Ultrasound Greater Occipital Nerve Block at C2 Level Compared to Landmark-based Greater Occipital Nerve Block

Hypothesis: A novel ultrasound-guided greater occipital nerve (GON) block at the level of C2 will result in significantly lower pain scores after 4 weeks when compared with a traditional landmark-guided approach at the superior nuchal line.

The greater occipital nerve (GON) has been implicated in several conditions that prompt referral to pain medicine specialists, including occipital neuralgia and cervicogenic headache. According to the International Headache Society, a local anesthetic block of the GON can aid in the diagnosis and treatment of occipital neuralgia. Many practitioners perform GON injections using a conventional approach, relying solely on superficial bone-based anatomic landmarks to infiltrate local anesthetic and corticosteroid around the nerve at the level of the superior nuchal line. The ambiguity of these injections poses a risk of anesthetizing adjacent structures or injecting into vessels, such as the occipital artery.

In an attempt to mitigate these risks and improve the efficacy of GON injections, ultrasound has been increasingly utilized. Multiple studies have demonstrated successful ultrasound-guided GON blockade at the superior nuchal line and improvement in pain scores compared to non-guided injections. The investigators' preliminary data confirms the feasibility, efficacy, and safety of an ultrasound-guided GON block technique at the level of C2, but it is not yet known whether this technique provides greater pain relief and functional outcomes compared to traditional injections.

Inclusion criteria

• Unilateral or bilateral headache symptoms attributed to occipital neuralgia or cervicogenic headache as defined by the International Headache Society's International Classification of Headache Disorders (3rd edition beta version)
• Age 18 years and older (no upper age limit defined)
• Imaging of cervical spine within last year (either x-ray, MRI or CT)

Exclusion criteria

• History of cervical spine surgery, trauma, or surgical procedure involving head or neck during the last year
• Use of new preventative medications 1 month prior or during study enrollment
• Evidence of impaired sensation in the GON dermatome region (posterior scalp to the vertex of the cranium) from neurological, dermatological, or other disease process
• Evidence of cranial defect or other anatomical abnormality near the target injection site
• History of bleeding diathesis, coagulopathy, or current use of anticoagulant medications
• Pregnancy
• History of adverse reaction or allergy to local anesthetic agents or corticosteroids
• Occipital nerve block within the past three months.
• Unavailability for appropriate follow-up throughout the whole duration of study