Authors: Mehrotra S, Eli B.
Trigeminal Neuralgia Treatment with Peripheral Nerve Blocks. Pract Pain Manag. 2022 July/August;22(4).
A small pilot study demonstrated that weekly trigeminal nerve block injections offer a relatively low-risk option to supplement conventional treatments and should be considered before referring for neurosurgery or escalating medication doses.
Trigeminal neuralgia is a painful condition that presents as sharp, electric shock-like pain in the face along one or more distributions of the trigeminal nerve. Also known as tic-douloureux, trigeminal neuralgia is widely regarded as one of the most painful orofacial pain conditions and its treatment can be challenging.¹
Trigeminal Neuralgia and Traditional Treatment Approaches
Typically, anticonvulsant medications are the first line of treatment for trigeminal neuralgia; these drugs lower the threshold of action potential generation, thereby inhibiting pain signaling in the brain.²
Carbamazepine is considered the most effective anticonvulsant in trigeminal neuralgia but can come with adverse effects including aplastic anemia and Stevens-Johnson syndrome in genetically susceptible individuals. As a result, constant bloodwork is required to monitor blood cell counts while a patient is on this medication.
Oxcarbazepine is another commonly used anticonvulsant for this disorder with fewer overall adverse effects but may cause hyponatremia; thus, routine bloodwork is also required.
Gabapentin, pregabalin, and lamotrigine are additional lower-risk medication alternatives but still come with adverse effects including sedation and unsteadiness, which can be problematic in older adults. These side effects represent the most common cause for medication discontinuation, as opposed to medication inefficacy.³
Neurosurgical procedures may help certain individuals with trigeminal neuralgia. Microvascular decompression (MVD) – that is, separating the offending vessel from the trigeminal nerve – is typically considered when a brain MRI shows vascular compression of the trigeminal nerve. In many cases, there is no evidence of such vascular compression and so the patient is not considered a candidate for the procedure.
Other factors to consider when determining if surgery is necessary include the patient’s age and overall health status as there may be higher risk of serious complications. An elderly individual in poor health would not be an ideal candidate for neurosurgery versus a young, healthy adult. Age is an important factor to consider as trigeminal neuralgia most commonly presents in females over the age of 50.
MVD has the best long-term pain relief outcomes with lower risk of facial sensory loss versus other surgical options including but not limited to gamma knife and glycerol rhizotomy.⁴ Adverse effects from the latter procedures can include facial sensory loss and/or anesthesia dolorosa. These procedures typically work for a number of years but may need to be repeated after the effects wear off and pain returns.
An emerging treatment option for trigeminal neuralgia involves repeated local anesthetic peripheral nerve blocks to anesthetize the trigeminal nerve. These injections work much like dental injections that are performed intraorally to achieve anesthesia prior to dental treatment.
The goal of this treatment modality is to anesthetize the distribution of the patient’s pain repeatedly in order to calm the hyperactive nerve branch that is generating the ectopic discharges. Nerve impulse transmission occurs through the opening of voltage-gated sodium channels on the neuronal membrane and subsequent influx of sodium. This transmission causes membrane depolarization and propagation of the impulse. Local anesthetic blocks the sodium channel opening thereby preventing the sodium influx and depolarization.⁵ Thus, anesthetizing the affected trigeminal nerve branch with local anesthetic blocks can be an effective way to interfere with painful nerve impulse transmission. During the period of anesthesia, painful episodes associated with trigeminal neuralgia could be relieved or reduced.
A retrospective pilot study was performed using clinical data from patients that received peripheral trigeminal nerve blocks in a private orofacial pain practice in Encinitas, CA. We analyzed patient-reported pain levels and symptomatic relief obtained after completing a series of trigeminal nerve block injections in 5 females diagnosed with trigeminal neuralgia.
The patient ages ranged from 53 to 85 years with the average age being 74 years. All patients had tried pharmacological treatments and/or neurosurgical treatments prior to initiating the nerve block series. One patient had already undergone MVD and two rounds of gamma knife surgery to treat her trigeminal neuralgia prior to initiating the injection series and continued to suffer from frequent trigeminal neuralgia attacks. All patients were concurrently taking or had previously tried anticonvulsant medication for their pain.
The injections were administered along the distribution of patient’s pain as anterior superior alveolar, middle superior alveolar, posterior superior alveolar, inferior alveolar, long buccal, and/or mental nerve blocks. None of the patients in this study had pain in the V1 region so supraorbital nerve blocks were not utilized. The patients received the appropriate blocks based on the distribution of their facial pain.
Patients were surveyed at follow-up appointments by the same clinician and asked whether they felt that the blocks provided any long-term relief, and if so, for how long (in hours) and to what extent (in percentage of pain reduction experienced).
All five patients verbally reported that their trigeminal neuralgia symptoms were relieved to some degree after the injections. The average reported time of relief obtained from each injection was 49.2 hours, and the average reported amount of relief obtained from each injection was 77% (see Table I). In other words, patients reported on average 77% relief from trigeminal neuralgia symptoms for 49.2 hours after each weekly injection. Two of the five patients reported short-lived relief (2 to 4 hours) and three of the five patients reported relief that lasted several days. The median reported duration of relief was 72 hours.
|Patient||Age (years)||Location of Blocks||Duration of relief from each block||Percentage of reported relief after blocks|
|1||83||Right ASA, MSA, PSA||2 hours||90%|
|2||53||Right ASA, MSA, PSA, IAN, LB, mental||4 hours||80%|
|3||85||Left IAN, LB||72 hours||40%|
|4||65||Left ASA, MSA, PSA, IAN, LB, mental||72 hours||100%|
|5||84||Left ASA, MSA, PSA||96 hours||75%|
No major adverse reactions were reported or observed after the nerve blocks. Mild discomfort at the injection site and post-injection soreness was occasionally observed.
The data from this pilot study suggest that repeated peripheral trigeminal nerve blocks may be a treatment modality to consider when managing trigeminal neuralgia, especially in those who are older or have failed conventional treatment methods. Three of the five patients in the study experienced a more significant period of relief (days) versus two of the five patients who only experienced a few hours of relief.
Our pilot study also suggests that conventional trigeminal neuralgia treatments may be supplemented with these injections to improve outcomes. Peripheral nerve block injections may be helpful to reduce the effective doses of medications required for symptom control, which can help reduce the side effects experienced by patients. Alternatively, if medications are used in combination with these injections, second-line medications with fewer adverse effects may be suitable as opposed to first-line medications like carbamazepine and oxcarbazepine, which have higher side effect profiles.
Conventional treatments for trigeminal neuralgia, including neurosurgical microvascular decompression and anti-convulsant medication, have associated adverse effects and risks. Trigeminal nerve blocks offer a relatively low-risk treatment option to supplement these treatments or to consider before referring for neurosurgery or escalating medication doses.
Apart from mild discomfort associated with the injections, no major adverse events occurred in the authors pilot study of five individuals with trigeminal neuralgia.
Weekly injections offer rapid relief and may be helpful to supplement medications and allow lower doses to be effective. In addition, given the age of most people with trigeminal neuralgia, milder medications such as gabapentin may be used effectively in combination with these injections as opposed to first-line medications that have higher side effect profiles and require frequent bloodwork.
Another use for nerve blocks at the trigeminal nerve may be to prevent individuals from having to seek care at emergency rooms for painful attacks that are nonresponsive to medications. Within minutes of these injections, patients who presented with pain reported significant reduction in their symptoms. The average reported duration of relief was 49.2 hours but the median reported duration of relief was significantly greater at 72 hours.
Disclosures: The authors declare that they have no conflict of interest nor relevant financial or non-financial interests to disclose. Informed consent was obtained from all individual participants included in the study. No funding was received to assist with the preparation of this manuscript. This study was performed in line with the principles of the Declaration of Helsinki.
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