Sunday 19 June 2016

Sacral Plexus-Pressure from the Fetal Head-Invasion by Malignant Tumors-Referred Pain from the Obturator Nerve-Caudal Anesthesia (Analgesia)

Sacral Plexus
The sacral plexus lies in front of the piriformis muscle on the posterior pelvic wall. It is formed from the anterior rami of the 4th and 5th lumbar nerves and the anterior rami of the first, second, third, and fourth sacral nerves. The fourth lumbar nerve joins the fifth lumbar nerve to form the lumbosacral trunk. The lumbosacral trunk passes down into the pelvis and joins the sacral nerves as they emerge from the anterior sacral foramina.

 
Pressure from the Fetal Head
when the fetal head has descended into the pelvis During the later stages of pregnancy, , the mother often complains of discomfort or aching pain extending down one of the lower limbs. The discomfort, caused by pressure from the fetal head, is often relieved by changing position, such as lying on the side in bed.

Invasion by Malignant Tumors
The nerves of the sacral plexus can become invaded by malignant tumors extending from neighboring viscera. A carcinoma of the rectum, for example, can cause severe intractable pain down the lower limbs.

Referred Pain from the Obturator Nerve
The obturator nerve lies on the lateral wall of the pelvis and supplies the parietal peritoneum. An inflamed appendix hanging down into the pelvic cavity could cause irritation of the obturator nerve endings, leading to referred pain down the inner side of the right thigh. Inflammation of the ovaries can produce similar symptoms.

Caudal Anesthesia (Analgesia)
Anesthetic solutions can be injected into the sacral canal through the sacral hiatus. The solutions then act on the spinal roots of the 2nd, 3rd, 4th and 5th sacral and coccygeal segments of the cord as they emerge from the dura mater. The roots of higher spinal segments can also be blocked by this method. The needle must be confined to the lower part of the sacral canal, because the meninges extend down as far as the lower border of the second sacral vertebra. Caudal anesthesia is used in obstetrics to block pain fibers from the cervix of the uterus and to anesthetize the perineum



















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