Effectiveness and safety profile of greater occipital nerve blockade in cluster headache: a systematic review

BACKGROUND: Greater occipital nerve (GON) blockade is a short-term preventive therapy for cluster headache (CH). We conducted a systematic review to evaluate the effectiveness and safety of GON blockade in patients with CH. METHODS: On 23 October 2020, we searched MEDLINE, Embase, Embase Classic, PsycINFO, CINAHL, CENTRAL and Web of Science databases from their inception date. Studies included participants with a CH diagnosis who received corticosteroid and local anaesthetic suboccipital region injections. Outcomes were change in the frequency/severity/duration of attacks; proportion of participants responding to treatment, time to attack freedom from an attack, change in attack bout length and/or the presence of adverse effects after GON blockade. Risk of bias was assessed with the Cochrane Risk of Bias V.2.0 (RoB2)/Risk of Bias in Non-randomized Studies - of Interventions (ROBINS- I) tools and a specific tool for case reports/series. RESULTS: Two RCTs, eight prospective and eight retrospective studies, and four case reports were included in the narrative synthesis. Every effectiveness study found a significant response in one or more of frequency/severity/duration of individual attacks or proportion of patients responding to treatment (47.8%-100.0%). There were five instances of potentially irreversible adverse effects. A higher injectate volume and use of concurrent prophylaxis may be associated with an increased likelihood of response. Methylprednisolone may have the best safety profile of available corticosteroids. DISCUSSION: GON blockade is safe and effective for CH prevention. Higher injectate volumes may improve likelihood of response, and the likelihood of serious adverse events may be reduced by using methylprednisolone. PROSPERO REGISTRATION NUMBER: CRD42020208435.