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Page 4 of 19 Gharagozloo et al. Mini-invasive Surg 2020;4:48 I http://dx.doi.org/10.20517/2574-1225.2020.35

more specifically in the spinal cord. The cell bodies that give rise to the preganglionic fibers of the SNS lie in
the intermediolateral columns of the thoracolumbar spinal cord from C8 to L2 or L3. The second ganglion
is located in the sympathetic chain or in peripheral ganglia. The short myelinated preganglionic fibers
which represent the axonal component of the first ganglion leave the spinal cord within the anterior nerve
roots, form white rami or rami communicantes albi (RCA), and synapse with the second ganglion. In the
chest, the second ganglion is in the thoracic or dorsal sympathetic chain. Axons from the second ganglion
in the sympathetic chain communicate with the peripheral organs via the gray rami or rami communicantes
grisei (RCG). RCG carry postganglionic fibers back to the spinal nerves for distribution to the sweat glands,
pilomotor muscles, and blood vessels of the skin and skeletal muscle. Twenty-two sets of paravertebral
ganglia are paired on either side of the vertebral column, connected to the spinal nerves by the white and
gray rami communicantes, and interconnected by nerve trunks to form the lateral chains. They include the
upper and middle cervical ganglia, the stellate ganglia (fusion of inferior cervical and T1 ganglia), and the
ganglia of the thoracic, abdominal, and pelvic sympathetic trunks. Unpaired prevertebral ganglia are found
in the abdomen and pelvis near the ventral surface of the vertebral column. Splanchnic nerves represent
preganglionic spinal nerves from the first order ganglia which pass through the sympathetic chain without
connecting with the second order ganglia in the sympathetic chain. The second order ganglia for the
[20]
splanchnic nerves are the peripheral vegetative ganglia and not the ganglia of the sympathetic chain .
The ganglia of the sympathetic chain are connected by the rami interganglionares (RI). The dorsal thoracic
sympathetic chain is composed of sympathetic ganglia that correspond to a specific spinal segment. The
dorsal sympathetic ganglia are connected by the RI. The preganglionic sympathetic nerves exit the spinal
cord from the eighth cervical segment (C8) until the second or third lumbar segment (L2 or L3). Ganglia
of the sympathetic chain are located at each of these segments. However, preganglionic spinal sympathetic
segments not only supply the corresponding second ganglion, but they supply second ganglia located
several segments above and below. Furthermore, Kuntz described the existence in some patients of an
[21]
aberrant intrathoracic nerve . In these patients, the postsynaptic fibers travel with the second intercostal
nerve to the brachial plexus. The C8 and T1 ganglia are fused into the stellate ganglion located above the
apical pleural reflection. The stellate ganglion supplies postsynaptic sympathetic fibers to the ipsilateral face,
eyelid, eyeball, and pupil. Interruption of the postganglionic sympathetic fibers from the stellate ganglion
leads to Horner’s syndrome. In a small percentage of individuals, the presynaptic sympathetic fibers from
C8 and T1 spinal nerves travel down the RI before synapsing within the stellate ganglion. Interruption
of the RI high in the sympathetic chain, even without damaging the stellate ganglion, can account for
Horner’s syndrome in these individuals. In addition, studies have shown that the stellate ganglion may
have a greater role in the sympathetic innervation of the upper limb than has been known previously. This
understanding may, in part, explain recurrence of hyperhidrosis in some individuals following thoracic
sympathectomy [22,23] . The intrathoracic ganglia of the dorsal sympathetic chain are located in the intercostal
spaces. The RI traverse the proximal portion of the ribs. The second and third sympathetic ganglia supply
the hand. The third, fourth, and fifth thoracic sympathetic ganglia supply the axilla. The fourth and fifth
ganglia supply the skin of the abdominal wall. The lower thoracic and upper lumbar ganglia supply the
lower limbs. The main effect of an upper thoracic sympathectomy is to abolish sweating of the palms and
the axilla. Sympathectomy produces a vasodilatory cutaneous effect. The improved skin blood flow is on
the thermoregulatory and not nutritive level. With sympathectomy, the circulation in the muscles of the
upper extremity is unaltered. It seems that chronic surgical sympathectomy does not change the vascular
function of the forearm. T2-T3 ganglionectomy significantly decreases pulse rate and systolic blood
pressure, reduces myocardial oxygen demand, increases left ventricular ejection fraction, and prolongs the
QT interval. Sympathectomy appears to decrease lung volumes as well as diffusion capacity.

Although the cause of hyperhidrosis is unknown, it is theorized to be the result of overactivity of the central
nervous system. The SNS has been likened to a river emanating from central sympathetic nuclei in the
brain with tributaries that emanate from the second nuclei in the periphery and carry sympathetic impulses