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7 Articles in Volume 14, Issue #7
Fibromyalgia: What Clinicians Need to Know
Interactions Between Pain Medications and Illicit Street Drugs
Arachnoiditis Part 1: Clinical Description
Meralgia Paresthetica—A Common Cause of Thigh Pain
Editor's Memo: Real Progress—Non-Opioid Advances in Pain Management
Ask the Expert: Dependence vs. Addiction
Letters to the Editor August 2014

Arachnoiditis Part 1: Clinical Description

Arachnoiditis is a rare, but extremely debilitating, chronic pain condition caused by injury to the arachnoid layer of the spinal cord. The goal of treatment is to improve a patient’s function and quality of life by alleviating (but not eliminating) symptoms, especially pain.

Mention the word “arachnoiditis” to experienced clinicians, and they are liable to ask, “What is it?” or state, “I’ve not heard of it.” It is no wonder that it is a poorly known disease because it is listed as “rare” by the National Organization for Rare Disorders. To those of us who deal with severe, intractable pain, however, arachnoiditis is well-known. It ranks at the top of the list of “worst pain conditions,” along with metastatic bone cancer, renal colic, chronic regional pain syndrome, and migraine. The most severe cases of arachnoiditis produce the worst form of lumbar pain. There are less severe cases, and pain practitioners might have encountered these patients without realizing it.

We prepared this article because arachnoiditis, unfortunately, has become more common in recent years. It is caused by any rupture, trauma, or infection that penetrates the dural lining of the spinal cord. Counted here are accidents that occur with epidural injection, trauma including that from war injuries and auto accidents, and spine surgery. The first part of this 2-part series is a clinical description of adhesive arachnoiditis (AA). Part 2  describes cases to illustrate measures to help improve patient quality of life.


Axial view of the MRI of the lumbar spine demonstrating ehhanced nerve roots (black arrows). Image courtesy of Dr. J. Antonio Aldrete.

 

The Function of Arachnoid Matter

The protective covering of the spinal cord consists of 3 meninges: the dura (outer layer), arachnoid, and pia (inner layer). Under the microscope, the fibers and filaments that make up the arachnoid layer resemble a spider web, hence the derivation of the name. If this layer becomes inflamed, it is called arachnoiditis. Between the arachnoid and the inner layer is the subarachnoid space, in which flows the cerebrospinal fluid (CSF) that is secreted within the ventricles of the brain (fluid-filled spaces deep inside the brain) and the ependymal cells lining the cerebral subarachnoid space. CSF circulates in the subarachnoid space, being absorbed into the venous sinuses via the arachnoid granulations and into the lymphatic system through spinal nerve-root pockets. The fluid provides a protective cushion between the brain and the skull, bathing the nervous system with nutrients and removing waste products.

Impaired CSF flow prevents this natural exchange from taking place, to the detriment of the affected nerve roots. The entire volume of CSF is produced, absorbed, and replaced about 3 times per day in a continuous manner. If flow is impeded, fluid can build up, causing increased pressure and pain. Additionally, an inflamed arachnoid lining may entrap nerve roots, scarring them and other neural elements inside and around the spinal canal. When this occurs, the term AA generally is used. Such adhesions within the spinal canal can disrupt many functions of nerves that lead to the extremities, bladder, bowel, and sex organs. Unbearable, suicide-provoking pain can result.

Arachnoiditis now is defined in medical dictionaries. It even has an International Classification of Disease, Ninth Edition (ICD-9) diagnostic code number. Dorland’s Medical Dictionary defines “chronic adhesive arachnoiditis” in a meaningful clinical way: “thickening and adhesions of the leptomeninges in the brain or spinal cord, resulting from previous meningitis, or other disease process or trauma; it is sometimes secondary to therapeutic or diagnostic injection of substances into the subarachnoid space. The signs and symptoms vary with extent and location.”

Note that the above definition states the 3 major causes of AA: infection, trauma, and injections of foreign substances (chemical). The most common form of trauma is surgery, and pain patients who have undergone multiple spine surgeries should be suspected of AA if they have the symptom profile described in Table 1.1,2 The same applies to pain that occurs following an epidural injection.

The cauda equina is the terminal portion of the spinal cord and the spinal nerves below the first lumbar nerve. “Cauda equina syndrome” is a term sometimes used to describe the patient who has AA and manifests loss of bowel, bladder, or sexual function, or has paraplegia.

The Controversy

The first wave of cases of AA occurred about 20 to 30 years ago, when pantopaque dye was used for myelograms. When use of this contrast material gave way to magnetic resonance imaging (MRI), new cases of AA dramatically decreased.

The new wave of cases of AA primarily have resulted from the widespread use of epidural corticosteroid injections.3,4 Fortunately, AA is a rare complication of epidural injections, which have increased by 130% from 2000-2011, or an annual increase of 7.3%.5 Unfortunately, the dura can be punctured accidentally during an epidural, exposing the arachnoid membranes to a foreign substance and/or infectious agent.3

In September 2012 a tragedy occurred, forcing AA into the limelight. A large, multistate outbreak of fungal meningitis occurred that was traceable to 3 lots of preservative-free methylprednisolone produced by the New England Compounding Center (NECC), in Massachusetts.3,4 The offending agent was a mold known as Exserohilum rostratum. This fungus normally is an opportunistic agent that only attacks immunocompromised or immunoincompetent human hosts. In the outbreak, 751 cases of central nervous system (CNS) infections with E rostratum were documented, and 64 persons died. An unknown percentage of these cases went on to develop AA.3,4

Between the fungal outbreak and the rare accidents of epidural injection, numerous lawsuits have been filed across the United States. Patients and families with AA are lobbying the FDA to ban epidural injections, and the FDA has appointed a task force to study the use of epidural corticosteroid injections. In April 2014, the FDA issued a safety warning that “injection of corticosteroids into the epidural space of the spine may result in rare but serious adverse events, including loss of vision, stroke, paralysis, and death.”6

While the author recognizes the controversies and supports the study of AA, our main intent is to educate pain practitioners about AA and call upon them to recognize it and intervene as early as possible. It is the author’s personal experience with AA that certain, early measures can prevent the progression of AA.

 

The Pathologic Process

Cascade of Events and Symptoms

Clinical management of the AA patient demands an understanding of the cascade of events and symptoms. The first event in the pathologic process of AA is one of inflammation, followed by nerve root entrapment, bundling, and adhesion formation (Figure 1). In addition to nerve roots, the other spinal layers—the pia and dura—may be encompassed in the scarred, adhesive, affected area. As noted, the scarred area interferes with the normal flow of CSF and electric currents. Since the cause of the scarring is inflammation, the process may be progressive. Severe pain develops rapidly in the process because nerve roots become entrapped and adhesions form. Both localized pain and radiating pain are present.

 

 

Centralized Pain Symptoms

The second event is centralization of pain and its attendant overstimulation of the sympathetic nervous and hormonal systems. AA produces centralization of pain rather early in its course. All the sequelae of centralized pain can be present, including fibromyalgia-type distribution, depression, fatigue, insomnia, hypertension, tachycardia, hyperhidrosis, and vasoconstriction manifested by cold hands and feet. There will be overstimulation of the hypothalamic-pituitary-adrenal-
thyroid-gonadal hormone system. The severe pain of AA can cause exhaustion of the hormonal system.7,8

Autoimmune Sequelae

The third event in the cascade is the development of autoimmunity, which causes intermittent, inflammatory attacks on tissue, joints, and lymph nodes (Table 2). Patients with AA may develop symptoms and signs of a typical autoimmune disorder, such as systemic lupus erythematosus. These symptoms include intermittent fever, lymphadenopathy, malaise, joint pain, skin rashes, dry eyes, allergies, and hypersensitivity to medications.1 Inflammatory biomarkers, such as erythrocyte sedimentation rate and C-reactive protein can be elevated in patients with AA. In addition, AA has autoimmune sequelae similar to those seen following traumatic brain injury (TBI).7-9 Brain and spinal cord tissue is antigenic if it enters the general circulation.6 As with TBI, AA may cause enough tissue damage that cord particles can reach the general circulation and cause an autoimmune, inflammatory disorder.

 


Making the Diagnosis

The use of imaging devices may cause some confusion. In some severe AA cases, MRI shows typical evidence of AA. Unfortunately, in other cases, MRI in not diagnostic. Consequently, the diagnosis of AA might have to be made on a history of trauma, infection, or penetration of the dural layer, along with the signs and symptoms described.

Symptoms

Most cases of AA occur in the lumbar spine, although it can also occur in the cervical and thoracic areas. Patients with lumbar AA describe their pain as excruciating, radiating into the buttock, groin, and/or legs. Headache occurs almost universally in patients with AA, perhaps due to obstruction of normal spinal fluid flow. A hallmark sign of AA is an inability to sit for long periods of time, if at all. Patients may request to lie on your exam room floor because they cannot sit in a chair or on an exam table. In severe cases, patients say they must stand to eat and lay down in a car or on a plane.

When the injury includes the lower spine, nerve roots that connect to the bladder, bowel, or genitalia can become entrapped. Consequently, bladder and bowel dysfunction almost always are present to some degree. Incomplete bladder emptying and constipation are the usual problems, and they usually require medical treatment. Sexual function can be severely impaired.

Patients frequently describe pain that appears to move or migrate around the upper torso. These pains may be described as tingling, burning, creeping, or pruritic.

Physical examination of the patient is variable. There can be increased pain with pressure over the primary pain site. In severe cases, there almost always will be some weakness of the lower extremities, as well as decreased reflexes. The weakness can affect walking, and many patients will require a cane and snug shoes to safely ambulate. Muscle wasting of the lower extremities can be evident.

Trapping of Electricity

It is my personal observation and intuitive reasoning that the AA site traps or collects electricity because normal nerve conduction is blocked by scarring and adhesions. Patients often describe themselves as harboring a lot of electricity and some report they “burn out” wrist watches and computer mice.

When I have attempted to use an electric current or electromagnetic device over an AA pain site, I sometimes have caused excruciating pain. The same device usually relieves pain in the usual spine patient who has simple arthritic degeneration or stenosis. I even have observed severe pain develop in some patients when a magnet is placed over the AA pain site.

Treatment Strategies

Early Treatment

As noted, clinical management of the AA patient demands an understanding of the cascade of events and symptoms. Pain practitioners should suspect AA is in the early, developing stage in any patient with severe back pain and a history of possible entry of a foreign substance into the subdural or subarachnoid spaces. This is important because it may be possible to prevent the progression of inflammation to adhesion formation.

When I suspect a case, I vigorously attempt to use systemic, not local or epidural, methylprednisolone or other corticosteroid plus anti-inflammatory agents in an attempt to prevent formation of adhesions. Acetazolamide should be attempted because, just as in glaucoma, it decreases the volume of lymph-related fluids, including spinal fluid. Pain relief with acetazolamide essentially is diagnostic of AA. My clinical experience is limited with minocycline (Minocin, Solodyn, others), but I believe this agent might suppress glial cell activation and inflammation in the spinal cord, as has been reported in animal studies.

Treating Established Cases

Once AA is established, treatment must be aggressive and comprehensive. Both peripheral and central pain components will have to be managed. There are no clinical guidelines for the treatment of AA, but it is prudent to follow established practices for treating other chronic pain conditions. Standard pharmacologic agents should be quickly and vigorously pursued; otherwise, a patient with AA will become disabled by pain, becoming bed-ridden and possibly suicidal.

Because the primary lesion in AA causes neuropathic pain due to scarring, a good first-line effort would be to start a patient on an antiepileptic agent such as gabapentin or pregabalin (Lyrica), and/or the serotonin-norepinephrine reuptake inhibitor duloxetine (Cymbalta, others). Attempts should be made to find an antidepressant that is effective. I’ve had good luck with amitriptyline given at bedtime. Anti-inflammatories, prescription and natural, should be added to the mix. Muscle relaxants, including baclofen and carisoprodol (Soma, others), are worth trying in patients without risk of addiction. Opioids usually are essential in AA. High dosages and multiple opioids may be necessary because AA is characterized by severe flares and breakthrough pain.

Since these patients may have severe, debilitating, constant pain, which may respond only partially to standard treatments, AA patients are willing to attempt non-standard measures. Non-standard agents and measures such as ketamine (Ketalar, others), low-dose naltrexone (ReVia, others), minocycline, stimulants, and neurohormones may help selected cases.

A backbone of AA treatment is specific stretching exercises that attempt to pull apart the scarred area of the spinal cord. To identify the site, I have patients assume different stretching or range-of-motion positions with both arms and legs. When the patient finds a position that GENTLY “tugs” or “pulls” at the AA site, I have the patient daily repeat that specific stretch position. Massage therapy has been helpful to many AA patients. The theory is that massage can help the flow of spinal fluid and electrical charges pass through the scarred area.

There are some absolute DON’TS:

  • Do not allow any therapist to perform physical therapies on a patient with AA without your direct supervision. I’ve seen some AA patients worsened and damaged because a well-meaning therapist was not familiar with AA and further damaged the spinal cord by over-
    exuberant spine manipulation.
  • Do not inject anything near the AA site because there may be small fistulae that connect the AA site to tissue outside the spinal column.
  • Attempts to treat AA with an electric current or electromagnetic device should be cautiously done for fear of causing a dramatic pain flare.

A new treatment approach that some patients report to be successful is reclining with head down on an inversion table. I have one patient who hangs upside down. The idea is to pull apart the scarred, adhesive site. Hydrotherapy and trampoline walking also have been excellent, comforting therapies in my hands.

Summary

AA is a profound calamity in pain and suffering. There is no greater pain or misery than that seen in a severe case. Some AA patients have milder forms, and aggressive therapies might prevent the full-blown condition. AA is increasing in incidence.

Pain practitioners need to suspect AA in any patient who complains of severe pain following an epidural injection, spine surgery, spine trauma, or an infectious illness. The spinal insult initially damages the arachnoid lining, causing pain. An adhesive scarring process then ensues. Pain practitioners are encouraged to survey their current spine caseload to, perhaps, identify patients who have AA.

The treatment of AA usually must be aggressive and comprehensive because AA produces a cascade of sequelae: 1) nerve root adhesions, 2) centralization of pain, and 3) an autoimmune, inflammatory disorder. AA is one of the painful conditions that can require opioids in a high dosage because the severity of pain in these patients might not respond to the usual and customary non-opioid measures and standard opioid dosages.

Last updated on: March 27, 2017
Continue Reading:
Arachnoiditis Part 2—Case Reports

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