Pain Surgery

Introduction

The information presented here is now historical to my cureent practice as the main pain surgery practice at Frenchay has been taken on first by my colleague Mr Nik Patel, whose expertise inthe the latest techniques of functional neurosurgery like deep brain stimulation will make a major contribution to this field and now by my new colleague Mr Adam Williams.  However I include the information here for reference as I still maintain an interest in this field and continue to treat some patients, helping out when waiting list pressures build (which is quite often) It was my experience of pain surgery that has led directly to my efforts to streamline patient diagnostics outlined in the section on SWIS Ltd.

Traditionally the neurosurgery used to treat intractable pain has consisted of various types of ablative therapy, cutting or destroying various bits of the nervous system. While these forms of treatment had some role in the treatment of cancer pain their role in the treatment of non cancer chronic pain (benign persistent pain) was limited. The main reason for this was that the effect of ablative therapy was almost always temporary. An effective surgical treatment of some forms of benign persistent pain was developed in the late 1970’s and early 1980’s in the form of stimulation of the nervous system. Dorsal Column Stimulation, now known as Spinal Cord Stimulation (SCS) was developed in the UK in Liverpool where I was fortunate to be trained as a registrar and where I learnt pain surgery techniques under the tutelage of John Miles in the Liverpool Pain Foundation. When I started in Bristol as a consultant I inherited an embryonic pain surgery practice from my predecessor, Michael Torrens and carried out over 100 SCS cases using the indications and techniques I had learnt in Liverpool. This early experience was audited independently internally. The findings were that 1/3 of my patients were not helped by the technique, 1/3 were helped but had technical problems with their stimulators while the final 1/3 had a good result from their treatment without technical problems other than the need for periodic battery replacement. The main indication for surgery was neurogenic (nerve damage) pain secondary to failed spinal surgery.

As a result of this audit the present pain surgery service was set up with a multidisciplinary team headed by Dr Cathy Stannard, pain physician. The aim was improve patient selection for pain surgery by taking a tripartite approach to a patient’s pain, examining the medical, psychological and surgical aspects of the pain syndrome together. The most recent audit of this joint practice is presented here -  link. My role has been to provide the sole surgical input to this service.

The service is aimed at treating three groups of patients:

1. Patients with benign persistent neurogenic pain syndromes with pain that has proven to be resistant to conventional therapy. The commonest group in this category are patients with failed spinal surgery syndrome.
2. Patients with pain generated by surgical pathology that require conventional neurosurgical treatment but who also require medical and / or psychological support in the management of their pain.
3. Patients with specific pain syndromes that are recognized as very difficult to treat. Examples are complex regional pain syndrome, phantom limb pain. Spinal cord injury pain and anaesthesia dolorosa.

Surgical techniques
Apart from the treatment of Trigeminal neuralgia, we hardly use ablative techniques for pain surgery. Even in this instance, decompressive surgery in the form of microvascular decompression id the treatment of choice. If trigeminal root injections are used then Glycerol injection, the least destructive of the surgical techniques is used in preference to radiofrequency lesioning of the nerve or peripheral nerve section.

The mainstay of my pain practice is the use of neurostimulation techniques. Spinal cord stimulation is the commonest technique. Others include motor cortex stimulation and peripheral nerve stimulation. I do not have personal experience of deep brain stimulation at the moment referring patient for this technique to my colleague in Oxford, Mr Tipu Aziz. Another technique that we use is the implantation of intrathecal drug delivery systems.

Spinal Cord Stimulation

This technique involves the implantation of electrodes next to the spinal cord, between the bone and the covering of the cord itself, the dura. We use a two stage procedure. The first is carried out by Dr Stannard under local anaesthetic. Here an epidural needle is inserted under X-Ray control and the stimulating electrode positioned under direct vision. The electrode is manipulated until optimal stimulation in the distribution of the patient’s limb pain is achieved. The patient then undergoes a period of temporary stimulation where the electrode is connected through the skin to a stimulating device not dissimilar to a TENS machine. We ask patients to test the stimulation in their home environment, deliberately trying to do things that would normally generate their chronic pain syndrome. In this way we assess the efficacy of the stimulator. We like to know what increased activity is possible with the stimulator, whether or not the stimulation can be used instead of regular drug therapy and finally we want to know if the stimulator has a pain killing effect of its own. I other words how long does it take for a patient’s pain to return after the stimulator has been switched off. We hope to have the answer to these questions within two weeks or so. If and only if temporary stimulation is having a beneficial effect do I proceed to the second stage of the procedure which is the implantation of the stimulator device itself under general anaesthetic. This consists of an electronic device similar to a cardiac pacemaker (It is the same technology) which is implanted under the skin. See Medtronic website.

Our recent results of spinal cord stimulation are presented here. We now achieve an 85% improvement in the patients selected for SCS, 35% continue to have technical problems with their stimulators. 50% now have uneventful stimulator insertions and do not require further surgery apart from battery replacement every few years.

What these results do is establish the efficacy of our multidisciplinary approach to complex pain patients. To achieve improvement in this proportion of patients that were otherwise untreatable is very worthwhile. What the results also show is that this service has to be properly resourced. The selection of patients can be improved upon. The service needs ring fenced resources both in terms of individual clinician’s time and in terms of inpatient beds and operating space. To have this level of infection rate when we are implanting such expensive hardware is unacceptable. However the business case for the establishment of a formal neuroscience based pain surgery service has been made and we will know in the next few weeks whether or not it has been accepted.

In the introduction to this section I referred to my pain surgery practice having a major influence on the formation of SWIS Ltd. This is because pain surgery for failed back syndrome is, in effect closing the door after the horse has bolted. The patients in the category that we were treating had, in large part been let down by the system in that their chronic illness had been generated by the time they had had to wait for treatment. From this experience we formulated the hypothesis that if spinal patients were assessed and treated in timely fashion outcomes would be better and the incidence of chronic, complex postoperative pain would be less. The SWIS experiment was a way of proving that it could be done.

High frequency SCS for back pain

Since I formally handed the pain surgery service over to my new colleagues, there has been considerable devleopment in the field. Rechargeable batteries systems have been devleoped. This has allowed the devleopment of high frequency stimulation systems that may be useful in treating back pain. The patient does not feel the stimulaiton itself, they simply report lack of pain. I dont have enough experience to comment on this form of treatment in any detail.

Other stimulation systems have also been developed such as occipital nerve stimulaiton for headache and deep brain stimulation for central pain syndromes. I had some epxerience of motor cortex stimulation but I was never certain as to efficacy of this technique. For more details of the newer techniques I will have refer the reader elsewhere.