2.3 Occipital Neuralgia
By Konstantin V. Slavin, MD, FAANS (USA)
It is common in a facial pain practice or headache clinic to hear from patients about pain in their face and head that originates, focuses or culminates in the back of the head, the region that is called occiput. A patient’s description of the pain location may — and usually does — help in making correct diagnosis, as most nerves in the head and neck region cover extremely specific anatomical distributions. The trigeminal nerve, for example, is the main provider of sensation to the entire half of one’s face. Similarly, the sensation in the region behind the ear and above the hairline in the back of one’s head is supplied by a specific group of nerves: the occipital nerves. There are three occipital nerves on each side, namely, the greater, the lesser, and the third occipital nerves, and all of them originate from the upper cervical spinal nerve roots, mainly from the second and third cervical levels (C2 and C3). (See Figure 2-3.)
Figure 2-3. The occipital nerves.
As the sensory information from the occiput is carried by the occipital nerves to the central nervous system (CNS), it travels through sensory ganglia and nerve roots and then enters the spinal cord in the upper part of the neck. There, it is processed in the same area as is involved with sensation from the face and the rest of the head, the so-called trigeminocervical complex. These intricate connections explain the frequent overlap of occipital pain with various migraine and headache conditions, as well as some instances of occipital pain radiating into the forehead or being aggravated by facial pain.
It is important to notice, however, that, among many painful conditions that involve the occipital region, true occipital neuralgia (the subject of this section) presents a specific pain syndrome that can be successfully treated in most patients, as long as it is accurately diagnosed and addressed.
So, what is occipital neuralgia (ON)? It is a relatively rare condition that manifests itself with pain on one or both sides of the head (unilateral ON is seen in 85% of cases). The pain usually starts in the occiput and travels toward the parietal region all the way to the vertex.
Editor’s Note: The parietal region of the scalp curves over the sides of the head, starting from the top and extending toward the ears. It contributes to the overall volume and shape of one’s hairstyle. The vertex (or cranial vertex) is the highest point of the head, formed by four bones of the skull: the frontal bone, the two parietal bones, and the occipital bone. It is an area prone to hair loss.
ON is described as shooting, electric-shock-like, or stabbing in nature; in medical terminology, this is referred to as paroxysmal, lancinating pain. Very often, there is also a dull aching pain between the shooting attacks located in the same general area. The duration of attacks lasting from a few seconds to minutes, the severe intensity of pain, the presence of either tenderness over the course of the occipital nerves or trigger points within the occipital area, and pain or discomfort observed with innocuous stimulation of the scalp or hair are all characteristic features of ON. Another classical feature that assists in making a proper diagnosis is the improvement or disappearance of pain in response to numbing of the nerve with an injection of local anesthetic in the vicinity of the nerve in question (nerve block). Such blocks are used to both diagnose and treat ON, as the pain relief from a single injection may last for quite a long time. For an ON diagnosis to be made, the patient should be asked or tested for all of the mentioned features, keeping in mind that other conditions that present with pain in the occipital region (migraines, cluster headaches and hemicranias, tension headaches, cervicogenic headaches that arise from dysfunction of the joints within the spinal column and neighboring cervical muscles, etc.) must first be ruled out.
Very frequently, to rule out associated anatomical pathology, it is necessary to perform appropriate imaging of the head and neck; this would usually include MRI of the brain and the cervical spine. The imaging would allow detection of Chiari malformations, cervical spondylosis, and vascular and neoplastic conditions; in most ON cases, the MRI studies are read as normal or almost normal.
Interestingly enough, the exact source of pain in ON remains unknown; it is commonly accepted as a neuropathic pain condition, meaning that the underlying process is the malfunction of the nervous system. The occipital nerves, the culprit of ON, appear to be hyperactive and irritated, but the reason for this irritation is often unclear. Multiple existing theories postulate compression or entrapment of the nerve or nerves anywhere along their course in the patient’s neck and head, but there is no consensus or universally accepted understanding of the underlying pathology.
As with all chronic pain syndromes, the treatment of ON is administered in systematic fashion, starting from conservative measures, medications, and interventions, perhaps ultimately leading to surgery. As the natural course of ON may be self-limiting and the pain may improve over time, it may be prudent to avoid risky interventions early in the course of the disease, but medically refractory cases are often considered for invasive treatments as the pain may become disabling, thus making risks of interventional or surgical treatment justified.
Common initial treatments include the application of cold and warm packs, massage, and physical therapy; rest may also frequently reduce the pain. Among available medications, initial preference is given to conventional anti-inflammatory drugs and muscle relaxants; the next level of treatment would include anticonvulsants and antidepressants commonly used for neuropathic pain conditions, including gabapentin, amitriptyline, pregabalin, carbamazepine, and nortriptyline. Although useful in relieving the pain, opioid medications are to be avoided in ON and other neuropathic pain conditions.
Nerve blocks are considered next, and here, one may use the block or blocks for both diagnostic and therapeutic purposes. Nerve blocks may include both short- and long-lasting local anesthetics; the medications are injected in the vicinity of each suspected nerve, and as a result of injection, the territory that the nerve supplies becomes temporarily numb. Along with numbness, patients experience improvement or complete relief of their ON pain, but the duration of this relief tends to be longer than the duration of the numbness, and sometimes, the pain relief may turn out to be long-lasting or even permanent. This course of events, however, is observed in only a small fraction of ON patients, and therefore, the nerve blocks have to be repeated, usually with the addition of corticosteroids to the local anesthetics, adding an anti-inflammatory effect to the anesthesia.
Other interventional (nonsurgical) ON treatment options include injections of botulinum toxin, pulsed radio-frequency treatments, and short-term electrical nerve stimulation (called percutaneous electrical nerve stimulation or PENS). Each of these interventional modalities is able to provide a significant reduction in pain intensity in a majority of ON patients, but the longevity of improvement varies from person to person and permanent pain relief is rarely seen.
Surgery is reserved for the most refractory patients who fail to respond to nonsurgical treatments and those with intolerable pain who experience pain recurrence after the use of less invasive approaches. Although many specific surgical procedures are available for individuals with ON, these treatments are divided into three main groups: decompression, neurodestruction, and neuromodulation.
Decompression surgery is based on the presumption that the pain arises from the compression of the occipital nerve(s) along their course through the muscles and fascial layers, with additional aggravation from neighboring arteries that are expected to travel next to the nerves. During surgery, the nerves are released at one or several points, usually by cutting the adjacent muscle and fascia, and the additional compression points from the vessels are protected by physical separation of neural and vascular structures. In case of unsuccessful decompression or the recurrence of pain due to scar formation, there is an option to interrupt the transmission of painful signals or remove the hyperactive neural structures. This is accomplished by destructive interventions including neurectomy or neurotomy, ganglionectomy, and rhizotomy, which are aimed at the nerves, spinal ganglia, and spinal nerve roots, respectively. All of these interventions are considered established treatment options for ON, but all patients are expected to discuss with their surgeons the associated risks of complications and possibility of improvement, as well as contingency plans in cases of insufficient pain relief or pain recurrence.
A quite different approach in the treatment of ON is based on pain suppression with electrical stimulation that is delivered by an implanted device. This technique, called occipital nerve stimulation (ONS), was developed in the 1970s and perfected to its current shape in the late 1990s. It is now considered a standard approach to the treatment of medically refractory ON pain. Several years ago, practice guidelines backed by a national neurosurgical society (the Congress of Neurological Surgeons) recommended ONS for ON patients based on evidence gathered through multiple peer-reviewed publications. Nevertheless, ONS remains one of those procedures that require a complicated approval process from most insurance companies.
The surgery for ONS includes implantation of one or two electrodes in the immediate vicinity of the nerve so that the electrical pulses can reach the nerve when the device is activated. During the initial testing period (the trial), the electrodes are connected to an external device to check for the degree of improvement and presence of any side effects; these temporary (externalized) electrodes are usually removed at the end of the trial. Later on, the implantation of the permanent device involves insertion of both the electrodes and an internal pulse generator that serves as the power source and “brain” of the ONS system. The devices available for ONS today allow patients to turn stimulation on and off, make it stronger and weaker, adjust settings, and switch between different programs based on the pattern and severity of their pain, and all of this is done with an external “remote control” that communicates with the implanted generator using telemetry. Among multiple generators and systems available for ONS today are some devices that are rechargeable and can last, with proper recharging, up to 15 years. Figure 2-4 presents an intraoperative anterior–posterior skull X-ray showing placement of a stimulating electrode across the occipital nerves at the base of the skull.
Figure 2-4. Intraoperative anterior–posterior skull X-ray showing placement of a stimulating electrode across the occipital nerves at the base of the skull.
No surgical treatment of ON is perfect—each modality has its own set of risks and limitations—but with proper diagnostic evaluation and clear expectations of treatment, it is possible to achieve lasting pain relief. Therefore, a diagnosis of ON should not be considered a lifelong burden but rather a treatable condition that can be improved and potentially cured as long as there is a well-informed patient and a team of experienced and enthusiastic physicians and surgeons.
Editor’s Note: If a diagnostic block is consistent with ON and medications have either failed or initially succeeded but now cause intolerable side effects, then the least invasive surgical option is neuromodulation. Because it makes use of equipment that is approved for human implantation, but not specifically for ON, insurance companies are required to consider it “experimental” and deny coverage. Ideally, your neurosurgeon should provide a well-reasoned explanation during the appeal process for their proposed trial of its effectiveness to be followed by an evaluation of that trial’s benefit and the need to proceed to a more permanent implantation. Depending on the insurance contract, there may be several layers of appeal, even to an independent entity. Success of the appeals process will need the involvement of you, the patient, to tell your story.
