Tuesday, July 24, 2007

Motor Cortex Stimulation and Motor Recovery

A recent paper published in Neurosurgery looked at motor recovery in patients with ischemic stroke at least four months out from the start of the study. All had moderate motor weakness. A treatment group had electrode implantation and the control group received the same three weeks of rehabilitation that the study patients received after their implants. Implanted patients were stimulated only during therapy.
All of the patients were followed for 12 weeks after their rehabilitation. And the results were pretty good: the implant group had significantly better scores on the Fugl-Meyer and hand function portion of the Stroke Impact Scale.
My conclusion was that motor cortex stimulation can improve motor recovery after a stroke, particularly in a patient without a dense hemiplegia and that motor cortex stimulation provides additional benefit to patients compared to rehabilitation, alone.
This is a nice example of improved motor recovery as a result of neuromodulation. I am going to have to go dig into my files to find a paper I read and tucked away that commented on the positive predictive value of TMS in anticipating a positive response to implanted motor cortex stimulators. Is anyone aware of any studies that compare motor recovery ( would that be a head to head study......anyone, Bueller????) with TMS vs implanted stimulation??

Wired Magazine TMS blurb

I just got the most current issue of Wired about and there was a nice little piece by Melinda Wenner on TMS and it's possibilities.
"Brains are electric — when neurons talk, they speak in voltage. Now, a new technique called transcranial magnetic stimulation may let neuroscientists hack those conversations. TMS translates electric signals into a magnetic field that passes through the skull and into the brain. Too much juice can cause seizures, but calibrate the machine just right and you can actually control brain activity. Treatments for drug-resistant depression, migraines, and post-traumatic stress disorder are in the offing. Further out, some researchers are trying to trigger more restful power naps, and others are working with autistic savants, hoping to inhibit the autism and bring forward the Rain Man level detail processing. That's right: We could all be perpetually happy, relaxed, and brilliant if they'd just mount this thing in a baseball cap."
Hmmm, a baseball cap with a figure 8 coil in it....maybe she is on to something here? As the scientific evidence grows, I am realizing she might not be so far off.

Sunday, July 1, 2007

Recent paper on rTMS and pain

The Journal of Pain just published a review article on the effects of rTMS on experimentally induced and chronic neuropathic pain. They looked at a seven studies that used rTMS to modulate experimentally induced acute pain brought on by ischemic muscle pain, cold immersion, capsaicin or laser stimulation. Those last tow really get to me, I am still recovering from a traumatic expericence as a child at a Mexican restaurant in California. I must have been about four and I grabbed a chip-full of homemade salsa that must have been served to the devil himself it was so hot. All I remember after being stunned by the growing four alarm fire in my mouth was the busboy grabbing a glass of milk and pouring it down my gullet. And anything involving lasers requires the obligatory reference to Dr. Evil's "sharks with lasers.."
It seems the findings in the acute pain papers were mixed. The authors conclude that "The varied effects of rTMS on acute pain may have been influenced by the type of experimentally induced pain, the stimulation frequencies used, and the cortical sites of rTMS stimulation." They noted some of the findings from this group of papers included that ability of single session rTMS to alter pain thresholds.
There were 16 chronic neuropathic pain papers that were included in this group that included approximately 250 patients with a wide variety of conditions including thalamic stroke, trigeminal neuralgia, CRPS, peripheral neuropathy, spinal cord injury, brahcial plexus injury, back pain, thalamotomy pain and osteomyelitis. The papers included used varying protocols including single session and multiple sessions.
In eight of the studies there was a "significant decrease in post-TMS VAS (visual analog scale, usually a 0-10 scale of pain) means as compared with pretreatment means...". To confuse issues there were some studies that reported a decreased in studies that used sham TMS to control for the placebo effect. However, the post-TMS VAS scores were significantly lower than the sham scores.
Some of the numbers that the authors present caught my eye: 62% of patients acheived at least 30% reduction in pain based on their VAS scores after TMS and almost 30% of those patients had at least a 50% drop in their pain score.
They then go on to make some generalizations about TMS protocols including the type of coil used, fast vs slow, the number of pulses used and the location of stimulation. None of the studies reported any adverse affects.
Once again, this presents some thought provoking information and causes me to continue to consider therapeutic neuromodulation with TMS may be in our future.
At what point does someone take the plunge and start offering this to patients with refractory neuropathic pain. I have seen these patients and they are miserable. Their pain is their life, and if you could offer someone a 30-50% reduction in their pain, even if it involved ongoing treatment, I have to wonder if this would be potentially life-altering. Just a thought....