A Study Investigating the Efficacy of GON Blocks.

Chronic migraine is characterised by frequency of headache ≥ 15 days per month for more than 3 months. The location can be unilateral or bilateral. Usually described as pulsating in nature, it may be aggravated by, or cause avoidance of, routine activities of daily living. There can be associated light and noise sensitivity. Greater occipital nerve (GON) blockade with local anaesthetics and steroids has been used as a preventative strategy for a range of headaches including, migraine, cluster headache and hemicrania continua. The occipital nerves have a sensory distribution in the occipital area. The greater occipital nerve derives most of its fibres from the C2 dorsal root \[6\]. It passes over the superior nuchal line, mid-way between the mastoid process and the occipital protuberance, just lateral to the insertion of the nuchal ligaments. The lesser occipital nerve passes lateral to the greater occipital nerve, over the nuchal ridge. Although the exact mechanism of action remains unclear, injection of steroid in the vicinity of GON nerve can have both a local effect (decreasing nociception) and a delayed central nociceptive response, possibly through an action on trigeminocervical relay Although GON block is carried out extensively in the prophylaxis of chronic migraine, the evidence remains equivocal. In the UK, the National Institute for Clinical Excellence have yet to include GON blocks in their guidance and protocols on the treatment of both chronic headache and migraine. This randomised, single-blinded, placebo-controlled multicentre cross-over study intends to assess the efficacy, safety and tolerability of greater occipital nerve block with local anaesthetic and steroid in patients with chronic migraine with the primary objective to investigate any improvement in disability associated with chronic migraine disorder. We also intend to identify any economic outcomes associated with these injections in the management of chronic migraine. GON block with local anaesthetic and steroid for chronic migraine and the placebo procedure will be performed in the outpatient setting. They will be carried out only by appropriately qualified members of the research team adhering to strict aseptic conditions and following standard operating protocols with regards to admission and discharge criteria in the outpatient settings. GON block is routinely carried out in the UK and poses minimal risks to the patient. Although GON block is carried out extensively in prophylaxis of chronic migraine, the evidence remains equivocal. In the UK, the National Institute for Health and Care Excellence (NICE) have yet to include GON blocks in their guidance and protocols on the treatment of both chronic headache and migraine. The aim of this study is to assess the efficacy, safety and tolerability of greater occipital nerve block with local anaesthetic and steroid in patients with chronic migraine of more than three months' duration.