Nerve blocks can be administered with a syringe and needle that are utilized to inject nerves on the outside of the skull (peripheral nerve blocks), OR with a soft, minimally invasive catheter that delivers numbing medicine to a targeted bundle of nerves via the nasal passages (sphenopalatine ganglion blocks).
A nerve block refers to the injection of a local anesthetic (numbing) medication and sometimes a steroid onto or near a nerve for the purpose of decreasing pain transmission. You may have had a local anesthetic injected for dental work in the past. Local anesthetics, lidocaine and bupivacaine (Marcaine), are numbing agents used to deaden the skin (or scalp).
Corticosteroids are strong anti-inflammatory medications. Locally acting forms of corticosteroids include methylprednisolone, triamcinolone, and dexamethasone. The goal of (temporarily) numbing the nerves in the periphery (outside the skull on the skin/scalp), is to decrease the amount of information (or pain signaling) that those nerves send into the central nervous system.
Pain relief can occur with startling rapidity, frequently within 15 minutes of the procedure. For those who experience relief, the duration of the therapeutic response can vary from day or so up to weeks... even months. Nerve blocks are generally safe (benign), but there can be side effects.
To understand the role of nerve blocks in headache medicine, it is important to understand certain classifications of headache treatment.
Headache medicine is divided into two different categories. Abortive therapy refers to treatments (medications or devices) used at the onset of a headache stop the progression of the headache and return the patient to a fully functioning pain-free state hopefully within minutes to a few hours. These are considered acute treatment options and are also referred to as attack medications. These include over-the-counter and prescription medications such as Tylenol, Excedrin, Advil, and a class of drugs specifically designed to treat migraine attacks called triptans. Triptans are considered the gold standard treatment for migraine attacks. However, not all people can tolerate triptans and some people have contraindications to many attack medications. Overuse of abortive agents can actually lead to more frequent headaches and headaches that are refractory (or resistant) to treatment.
Conversely, preventive therapy refers to treatments (medications and devices) that are used to decrease the frequency of headaches over time. Most preventive (also called prophylactic) drugs are taken by mouth daily. Examples include topiramate, amitriptyline, and propranolol. Botox (registered trademark symbol here R with circle) is approved for chronic migraine prevention, and the procedure includes 31 subcutaneous injections in the head, neck and face administered quarterly. A new class of preventive drug therapy will be commercially available in spring of 2018 that will be delivered by a monthly or quarterly injection or IV. Effective preventive therapy not only reduces the number of days per month with headache, but may also decrease the severity of the headaches that still occur, minimize disability from headaches, and make abortive treatments work more consistently. Maximum benefits of preventive therapy usually take several weeks to months to achieve success.
The effects of nerve blocks frequently last longer than the effects of the numbing medicine itself and longer than a single refractory headache attack, and thus nerve blocks can act as a preventive therapy. Responses to nerve blocks varies. Some unlucky patients receive no pain benefit. However, more commonly, headache relief lasts days to weeks after the procedure. This is remarkable considering that the numbing medicine typically wears off within 7 hours or less. Many patients with a positive response repeat them every 4-6 weeks as a preventive therapy. Response duration is variable among headache patients.
Nerve blocks therefore fill a unique role in headache medicine as they can be use as both abortive treatment and preventive therapy.
When traditional abortive treatment plans fail, nerve blocks may be utilized by headache specialists as "rescue" therapy. This is very useful in keeping patients out of Emergency Departments, avoiding unnecessary hospitalization for intractable headaches, and also keeps patients off of harmful opioids and barbiturates that often cause tachyphylaxis resulting in more frequent and refractory headaches, more disability and often addiction and dependency.
Headache medicine experts commonly use nerve blocks as "transitional" therapy or "bridge" therapy. Meaning, while weaning off an offending attack agent that may be causing medication-overuse-headache and/or while initiating a preventive therapy, nerve blocks are utilized to assist with pain during the transition. Nerve blocks are frequently used in between Botox treatments while the effectiveness of the treatments may be wearing off. Due to restrictions on the FDA-approved treatment protocol, Botox injection treatments must not be repeated until 12 weeks have passed since the last dose.
Nerve blocks for headaches are injected in the back of the head over the occipital nerves on each side, on the sides of the head over the auriculotemporal nerves which innervate the temples and face, and in the front of the head above the eyes where the supraorbital nerves and the supratrochlear nerves exit the skull. The occipital nerve arises from the upper neck (C-2) and provides sensation to the back of the head. The auriculotemporal nerve innervates the lower half of the face, the ear and the temple. The supraorbital nerve and the supratrochlear nerve innervate the forehead and the top of the head.
Trigger point injections over the cervical and trapezius muscles are also utilized in headache treatment since so many patients with headache report associated neck pain with their headaches.
This is due to the role of the trigeminocervical complex (see Medscape article), which is activated in migraine.
Many providers mistakenly believe that neck pain associated with headaches, or that headaches that start in the neck before moving to the front or activating a headache, are due to an organic injury or problem with the cervical spine and muscles. This misdiagnosis of cervicogenic headache (sometimes referred to as occipital neuralgia) has been debunked by scientists that study the pathophysiology of migraine in animal models and humans.
Predicting who will benefit from nerve blocks can be difficult.
Cluster headaches are the only headache disorders that benefit from the addition of corticosteroid with lidocaine (short-acting anesthetic agent) or bupivacaine (longer-acting anesthetic agent). Occipital nerve blocks with corticosteroids have proven efficacy in the treatment of cluster headache. Corticosteroids should never be injected into any other nerve than the occipital nerve when treating headache disorders.
Other primary headache disorders, categorized as trigeminal autonomic cephalalgias (TACs), may see a treatment benefit from nerve blocks, utilized as an abortive, transitional, or prophylactic treatment. Nerve blocks with lidocaine and/or bupivacaine are most often used in the treatment of episodic or chronic migraine.
Migraine is the most common primary headache disorder, and it effects over 37 million people in the US. True cervicogenic headache is highly associated with trauma to the head and/or neck including whiplash injuries. Chronic migraine, as mentioned before, often mimics this disorder.
Cervicogenic headaches, post-traumatic headaches, occipital neuralgia, neck pain with or without neck spasm may all benefit with nerve blocks administered by a trained headache specialist. People with reproducible pain with palpation over a nerve in the scalp and those with cutaneous allodynia are also possible responders to nerve blocks.
Pregnant women with refractory headache disorders that are limited in safe medication options often elect to get nerve blocks to prevent pain and disability associated with headaches using lidocaine which is a pregnancy category B drug (relatively safe during pregnancy).
Nerve blocks are considered a generally safe procedure. They are performed in the clinic without the need for fluoroscopy or EMG guidance. The procedure only takes about 5-15 minutes. Following the procedure, the patient is observed for approximately 30 minutes.
Most patients are able to ambulate without assistance and drive following nerve blocks. Many are eager to return directly to work because they are fully functioning without disability. This increase in productivity improves the patient's quality of life greatly. Side effects are generally mild and resolve within hours.
Common side effects include injection site soreness (which may last a few days), numbness (an anticipated sign that the local anesthetic is working) and dizziness. This typically resolves after several minutes to an hour and is usually mild. Eyelid drooping may occur with auriculotemporal blocks and is also transient and mild. Locally-acting steroids rarely cause undesirable cosmetic side effects such as hair loss and loss of underlying fat and loss of skin color at the site of the injection.
In addition, steroids may suppress the immune system and can cause local infections know as abscesses. This is why steroids are avoided by most headache specialists except in the rare circumstance of cluster headaches and only in the back of the head over the occipital nerve. Epinephrine (a common lidocaine additive) is typically avoided, as is it reduces blood flow and can cause serious skin injury (death of skin at the site).
Less common and more serious adverse events include fainting spells that mimic seizure activity. This can happen to anyone stuck with a needle for any procedure (such as venipuncture) even when lying down and looking away from the needle. Transient difficulty speaking or swallowing has also been reported (resolves within hours).
- If you have any skull defects, prior brain surgeries, shunt placements or permanent nerve stimulators, please make sure your provider is aware.
- If you have had a bad experience with nerve blocks in the past, make sure you let this be known to your headache specialist.
- If you have a tendency to pass out or lose consciousness with any procedure involving a needle, please tell the provider and staff. All known drug allergies should be listed on the consent form.
- Do not sign any consent form for nerve blocks for headache unless all your questions and concerns have been answered and addressed.
- If you are nervous about the procedure and your possible reaction, it is a good idea to have a friend or family member present to drive you home after the procedure.
- Find out if your insurance covers nerve blocks beforehand, and what amount you will be responsible for paying if your insurance refuses to pay for the procedure.
- You have the right to decline consent for any procedure.
- The best providers for headache procedures are headache specialists. Headache specialists are trained in headache medicine perpetually by the scientific journal articles published by American Headache Society and by educational conferences and workshops sponsored by the American Headache Society and the National Headache Foundation. Pain management providers, general neurologists and primary care providers that are not dedicated headache specialists and that are not active members of these organizations do not have the same training that headache specialists receive.
- Lastly, keep a good headache diary or journal after the procedure to document any and all benefits noted from the nerve blocks. Schedule a follow-up appointment in 4-6 weeks to review the results with your headache specialist.