The patient's experience
Sean Cannon tells of how deep brain stimulation (DBS) finally freed him from years of constant neuropathic pain.
I had been struggling with a condition called neuropathic pain for several years. The condition means that my nervous system is constantly generating pain signals, so even when there is no physical cause, I can suffer severe pain over large parts of my body.
It is difficult to pinpoint the exact cause, but my partner Carole thinks it started when my car was hit from behind about eight years ago. There was damage to my spine which necessitated three discs being replaced and part of the spine being supported with titanium rods.
It was pioneering surgery at the time, and it seemed to go really well. Quite naturally, I thought that was it.
Some time later, I started experiencing pins and needles in the fingertips of my left hand, which gradually moved up my arm and then moved across to the right arm. Then my legs started to be affected. I couldn’t feel the ground properly beneath my feet, it felt like walking on a trampoline and I started to stagger. My GP referred me to a neurologist who sent me for a brain investigation.
After two MRI scans, they discovered a narrowing of part of the spinal cord and I was referred to a leading neurosurgeon, Mr Donncha O’Brien. He immediately realised the seriousness of the situation and told me that without prompt intervention I could end up completely paralysed and needing mechanical assistance to breathe.
Mr O’Brien needed to perform two procedures to relieve all the pressure around the damaged area, but even so there were no guarantees of success. I could still end up paralysed after the surgery, but without the procedures, paralysis was almost a certainty. I felt I might as well go ahead.
Afterwards, I pretty much had to learn to walk again. Progress was initially good, then suddenly I started getting drop attacks, where I would suddenly fall for no reason. I would be conscious, know I was falling, but be unable to do anything to protect myself. I couldn’t even put my hands out to break the fall. Once, I fell onto my face, breaking my nose and suffering from concussion for about two months.
I knew that part of the sleeve of my spinal cord was damaged and things were getting worse, so I started doing research into possible solutions. I found Dr Declan O'Keeffe, who specialises in spinal cord simulators, and he agreed to take me on as a patient.
After prescribing ketamine infusions for the pain, he performed the nerve stimulation procedure. This entailed inserting a probe to simulate nerve activity in specific areas around the damage.
The operation solved my physical issues, but I sill suffered severe pain and had to continue with the ketamine alongside other pain medication. The problem was, it would have taken a second simulator in the neck region to cure my pain as well, and there was simply not enough room.
It was Dr O’Keeffe who approached Prof Tipu Zahed Aziz about performing the deep brain stimulation (DBS) procedure to cure the pain.
I came over to The London Clinic from Dublin for the operation. I was a bit nervous, but Prof Aziz told me I was in very good shape for someone with this condition, which improved the chances of a good outcome. This was very heartening to hear.
After the operation, Prof Aziz told me that things had gone very well, so I was confident and excited about turning on the electrodes. There wasn’t a ‘wow’ moment when we finally switched them on. It was more a case of slowly easing into the realisation that the ‘pain’ wasn’t bothering me as it had been. I realised I no longer felt any need to reach for the bottle of liquid ketamine I always kept nearby.
I am now free of all pain medication, which is wonderful. I had been on a real cocktail of drugs to control the pain and was having to live with the side effects. Coming off them contributed a great deal to my improved quality of life.
In terms of the effect of the electrodes, it’s quite strange in as much as the pain hasn’t gone away. Insead, it has been transformed to a different kind of sensation. The key thing is that this sensation doesn’t cause me discomfort or distress. The electrodes trick my brain into experiencing the sensation in a way that is not ‘painful’.
WHAT IS DEEP BRAIN STIMULATION?
Professor Tipu Zahed Aziz, founder and head of Oxford Functional Neurosurgery, professor of neurosurgery at the University of Oxford and consultant neurosurgeon at The London Clinic, provides a summary.
Neuropathic pain is defined as pain resulting from injury to the brain or to the nerves that generate or transmit pain signals. What happens is that somewhere along the nerve pathways, nerve cells start firing out of control, which usually starts after some type of damage.
It seems that because they have lost the type of signal input they normally receive, they become confused and just fire off signals at random, generating a sensation which the patient perceives as pain.
This type of pain has been described as a crushing or burning sensation. The patient can suffer from extreme sensitivity, where a slight touch can send a huge burst of pain through the body. It is not like the pain most of us are familiar with; in fact, almost all patients say that someone who isn’t suffering from the condition would not recognise the feeling.
In Sean’s case, despite successful surgery, some damage to his spinal cord remained, which was the cause of his condition. Because the injury was located so high up the spine, Sean feels the pain throughout his body. This meant that we could not target a specific region of the brain to reduce all of his symptoms. We needed something that would effectively treat his whole body.
The approach we took doesn’t stop the nerve signals from reaching the brain, thereby stopping the pain, but it does change the way in which the brain interprets the signals when they arrive. When working well, it will transform the patient’s perception of the signals. The ‘pain’ is being reduced to a neutral sensation, like touching a carpet.
You can still feel something, but there are no negative emotions attached to the incoming signals. In effect, we diminish the emotional importance of the signals, so the patient no longer perceives them as distressing.
During the operation, we implant electrodes very precisely into both sides of an area of the brain called the anterior cingulate. We then run wires under the skin from the electrodes to the programmable pacemaker which powers them.
We usually wait for six weeks for any post-operative swelling to calm down before turning on the electrodes, but Sean responded well enough to the procedure for us to turn them on after five weeks. The pacemaker sends a precisely calibrated electrical charge to the electrodes and the strength of the charge determines the effect the electrodes have.
So far, things have gone extremely well. The operation to implant the electrodes went smoothly and since switching them on I have been very pleased with the results. I will continue to be in regular contact with Sean so we can make the necessary adjustments to the settings to best manage his pain.
It will take a little time, but we will find the precise power settings that mitigate Sean’s pain as much as possible, allowing him to return to enjoying life to the full.
- Neuropathic pain
Pain caused by damage or disease affecting the somatosensory nervous system
A medication primarily used for starting and maintaining anaesthesia. It induces a trance-like state, providing pain relief, sedation, and amnesia
- Anterior cingulate
Part of the brain with connections to both the 'emotional' limbic system and the 'cognitive' prefrontal cortex
Part of the sensory system concerned with the perception of touch.
This article appears in the current issue of Prognosis magazine.
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