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Updated March 12, 2014

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Dermatomes - A Map of Nerve Ennervation

Dermatomes - A Map of Nerve Ennervation

(c) Anne Asher licensed to About.com 2006

Question: Arachnoiditis


Arachnoiditis is a rare chronic pain condition that can occur when something - back surgery, for example - is done to your spine. With that said, the cause of arachnoiditis is not limited to back surgery. (I'll talk about that in more depth below.)

For example, do you remember the many news reports in late 2012 regarding tainted spinal epidural injections? The Fungal Meningitis Outbreak of 2012 put 14,000 back pain patients at risk for a rare and deadly form of meningitis. As of March 4, 2013, the CDC reports that 720 cases and 48 deaths occurred in a total of 20 states during the course of this outbreak.

The CDC has also reported that arachnoiditis - as well as other localized infections - are now showing up – either on their own in in addition to the meningitis - at the injection site in some patients.

Related: 2012 Fungal Meningitis Outbreak – the Symptoms Keep Coming



What Is Arachnoiditis?

Arachnoiditis is an inflammation or irritation of the arachnoid membrane of the meninges. To help you understand what this means, a short anatomy lesson is in order:

The meninges is a 3 layer the tissue covering around the spinal cord and brain; together, the brain and cord make up the central nervous system. The arachnoid membrane is the middle layer of this covering. The top layer, called the dura mater - which means “tough mother” - is, as the name implies, a strong tissue designed to provide protection from the forces that act on the cord from the outside. The pia mater, which is the deepest layer of the meninges, is a delicate tissue with many fine blood vessels embedded into it. The arachnoid membrane also contains blood vessels, and both the pia and the arachnoid contain cerebrospinal fluid, another protective mechanism for the central nervous system. The pia mater is located beneath the arachnoid membrane, which is located beneath the dura mater. In other words, the pia mater is the layer located most closely to the spinal cord itself.

As with most inflammatory conditions, when the arachnoid membrane becomes irritated, it can cause pain. As I mentioned above, and will delve into further below, this irritation may occur when the spinal cord gets compressed, whether from an injury or a spinal procedure.

In arachnoiditis, inflammation leads to scar tissue formation. Scar tissue, in turn, can cause spinal nerves to stick together inappropriately. One way to think of arachnoiditis is as a gob nerves that are located inside the spinal canal.

"If you can imagine nerves as strands of spaghetti that clump together, that’s what arachnoiditis is like," says Dr. Anand Gandhi, interventional physiatrist. Gandhi is a physician specializing in minimally invasive procedures. He maintains a practice at the Laser Spine Institute in Tampa, Florida.

The clumping tends to occur in a specific area in the spinal canal. This corresponds to the area just on the inside of (technically called "medial to") the spinal nerve roots, Gandhi informs me. You might understand the location of the clumping as the place in the cord just prior to where it begins to branch out and develop into peripheral nerve(s). FYI, peripheral nerves are the individual nerves that traverse out from the cord to the rest of your body; these nerves enable you to feel, respond and move.

Causes of Arachnoiditis:

Arachnoiditis is usually due to some kind of injury or disruption to the spine. As I mentioned above, it often occurs as the result of something done to the spine.

According to Dr. Gandhi, the top 3 causes of arachnoiditis, in order, are: Spine surgery, especially the non minimally invasive type, infections of spine (this could be bacterial, viral, or both) and trauma. Other causes, he says, are tumors, CT myelograms, which are sometimes given to diagnose lesions in the sub-arachnoid space. ( The sub-arachnoid space is also called the intrathecal space, and ironically enough, steroid injection treatments delivered to the intrathecal space.



Arachnoiditis Symptoms:

The severity of back pain associated with arachnoiditis can range from mild to excruciating, Gandhi tells me. He says that symptoms may include nerve sensations such as stinging and burning in the low back and legs. He notes that arachnoiditis is sometimes accompanied by paresthesia (i.e., tingling, the feeling of pins and needles, and/or numbness down an arm or leg). This pain and paresthesia often occurs in patchy areas that are not related to dermatomal distribution, he says. (Dermatomal distribution simply refers to the pattern throughout the body into which the nerves “fire”. For reference, see the illustration.)

Symptoms may also include debilitating muscle cramps, twitches, or spasms. Arachnoiditis may affect bladder, bowel, and sexual function, and in severe cases, may cause paralysis of the lower limbs, Gandhi says.

Arachnoiditis Treatment:

Arachnoiditis is a chronic pain disorder that, for the most part, does not really responds to current available treatments. On top of that, its prognosis is often complicated by the lack of a predictable pattern of symptoms.

Gandhi acknowledges that arachnoiditis can be difficult to treat. This is, he says, because the treatment and side effects from the treatment are often the same. Reaching the arachnoid space without doing further damage to it makes invasive type treatment precarious. Not only that, but invasive treatments may result in more scar tissue formation in the space. That's the last thing you want in cases of arachnoiditis (as well as other spinal conditions). Let's look at these two limitations one at a time to get really clear about why arachnoiditis treatment is not always straightforward:

  • Treatment Location: The idea behind treatment for arachnoiditis is to relieve pressure (in the sub-arachnoid space) that is caused by the “clumped spaghetti,” Gandhi says. “But the sub-arachnoid space can be very hard to reach without further irritating that delicate area,” he adds. Unfortunately, this presents a quandary for physicians who treat the condition.
  • Scar Tissue Begets Scar Tissue: Although there are many methods by which doctors can treat scar tissue, most cause more scar tissue in the arachnoid space, as I mentioned above. Translated: Treatments for scar tissue that are focused in the sub-arachnoid space tend to raise your risk for increasing the amount of “clumped spaghetti” in your spinal cord.


So what's the most effective treatment for arachnoiditis? That may depend on how debilitating it is, Gandhi informs me. Also, there is no guarantee that any treatment will be effective in relieving symptoms.

“Arachnoiditis is a challenging conditions with few treatments. There is no one gold standard for treating it,” he says. “If you have arachnoiditis, speak with your doctor about your options.”

The National Institutes of Health states that most treatments for arachnoiditis focus on pain relief and improvement of symptoms - to enable you to function better in your daily life. They also say that surgery is controversial, mainly because at best, relief is only short term.

With that said, Gandhi says treatment generally starts conservatively and proceeds to certain kinds of invasive procedures. Here's a rundown (in order):

  1. Physical Therapy
  2. (Oral) medications for nerve pain, for example: Lyrica or Neurotonin
  3. Intrathecal steroid injection into sub-arachnoid space, which is essentially an anti-inflammatory medication meant to calm down the irritation in the space
  4. Implanted (a minimally invasive procedure) spinal cord simulation which may help mask the pain signals so you don't feel them as readily
  5. Thelacosopy, is new, largely unproven minimally invasive procedure that was developed after doctors began using an endoscope to diagnose arachnoiditis. The doctors realized that the diagnostic procedure could be modified into a surgery that relieved the pressure caused by the “clumped spagetti” nerves. So far, though, this treatment has reportedly only been tried on 23 patients; in other words, not much research on theloscopy has been done, and therefore not all the questions about its safety and effectiveness has been answered.


Mind you, it is not necessary to have theloscapy done in order to get an arachnoiditis diagnosis. Theloscopy is only one possibly route. In fact, Gandhi tells me that the gold standard for getting a diagnosis is an MRI.

The best treatment for archnoiditis is prevention, Gandhi says. This circles back to the main cause of most cases – scar tissue formation after something is done to your spine. The idea here is to minimize your risk for scar tissue formation. To this Gandhi says that if you’re planning on having spine surgery, consider a minimally invasive procedure. Choosing to go minimally invasive (where appropriate for your condition) may reduce your risk for excess scar tissue formation, and hence, reduce your risk for arachnoiditis. As with any potential spine treatment, speak with your doctor when determining the best course of action for you.

What research is being done?

The field of arachnoiditis medicine is a niche that few providers and researchers have stepped up to fill. The most comprehensive and reliable research is likely being done at the National Institutes of Health. Therefore, arachnoiditis research is pretty much lumped together with research on other chronic pain treatments. If you wish to expand your treatment options, again, talk to your doctor about the items listed above.


Cerebral spinal fluid (CSF) collection. Medline Plus. Last Updated: June 2011. Accessed: May 2013.http://www.nlm.nih.gov/medlineplus/ency/article/003428.htm

Di leva, A., et al. Lumbar Arachnoiditis and Thecaloscopy: Brief Review. Cent Eur. Neurosurg 2012.

Gandhi, A., Interventional Phsyiatrist, Laser Spine Institute, Tampa, Fla. Telephone Interview. May 2013.

Information for Patients: Multistate Outbreak of Fungal Meningitis and Other Infections. CDC Website. Accessed: May 2013.

Meninges of the Brain. Medline Plus. Last Updated: Oct. 2012. Accessed: May 2013.http://www.nlm.nih.gov/medlineplus/ency/imagepages/19080.htm

NINDS Arachnoiditis Information Page. National Institute Neurological Disorders and Stroke web page. Last Updated: Jan. 2011. Accessed May 2013.http://www.ninds.nih.gov/disorders/arachnoiditis/arachnoiditis.htm

Notice to Clinicians: Continued Vigilance Urged for Fungal Infections among Patients Who Received Contaminated Steroid Injections. CDC Website. Accessed: May 2013. http://emergency.cdc.gov/HAN/han00342.asp

Tetsuryu Mitsuyama, Shunji Asamoto, Takakazu Kawamata. Novel surgical management of spinal adhesive arachnoiditis by arachnoid microdissection and ventriculo–subarachnoid shunting. Journal of Clinical Neuroscience 18 (2011).


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