Microstimulators Hold Promise for Some Medically Refractory Headaches

The challenge

• More than 32 million Americans, 70% of whom are women, have migraines, and many of those affected progress to a chronic migraine condition, experiencing headaches more than 15 days per month.
• An estimated 40,000 people in the United States do not respond to existing treatments, and many may be candidates for alternative therapies.

Occipital nerve stimulation (ONS) for medically refractory headache pain has been available since the late 1990s. Offered at all 3 Mayo Clinic sites, it is most commonly used to treat migraine and cluster headaches that do not respond to conventional medications. Mayo Clinic has also been involved in several studies of ONS, including work on a microstimulator that is not yet commercially available.

Traditional occipital nerve stimulation system

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In traditional ONS, a thin wire containing electrodes is implanted under the skin in the back of the head. The wire extends to an implantable, battery-driven impulse generator. The patient controls the rate and intensity of the pulses using a remote, hand-held programmer.

The pulses create paresthesias, often described by patients as light tingling or buzzing, in the area of the occipital nerve and the distal branches of the second and third cervical nerves. Although the mechanism is not entirely understood, peripheral nerve stimulation may influence deep brain centers that are responsible for pain modulation and may gate or block pain signals from ascending from the trigeminal-cervical complex in the lower brainstem and upper cervical spinal cord.

Advantages of microstimulators

Lead migration has been one of the biggest frustrations experienced with the occipital stimulator. Microstimulators avoid that risk because both the electrodes and the impulse generator are contained within the stimulating device, which is about the size of a paperclip.

Additionally, the microstimulator is less invasive and the surgery to implant it carries fewer risks. Traditional stimulators have long wires and require 3 incisions, while microstimulators require only 1 incision and have no wires.

Patient response to ONS

At Mayo Clinic, ONS is reserved for patients for whom all other treatments have failed. These are people who have had chronic daily headache and continuous, severe headaches for years—who have tried everything from multiple medications to psychological, behavioral, and alternative approaches to pain management.

ONS complications can include infection and an increase in pain. Traditional ONS is first conducted on a trial basis to screen for increased pain. Because ONS takes time to work, patients may not experience improvement in the 5- to 7-day trial period. After the stimulation trial, the patient and physician decide if the response to the trial supports permanent implantation.

Recently, Mayo Clinic researchers conducted the first test of microstimulators. In a small series of patients with medically refractory chronic cluster headache, 75% reported a positive response 3 months after implant. They have also found microstimulation to be effective in patients with hemicrania continua. These devices are still experimental and not yet approved by the US Food and Drug Administration.

Points to remember

• Although the mechanism is not entirely understood, peripheral nerve stimulation may influence deep brain centers that are responsible for pain modulation in headache.
• At Mayo Clinic, occipital nerve stimulation is most commonly used to treat migraine and cluster headaches that do not respond to conventional medications or psychological, behavioral, and alternative approaches to pain management.
• Microstimulators offer a less invasive way to treat refractory headaches while avoiding the risk of lead migration associated with occipital stimulators.
• These devices are still experimental and not yet approved by the US Food and Drug Administration.