Arachnoiditis

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Clinically Relevant Anatomy

Arachnoid mater: the membranous layer between the pia mater and the dura mater that surround the brain and the nerves of the spinal cord[1].

Spinal nerves: 31 pairs of nerves that exit the vertebral column through intervertebral foramina as 2 rootlets. One anterior nerve root and one posterior nerve root.

Mechanism of Injury / Pathological Process

Definition/description

Arachnoiditis is a rare condtion of chronic inflammation of the arachnoid. It can involve the brain and/or the spinal cord.
It develops in 3 stages, namely[2]:
1) inflammation of the spinal nerves, distension of the adjacent blood vessels, subarachnoid space disappears and the scare tissue begins
2) the scar tissue increases, the nerves adhere to each other and the dura
3) complete encapsulation of the nerve roots, compression causes atrophy of the nerve roots and the scarring tissues prevent the production of spinal fluid in that area. It is terrmed Arachnoiditis Ossificans if the scar tissue calcifies.

Epidemiology/Etiology

The inflammation has 3 main causes:
1) Trauma–surgery: complications after multiple back surgery may result in blood penetration in the subarachnoid space, causing inflammation.
2) Chemical: exposure to oil based radiographic contrast agents used in myelograms, or drugs used for epidural injections.
3) Infection: viral or bacterial meningitis, tuberculosis and syphilis affect the spine.
This disorder is the third most common cause of Failed Back Surgery Syndrome (FBSS).
Arachnoiditis due to surgery is precisely localised, meanwhile the arachnoiditis due to epidural injections is more diffuse.[2]

Clinical Presentation

Most patients have symptoms in the lower back, hip, legs, feet, perineum, abdomen or ,in the most severe cases, throughout the body. These symptoms are: chronic, burning pain; tingling; weakness in the legs; sensory loss; muscle cramps; spasms; uncontrolled twitching; bladder and sexual dysfunctions[3].

Diagnostic Procedures

Magnetic resonance imaging (MRI) is the study of choice for the diagnostic evaluation of arachnoiditis[4]. For patients in whom MRI is contraindicated, computed tomography (CT) myelography is an acceptable alternative.

Outcome Measures

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Management / Interventions

Medical/Surgical Management:

There is no cure, only treatment of the chronic symptoms.
-Oral medication or medication through an intrathecal pump such as: non-steroidal anti-inflammatory drugs (NSAIDs), methadon, morphine, can be used to release neuropathic pain. Antidepressants may reduce burning neuropathic pain, but in much lower doses than for depression. Diazepam is used for muscle relaxation.
-Invasive treatment such as intraspinal narcotic analgesia (INA), epidural steroid and local anaesthetic injections are not indicated because there is a risk of exacerbating the inflammation and worsening the patient’s condition.
-Spinal cord Electrostimulation (SCS) stand for electrical stimulation by implanted electrodes around the spinal cord in the area that is most involved in causing pain. Some studies indicate a 50% success rate when all types of chronic pain are considered[5].
-Surgery is not recommended because it causes more scar tissue and more trauma to the already irritated spinal cord.

Physiotherapy:

Physiotherapy has a role in the management of the chronic pain caused by Arachnoiditis.

Differential Diagnosis

Disc fragments, recurrent disc herniation, stenosis, spondylosis, epidural fibrosis and other causes of polyneuropathy such as multiple sclerosis.

Key Evidence

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Resources

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Case Studies

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References

  1. MOORE, K.L., DALLEY, A.F., AGUR, A.M.R., Clinically oriented anatomy, Wolters Kluwer, Lippincott Williams and Wilkins, 2010
  2. WRIGHT, M.H., DENNEY, L.C.,’ A comprehensive review of spinal arachnoiditis’, Orthop Nurs., may-jun 2003, vol: 22(3), p.215-9
  3. MATLOCK, C.L., ‘Physiotherapy and spinal nerve root adhesions: a caution’, Physiotherapy research international, vol: 9(4), p. 164-173,2004.
  4. Malani AN, Vandenberg DM, Singal B, Kasotakis M, Koch S, Moudgal V, et al. Magnetic resonance imaging screening to identify spinal and paraspinal infections associated with injections of contaminated methylprednisolone acetate. JAMA. Jun 19 2013;309(23):2465-72.
  5. FREY, M.E., MANCHIKANTI, L., BENYAMIN, R.M., SCHULTZ, D.M.,SMITH, H.S.,COHEN, S.P., ‘Spinal Cord Stimulation for Patients with Failed Back Surgery Syndrome: A Systematic Review’, Pain Physician, vol: 12:379-397, 2009