Motor Cortex Stimulation for Intractable Pain

Richard K. Osenbach, M.D.

Disclosures

Neurosurg Focus. 2006;21(6) 

In This Article

Preoperative Evaluation

Patients considered for MCS undergo a comprehensive preoperative evaluation and screening, including a detailed history of their pain problem listing all prior treatments, along with a thorough neurological examination. Imaging studies appropriate to the particular problem should be reviewed to clarify the underlying pathological process if possible and to exclude a potentially correctable primary surgical problem. Evaluation tools such as the McGill Pain Questionnaire and VAS scores are useful in characterizing the type and intensity of pain and should be completed before surgery and at fixed postoperative intervals to monitor the effectiveness of therapy. Unfortunately, changes in VAS scores alone often do not reflect the true effectiveness of a particular therapy and clearly are inadequate for determining its benefit with regard to functional capacity, quality of life, and so on. Consequently, in my institution we have recently begun to administer standardized validated questionnaires such as the Health Status Questionnaire 2.0 and Quality of Life In ventory (the Pearson NCS) to assess the impact of MCS as well as other implantable pain-relief devices before surgery and at 6-month intervals thereafter. These tests provide us with the ability to generate reports and comparable data for a more objective assessment of the effectiveness of a given therapy.

Because nearly all patients with chronic pain demonstrate at least some degree of psychosocial stress, a baseline neuropsychological evaluation is customarily a standard part of the screening process. In my colleagues' and my opinion, evaluation by a skilled pain psychologist is in valuable for identifying factors such as significant depression, external psychosocial stressors, and the like that might influence the effectiveness of treatment. An experienced pain psychologist is also helpful in reinforcing reasonable expectations regarding the effectiveness of a particular treatment and assisting the patient in coping with residual pain that is not alleviated by the procedure. This is very important because MCS, or any other pain procedure for that matter, is unlikely to eliminate completely or "cure" the condition(s) for which this therapy is applied. In fact, my colleagues and I have anecdotally noted improved results in patients treated with SCS who participate in various behavioral therapies such as biofeedback, stress relaxation training, coping skills, and so on, in addition to receiving their SCS implant.

Identification of psychological factors that are believed to affect the patient's pain should not necessarily be viewed as a contraindication to surgery, because nearly all patients with chronic pain have some psychological factors that contribute to their overall pain and suffering. Virtually all patients with chronic pain suffer at least some element of depression that often improves with better pain control. Nevertheless, patients with major depression accompanied by suicidal thoughts or gestures require in tense psychiatric intervention and are not appropriate candidates for any surgery until these issues have been addressed and brought under control. Other psychosocial stressors such as job dissatisfaction, marital problems, and the like should be addressed because surgery is not going to alter those issues fundamentally. Patients with major personality disorders often do not have favorable outcomes from procedures to treat chronic pain, and one should use caution in selecting these patients for procedures such as MCS. Finally, careful judgment and caution should be exercised in considering implantable devices for pain therapy in patients in whom problems such as alcoholism or drug addiction have been identified as ongoing issues. The presence of these behaviors usually portends a poor prognosis with any type of implantable device placed for pain therapy.

Unfortunately, and perhaps all to commonly, some patients with chronic pain and even some physicians subscribe to the belief that "if the pain is relieved everything else will be fine." Clearly, it is overly simplistic (and, frankly, foolish) for the patient and especially for the treating physician to believe that any surgical procedure is going to correct everything that is wrong in a patient's life. Application of therapies such as MCS under these circumstances will more often than not result in treatment failures as well as a variety of other problems. It is important to remember that, even under ideal circumstances, not everyone can be helped with surgery, and the decision not to perform a pain relief procedure is sometimes in the patient's best interest rather than have him or her go ahead with an operation in which the risks significantly outweigh the potential benefits.

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