H. Hooshmand, M. D.

DIPLOMATE AMERICAN BOARD OF PSYCHIATRY AND NEUROLOGY

BOARD CERTIFIED IN ELECTROENCEPHOLOGRAPHY

BOARD CERTIFIED IN ELECTROMYOGRAPHY  

BOARD CERTIFIED IN AMERICAN BOARD OF ELECTODIAGNOSTIC MEDICINE

INTRACTABLE NEUROLOGY

EPILEPSY, PAIN, MS

An International Referral Center dedicated to Treatment, Education and Research

RSD PUZZLE # 23
WHY NOT SPINAL CORD STIMULATOR (SCS)? (Revised on 3/29/2002)
Please see RSD Puzzles 74 and 106 also regarding SCS

Spinal cord stimulator (SCS) has a limited role in treatment of CRPS. As you are well aware, there are two different types of pain, in two different stages of CRPS. In the early stages, in the first few months, the pain is sympathetically maintained pain (SMP) meaning that the pain responds to sympathetic ganglion blocks. However, on the average of almost a year, the nature of the pain changes from sympathetically maintained pain (SMP) to sympathetically independent pain (SIP).

The spinal cord stimulator is effective in the SMP phase of the CRPS, not the SIP. The recent research has shown that the later in the course of the disease spinal cord stimulator (SCS) is started, the less likelihood SCS will relieve the pain.

As a rule of Thumb, if the stellate ganglion nerve blocks have lost their effect, about the same time the SCS loses its effect. This is because both treatments aim at the sympathetic system. With passage of time, as the pain gradually changes to SIP, such treatment cannot be expected to help.

What it boils down to, is the fact that if the stellate ganglion nerve blocks have lost their therapeutic effect, then what is the sense of doing SCS? If the pain has become SIP, what is the sense of doing SCS treatment?

SCS is a digital stimulator utilized for treatment of an analog symptom (the analog pain modality is random and not time locked or digital). It is not a type of treatment that would be successful in every form of chronic pain.

The reason we do not apply SCS is because if the sympathetic ganglion nerve blocks do not work, then epidural nerve blocks which contain Depo- Medrol^® applied to the epidural space in the spinal canal are far more effective, and their pain relief lasts longer. On the other hand, even in a patient who suffers from SMP type of pain, after about a year, the successful treatment with SCS will fade away because the SMP has changed to SIP. Then, the patient is left with a foreign body in the spinal canal not providing any decent pain relief. This foreign body causes disturbance of immune system resulting in skin rash, and dermatitis[1] and skin lesions and allergic reaction to SCS [2].

In CRPS/RSD, the immune system is rogue. This is because the immune system is modulated by sympathetic system. The sympathetic system, under pain input, responds by releasing T-cell lymphocytes (in early stages CD4 or helper lymphocytes, and in late stages CD8 or killer T-cell lymphocytes)[3]. So, after the SCS has lost its effect, the sympathetic system considers the foreign body of the spinal stimulator as a source of sympathetic dysfunction. This causes neuroinflammation manifested as skin rash, edema, and infection.

As the condition becomes chronic, the SCS can lead to spread of pain from the original site to other parts of the body[3].

In rare cases, there are other complications noted with SCS application. These complications consist of the following:

1. Epidural abscess or blood clots.

2. In occasional cases, the sensitization of the spinal cord by the spinal cord stimulator causes spinal cord sensitization in the form of myoclonic akinetic seizures [3]. The sensitization is due to prolonged electrical stimulation causing exhaustion of the inhibitory nerve cells. Treatment with Klonopin^®, and removal of the stimulator prevents the sensitization.

Such attacks of myoclonic seizures originating from the spinal cord due to the spinal cord sensitization are not limited to the SCS. They are also seen in other spinal procedures[4]. The diagnosis of spinal cord originated myoclonic seizures is quite difficult, and usually these patients are labeled as "functional" or "hysterical." Such patients respond very nicely to treatment with Klonopin^®, brand name rather than generic.

The removal of SCS, as well as Multidisciplinary treatments, aiming at desensitizing the spinal cord, help this condition.

Another problem with the SCS is the tendency for electrode movement due to improper anchoring, and the necessity for the surgeon try to correct the position of the stimulator. Every operation is going to be another new source of CRPS pain.

In the rare and severe cases of spinal cord sensitization, the patient may develop myoclonic jerks, and urgency, frequency, and even incontinence of urine, secondary to SCS irritating the urinary bladder and interstitial cystitis.

H. Hooshmand, M.D.

 References

1.McKenna KE and McCleane G: Dermatitis induced by spinal cord stimulator implant. Contact Dermatitis.1999; 41: 229.

2. Ochani TD, Almirante J, Siddiqui A, et al: Allergic reaction to spinal cord stimulator. Clin J Pain. 2000; 16; 178-180.

3. Hooshmand H, Hashmi H: Complex regional pain syndrome (CRPS, RSDS) diagnosis and therapy. A review of 824 patients. Pain Digest. 1999; 9: 1-24. (Click on link to view abstract)

4. Rosenblum, JA: Spinal abdominal myoclonus. The Neurologist. 1996; 2: 784-787.