The interaction of cortico-spinal pathways and sacral sphincter reflexes in subjects with incomplete spinal cord injury: a pilot study.

AIMS: To reveal the effectiveness of corticospinal drive in facilitating the pudendal reflex in the anal sphincter muscle, as a surrogate marker for the urethral sphincter, in incomplete spinal cord injury (iSCI). METHODS: Three neurologically normal subjects and twenty-six subjects with incomplete, supra-sacral spinal cord injuries and symptoms of a neuropathic bladder were recruited. Incontinence was assessed using the International Consultation on Incontinence Modular Questionnaire (ICIQ). Electromyographic activity of the external anal sphincter was recorded. The pudendo-anal reflex (PAR) was elicited by electrical stimulation of the dorsal penile nerve (DPN). Motor cortical excitation was achieved using transcranial magnetic stimulation (TMS). RESULTS: Preliminary findings in normal and iSCI subjects showed facilitation of the PAR by prior TMS with an optimal interval of 20-40 msec. Of 23 iSCI subjects, 12 showed facilitation to TMS applied 30 msec before DPN stimulation. Eight of the 12, and a further five iSCI subjects, had an anal sphincter MEP in response to TMS alone. There was a weak tendency (r(2) = 0.22, P = 0.03) for those with higher ICIQ values to have larger PAR responses but no significant difference in ICIQ scores between those with (ICIQ = 4.9 ± 4.0 mean ± SD) and those without (ICIQ = 7.2 ± 4.7) cortical facilitation of the PAR. CONCLUSIONS: Cortical TMS was effective in facilitating the PAR in some iSCI subjects. The presence of cortical facilitation of the PAR was not related to the degree of urinary continence.

Intraoperative assessment of human spinal cord perfusion using near infrared spectroscopy with indocyanine green tracer technique.

BACKGROUND CONTEXT: Despite the significant interest in the assessment of human cerebral perfusion, investigations into human spinal cord perfusion (SCP) are scarce. Current intraoperative monitoring of spinal cord relies on the assessment of neural conduction as a surrogate for SCP. However, there are various inherent limitations associated with the use of these techniques. Near infrared spectroscopy (NIRS) has been successfully used for monitoring and assessment of human cerebral perfusion and has shown promising results in intraoperative assessment of SCP in animal models. PURPOSE: The aim of this study was to investigate whether it is possible to monitor physiological changes in human SCP intraoperatively using NIRS with indocyanine green (ICG) tracer technique. We used this technique to calculate the human spinal cord carbon dioxide (CO2) reactivity index. In addition, we investigated whether the lamina causes significant attenuation of NIRS signals. STUDY DESIGN/SETTING: Intraoperative human experimental study. PATIENT SAMPLE: Eighteen patients undergoing elective posterior cervical spine surgery. OUTCOME MEASURES: Carbon dioxide reactivity of human SCP. METHODS: Nine patients underwent transdural assessment of SCP, with an additional nine patients undergoing translaminar measurements. Patients' SCP was continuously monitored using an NIRO-500 NIRS monitor via a set of purpose built optodes. Their arterial ICG concentration was simultaneously assessed using a pulse dye densitometer. Patients' end-tidal CO2 was gradually increased by 7.5 mm Hg and then returned back to baseline. Three sets of measurements were taken: baseline, hypercapnic, and return to baseline. RESULTS: After hypercapnia, SCP increased by a mean of 57.2 ± 23.3% in the transdural group and 46.6 ± 36.3% in the translaminar group. Carbon dioxide reactivity index was 7.6 ± 3.2%ΔSCP/mm Hg in the transdural group and 6.4 ± 5.3 %ΔSCP/mm Hg in the translaminar group. There was no significant difference in the increase in SCP (p=.475) or the CO2 reactivity index (p=.581) observed between the transdural and the translaminar groups. CONCLUSIONS: Intraoperative NIRS with ICG tracer technique can identify an increase in the SCP in response to hypercapnia. It is possible to use this technique for monitoring SCP over the dura and the lamina. This technique could potentially be used to provide insight in to the pathophysiology and autoregulation of commonly acquired spinal cord conditions. Further research assessing the use of NIRS for monitoring of SCP is required.

Functional electrical stimulation for bladder, bowel, and sexual function.

The principles of using electrical stimulation of peripheral nerves or nerve roots for restoring useful bladder, bowel, and sexual function after damage or disease of the central nervous system are described. Activation of somatic or parasympathetic efferent nerves can produce contraction of striated or smooth muscle in the bladder, rectum, and sphincters. Activation of afferent nerves can produce reflex activation of somatic muscle and reflex inhibition or activation of smooth muscle in these organs. In clinical practice these techniques have been used to produce effective emptying of the bladder and bowel in patients with spinal cord injury and to improve continence of urine and feces. Stimulation of parasympathetic efferents can produce sustained erection of the penis, and stimulation of the nerves to the seminal vesicles can produce seminal emission. Reflex erection and ejaculation can also be produced by stimulation of afferent nerves. Experimental techniques for controlling emptying and continence by a single device, and prospects for comprehensive control of bladder, bowel, and sexual function by electrical techniques are described. These may include more selective electrodes, inactivation of nerves by specific stimulus parameters, greater use of sensors, and networking of implanted components connected to the central and peripheral nervous system.

Orthostatic hypotension following spinal cord injury: impact on the use of standing apparatus.

INTRODUCTION: Upright posture confers numerous medical and social benefits to a spinal cord injured (SCI) patient. Doing so is limited by symptoms of orthostatic hypotension. This is a common secondary impairment among tetraplegic sufferers. OBJECTIVE: Establish the proportion of SCI patients who are restricted from using standing apparatus, such as standing frames and standing wheelchairs, because of inducing symptomatic orthostatic hypotension or the fear of developing these disabling symptoms. STUDY DESIGN: Survey conducted by Internet-accessible electronic questionnaire. Questionnaire validated for reliability and accuracy. RESULTS: 293 respondents. Mean age 44.6; 76% male. Median time from injury: 7 years. 38% suffered with orthostatic hypotension; majority were complete injuries and all (except one - T12) were T5 or above level. 52% replied that they were using standing wheelchairs or frames. Of these, 59 (20% of total) stated that orthostatic hypotension symptoms were limiting the use of their upright apparatus. Of those who did not use standing wheelchairs or frames, 16 (5.5% of total) reported that this was because of the fear of worsening their orthostatic hypotension. CONCLUSION: Orthostatic hypotension restricts standing apparatus use in a large proportion (a total of 25.5% of respondents in this survey) of SCI patients.

Interface pressure and cutaneous hemoglobin and oxygenation changes under ischial tuberosities during sacral nerve root stimulation in spinal cord injury.

Noninvasive functional magnetic stimulation (FMS) of the sacral nerve roots can activate gluteal muscles. We propose the use of sacral anterior root stimulator (SARS) implants to prevent ischial pressure ulcers in the spinal cord injury (SCI) population. In this study, we (1) investigated the acute effects of sacral FMS on ischial pressure, skin blood content, and oxygenation changes in people with SCI and demonstrated the utility of FMS as an assessment tool, and (2) showed that similar effects are possible with electrical stimulation via a SARS implant. Results indicated that sacral nerve root stimulation, either by FMS or implanted electrical stimulation, induced sufficient gluteus maximus contraction to significantly change subjects' ischial pressures and cutaneous hemoglobin and oxygenation during sitting. In addition to these beneficial acute effects, chronic stimulation via a SARS implant may build gluteal muscle bulk and prevent or reduce pressure ulcers in the SCI population.

Pressure changes under the ischial tuberosities of seated individuals during sacral nerve root stimulation.

Neuromuscular stimulation via the sacral nerve roots is proposed for prevention of ischial pressure ulcers following a spinal cord injury (SCI). Acute effects of sacral functional magnetic stimulation (FMS) on seat interface pressure changes were investigated in five nondisabled volunteers. Similar effects were demonstrated with functional electrical stimulation in people with SCI who used a sacral anterior root stimulator implant. The results indicated that sacral nerve root stimulation, either by FMS or implanted electrical stimulation, induced gluteus maximus contraction and mild pelvic tilt sufficient for clinically significant reductions in ischial pressures during sitting.

Aberrant reflexes and function of the pelvic organs following spinal cord injury in man.

Spinal cord injuries can be devastating on quality of life and lost opportunities due to their impact on bladder, bowel and sexual functions. Supra-sacral spinal lesions can cause incontinence by interrupting those pathways, which normally coordinate the bladder, bowel and sphincters. From a scientific perspective, neural control of the pelvic organs is one of the most intriguing in the body, involving both somatic and autonomic pathways participating in an exquisitely fine integration of lumbo-sacral reflexes. This review details the interactions of somatic and autonomic lumbo-sacral pathways responsible for coordinating the bladder and sphincters, the nature of their aberration post-injury and those aspects of neural control of the pelvic organs that are amenable to neurophysiological examination in man. It will focus in greater detail on how measurement of pelvic floor and sphincter reflexes can be used to assess the modulatory effects of sacral autonomic pathways on sacral somatic reflexes and vice versa including the so called "guarding reflex" and vesical inhibitory reflexes. The effects of volitional modulation of these reflexes will be discussed in relation to people with both complete and incomplete lesions. Finally the possible utility of such neurophysiological measures for complementing the established neurological classification and the assessment of somatic sensory-motor impairment in spinal cord injury will be discussed.

A new artificial urinary sphincter with conditional occlusion for stress urinary incontinence: preliminary clinical results.

OBJECTIVES: To perform a preliminary clinical investigation to determine the safety and efficacy of a novel artificial urinary sphincter (AUS) with conditional occlusion for the treatment of stress urinary incontinence. METHODS: Male patients with urodynamically proven stress urinary incontinence after a prostatectomy were implanted with the novel AUS. They were followed up over a period of 12 months and the device tested for efficacy by using objective measurements of urinary leakage and continence. We derived a new measure for continence called the Continence Index. RESULTS: We have demonstrated that the patients receiving the new AUS showed a reduction of greater than 10-fold in mean daily leakage volume from 770.6 ml to 55.1 ml. There was an overall improvement in the Continence Index from 54% to 97%. CONCLUSIONS: The new AUS with conditional occlusion provides good continence rates and enables adjustment of regulating pressure in situ.

Pelvic somato-visceral reflexes after spinal cord injury: measures of functional loss and partial preservation.

For people with spinal cord injuries, the impact of bladder, bowel and sexual problems on quality of life and lost opportunities can be devastating. Supra-sacral spinal lesions can cause incontinence by interrupting those pathways that normally coordinate the function of the bladder, bowel and sphincters. From a scientific perspective, neural control of the pelvic organs is one of the most intriguing in the body, involving both somatic and autonomic pathways participating in an exquisitely fine integration of lumbo-sacral reflexes. This chapter aims to review briefly those aspects of neural control of the pelvic organs that are amenable to neurophysiological examination in man. More specifically, it will focus in greater detail on the interactions of somatic and autonomic lumbo-sacral pathways responsible for coordinating the bladder and sphincters. Where appropriate, it will make comparisons with those controlling the bowel. It will describe how measurement of pelvic floor and sphincter reflexes can be used to assess the modulatory effects of sacral autonomic pathways on sacral somatic reflexes and vice versa including the so-called "guarding reflex" and vesical inhibitory reflexes. Aberrant activity following spinal cord injury (SCI), such as bladder hyperreflexia and sphincter dyssynergia, will be discussed in relation to these reflexes. The effects of volitional modulation of pelvic floor reflexes in people with both complete and incomplete lesions will be described. Finally, the chapter will address the possible utility of neurophysiological measures for complementing the established neurological classification and the assessment of somatic sensory-motor impairment in SCI.

Objective measurement of bladder sensation: use of a new patient-activated device and response to neuromodulation.

Detrusor overactivity is the primary objective focus of most investigations into the diagnosis and management of patients with urgency incontinence. Patients with an overactive bladder are characteristically troubled by subjective sensations of bladder fullness and urinary urgency, and frequently void at low bladder volumes attained before noticeable detrusor overactivity occurs. Bladder sensations are therefore crucial to understanding voiding patterns and symptoms, but little progress has been made in objectively describing the range of these sensations, and adequate information is lacking about their response to neuromodulation. Towards this end, a keypad 'urge score' device was designed to measure sensations during bladder filling. This patient-activated device gathers information about patient perceptions of bladder filling and the successive stages of increasing bladder sensation, without prompting or intervention by the investigator. The accuracy of the 'urge keypad' during filling cystometrography was validated in patients with urgency incontinence, and compared with data abstracted from patient voiding diaries. The device provides reliable and repeatable measures of different bladder sensations, with excellent, statistically significant consistency between bladder volumes and corresponding levels of sensation. Subsequently, it was shown that the sensation of urgency can be suppressed by neuromodulation in most patients tested; this suppression occurs with improvements in bladder capacity and voided volumes. It is therefore suggested that urodynamics with concurrent sensory evaluation may offer a more useful assessment tool for selecting those patients for therapies such as neuromodulation who present predominantly with the symptom of urgency.