Sacral nerves

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Nerve: Sacral nerves
Areas of distribution of the cutaneous branches of the posterior divisions of the spinal nerves. The areas of the medial branches are in black, those of the lateral in red. Sacral nerves are those labelled S1-S5.
LatinNervi sacrales
Gray'ssubject #209 924
 
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Nerve: Sacral nerves
Areas of distribution of the cutaneous branches of the posterior divisions of the spinal nerves. The areas of the medial branches are in black, those of the lateral in red. Sacral nerves are those labelled S1-S5.
LatinNervi sacrales
Gray'ssubject #209 924

The sacral nerves are the spinal nerves which arise from the sacrum at the lower end of the vertebral column. The roots of these nerves begin inside the vertebral column at the level of the L1 vertebra and extend until the sacrum forms a structure called the cauda equina.[1][2]

Anatomy[edit]

There are ten sacral nerves, and half of them arise through the sacrum on the left side and the other half on the right side. Each nerve emerges in two divisions: one division through the anterior sacral foramina and the other division through the posterior sacral foramina of the sacrum.[3]

The nerves divide into branches and the branches from different nerves join with one another, some of them also joining with lumbar or coccygeal nerve branches. These anastomoses of nerves form the sacral plexus and the lumbosacral plexus. The branches of these plexus give rise to nerves that supply much of the hip, thigh, leg and foot.[4][5]

The sacral nerves have both afferent and efferent fibers, thus they are responsible for part of the sensory perception and the movements of the lower extremities of the human body. From the S2, S3 and S4 arise parasympathetic fibers whose electrical potential supply the descending colon and rectum, urinary bladder and genital organs. These pathways have both afferent and efferent fibers and, this way, they are responsible for conduction of sensory information from these pelvic organs to the central nervous system (CNS) and motor impulses from the CNS to the pelvis that control the movements of these pelvic organs.[6]

Anastomosis between first sacral nerve and sacral sympathetic

Nerve stimulation[edit]

Sacral nerve stimulation for diseases in the urinary tract[edit]

Chronic lower urinary tract voiding dysfunction includes a large number of diseases that are difficult to treat. Conservative procedure (like biofeedback) and pharmacologic therapy show no benefits to 40% of patients. For those people, the most common treatment is the surgical intervention that has an inconstant efficiency.

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 or carcinoma in-situ) have to be treated differently. Once the patient is selected, he receives a temporary external pulse generator connected to wire leads at S3 foramina 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 the subcutaneous tissue. 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. Battery life is expected to continue to increase with advancements in technology. This procedure has shown long term success rate that ranges from 50% to 90%. Thus, SNS is a good option for patients with lower urinary tract dysfunction refractive to conservative and pharmacological interventions.[7]

Sacral nerve stimulation for treatment of anal fissure[edit]

Anal fissure is a crack in the epithelium of the anus that causes anal pain and bleeding during or after defecation. The pathogenesis is not well understood and healthy people of all age can be affected.

The most common treatment of chronic anal fissure is surgical intervention. It has reached cure to more than 90%, but it has led to fecal incontinence to 17%-30% of the patients. Drugs have been also used for the treatment in attempt to reduce the sphincter pressure. However, they are not very satisfactory, showing transient action or side effects like headache.

Yakovlev and Karasev (2010) report a case of a woman 20 years old. She was diagnosed with chronic anal fissure and had already used pharmacological treatments which she suffers with headache, incontinence of flatus and the recurrence of the disease. The patient underwent placement of wire leads in the sacrum between S1 and S4 and received stimulation for two weeks 24 hours a day. She reported having no more pain in the 10th day and she got healed of the anal fissure after these two weeks under electrical stimulation. There was not any related complication and the disease did not come back during the 20 months of follow-up.

Thus sacral nerve stimulation (SNS) is a rapid and effective option to treat anal fissures without complications. Also the therapy can be adjusted according to the patient and is completely reversible. In the literature the major complications related to SNS are discomfort and infection (that can afflicted 3% - 17% of patients that underwent SNS).[8]

Sacral nerve stimulation for treatment of fecal incontinence[edit]

Fecal incontinence is the involuntary defecation and flatus release that afflict mainly elder people. The etiology is not well understood yet and both conservative (like antidiarrheics, special diet and biofeedback) and surgical treatments for this disorder are far from ideal option.[9]

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 confirmed that the SNS was decreasing the incontinence episodes, the patients received the definitive electrode and pulse generator that was implanted in the gluteus or in the abdomen. 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 1 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 seems to be a good option of treatment of anal incontinence.[10]

References[edit]

  1. ^ 1. Anatomy, descriptive and surgical: Gray's anatomy. Gray, Henry. Philadelphia : Courage Books/Running Press, 1974
  2. ^ 2. Clinically Oriented Anatomy. Moore, Keith L. Philadelphia : Wolters Kluwer Health/Lippincott Williams & Wilkins, 2010 (6th ed)
  3. ^ 1. Anatomy, descriptive and surgical: Gray's anatomy. Gray, Henry. Philadelphia : Courage Books/Running Press, 1974
  4. ^ 1. Anatomy, descriptive and surgical: Gray's anatomy. Gray, Henry. Philadelphia : Courage Books/Running Press, 1974
  5. ^ 3. Human Neuroanatomy. Carpenter, Malcolm B. Baltimore : Williams & Wilkins Co., 1976 (7th ed)
  6. ^ 3. Human Neuroanatomy. Carpenter, Malcolm B. Baltimore : Williams & Wilkins Co., 1976 (7th ed)
  7. ^ 4. Hubsher C.P., Jansen R., Riggs D.R., Jackson B.J., Zaslau S. Sacral nerve stimulation for neuromodulation of the lower urinary tract. Can J Urol. 2012 Oct;19 (5):6480-4.
  8. ^ 5. Yakovlev A, Karasev SA. Successful treatment of chronic anal fissure utilizing sacral nerve stimulation. WMJ. 2010 Oct;109(5):279-82.
  9. ^ 6. Hayden DM, Weiss EG. Fecal incontinence: etiology, evaluation, and treatment.Clin Colon Rectal Surg. 2011 Mar;24(1):64-70.
  10. ^ 7. Pascual, I., González-Gómez, C.C., Ortega, R., Jiménez-Toscano, M., Marijuán J.L., Lomas-Espadas, M., Fernández-Cebrián, J.M., García-Olmo D., Pascual-Montero, J.M.. Sacral Nerve Stimulation for fecal incontinence. Rev Esp Enferm Dig. 2011 Fev;103(7):355-359.

External links[edit]

This article incorporates text from a public domain edition of Gray's Anatomy.