Neuromodulation for Refractory Trigeminal Neuralgia: Expert Feedback
First-line therapies for trigeminal neuralgia include anticonvulsants such as carbamazepine and oxcarbazepine, which may be supplemented with baclofen and analgesics.
Trigeminal neuralgia affects 70 individuals per 100,000, has a higher prevalence in women vs men, and has an annual rate of 12 new cases per 100,000.1,2 The disorder is characterized by severe facial pain, with sharp, intense, electric shock-like pain episodes often triggered by external stimuli to the face typically lasting 1 to 120 seconds. During severe attacks, the patient's ability to speak, eat, and participate in daily activities may be affected.3 The attacks are often recurring, with a fraction of patients experiencing continuous background pain.
First-line therapies for trigeminal neuralgia include anticonvulsants such as carbamazepine and oxcarbazepine, which may be supplemented with the muscle relaxant baclofen and analgesics.3,4 In patients who are unresponsive to drugs or who become drug-resistant, surgery may be considered. Available surgical procedures include Gasserian ganglion percutaneous techniques, microvascular decompression, and gamma knife radiosurgery.1,5
However, some patients with trigeminal neuralgia do not achieve adequate pain relief with pharmacologic therapies and surgical interventions, and continue to present with severe refractory pain. In several recent studies, neuromodulation techniques have been explored as alternative treatment options in this group of patients.5-7
In an interview with Clinical Pain Advisor, Karina Gritsenko, MD, associate professor in the Department of Anesthesiology at Albert Einstein College of Medicine and program director of the Regional Anesthesia and Acute Pain Medicine Fellowship at Montefiore Medical Center, discussed the latest trends in the use of neuromodulation and, specifically, peripheral nerve stimulation (PNS), for the treatment of refractory trigeminal neuralgia.
Clinical Pain Advisor: Can you describe the mechanisms whereby PNS can effectively manage trigeminal neuralgia-associated pain?
Dr Karina Gritsenko: PNS is a commonly used technique to treat chronic pain. PNS was invented in the mid-1960s, even before the widely utilized spinal cord stimulation, but it is still relatively new in the world of pain in the United States. A PNS device, a small electrical wire, is placed next to the peripheral nerve suspected to be the source of pain for a patient. A complex electrode system delivers electrical signals and causes a change in the sensation of pain. As a result, instead of a painful stimulus, the patient will experience paresthesia, which is intended to be a more pleasant sensation. There are different programming options for such devices that enable tailoring the level of stimulation and choosing the best setting, or frequency, for the patient's needs. Initially, the patient will undergo a test period typically lasting a few days, during which a wire will be connected to an external device. The patient can control the stimulus delivered through the wire, similar to the volume on a radio. If the patient determines that the pain sensation has lessened, the trial is considered successful. The temporary wire is then removed, and a permanent device with a small generator is implanted for long-standing relief.
Clinical Pain Advisor: In a case report published in 2015, your research team tested a new interventional technique with supraorbital and infraorbital neurostimulation for the treatment of refractory trigeminal neuralgia.7 What were the study's main findings?
Dr Gritsenko: It is amazing to say this, but the technology we introduced only a few years ago is already dated. The field of neurostimulation is a uniquely specialized field that is constantly advancing with new technology. At the time this case report was published, the idea of PNS was relatively novel and was found to have outstanding results for the right patient who would otherwise be in pain.
Neurostimulation is changing in real time with nuances in the frequencies and pulse waves that are shown to profoundly affect the results. Thus, neuromodulation does not only require a precise anatomic procedure to place the stimulator in the correct spot, a unique concept at the time, but also fine-tuning the electricity selection used for the device itself. Just like a cardiac pacemaker for the heart, we find that patient specificity is important.
Clinical Pain Advisor: Which types of patients with trigeminal neuralgia are most likely to benefit from PNS?
Dr Gritsenko: Patients with refractory pain are candidates for PNS. We have found that any patient who presents with pain must first undergo conservative management, which may include both medications and interventional procedures that do not include a permanent device, before considering implantation of a peripheral stimulator. Those patients who display signs of severe shooting pains and are not responsive to analgesic medications or injections may be suitable candidates. Of course, any candidate for implantation of a peripheral stimulator would first need to undergo a peripheral stimulator trial before having a permanent device implanted.
Clinical Pain Advisor: What are some challenges associated with PNS?
Dr Gritsenko: PNS can be a wonderful treatment option, but it is not for everyone. It is an expensive, specialized treatment, and an invasive technology, which requires careful patient selection. Not every patient with trigeminal neuralgia needs a peripheral stimulator; this treatment option is reserved for patients who have failed conservative medication management or more common basic pain procedures.
It is important for the patient to have an understanding that a permanent device is being implanted, as well as how the device works. For example, devices with rechargeable batteries need to be recharged or they can become inactive. Also, before implantation, the physician must make sure that the patient's wound healing potential is not compromised, and that he/she is at low risk for infection or bleeding. Simply put, the patient must be a good candidate for a surgical procedure.
Clinical Pain Advisor: What other advantages does the treatment of refractory trigeminal neuralgia with neuromodulation offer?
Dr Gritsenko: Patients with refractory trigeminal neuralgia are at high risk for opioid tolerance and addiction, as they may have been unresponsive to neuropathic agents. In the context of the opioid epidemic, we need to do what we can to avoid this pitfall and prevent any excessive use of opioids by treating pain in this novel way.
Clinical Pain Advisor: What is the outlook for neuromodulation techniques in the treatment of trigeminal neuralgia and related craniofacial pain disorders?
Dr Gritsenko: I believe we should be hopeful. In terms of the literature on neuromodulation, we are experiencing exciting times. New data are beginning to show that optimizing the settings of spinal cord stimulators may lead to better outcomes and quality of life for many patients with pain, and this may be applicable to peripheral nerve disease as well. For example, in neuraxial stimulation, the focus is now on learning more about dorsal root ganglion stimulation and its effects on the sensation of pain. I believe that learning more about the field of neuromodulation as a whole will also lead to improved treatment accuracy for specific conditions that include trigeminal neuralgia.
- Weber K. Neuromodulation and devices in trigeminal neuralgia. Headache. 2017;57(10):1648-1653.
- National Institute of Neurological Disorders and Stroke. Trigeminal neuralgia fact sheet. https://www.ninds.nih.gov/Disorders/Patient-Caregiver-Education/Fact-Sheets/Trigeminal-Neuralgia-Fact-Sheet. Accessed December 13, 2017.
- Obermann M. Treatment options in trigeminal neuralgia. Ther Adv Neurol Disord. 2010;3(2):107-115.
- Stidd DA, Wuollet AL, Bowden K, et al. Peripheral nerve stimulation for trigeminal neuropathic pain. Pain Physician. 2012;15(1):27-33.
- Fontaine D, Bozzolo E, Chivoret N, et al. Salvage treatment of trigeminal neuralgia by occipital nerve stimulation. Cephalalgia. 2014;34(4):307-310.
- Klein J, Sandi-Gahun S, Schackert G, et al. Peripheral nerve field stimulation for trigeminal neuralgia, trigeminal neuropathic pain, and persistent idiopathic facial pain. Cephalalgia. 2016;36(5):445-453.
- Shaparin N, Gritsenko K, Garcia-Roves DF, et al. Peripheral neuromodulation for the treatment of refractory trigeminal neuralgia. Pain Res Manag. 2015;20(2):63-66.7.