What Is Arachnoiditis?


The arachnoid membrane is one of the three meninges (protective membranes) that surround and protect the brain and spinal cord. Inflammation of the arachnoid membrane is known as arachnoiditis. Inflammation and swelling of the arachnoid lining causes irritation, leading to the development of scar tissue. This scar tissue can adhere to nerve roots or blood vessels and bind them together.

Signs and symptoms

Symptoms of arachnoiditis typically occur in the lower back or lower limbs. The most common symptom of arachnoiditis is constant, severe pain that worsens with activity. The pain is often described as stinging, shooting or burning. Other symptoms of arachnoiditis include, but are not limited to, the following:

  • Numbness, weakness, tingling, paresthesia, or hyporeflexia in the legs
  • Muscle cramps/spasms or jerking/tremors in the legs
  • Pain and weakness when standing too long, trouble walking, or an abnormal gait
  • Dizziness or loss of balance
  • Burning sensations in the feet
  • Decreased range of motion in the upper and lower extremities
  • Bowel, bladder, or sexual dysfunction
  • Blurred vision
  • Severe headaches
  • Fatigue
  • Tinnitus or ringing of the ears
  • Nausea
  • Intense periods of heat/sweating or the inability to sweat normally
  • Depression

In severe cases, paralysis of the legs may occur.


Arachnoiditis occurs as a result of inflammation of the arachnoid membrane. There are three main causes: trauma/surgery induced, chemically induced, and infection induced.

  • Trauma/surgery induced
    Arachnoiditis is a rare complication of spinal surgery. It can also occur as a result of multiple spinal taps, degenerative spinal conditions, chronic compression of spinal nerves, or direct trauma to the spine.
  • Chemically induced
    The dye used for myelograms has come under investigation as a possible cause of arachnoiditis. Preservatives in epidural injections may also be a cause, especially if the medication enters the cerebral spinal fluid. Chemotherapy drugs that are injected into the spine may also be a possible cause.
  • Infection induced
    Infections of the spine, such as meningitis or tuberculosis, can cause arachnoiditis.

Risk factors

Factors that increase the risk of arachnoiditis include, but are not limited to, the following:

  • Spinal surgery or invasive spinal procedures, such as spinal taps
  • Traumatic injury to the spine
  • Degenerative disc disease
  • Spinal stenosis
  • Infection(s) of the spine
  • Repeated myelograms
  • Epidural anesthesia or epidural steroid injections
  • Injection of chemotherapy drugs, such as methotrexate, into the spine
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