Sacral nerve stimulation, also termed sacral

neuromodulation Neuromodulation is the physiological process by which a given neuron uses one or more chemicals to regulate diverse populations of neurons. Neuromodulators typically bind to metabotropic, G-protein coupled receptors (GPCRs) to initiate a second m ...

, is a type of medical

electrical stimulation Functional electrical stimulation (FES) is a technique that uses low-energy electrical pulses to artificially generate body movements in individuals who have been paralyzed due to injury to the central nervous system. More specifically, FES can ...

therapy. It typically involves the implantation of a programmable stimulator

subcutaneously The subcutaneous tissue (), also called the hypodermis, hypoderm (), subcutis, superficial fascia, is the lowermost layer of the integumentary system in vertebrates. The types of cells found in the layer are fibroblasts, adipose cells, and macro ...

, which delivers low amplitude electrical stimulation via a lead to the

sacral nerve A spinal nerve is a mixed nerve, which carries motor, sensory, and autonomic signals between the spinal cord and the body. In the human body there are 31 pairs of spinal nerves, one on each side of the vertebral column. These are grouped into the ...

, usually accessed via the S3

foramen In anatomy and osteology, a foramen (;Entry "foramen"
in

. The U.S.

Food and Drug Administration The United States Food and Drug Administration (FDA or US FDA) is a List of United States federal agencies, federal agency of the United States Department of Health and Human Services, Department of Health and Human Services. The FDA is respon ...

has approved InterStim Therapy, by

Medtronic Medtronic plc is an American medical device company. The company's operational and executive headquarters are in Minneapolis, Minnesota, and its legal headquarters are in Ireland due to its acquisition of Irish-based Covidien in 2015. While it ...

, as a sacral nerve stimulator for treatment of

urinary incontinence Urinary incontinence (UI), also known as involuntary urination, is any uncontrolled leakage of urine. It is a common and distressing problem, which may have a large impact on quality of life. It has been identified as an important issue in geria ...

, high

urinary frequency Frequent urination, or urinary frequency (sometimes called pollakiuria), is the need to urinate more often than usual. Diuretics are medications that increase urinary frequency. Nocturia is the need of frequent urination at night. The most common c ...

and

urinary retention Urinary retention is an inability to completely empty the bladder. Onset can be sudden or gradual. When of sudden onset, symptoms include an inability to urinate and lower abdominal pain. When of gradual onset, symptoms may include loss of bladd ...

. Sacral nerve stimulation is also under investigation as treatment for other conditions, including

constipation Constipation is a bowel dysfunction that makes bowel movements infrequent or hard to pass. The stool is often hard and dry. Other symptoms may include abdominal pain, bloating, and feeling as if one has not completely passed the bowel movement ...

brought on by nerve damage due to surgical procedures. An experimental procedure for constipation in children is being conducted in Nationwide Children's Hospital. In the event that the nerves and the brain are no longer communicating effectively, resulting in a bowel/bladder disorder, this type of treatment is designed to imitate a signal sent via the central nervous system. One of the major nerve routes is from the brain, along the spinal cord and through the back. This is commonly referred to as the sacral area. This area controls the everyday function of the

pelvic floor The pelvic floor or pelvic diaphragm is composed of muscle fibers of the levator ani, the coccygeus muscle, and associated connective tissue which span the area underneath the pelvis. The pelvic diaphragm is a muscular partition formed by the lev ...

, urethral sphincter, bladder and bowel. By stimulating the sacral nerve (located in the lower back), a signal is sent that manipulates a contraction within the pelvic floor. Over time these contractions rebuild the strength of the organs and muscles within it. This effectively alleviates all symptoms of urinary/faecal disorders, and in many cases eliminates them completely.

Medical uses

Urge incontinence

Many studies have been initiated using the sacral nerve stimulation (SNS) technique to treat patients that suffer with urinary problems. When applying this procedure, proper patient screening is essential, because some disorders that affect the urinary tract (like

bladder calculus A bladder stone is a stone found in the urinary bladder. Signs and symptoms Bladder stones are small mineral deposits that can form in the bladder. In most cases bladder stones develop when the urine becomes very concentrated or when one is d ...

carcinoma in-situ Carcinoma ''in situ'' (CIS) is a group of abnormal cells. While they are a form of neoplasm, there is disagreement over whether CIS should be classified as cancer. This controversy also depends on the exact CIS in question (i.e. cervical, skin, bre ...

) have to be treated differently. Once the patient is selected, he receives a temporary external pulse generator connected to wire leads at S3

foramina In anatomy and osteology, a foramen (;Entry "foramen"
in

for 1–2 weeks. If the person's symptoms improve by more than 50%, he receives the permanent wire leads and stimulator that is implanted in the

hip In vertebrate anatomy, hip (or "coxa"Latin ''coxa'' was used by Celsus in the sense "hip", but by Pliny the Elder in the sense "hip bone" (Diab, p 77) in medical terminology) refers to either an anatomical region or a joint. The hip region is ...

in the

subcutaneous tissue The subcutaneous tissue (), also called the hypodermis, hypoderm (), subcutis, superficial fascia, is the lowermost layer of the integumentary system in vertebrates. The types of cells found in the layer are fibroblasts, adipose cells, and macr ...

. The first follow up happens 1–2 weeks later to check if the permanent devices are providing improvement in the user's symptoms and to program the pulse generator adequately. Bleeding, infection, pain and unwanted stimulation in the extremities are some of the complications resulting from this therapy. Currently, battery replacements are necessary 5–10 years after implementation depending upon the strength of the stimulation therapy. (The newest interstim's battery can be wirelessly recharged (roughly weekly) using a paddle placed against the skin outside the implant.) This procedure has shown long term success rate that ranges from 50% to 90%, and one study concluded that it was a good option for patients with lower urinary tract dysfunction refractive to conservative and pharmacological interventions.

Fecal incontinence

Fecal incontinence Fecal incontinence (FI), or in some forms encopresis, is a lack of control over defecation, leading to involuntary loss of bowel contents, both liquid stool elements and mucus, or solid feces. When this loss includes flatus (gas), it is referred ...

, the involuntary loss of stool and flatus release afflicting mainly elderly people, can also be treated with sacral nerve stimulation as long as patients have intact

sphincter muscle A sphincter is a circular muscle that normally maintains constriction of a natural body passage or orifice and which relaxes as required by normal physiological functioning. Sphincters are found in many animals. There are over 60 types in the hum ...

s. The FDA approved the approach for treating the fecal incontinence in March 2011. The

etiology Etiology (pronounced ; alternatively: aetiology or ætiology) is the study of causation or origination. The word is derived from the Greek (''aitiología'') "giving a reason for" (, ''aitía'', "cause"); and ('' -logía''). More completely, e ...

is not well understood yet and both conservative treatments (like antidiarrheics, special diet and

biofeedback Biofeedback is the process of gaining greater awareness of many physiology, physiological functions of one's own body by using Electronics, electronic or other instruments, and with a goal of being able to Manipulation (psychology), manipulate t ...

) and surgical treatments for this disorder are not regarded as ideal options. Pascual et al. (2011) revised the follow up results of the first 50 people that submit to sacral nerve stimulation (SNS) to treat fecal incontinence in Madri (Spain). The most common cause for the fecal incontinence was obstetric procedures, idiopathic origin and prior anal surgery, and all these people were refractory to the conservative treatment. The procedure consisted of placing a temporary pulse generator connected to a unilateral electrode at S3 or S4 foramen for 2–4 weeks. After it was confirmed that the SNS was decreasing the incontinence episodes, the patients received the definitive electrode and pulse generator that was implanted in the

gluteus The gluteal muscles, often called glutes are a group of three muscles which make up the gluteal region commonly known as the buttocks: the gluteus maximus, gluteus medius and gluteus minimus. The three muscles originate from the ilium and s ...

or in the

abdomen The abdomen (colloquially called the belly, tummy, midriff, tucky or stomach) is the part of the body between the thorax (chest) and pelvis, in humans and in other vertebrates. The abdomen is the front part of the abdominal segment of the torso. ...

. Two patients did not show improvement in the first step and did not receive the definitive stimulator. Mean follow up was 17.02 months and during this time the patients showed improvement in the voluntary contraction pressure and reduction of incontinence episodes. Complications were two cases of infection, two cases with pain and one broken electrode. Therefore, although the reason the SNS is effective is unknown, this procedure had satisfactory results in these clinical cases with a low incidence of complications, and the study concluded that it was a good option for treatment of anal incontinence. Limited evidence from a

Cochrane review Cochrane (previously known as the Cochrane Collaboration) is a British international charitable organisation formed to organise medical research findings to facilitate evidence-based choices about health interventions involving health professi ...

of randomised controlled trials suggests that sacral nerve stimulation may help to reduce fecal incontinence.

Method

TENS (

transcutaneous electrical nerve stimulation Transcutaneous electrical nerve stimulation (TENS or TNS) is the use of electric current produced by a device to stimulate the nerves for therapeutic purposes. TENS, by definition, covers the complete range of transcutaneously applied currents ...

) was patented and first used in 1974 for pain relief. TENS is non-invasive; it sends electric current through electrodes placed directly on the skin. Although predominantly carried out as a percutaneous procedure, it is possible to apply sacral nerve stimulation with the use of these external electrodes. It is not known if TENS helps with chronic pain in people with fibromyalgia or neuropathic pain. There are currently no studies into the efficacy of this on an overactive bladder and other associated symptoms of urinary incontinence, however, in a report carried out by GUT (an international peer-reviewed journal for health professionals and researchers in gastroenterology and hepatology) it was found that 20% of the group tested achieved complete continence. All others saw a significant reduction in the frequency of FI episodes and an improvement in the ability to defer defecation. The first percutaneous sacral nerve stimulation study was performed in 1988. By penetrating the skin, sacral nerve stimulation aims to give a direct and localized electric current to specific nerves in order to elicit a favored response. Today it is one of the most common neuromodulation techniques.

Percutaneous procedure

Patients interested in getting a sacral nerve stimulator implanted in them because less severe methods have failed all must go through a trial for their own safety, known as the PNE (percutaneous nerve evaluation). PNE involves inserting a temporary electrode to the left or right of the S3 posterior foramen. This electrode is connected to an external pulse generator, which generates a signal for 3–5 days. If this neuromodulation has positive results for the patient, the option of implanting a permanent electrode for permanent sacral neuromodulation is possible. The procedure has low level of invasiveness, as all incisions are relatively small. A pulse generator is implanted in a subcutaneous pocket in the upper, outer quadrant of the buttock or even the lower abdomen. The generator is attached to a thin lead wire with a small electrode tip which is anchored near the sacral nerve. The most common postoperative complaints are pain and lead migration. In most studies, usually 5-10% of subjects need post-operative correction to lead migration, but since leads can be anchored near the sacral nerve, subsequent operations are generally unnecessary.

Mechanism

Stimulation of the sacral nerve causes contraction of external sphincter and pelvic floor muscle, which in turn causes the inhibition of bladder contractions which may be involuntarily releasing urine. Researchers currently believe that the sacral neuromodulation blocks the c-afferent fibers, which are a critical part of the afferent limb of a pathological reflex arc believed to be responsible for incontinence.

References

Bibliography

* * * * * * * * * * {{cite journal , vauthors=Yakovlev A, Karasev SA, Dolgich OY , title=Sacral nerve stimulation: a novel treatment of chronic anal fissure , journal= Diseases of the Colon and Rectum, year=2011 , pmid=21304304 , doi=10.1007/DCR.0b013e318202f922 , volume=54 , issue=3 , pages=324–7, s2cid=33759169

External links

Fecal Incontinence
Neurotechnology