What is Arachnoiditis? Symptoms & Treatments

This complaint describes a chronic inflammatory disorder of the arachnoid layer of the meninges. The meninges consist of three layers of protective membranes which encase the brain and spinal cord, they lie beneath the skull and vertebral canal. arachnoiditis The outer tougher layer is known as dura mater, the middle layer – arachnoid mater and finally the inner layer is referred to as pia mater. The arachnoid layer acquired its name due to its appearance, an interwoven mesh of tissue, reminiscent of a spider’s web.

The subarachnoid space, between the arachnoid mater and the pia mater contains cerebrospinal fluid, this supports the brain and spinal cord, circulating to and from the brain and sacral area.

In the case of adhesive arachnoiditis, nerve root endings clump and adhere together as they descend into the subarachnoid space containing the fluid; this is usually the result of the formation of scar tissue, due to a variety of possible causes. The build up of scar tissue compresses nerve root endings, causing them to adhere together and cutting off their blood supply. Mild arachnoiditis may only cause mild or no symptoms at all, however in the case of clinically significant adhesive arachnoiditis, a range of serious and painful symptoms may occur.


This condition can be difficult to accurately diagnose, as it often presents a somewhat confusing set of symptoms, many of which may be mistakenly identified as symptoms of other conditions. Arachnoiditis is frequently confused with epidural fibrosis, a condition where scarring occurs outside the meninges. A detailed medical history and thorough examination will be required, MRI scans may also be useful in the diagnosis.

Possible Causes of Arachnoiditis

epidural injection of steroidsThere are many possible causes, however a high proportion of cases of clinically significant adhesive arachnoiditis most commonly arise as an adverse side effect of invasive medical procedures.

Epidural Injection of Steroids and Anaesthetic

Preservatives found in steroids intended to reach the cerebrospinal fluid in the spinal canal, may inadvertently cause inflammation in the arachnoid layer of the meninges, this can stimulate scar tissue to form, compressing the nerve root endings of that area and causing them to adhere together.

Myelogram Dye Injection into the Spinal Cord

The introduction of the contrast material injected into the spinal column used to evaluate the spinal cord and nerve roots. This invasive procedure can provoke the same adverse reactions as listed in the above injections.

Spinal Surgery

Complications from spinal surgery may cause scar tissue to form and ultimately cause arachnoiditis.

Lumbar Puncture

The process of taking a sample of fluid from the spinal canal using a hollow needle, a procedure usually carried out for diagnostic purposes, may possibly cause arachnoiditis.

Injury or Trauma to the Spinal Cord

Any type of injury or severe trauma to the spine can cause inflammation in the surrounding tissues.

Other Spinal Conditions

  • Degenerative disc disease

In the case of a ruptured disc, scar tissue may form as a reaction to leaked disc material.


Infection from bacteria or viruses such as meningitis or fungal meningitis, the latter is likely to arise from another part of the body and may be caused by a contaminated injection.

Subarachnoid Haemorrhage

Cases of arachnoiditis have been documented in patients following a subarachnoid haemorrhage.


There are many symptoms that may present themselves as a result of clinically significant arachnoiditis, most commonly reported include sensory disturbances and weaknesses.

One or more of the following may occur:

  • Chronic neuralgia, frequently occurring in the lower back
  • Tingling/burning/throbbing sensations, often described as a general dysesthesia
  • Crawling sensation on the skin (patients have reported a sensation of insects crawling over their bodies)
  • Bladder, bowel and sexual dysfunction
  • Gait abnormalities
  • Motor nerve damage may cause a weakness in muscle strength, some patients may find a loss of strength especially in their legs and require support in the form of walking aids.


Adhesive arachnoiditis is best treated using a pain management clinic via a multidisciplinary approach. Possible treatments include:

  • Pain medication

  • Physiotherapy and exercise

  • Psychological treatments

When there is a clear diagnoses, pin pointing the exact source of the irritation, single target surgery minimally invasive surgery may be an option.

Image credits: Blausen.com staff. "Blausen gallery 2014". Wikiversity Journal of Medicine.

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