Please note that VNS is no longer funded as part of our Service Level Agreement (SLA). This means that whilst Scottish NHS Boards can make a referral for consideration for specialist treatment at no additional cost, if VNS is the preferred option additional funding will be required.
VNS as a treatment for depression
VNS was postulated as a method of stimulating higher brain activity as early as 1938. The first human VNS implant was performed in 1988 for treatment of epilepsy. Since that time, VNS has become established for treatment-resistant partial onset seizure disorder and by 2004, more than 28000 epilepsy patients in 24 countries have been treated with VNS.
The vagus nerve is the longest of the cranial nerves, deriving its name from the Latin for 'wandering'. It runs from the brain stem through the neck, thorax, and abdomen. It carries signals responsible for controlling smooth muscle in the lungs and gastrointestinal tract, and is responsible for slowing down heart rate.
However, the vagus nerve is not only a parasympathetic efferent nerve. 80% of its fibres are sensory fibres, transmitting information from the body to the brain. These fibres carry information to the brain stem, and on to the forebrain, amygdala, hypothalamus, thalamus, orbitofrontal cortex, and other parts of the limbic system involved in the regulation of mood.
VNS involves subcutaneous implantation of a pulse generator, of a similar size and in a similar location to a cardiac pacemaker. Bipolar electrodes extend from the device and are wrapped around the left cervical vagus nerve in the neck, near to the carotid artery. In most cases, the stimulator will be on for 30 seconds every five minutes but the frequency and intensity of the stimulation is controllable using a telemetric wand connected to a palmtop computer.
Outcomes from VNS for depression
So far, the number of patients which comprise the world literature is comparatively small.
A summary of published research on VNS can be found on our VNS Research page.
Adverse effects from VNS
VNS is generally well tolerated. Some patients will, however, experience some adverse effects in the early stages of treatment. Almost invariably, these adverse effects are associated with the times that the stimulator is on (30 seconds every 5 minutes). At 3 months, common side effects include the following:
- Voice alteration (53%)
- Headache (23%)
- Neck pain (17%)
- Cough (13%)
At 12 months, most adverse effects have reduced, with the exception of voice alteration which may still persist in up to 21% of people. Changing the frequency or intensity of stimulation can improve adverse effects, and patients are also given magnets which can temporarily switch off the stimulator when held over the device.
There are isolated reports of cardiac effects of VNS, with asystole occurring in 0.1% of cases when the stimulator is first turned on. No fatalities or long-term sequelae have occurred.
Psychiatric adverse effects are uncommon, although there have been two cases of mania in 30 patients receiving VNS for treatment-refractory depression (Marangell, Rush, George, et al, 2002).
VNS in Dundee
Media coverage in VNS has undoubtedly stimulated interest in this new therapy for treatment-refractory depression. We recognise that these 'success stories' can be very attractive for people who have been suffering from chronic depression, but it is important to remember that we are more likely to hear from those people for whom it has worked than those where it hasn't.
For those wishing further information on VNS for depression in Dundee, we suggest that you read our VNS Frequently Asked Questions.