder in all animals. Finally, the 12 animals of group C were rendered paraplegic as described in group B, and microelectrodes were placed over the sacral nerves as in subgroup A1. By applying a specific sequence of sacral nerve stimulation we succeeded in satisfactory urinary bladder emptying as confirmed by the micturition parameters studied: The urinary bladder pressure decreased from 65 +/- 3 to 28 +/- 3 mm Hg. The pelvic floor muscle amplitude was lowered from 130 +/- 7 to 20 +/- 3 microV, and finally the radiological bladder size also decreased from 38 cm2 before voiding to 18 +/- 3 cm2 after voiding. These results indicate that microelectric current stimulation of the sacral nerves, when applied under a specific sequence, could rather satisfactorily restore micturition disturbances, at least in this experimental animal.

Animals↗