ZHANG Shaocheng, M.D.¹, JOHNSTON, Laurance Ph.D.², HU Yuhua, M.D.¹, MA Yuhai, M.D.¹, ZHANG Zhenwei, M.D.¹, ZHANG Chuanshen, M.D.¹, and DANG Ruishan, M.D.¹

ABSTRACT:

Objective: To restore bowel and bladder function in chronically injured patients with paraplegia.

Methods: Two normal vascularized intercoastal nerves above the spinal cord injury site were harvested by cutting in at their distal ends at the midclavicular line and separating the proximal ends from the levatores costarum. The nerves were then transferred to the vertebral canal through a submuscular tunnel. A sural nerve segment that had been harvested and sheared into two segments was sutured to the intercostal nerves by epiperineurial neurorrhaphy and then to the sacral 2-4 nerve roots by interfascicular neurorrhaphy.  Thirty patients were postoperatively followed for 2-11 years (average 5 years), of which 1) 26 (87%) recovered partial defecation and urination sensation, 2) 23 (77%) regained the micturition reflex and uriesthesis; 3) 19 (63%) recovered partial function of the detrusor and sphincter urethra muscles; 4) 20 (67%) recovered partial defecation function and sphincter contraction; and 5) 8 (27%) regained the previous two functions (i.e., 3 & 4).

Conclusion: Because this surgical intervention creates an intercostal-sural nerve bridge that bypasses the injury site, significant bowel and bladder function can be restored in paraplegic patients with chronic spinal cord injuries.

INTRODUCTION:

Recently, Zhang et al.¹ reported the restoration of stepping-forward and ambulatory function in patients with paraplegia by rerouting vascularized intercostal nerves to lumbar nerve roots using interfascicular anastomosis. This article discusses a similar nerve-transfer procedure to restore bowel and bladder function in individuals with paraplegia.

In spite of society’s frequent focus on walking, people with SCI consistently indicate that restoration of bowel and bladder function is their foremost priority, in part, because of the personal independence and opportunities for societal integration such restoration can provide. This article describes surgical procedures that help restore these high-priority functions. Specifically, since 1990, we have transferred vascularized intercostal nerves connected to an intervening sural nerve segment to the S_2-4 nerve roots with selected interfascicular anastomosis to restore significant bowel and bladder function in patients with paraplegia.

MATERIALS AND METHODS:

Subjects: Nineteen subjects were male and 11 female. Their age ranged from 19 to 46, averaging 31years. Seventeen cases were traumatically injured in the T_9-11 level and 13 cases at the T₁₂ - L₂ level. Eighteen, 4, 5, and 3 cases, respectively, had been injured by motor vehicle accidents, falls from high places, falling objects, and firearms. The time between injury and surgery ranged from 6 to 36 months, averaging 18 months. All subjects had undergone vertebral lamina decompression and internal fixation, 24 of whom had an additional operation to remove the fixation.

Surgical Procedures: The surgical intervention involves three key components: 1) detaching from above the injury site intercostal nerves which are still connected to the spinal cord, 2) linking their distal ends to a sural nerve segment isolated from the calf, and 3) attaching this combined nerve bridge to the sacral nerve roots below the injury site. Although several procedural variations have been used, a representative one is as follows.

Placed in the lateral position with the operating side upward, patients were subjected to tracheal intubation with general anesthesia. Two normal intercostal nerves were chosen for the procedure, avoiding the selection of lower nerves that may result in the post-surgical ascension of the paraplegia level (especially sensation). Along the indicated intercostal space, an incision was made from the sacrospinal muscle to the midclavicular line. The selected intercostal nerves were separated from the abdominal muscle, cutoff at the distal nipple line, and their severed blood vessels ligated. The intact blood vessels’ proximal ends were moved freely to the edge of the levator muscle. A channel was created between the vertebral canal, and a lateral thoracic incision made under the sacrospinal muscle.

Depending on whether the reconnection to the sacral nerve roots was to be done in the intradural or extradural space, a median incision was made posterior to either the T₁₂-L₂ (intradural) or L₅ –S₂ (extradural) level. The old operative scar was removed, and, if necessary, further decompression of the vertebral lamina was carried out. The S_1-2 vertebral laminas and nerve root tube were cut open with a bone rongeur to expose the starting ends of the S_2-4 nerve roots. If the dura mater was not injured, the segment was incised to specifically expose the S_2-4 nerve roots.

A homolateral sural nerve segment twice the length of the distance from the intercostal nerve to the sacral nerve roots was obtained. Because each intercostal nerve has a sensory and motor branch, one end of the sural nerve segment was divided to create a Y-shaped segment. The segment’s proximal ends were extra-fascicularly sutured with the intercostal nerve, and the distal end, after passing through the submuscular channel, was branched and sutured with either the S_2-3 or S_3-4 nerve roots.

In order not to damage the lower reflex arc and reduce muscle tone postoperatively, the anastomostic sacral nerve root was only cut to match the diameter of intercostal-sural nerve, corresponding to about 1/4-1/3 of the targeted nerve-root fascicula. An inter-tract suture was made between the grafted sural nerve and the distal nerve tract ends, two stitches being sufficient for connecting each nerve bunch.

For patients who were subjected to intradural anastomosis, because the grafted sural nerve segment is wider than the nerve root (cauda equina) in the intradural space, the sural nerve was divided into 2-3 fasciculus, each of which was anastomosed with one nerve root. As such, one intercostal–sural nerve segment can be connected to 2-3 nerve roots.

Finally, the connected nerves were bedded within a thin layer of sacrospinalis muscle, and the vertebral canal was covered with a muscle flap. Antibiotics and neurotrophic agents were usually postoperatively administered, as well as hypertonic glucose and potassium in the few patients who lost excessive cerebral spinal fluid. Back bending was post-surgically restricted for four weeks 

Assessments: Urodynamic measurements included uroflow ratio, urethral pressure distribution, CMG (cystometrogram) and cine-pressure-flow assessments. Statistical significance was assessed using the t-student and X² tests.

SLSEP (short-latency somatosensory evoked potential) examination was performed using a Japanese-made MBE-2200 evoked-potential meter to record cauda equina (CE) electric potential and N28 at 3 Hz stimulating frequency, 0.2 ms wave width, 5 ms/div scanning rate, 20 UV input voltage and 10 Hz – 2 kHz frequency width. To assure good repetition of different waves, the mean superposition was 1024 cycles.

RESULTS:

Thirty subjects were postoperatively followed for 2-11 years with a 5-year average. Their outcomes are summarized in the Table. Of the 30 subjects: 1) 26 (87%) recovered partial defecation and urination sensation, 2) 23 (77%) regained the micturition reflex and uriesthesis; 3) 19 (63%) recovered partial function of the detrusor and sphincter urethra muscles; 4) 20 (67%) recovered partial defecation function and sphincter contraction; and 5) 8 (27%) regained the previous two functions (i.e., 3 & 4).

Defecation sensation appeared 3-16 months (average 8) after the operation; the fecal and urinary reflex 7-24 months (average 12); constriction of the detrusor and sphincter urethra muscles 24-48 months (average 28); and gluteal and perineal sensation 9-18 months (average 12).

Electrophysiological assessments indicated that the central nervous system had connected with the target system through the transferred intercostal nerves. Specifically, the preoperative wave width of CE and N28 was very low, and the latent period was either prolonged or could not be elicited. After surgery, in 26 cases, the latent period of CE was much shorter than the preoperative one. The wave amplitude tended to be normal, and an N28, albeit abnormal, signal appeared.

Table 1: Comparison of Urodynamic Outcomes before & after Nerve Transfer

DISCUSSION:

Although the lower defecation and urination center or reflex arc still exists in paraplegia above T12, these functions are absent because the injury disrupts the connection to the brain ². As such, if a functional nerve-conduction pathway to the brain can be re-established, some bowel and bladder function can be restored. To restore this function, the reflex arc needs the assistance of only a small amount of intact nerve fibers ^3,4. The nerve-bridging procedures described in this article used transferred intercostal nerves to reach paralysis-affected nerves via the sacral nerve roots and pelvic nerve plexus. As a result of re-establishing an intact pathway from the brain to this plexus below the injury level, partial bowel and bladder function was restored ⁵.

Although postoperative urodynamics and extra-sphincter EMG confirmed new nerve connections ^6,7,8,9, restored bowel and bladder function does not solely derive from these connections. Some patients can establish a so-called “trigger point” to obtain urination reflex through percussing the muscle tendon ¹⁰. Suturing the intercostal nerve or spinal nerve root with pelvic plexus or sympathetic nerves can also restore this reflex. Although the success rate by this alternative surgical approach was slightly higher than that obtained through the percussion training, it was evidently lower than that produced by the procedures discussed in this article. Furthermore, quality of improvement was greater with the currently discussed procedures, which also enhanced extra-sphincter muscle automatic sensation and constriction.

Postoperative functional training is important, especially for patients who have depended on urethral intubation. Patients were advised to do deep-breathing and breath-holding training to establish urinary reflex because for the average person, both intercostal-nerve-governed motor function and urination-and-defecation activities involve coordinative muscular movements. It is quite natural for patients who have recovered well after the operation to reconstruct these functions. Concerning sphincter muscle constriction, patients who lacked expert instructions or who did not persist with their training often had poorer outcomes.

Postoperative outcomes were often less in patients whose paraplegic level was below T₁₂, who did not have typical spastic paralysis, or who had traumatic or MRI-confirmed atrophic changes in the medullary. Most of these patients suffered from urine incontinence rather than retention, a situation in which the motor nerve roots governing the sphincter muscle have became erosive. For these patients, surgery should be performed within six months of injury, or, alternatively, use the procedure in which the intercostal nerve is connected to the pudendal nerve ^11,12.

Finally, because benefits diminish with increasing age, the procedure will be most suitable for patients younger than 40.

CONCLUSION:

Restoration of bowel and bladder function is a high priority for individuals with SCI and has been the focus of other therapeutic interventions, such as functional electrical stimulation. This specific surgery can consistently restore a significant amount of such function. Although dramatic improvements have been observed with the procedure, even modest benefits can have often have profound quality-of-life implications by greatly increasing the personal independence of individuals with SCI and, in turn, their societal participation.

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