Nerve Blocks for Headaches
Joshua Tobin, MD
- A nerve block is an injection onto or near a nerve. It involves use of a syringe, a small needle, and medication to decrease or stop passage of nerve impulses.
- Nerve blocks are a unique treatment for controlling headaches.
- Most nerve blocks for headaches are done in the back of the head over the occipital bone and nerve. Any nerve on the scalp can be injected.
- Predicting who will respond to a nerve block is tricky.
- The medications injected include a local anesthetic and less often also a steroid.
- Nerve blocks are generally benign, but there can be side effects.
Nerve blocks fill a unique role in headache medicine.
A nerve block is the injection of medication onto or near a nerve. With certain methods used in occipital nerve blocks, only muscle may be injected. The purpose is to decrease the amount of information that the nerve passes from another nerve, muscle, ligament, bone or skin receptor into the central nervous system. To understand the unique role that nerve blocks fill in headache medicine, one must first understand the difference between “abortive” and “preventive” or “prophylactic” headache therapies. Abortive therapy is a treatment for a single headache. The intent is to make that particular headache go away now. It is not expected to do anything for the next headache. Overuse of abortive agents can actually lead to more and more headaches. Acetaminophen (Tylenol), ibuprofen (Motrin), and Excedrin Migraine are examples of abortive therapies. Preventive drug therapy is a medication taken daily to decrease headaches over time. Benefit usually takes several weeks to months. For example, a patient might hope of going a week between headaches instead of going two days between headaches. Nortriptyline (Pamelor), propranolol (Inderal) and topiramate (Topamax) are examples of preventive therapies.
Nerve blocks can be used to stop or abort a headache. Their effects, however, usually last longer than for a single headache. As a result, they are more than a simple abortive therapy. A typical duration of effect varies. Unlucky patients derive no pain benefit, but more commonly, headache relief lasts for days to weeks after the nerve block. However, the only way to use nerve blocks as a preventive therapy is to repeat them every 4 – 6 weeks. Most patients prefer not to do so.
Nerve blocks therefore fill a unique role in headache medicine. They are neither simple abortive, nor common preventative. They are commonly used as transitional therapy. This term means that they are used during the several weeks to months after starting a preventive agent, but before the preventive agent starts to work. They are also sometimes used as “rescue” therapy when a patient’s usual abortive(s) don’t work.
Most but not all nerve blocks performed are regional occipital nerve blocks.
The most common nerve block for headache is the regional occipital nerve block (ONB). The occipital bone forms the back of the head. The occipital nerves arise from the upper neck and provide sensation to the back of the head. The exact site of injection varies from injector to injector. The general area is where the back of the head meets the back of the neck.
Almost any other nerve in the head that is close to the skin can also be injected. For example, the supraorbital nerve provides sensation to the forehead and top of the head. This nerve exits the skull just above the eyes. The injection site for the supraorbital nerve is generally in the forehead, at the eyebrow.
Predicting who will benefit from a nerve block can be difficult.
Occipital nerve blocks seem not to work for several primary headache disorders. Several published articles report poor results for tension headaches, paroxysmal hemicrania, and hemicrania continua. Yet, even the hemicrania disorders may respond. Providers frequently perform nerve blocks for the following conditions:
- Cluster headaches often appear as very severe stabbing poker-like pain in or around one eye. It lasts 15 minutes to 3 hours. These short lasting headaches typically occur 1-2 times per day for 4-6 weeks. The pain tends to make the sufferer move or bang their head. Occipital nerve blocks with lidocaine and steroids are proven to be effective for cluster headaches.
- Cervicogenic headache or cervical headache can be defined as one sided head pain that is triggered by neck movement or pressure on an occipital nerve. True cervicogenic headache is highly associated with trauma to the neck/head. Chronic migraine often mimics this disorder (see next). Additional supportive findings are reduced neck range of motion or sensory changes in the back of the head. Occipital nerve blocks are proven to be effective for cervicogenic headaches, provided they are defined this way. However, response to occipital nerve block does not define the pain as cervical in origin.
- Cervicogenic chronic migraine is a type of chronic migraine with attacks of pain starting in the neck. Pain responded to either one or both sided ONBs in a recently reported study. Migraine, an especially common type of headache, usually appears as a moderate or severe pain on one side of the head. It usually is throbbing, lasts hours to days, and is worse with physical activity. Nausea, vomiting, or light and noise sensitivity may accompany migraine. While there is no definite proof that nerve blocks work for migraines, injectors frequently perform nerve blocks for migraine sufferers, because the blocks frequently work. Studies suggest that the occipital nerve must be tender to touch for the blocks to work.
- Post spinal tap headache goes by several names. These include post lumbar puncture headache or post-dural puncture headache. Post spinal tap headache is caused by puncturing the sac surrounding the brain and spinal cord during lumbar punctures or spinal anesthesia. Fluid leaking from the sac around the brain and spinal cord causes the headache. While not standard care, several authors reported occipital nerve blocks to be effective.
- Headache from overuse of abortive therapy is another possible use for nerve blocks. This use is unproven at this time. The hope is to decrease the pain associated with analgesic withdrawal.
- Occipital neuralgia manifests as stabbing pains in the back of the head. Compared to the prior disorders, it is quite a rare diagnosis. By definition, it responds to occipital nerve blocks. Other problems can produce the same symptoms, however, such as arthritis in the upper neck and the prior disorders.
- Many headaches do not fit into any one particular headache syndrome. Under these conditions, injectors use other features to predict who will respond. These characteristics include: tenderness to palpation of the nerve
- reproduction of headache pain with palpation of the nervepain in the distribution of the nerve
- allodynia, pain from non painful triggers such as light touch
- prior injection response
- neck pain or neck muscle spasms (for occipital nerve blocks)
Unfortunately, none of these typical features have been studied in well designed clinical trials, but in the absence of good clinical data, providers use these features.
Performing the nerve block
Injectors have yet to agree on the best way to do a nerve block. Injection methods vary from provider to provider. Methods vary. Differences exist for the exact place to inject and medication to use. All injectors use a local anesthetic. This is given alone or with a locally acting corticosteroid. Local anesthetics are numbing medications that deaden the skin. They also decrease nerve impulses passing along pain nerves. You may have had a local anesthetic injected for dental work in the past. Lidocaine and bupivicaine are two common local anesthetics used for headaches. Corticosteroids are strong anti-inflammatory medications which differ from NSAIDs (nonsteroidal anti-inflammatories). Examples include methylprednisolone, triamcinolone, and dexamethasone. Locally acting forms of these corticosteroids are used for nerve blocks. Many providers believe that the local anesthetic produces the rapid onset of headache relief, like an abortive agent, and that the locally acting steroid produces the preventive like action of up to 6 weeks.
One clinical trial of occipital nerve blocks for a severe form of migraine called transformed migraine reported no significant differences in results with or without a low potency locally acting corticosteroid. Whether this finding means that locally acting corticosteroids don’t really work is unclear however. Current studies only prove benefit for cluster headache patients.
Finally, there is some evidence suggesting that when nerve blocks are repeated over and over, each nerve block works better than the previous nerve block, raising the possibility that enough nerve blocks could cure some headaches or produce a more prolonged preventive effect.
Nerve blocks do have side effects, but they are few and generally mild.
Locally-acting steroids rarely cause undesirable cosmetic side effects such as nearby hair loss, loss of underlying fat, and loss of local skin color. In addition, frequent use may suppress the immune system and steroids might cause local infections known as abscesses. Therefore, given these side effects, many injectors prefer not to use steroids repeatedly or when injecting nerves on the face. Epinephrine is typically avoided. It is a drug used to limit bleeding by reducing blood flow in the artery. When used serious skin injury (death of the skin at the site of injection) may occur. The most common side effects of a nerve block include:
- Injection site soreness, which may last for a few days, and is probably an effect of the steroid.
- Numbness, which is a sign that the local anesthetic is working.
- Dizziness, if it occurs, it is usually mild.
Skull defects and prior brain surgeries present one serious risk for patients. Any injection through the defect into the nervous system can cause loss of consciousness for days. Inform your provider of any changes to your head from injury or surgery. Remind your provider of your skull defect at the time of any injection to ensure the best injection planning.
If you have cluster headaches, cervicogenic headaches, occipital neuralgia (rare) or a very tender occipital area consider a nerve block. If you have intractable migraines, consider a nerve block but find out if at least one of your occipital nerves is tender to touch. Find out if your insurance covers the nerve block beforehand, and if your insurance refuses to pay after it is done, whether you will be responsible for paying the bill. Think of questions and offer your worries and concerns. Expect empathy for your worries and clear answers to your concerns. If not given, either decline the blocks, or request referral to another injector. Make any allergies clear to the injector. Finally, let your injector know the results, both the good and the bad, at the follow up visit. If well tolerated and effective, a series of injections may provide further benefit.
Joshua Tobin, MD; 21st Century Neurology, Phoenix, AZ.