Neurosurgical forum Letters

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Documenting Results of Neurostimulator Implantation

plications pertaining to the use of implanted electronic devices, many of which have become apparent only after years of use and study. 6 Dr. Pineda mentions that many of his complications occurred with monopolar instrumentation, which has not been marketed in the United States for at least 2 years. Once again, the information as to the specific electrode configuration of the instrumentation used as well as other specifics relating to the type of product and manufacturer are not given. The amount of useful information that can be drawn from this article in order to improve future technique and clinical success is meager for the reasons given above. Considering the amount of effort expended, this is, quite simply, a shame. It is because of the concern regarding the lack of specificity in medical device-related publications that a request was made in the September 1976 issue of the Journal of Neurosurgery s that "This waste of scientific effort could have been prevented by editorial policies requiring specific identification of referenced materials," and that "surgeons be asked to record in their operative notes specific identification of any implanted medical devices." In addition to better documentation, ft would seem that, in an article published regarding medical device complications in which much of the instrumentation and the technique employed have been obsolete for a significant period of time, some review of updated instrumentation and technique also be included to present a balanced view of the present state of the art. CHAgLESBURTON,M.D. Minneapolis, Minnesota

To THE EDITOR: In a recent article (Pineda A: Complications of dorsal column stimulation. J Neurosurg 48:64-68, January, 1978), Dr. Anselmo Pineda presents a review of the complications encountered with a series of 92 dorsal column stimulators (DCS's). While the Journal and its Editorial Board are to be complimented for their interest in publishing information on medical device complications and adverse effects, it is important to point out that this article fails to include sufficient basic information to allow many meaningful conclusions to be drawn from the data presented. The American Association of Neurological Surgeons and the Congress of Neurological Surgeons, through the Joint Committee on Procedures and Terminology, have established nomenclature for implanted neurostimulators which was published in the American Medical Association's most recent volume of Physician's Current Procedural Terminology." This terminology includes designations regarding electrode placement, such as, epidural, endodural, subdural, and subarachnoid. Dr. Pineda's article contains no specific mention of the site of electrode placement, and complications seen with DCS's relate directly to this important consideration. One can assume that, from the complications reported, Dr. Pineda's implants were of the subarachnoid variety. Drs. Reichert? Sweet, 7 and Burton 1'~ have independently presented information indicating that by the endodural placement of DCS electrodes, many of the significant complications reported previously could be avoided. These specifically include spinal cord compression, References cerebrospinal fluid leakage, meningitis, and 1. Burton C: Dorsal column stimulation: opprogressive arachnoidal inflammatory timization of application. Surg Neurol 4: response. The avoidance of these problems 171-179, 1975 has been documented in a number of papers 2. Burton C: The intradural site for dorsal column over the past years by both neurosurgeons stimulator (DCS) electrode implantation. and biomedical engineering scientists. Even Presented at the Dorsal Column Study Group Meeting, Boston, Massachusetts, April 16, with these improvements in technique, 1972 however, there still remains a myriad of com,t72

J. Neurosurg. / Volume 49 / September, 1978

Neurosurgical forum 3. Burton CV, McFadden JT: Special article: Neurosurgical materials and devices. Report on regulatory agencies and advisory groups. J Neurosurg 45:251-258, 1976 4. Physician's Current Procedural Terminology, ed 4. Available from: CPT-4 Publication, American Medical Association, 535 N. Dearborn, Chicago, Illinois 60610. 5. Reichert T: Personal communication, 1972 6. Smith C: Instrumentation problems. Neurosurgery 1:224-225, 1977 7. Sweet W: Personal communication, 1972 RESPONSE: Although the manufacturer and type of dorsal column stimulator (DCS) might be of importance, in principle the basic mechanism of the device is the same, except perhaps for Med-General's electrodes. In our patients, all 92 electrodes were implanted posterior to the dorsal column. The longrange follow-up study did not provide distinctions among the three types of electrodes. For information, however, these data are shown in Table 1. TABLE 1 Dorsal column stimulators in study

Manufacturer Avery Med-General Medtronic total

Unipolar Bipolar Total 0 0 44 44

9 6 33 48

9 6 77 92

In a previous paper, 1 I made detailed reference to the site of the electrode placement, in relation not only to the dura (endodural, subdural, arachnoid, or median and paramedian to the midline), but also to the preferential vertebral level according to location and distribution of pain. Therefore I would like to refer Dr. Burton and others to that publication if more meaningful data are sought. Although endodural implants decrease complications, in our experience such placement is only efficacious for pain syndrome with no involvement of the lower extremities. The cutoff date for the paper published in January, 1978, was January, 1976. This coincides with the time unipolar electrodes were no longer available, but only one unipolar and 12 bipolar were added after that time, with a total of 92 implants from the initial number of 79 published earlier? For clarification, J. Neurosurg. / Volume 49 / September, 1978

TABLE 2 Location and type of electrode

Location endodural subdural subarachnoid total

Unipolar Bipolar 16 28 -44

1 42 5 48

Total 17 70 5 92

therefore, the updated information (to January, 1976) is shown in Table 2. It was obvious from our results that whether the implant was subdural (extraarachnoid) or endodural, the long-range efficacy of the implants was approximately the same, except for patients with unipolar electrodes. Although initially we had five subarachnoid implants, this location did not improve the results. Cerebrospinal fluid leakage often occurred, whether or not careful manipulation of the arachnoid membrane was done in a subdural implant, if careful dural closure was not accomplished. I did not include in my paper recent advances of the DCS using the percutaneous method. Because of limited experience with this procedure, I cannot endorse it as a permanent implant. It does, however, provide excellent temporary stimulation, which I sometimes use as a preliminary maneuver to an open surgical implant using standard electrodes. I endorse Dr. Burton's view that more specific identification of source material ought to be included in clinical accounts. I regret that my report seemed remiss in this area, and I appreciate the opportunity provided by his letter to clarify these points. ANSELMOPINEDA,M.D. Long Beach, California Reference 1. Pineda A: Dorsal column stimulation and its prospects. Surg Neurol 4:157-163, 1975 Use of Cyanoacrylates To THE EDITOR: In a letter to the Editor, January, 1978, Drs. Crowell, Morawetz, DeGirolami, and Joris commented on complications of the use of Aron Alpha tissue adhesive (Crowell RM, Morawetz RB, DeGirolami U, et al: Vascular tissue adhesives. J Neurosurg 48:154, January, 473

Documenting results of neurostimulator implantation.

Neurosurgical forum Letters to the editor Documenting Results of Neurostimulator Implantation plications pertaining to the use of implanted elect...
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