Superior Hypogastric Sympathetic Plexus

(1)

Marina Spine Center, Marina del Rey, CA, USA

The preaortic sympathetic plexus is a continuation of the thoracolumbar sympathetic chain extending down anterior to the aorta and vertebral bodies in the retroperitoneal space (Fig. 36.1). The inferior hypogastric plexus is at approximately the L3–L4 level and the superior hypogastric plexus at L4–S1. There is considerable variation in the structure of the superior hypogastric plexus [1]. As the superior hypogastric plexus fibers arch over the L5–S1 disc in the bifurcation of the aorta, the predominance of fibers are usually closer to the left iliac artery. These fibers may have the form of multiple strands or one predominant large simple nerve trunk. The superior hypogastric plexus contains the sympathetic function for the urogenital system.

Fig. 36.1

The superior hypogastric plexus within the bifurcation of the aorta. Methods to avoid damaging the hypogastric plexus: (1) Use blunt dissection, retraction, and spreading to remove the prevertebral tissue from the sacral promitory. (2) For the transperitoneal midline approach, very carefully open the posterior peritoneum and bluntly dissect the prevertebral tissue from right to left. (3) With spreading and blunt dissection, attempt to retract the middle sacral vein and artery without electrocautery. Avoid electrocautery on the anterior surface of L5–S1. When this vessel is of considerable size, use vascular clips or ligation. (4) Opening the posterior peritoneum higher over the bifurcation and extending the opening down over the sacral promitory may allow better visualization and retraction of these tissues

Parasympathetic function for the urogenital system is supplied by the S1–L4 nerve roots that contribute to the pelvic splenic nerves. Somatic function from S1, S2, S3, and S4 is carried predominantly by the pudendal nerve.

Ejaculation is predominantly a sympathetic function, whereas erection is predominantly a parasympathetic function through control of the vasculature of the penis. Disruption to the sympathetic plexus results in retrograde ejaculation and sterility. Although the sympathetic fibers also have some effect on the motility of the vas deferens, important in transportation of the spermatoza from the epididymis to the seminal vesicle [2], the main effect of damage to the superior hypogastric plexus is improper closing of the bladder neck, with resultant retrograde ejaculation [2].

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