Spinal Cord Stimulation

This technique involves the placing of one or more electrodes in the epidural space, percuta-neously or at open surgery. Stimulation of the electrode(s) with varying electrical current in the frequency range 20-200 Hz produces analgesia in the area where the stimulus is appreciated. The mode of action remains obscure, despite four decades of research.

Indications for this treatment are unclear but current opinion would support its use in the following conditions - deafferentation syndromes, chronic regional pain syndrome (CRPS), arachnoiditis, failed back surgery, radicular pain and vascular disease (peripheral and angina).

There are no randomized controlled trials (RCTs) to support its use, not least because it is impossible to blind patient and operator as to the treatment. The technique is expensive and is therefore used erratically, depending upon the sources of healthcare funding. At various consensus meetings for its use in conditions such as angina pectoris, it has been placed low in the list, often coming to represent a last resort. It is said to be relatively free from major deleterious side effects, but most series report significant incidences of complications, largely related to electrode positioning, movement and breakage. The patients are thus often continu-ingly dependent on the implanting physician for aftercare.

Patient selection for these treatments has proved difficult, with psychological assessment being said to be important but with little objective evidence for the benefit of this.

The technique involves the placement of a trial electrode percutaneously, such that the electrode tip is at or near the appropriate dermatomal level. Trial stimulation allows manipulation of the electrode to obtain ideal placement. In many centers, the trial electrode is then connected to an external pulse generator to allow prolonged testing (in some series up to 2 weeks) of effect. If benefit by a previously agreed yardstick with the patient is obtained, then permanent implantation is undertaken by fashioning a subcutaneous pocket, usually on the abdominal wall, for the pulse generator. The electrode is connected by tunnelling the catheter from the spine. Firm anchoring of the catheter is important, as movement is a common cause of failure. The electrode can also be placed on and stitched to the dura under general anesthesia and mini-laminectomy, but this is more prone to inaccurate siting of the electrode.

Various electrodes are available that are able to cover differing amounts of the spinal cord. Multi-electrode devices allow for fine tuning post-implant and will, to a certain extent, compensate for some movement post-procedure.

The devices are battery powered and have, therefore, a limited life, depending on usage, power settings, etc. The modern devices allow the patient some freedom to alter stimulation parameters and turn the device on and off [12].

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The term vaginitis is one that is applied to any inflammation or infection of the vagina, and there are many different conditions that are categorized together under this ‘broad’ heading, including bacterial vaginosis, trichomoniasis and non-infectious vaginitis.

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