From this month's Neurotech Insights investment newsletter focused on the depression market:
While drugs to treat depression have proven effective for millions of individuals there exist a significant number of patients who do not respond to antidepressants. Treatment resistant depression, or refractory depression, is a condition that affects an estimated 4 million people in the U.S. and 11 million worldwide. Until recently, there were no options for these individuals beyond treatment with electroconvulsive therapy (ECT), which commonly induces memory loss among other issues. Today, several neurodevice approaches for the treatment of refractory depression are emerging including Vagus Nerve Stimulation (VNS), Deep Brain Stimulation (DBS) and repetitive Transcranial Magnetic Stimulation (rTMS).
The first neurodevice to be approved by the FDA for depression was Cyberonics’ VNS Therapy system. On July 15, 2005, the FDA approved Cyberonics’ VNS Therapy as a long-term adjunctive treatment for patients 18 years of age or older with chronic or recurrent treatment-resistant depression in a major depressive episode that have not responded to at least four adequate antidepressant treatments. Chronic treatment-resistant depression is defined as being in the current depressive episode for more than two years. Recurrent treatment-resistant depression is defined as having a history of multiple prior episodes of depression. The approved indication for use includes patients with unipolar or bipolar depression in a major depressive episode.
This is the first time an implanted device has been approved by the FDA for treatment of a psychiatric illness. VNS Therapy was already approved for sale in the European Union and in Canada as a treatment of depression in patients with treatment-resistant or treatment-intolerant major depressive episodes including unipolar depression and bipolar disorder, also known as manic depression. Currently over 550 people have a VNS implant for treatment resistant depression. Another 7,000 people are currently seeking approval from their insurance companies for the $25,000 operation, according to the Washington Post.
The second neurodevice technique being investigated as a potential treatment for refractory depression is Deep Brain Stimulation (DBS). Over 30,000 people have been implanted with DBS systems for the treatment of movement disorders in people with severe tremor or Parkinson’s disease and now there are attempts to use it to treat depression. DBS devices resemble cardiac pacemakers, except that the stimulation electrodes are implanted in specific areas of the brain rather than the heart. Medtronic is currently developing a DBS product called Kinetra for depression. For the foreseeable future, the market for neurostimulators for depression is limited to the severest population of approximately 300,000 in the U.S. with 15,000 new cases emerging each year.
A third neurostimulation technique that is currently being used to treat severe depression is repetitive Transcranial Magnetic Stimulation (rTMS). rTMS has one very important advantage over the other techniques, it does not require brain surgery. Instead the external devices deliver brief magnetic field pulses through the cranium. The pulses induce a perpendicular electrical current that affect neurons in the superficial cortical layers—either increasing or diminishing activity. There are some studies that suggest that TMS directed at the left dorsolateral prefrontal cortex might be useful as an alternative to electroconvulsive therapy in treating severe or treatment-resistant major depression.
Canada’s MindCare Centres opened their first rTMS clinics for depression in 2004 where rTMS is now approved for treatment resistant depression. MindCare uses a computer controlled magnetic beam applied 20 minutes a day. Some researchers believe that rTMS may apply to many treatment resistant patients in the following markets: depression, anxiety, PTSD, OCD, tinnitus, pain, Parkinson's, migraines, aphasia, stroke (right after event), eating disorders, and addiction.
Note, more technologies, like transcranial direct current stimulation may be on the way.