Somato-sensory Reflex Arch in Spinal Cord Injury - Effect on Colorectal Transport

Introduction:

Spinal cord injury has a profound impact on the lives of those affected. Quality of life is restricted not only by immobility but also by severe neurogenic bladder and bowel dysfunction. For example, 66% of spinal cord injury (SCI) patients have to empty their rectum digitally, 75% suffer from faecal incontinence and 9% spend more than 60 minutes each time they defecate. Neurological impairment due to SCI is permanent and the average age at injury is only 28 years. The longevity of individuals with SCI is approaching that of the general population and, accordingly, most patients have to live for several decades with severe bladder and bowel symptoms. It is estimated that the number of individuals with SCI in Denmark is 3.000 and each year 10.000 persons in the European Union sustain a SCI. Even though clean intermittent catheterization has successfully reduced mortality due to urinary tract infections or reflux and though several new treatment modalities for neurogenic bowel dysfunction have been introduced, both bladder and bowel dysfunction still rank among the top three causes of impairment of quality of life after SCI.

Somato-sensory reflex arch:

The concept was pioneered by professor Xiao. Animal studies and basic clinical research were performed in the United States and later human clinical studies have been done in Wuhan, China. The surgical procedure principle can briefly be summarized as follows:

All spinal nerves have an anterior efferent root and a posterior afferent root. For the somato-sensory reflex arch (or "Xiao procedure") the posterior (afferent or sensory) root of the 5th lumbar nerve (L5) is kept while the anterior root is cut and anastomosed to the anterior root of a lower segment, usually the third sacral segment (S3). Thereby, a new reflex arch has been created from the skin of the leg through the sensory part of L5 to the spinal cord and further through the anastomosis via S2 or S3 to the bladder and bowel. Strong stimuli at the L5 dermatome, i.e. scratching or electrical stimulation, will then initiate voiding (6,7). Effects of the somato-sensory reflex arch on neurogenic bowel dysfunction have not been studied, but clinical experience indicates that bowel management is substantially facilitated.

The Xiao procedure introduces a completely new concept for management of spinal cord lesions and it has been greeted with optimism worldwide. The number of patients operated in China alone is now more than 3.000 and centres in the United States, Germany and Israel have introduced or modified it. Furthermore, centres in Australia, Finland and Denmark plan to introduce it within the present year. There are, however, serious concerns that need to be addressed:

1. Clinical follow-up has only been done in very few patients and physiological studies after the procedure are equally few and small.
2. In spite of the very large number of patients operated in China logistic or cultural factors have prohibited effective follow-up.
3. A minor improvement in bladder and bowel function may be important to a Chinese patient without access to other treatment but it is unknown whether the Xiao procedure will be an advantage to patients in a western healthcare system.
4. The mode of action of the somato-sensory reflex arch is very incompletely studied and the mode of action on bowel function not studied at all.

Before the widespread use of somato-sensory reflex arch we find it of utmost importance that well designed studies with validated or even objective endpoints are performed. Results of such studies will have an international impact in either defining indications for a completely new treatment principle or, otherwise, in preventing the widespread use of an ineffective treatment.

Hypotheses:

In March 2009 the core members of our multidisciplinary study team went on a study tour to Wuhan, China. In Wuhan a staggering number of 600 patients had the somato-sensory reflex arch procedure performed in 2008. Based on experience from our visit we pose the following hypotheses:

1. Somato-sensory reflex arch increases colorectal transport between defecations.
2. Somato-sensory reflex arch improves colorectal emptying at defecation.

Patients and Methods:

Spinal cord injured patients

Internationally, two indications for the somato-sensory reflex arch are emerging:

1. Adult patients with bladder dysfunction due supraconal SCI (above the medullar conus) and
2. Children with bladder dysfunction due to spinal bifida. Most children with spinal bifida have motor incomplete lesions and, accordingly, the surgical procedure carries a risk of long-lasting or even permanent loss of motor function - typically loss of dorsiflexion of the foot. Whether results from the procedure justify that risk remains to be determined. In contrast, patients with motor complete supraconal SCI, and thereby complete loss of voluntary muscle function below the level of injury, do not run that risk. Therefore, it has been decided that patients in group a) above will be offered the procedure at the Department of Neurosurgery. Initially, 20 patients will undergo the procedure. As the method is new, surgery and follow-up will be performed under strict monitoring with emphasis on neurophysiologic testing and potential complications. Approval will be obtained from the Ethics Committee, patients will be very carefully informed by the neurosurgeon and informed consent will be signed.

Surgical procedure:

The relatively minor surgical procedure has been described in previously. In summary: A hemilaminectomy of L5-S1 is performed. By means of neurophysiology testing the 5th lumbar root and 2nd or 3rd sacral roots are identified on one side. The perineurium is opened and the motor roots are separated from the sensory. The motor roots are transsected and a microanastomosis is created between L5 and S2 or S3. After surgery sprouting occurs and after 12-18 months the reflex arch is functional. Time till clinical effect is therefore also 12-18 months. The advantage of the procedure is that it is performed through a hemilaminectomy of only two segments and the surgical stress in relatively small. The patients are expected to be in their habitual condition within 48 hours.

Post surgical monitoring:

Even if patients void during somato-autonomic reflex arch stimulation, they usually do not defecate. In spite of this, it is the clinical experience in China that bowel function improves significantly. This is possible because the left colon and rectum receive stimulatory parasympathetic innervation from the same spinal cord segments (S2-S4) as the bladder. It has been shown in several papers, including some from our own group, that colonic transit times are significantly prolonged in SCI patients. Somato-autonomic reflex stimulation may therefore improve bowel function by increasing colorectal transport during stimulation even in the absence of defecation. As most patients stimulate several times each day the cumulative effect on the colorectum may be considerable and facilitate colorectal emptying when it is otherwise induced.

Our centre has been leading internationally in developing scintigraphic techniques for assessment of colorectal transport at defecation and previously we have found that patients with low SCI have extremely reduced colorectal emptying at defecation. We find that our scintigraphic technique is extremely well suited for the study of colorectal effects from the Xiao procedure.

Scintigraphic procedure:

The total gastrointestinal and segmental colonic transit times of each individual is determined. Based on this information two doses of 111Indium are taken on day-1 (2.6 MBq) and on day-2 or-3 (3.3 MBq). On day-0 patients arrive at our Department of Nuclear medicine at 8 A.M. A double headed Picker Gamma camera is used to image the whole abdomen for ten minutes with patients lying flat on their back (period 1). Then another ten minutes recording will be performed while the relevant dermatome for the somato-autonomic reflex arch is stimulated (period 2). Then subjects are allowed a standardized meal to stimulate the gastrocolonic reflex. Within 30 minutes SCI subjects initiate defecation in their standard way (through staining, digital stimulation, suppositories or micro enema) while sitting at the toilet. Finally, another ten minutes recording is performed to determine colorectal contents after defecation (period 3). The number of counts for each of the ten minutes periods is approximately 80.000. Comparison of the number of counts in each of four segments (the coecum/ascending colon, the transverse colon, the descending colon and the rectosigmoid) allows highly specific description of luminal colorectal transport during stimulation or at defecation. All subjects will only be studied twice: Before surgery and after 18 months. Based on this relatively simple experiment the following three sub-studies can be published:

B1)Colorectal transport at defecation in patients with spinal cord lesions By comparing results from scintigraphy before surgery in patients with supraconal SCI with our previous results among healthy volunteers and patients with low SCI valuable information about colorectal dysfunction in SCI will be obtained.

B2)Colorectal transport during somato-autonomic reflex stimulation By comparing the localization of colorectal contents in periods 1 and 2 before both surgery and after 18 months very detailed information about colorectal transport during somato-autonomic reflex stimulation will be provided.

B3)Colorectal emptying at defecation after somato-autonomic reflex stimulation Substraction of counts in period 3 from those registered in period 2 differences between colorectal emptying and segmental transport at defecation before and after creation of the reflex arch will give detailed objective information about the effects of the Xiao procedure on colorectal emptying.