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Sympathetic Nervous System

Understanding Anatomy:

autonomic nervous sympatheticThe Sympathetic Nervous System (SNS) is part of the peripheral nervous system and makes up one half of the autonomic nervous system. Along with its counterpart, the Parasympathetic Nervous System (PNS), the SNS is aids in control of the most of the body’s internal organs. The SNS and PNS could be compared to two sides of a coin, as each tends to counteract the other and provide balance to the body. The SNS is known for allowing the body to function under stress in what is known as the fight or flight response. As it pertains to the subject of pain, research has shown that the sympathetic nervous system plays a role in regulating neuropathic pain.[1]
Some of its functions in the body include:

  • Eye: Pupil dilation
  • Heart: Increasing heart rate and the force of contraction
  • Lungs: Dilates the bronchioles
  • Skin: Activates sweat glands
  • Adrenal Glands: Increases circulating amounts of adrenaline in the blood
  • Muscles: Increases blood flow to skeletal muscles
  • Stomach and Intestines: Slows motility through the gut

Spinal Cord Cross Section SNSLike the brain and spinal cord, the SNS is made up of neurons – specialize cells designed to transmit electrical signals throughout the body to help different organs communicate with one and other. These signals are then transmitted with substances known as neurotransmitters (norepinephrine, acetylcholine, etc).
Neurons in the sympathetic nervous system tend to bundle together into small structures called “ganglia.” These ganglia lay next to the vertebral bodies (slightly to the front) at various locations up and down the spinal column. As all signals in the SNS travel through these ganglion at some point or other, they provide appropriate targets for pain management to aid in the treatment of “sympathetically-mediated” pain.[2]

Related Content

Stellate Ganglion Block
A Stellate Ganglion Block is a an exciting treatment option for headaches, facial pain, arm pain, neuropathy, even RSD and CRPS. This procedure takes just minutes to perform, and the results can sometimes be felt immediately. Patients who qualify for this procedure may need to have more than one treatment before the effects truly take effect.

Lumbar Sympathetic Block (SCS)
A Lumbar Sympathetic Block is a truly versatile procedure used to treat a large number of pain syndromes. It can used on everything from neuropathy and cancer pain to sciatica and CRPS/RSD. This procedure is effective and has been shown to effectively treat even the most stubborn types of chronic pain. The treatment is performed as an outpatient right in your doctor’s office.

Sympathetic nerves originate from inside the vertebral column, near the middle of the cord, in the intermediallateral column and extend from the upper thoracic region (TI) to the upper lumbar (L2). Preganglionic axons exit the spinal cord and enter the white communicating rami to join a network of prevertebral and paravertebral ganglia. These preganglionic axons are myelinated fibers and are relatively. Postganglionic axons exit the ganglia through the gray communicating rami and travel with the peripheral nerves and blood vessels to innervate the internal organs and other body parts. ganglion.jpgThese postganglionic axons are long and unmyelinated. Another main difference between the pre- and postganglionic fibers:

  • Preganglionic are cholinergic
  • Postganglionic are primarily adrenergic, except for the innervation of the sweat glands, which are cholinergic.

General visceral (the abdomen or gut) sensations are mostly unconscious sensations that are transmitted through the SNS and PNS to the Central Nervous System through the general visceral afferent fibers. These fibers will ultimately travel along side other peripheral nerves that provide sensation to particular conscious body parts (i.e. areas of the skin, joints, genitalia, etc). While these visceral sensations are normally undetectable, in certain instances they may send pain sensations to the brain masked as “referred pain.”
For example, if a particular visceral body part or organ becomes inflamed, it will send a signal along these visceral afferent fibers, through the SNS, to the spinal cord and brain. The brain will in turn interpret this signal as pain (i.e. pelvic pain or leg pain) as that signal was traveling through visceral afferent fibers that were close to or synapsed next to a peripheral nerve that transmits information about a body part in the direct vicinity (i.e. uterus, bladder, a blood vessel in the leg). The pain in these instances is difficult to localize as the brain is having difficulty parsing out which signal is the correct one.
It is for this reason nerve blocks that target the SNS may help to alleviate pain from conditions such as pain from spasms in the blood vessels, complex regional pain syndrome, previously called reflex sympathetic dystrophy and causalgia, Raynaud’s syndrome and some types of chronic abdominal pain.[3]

Some particular targets include:
Stellate Ganglion: implicated in facial, neck, chest, upper extremity pain as well as headaches and Complex Regional Pain Syndrome (CRPS)/Reflex Sympathetic Dystrophy (RSD)

Learn More about Stellate Ganglion Blocks

Celiac Ganglion: provides innervation to the stomach, liver, gallbladder, spleen, kidney, small intestine, and the ascending and transverse colon; it is implicated in abdominal pain, particularly pain stemming from certain types of cancer (i.e. pancreatic cancer and the surrounding organs)

Learn More about Celiac Ganglion Blocks

Lumbar Sympathetic Ganglion: implicated in lower extremity pain, CRPS, RSD, and certain types of neuropathy

Learn More about Lumbar Sympathetic Ganglion Blocks

Superior Hypogastric Plexus: implicated in pelvic and genital pain

Learn More about Superior Hypogastric Plexus Blocks

Ganglion of Impar (Ganglion of Walther): along with the Superior Hypogastric Plexus, it is implicated in pelvic and genital pain, although more externally felt pain, as well as the perineum and the anus

Learn More about Ganglion of Impar Blocks

SNS diagramSympathetic nerve fibers are shown in red and note their direct interaction with the spinal cord is at thoracic level T1 down to upper lumbar level down to L3.[4]

Get Answers to Your Questions at the Ainsworth Institute
The key to finding the proper treatment for any type of pain is getting a proper diagnosis.  Not all types of pain respond to the same treatments and the window for improvement can be limited. The experts at Ainsworth Institute offer the most advanced pain management treatments available today, including advanced clinical trials that aren’t yet available to the general public. Call us today for an appointment so we can get you started on your road to recovery.


[1] Lanz S, Maihöfner C: Symptoms and pathophysiological mechanisms of neuropathic pain syndromes. Nervenarzt. 2009; 80:430-444
[2] Roberts WJ: A hypothesis on the physiological basis for causalgia and related pains. Pain. 1986; 24:297-311
[3] Chaturvedi A1, Dash HH., Sympathetic blockade for the relief of chronic pain, J Indian Med Assoc. 2001;99(12):698-703.
[4] Image from Gray’s Anatomy