Patients presenting with a headache originating at the posterior skull base should be evaluated for ON. This condition typically presents as a paroxysmal, lancinating or stabbing pain lasting from seconds to minutes, and therefore a continuous, aching pain likely indicates a different diagnosis. ICHD-3 criteria require that the patient also have tenderness, dysesthesia, or allodynia over the area affected. A positive Tinel’s sign may be present over the distribution of the nerve, especially where the GON emerges at the base of the skull over the greater occipital notch. Pain may be unilateral or bilateral, but almost always begins unilateral and then may extend into a bilateral distribution over time. Bilateral symptoms are present in one-third of cases.[7]

After completing a focused history and physical examination, the diagnosis is confirmed by a local anesthetic blockade of the suspected nerve. This is a required step for diagnosis per ICHD-3 standards. The patient should have pain relief with the nerve block for at least the duration of the local anesthetic. Single diagnostic blocks carry false-positive rates up to 40%, so the performance of a second block is prudent. If both blocks are positive the provider may be more confident as to the correct diagnosis. As compression is thought to be the main etiology for ON, imaging should be considered if there is suspicion of a lesion or mass at the affected site. [3]

There are multiple treatment options for ON. The most conservative treatments, such as immobilization of the neck by the cervical collar, physiotherapy, and cryotherapy have not been shown to perform better than placebo.[7] Non-steroidal anti-inflammatory drugs, tricyclic antidepressants, serotonin-norepinephrine reuptake inhibitors, and anticonvulsants may help to alleviate symptoms. Following diagnostic nerve blocks, therapeutic blocks may be attempted. Typically, a steroid is added to the local anesthetic with variable results. Botulinum Toxin A injection has emerged as a treatment with a conceptually lower side effect profile than many other techniques described here, with most recent trials demonstrating 50% or more improvement.[4][7]

It remains a common practice to utilize a landmark-only approach when performing greater and lesser occipital nerve blocks. For blockade of both nerves, medication is infiltrated along the nuchal ridge. This technique, while easy to perform and relatively safe if done correctly, may not be particularly accurate and as a result, could theoretically increase the risk of a false-positive result. To improve accuracy, ultrasound-guided techniques were developed. The original ultrasound-guided technique for injection of the GON (utilized routinely by this article's editor for diagnostic injection and for cryoablation) was described by Greher et al in 2010; it targets the nerve as it courses superficial to the obliquus capitis inferior muscle at the C1-C2 level.[8]

There are several advanced interventional procedures in clinical use.

• Pulsed or thermal radiofrequency ablation (RFA) may be considered for longer-lasting relief after a local anesthetic blockade confirms the diagnosis. Thermal RFA aimed at destroying the nerve architecture can render long-term analgesia but also comes with the potential risks of hypesthesia, dysesthesia, anesthesia dolorosa, and painful neuroma formation. Chemical neurolysis with alcohol or phenol carries the same risks as thermal RFA.[8][5] There is no such risk with pulsed RF, however, some question its efficacy as compared to other procedures.
• Neuromodulation of the occipital nerve(s) involves the placement of nerve stimulator leads in a horizontal or oblique orientation at the base of the skull across where the greater occipital nerve emerges. Patients should be trialed with temporary leads first, and greater than 50% pain relief for several days is considered a successful trial after which permanent implantation may be considered. Risks include surgical site infection and lead or generator displacement or fracture after the operation.[4][5]
• Ultrasound-guided percutaneous cryoablation of the GON is commonly performed by the article’s editor. At the correct temperature, there should be stunning but not permanent damage of the nerve, but at temperatures below negative 70 degrees Celsius, nerve injury is possible. Most recently in the literature, a 2018 article by Kastler et al. described 7 patients who underwent cryoneurolysis in a non-blinded fashion to good effect, but the follow-up was limited to 3 months.[9] This editor has seen between 3 months to 1.5 years of benefit (typically around 6 months) with each treatment. 
• Surgical decompression is often considered to be the last resort. In one study of 11 patients, only two patients did not experience significant pain relief postoperatively and mean pain episodes per month decreased from 17.1 to 4.1, with mean pain intensity scores also decreasing from 7.18 to 1.73.[6] Resection of part of the obliquus capitis inferior muscle has shown success in patients who have an exacerbation of their pain with flexion of the cervical spine.[4] Another popular surgical technique is C2 gangliotomy, even though patients are left with several days of intermittent nausea and dizziness.[7] As with any large nerve resection, there is a theoretical risk of developing a deafferentation syndrome, though arguably the risk is lower if the resection is pre-ganglionic.

The differential diagnosis for ON includes any disorder which similarly presents with a headache or facial pain. Because connections are possible between the occipital nerves and cranial nerves VIII, IX, and X, patients can sometimes present with confusing symptoms, such as vision impairment, dizziness, or sinus congestion.[4] The conditions most easily mistaken with ON for other headache and facial pain disorders include migraine, cluster headache, tension headache, and hemicrania continua. Mechanical neck pain from an upper disc, facet, or musculoligamentous sources may refer to the occiput, but is not classically lancinating or otherwise neuropathic and should not be confused with ON. A crucial step in differentiating ON from other disorders is relief with an occipital nerve block. 

A short term relief is common with basic interventional treatments.  Rarely, diagnostic injections of local anesthetic with or without steroids can yield up to several months of analgesia.[4] Advanced treatments mentioned above may result in improvements ranging from weeks to years.

Complications from procedures have been reported in the literature. In a case series reviewing over a hundred thermal RFA procedures, one patient developed intraventricular hemorrhage and died after the case, which the authors attribute to hypertension during the procedure.[7] The same paper reported a patient who developed Brown-Sequard syndrome from post-traumatic cervical syringomyelia, also after RFA.

As with all medical diagnoses, diagnostic tests, medication trials, and interventional treatments, patients should have the condition explained to them in a manner they understand based on their education level and background. It is important to consider important aspects of the patient’s lifestyle, and how the condition and any proposed treatment may affect them. The risks, benefits, and alternatives of any medication trial or procedure should be conveyed, and a shared medical decision-making model should be utilized with the patient.

It is natural to expect that as a patient progresses through various stages of treatment, several providers will be involved, such as primary care physicians and physician-extenders, neurologists, pain management physicians, and neurosurgeons, all operating as a cohesive interprofessional team. Pain psychologists are regularly utilized to assess any psychosocial barriers to improvement (as with any chronic pain condition), evaluate whether patients are suitable candidates for the more invasive procedures, and help guide patients through emotional aspects affecting care. Physical therapists or chiropractors may be utilized if there is a movement component associated with pain, and they can also address detrimental movement patterns that exacerbate the pain state. During interventional procedures, having a competent operating room staff including operating room nursing staff leads to better outcomes and can confer a comforting experience to the patient. With these interprofessional methods, open communication and data sharing, and coordinated effort between various disciplines, patients will experience improved outcomes. [Level 5]