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Arachnoiditis

Arachnoiditis is a form of chronic scarring around nerves inside the dura, a spinal sac which contains spinal fluid, spinal cord, and nerves.  This disease was first described following infections involving the spine which cause meningitis.  Meningitis occurs when the infection is actually inside the dura around spinal cord and nerves and in the spinal fluid.  Nowadays, the most common cause of arachnoiditis is following surgery without any infection.  The condition can occur as a complication of several spinal diseases, and can result from the injection of almost any medication or substance into the spinal sac in unusual situations. 

There is much debate about whether arachnoiditis causes symptoms, and if it does, when these symptoms should be diagnosed to be definitely a result of the arachnoiditis.  At one time it was thought that there was a specific syndrome of burning pain which was characteristic of arachnoiditis.  We now know that burning pain can follow any kind of nerve injury and that arachnoiditis is just one of them   This means that the history and physical examination alone are unlikely to make a definite diagnosis.

The problem can generally be diagnosed with MRI.  Occasionally, a study known as a myelogram is required.  With this study a contrast agent (dye) is actually injected into the spinal sac, and thus, the nerves can be especially well seen.  Imaging studies usually tell how serious the problem is and where it is.  They do not predict whether arachnoiditis will be symptomatic or not.  Most patients with symptomatic arachnoiditis have pain.  The pain is most commonly in the legs, but can spread to any part of the body depending upon where the scarring has occurred around nerves.  Most patients with arachnoiditis are stable.  That is, they simply remain the same over long periods of time.  Rarely the process will be progressive and patients will actually have worsening pain and loss of strength, sensation, and bowel or bladder control.  This is extremely rare now, but was the rule following infections before the era of antibiotics.  This progressive form of arachnoiditis is almost unknown today.

Most patients with arachnoiditis also have other spinal problems.  Therefore it is important to determine what is causing the symptoms, just as it is with virtually every other spinal condition.  That is generally done with the same techniques that are used in the diagnosis of other spinal diseases.  Symptoms are related to arachnoiditis when no other cause is found.

Once it has been established that arachnoiditis is the likely cause for symptoms there are two basic forms of treatment.  One is to use medications known to effect nerve injury – called neuropathic pain.  The other is to control the symptoms with spinal cord stimulation.  Over the years the most common indication for spinal cord stimulation for pain has been arachnoiditis.  The technique is successful for the majority of patients and typically is employed if medications are not satisfactory or side effects of those medications are seriously preventing their use. 

Mild degrees of arachnoiditis are common in patients who have undergone spinal surgery and seem to cause no symptoms.  The important issue is to determine  causes of any serious ongoing complaints of pain or loss of function.  Treatable causes should be identified and treated.  Arachnoiditis generally is treated with medication or indirect pain relief with spinal stimulation.  Occasionally, a patient with arachnoiditis develops pressure on nerves which worsens with time and causes increased pain and progressive loss of neurological function.  Rarely does such a patient require surgery for relief.  I have a longstanding interest in this problem of arachnoiditis and have collected the largest group of patients reported in the literature.  Determining when the arachnoiditis is clinically important is an area to which I have devoted much time and effort.