Neurophysiological correlates of clinical improvement after greater occipital nerve (GON) block in chronic migraine: relevance for chronic migraine pathophysiology

Abstract

BackgroundTherapeutic management of Chronic Migraine (CM), often associated with Medication Overuse Headache (MOH), is chiefly empirical, as no biomarker predicting or correlating with clinical efficacy is available to address therapeutic choices. The present study searched for neurophysiological correlates of Greater Occipital Nerve Block (GON-B) effects in CM.MethodsWe recruited 17 CM women, of whom 12 with MOH, and 19 healthy volunteers (HV). Patients had no preventive treatment since at least 3 months. After a 30-day baseline, they received a bilateral betamethasone-lidocaine GON-B of which the therapeutic effect was assessed 1 month later. Habituation of visual evoked potentials (VEP) and intensity dependence of auditory evoked potentials (IDAP) were recorded before and 1 week after the GON-B.ResultsAt baseline, CM patients had a VEP habituation not different from HV, but a steeper IDAP value than HV (p = 0.01), suggestive of a lower serotonergic tone. GON-B significantly reduced the number of total headache days per month (− 34.9%; p = 0.003). Eight out 17CM patients reversed to episodic migraine and medication overuse resolved in 11 out of 12 patients. One week after the GON-B VEP habituation became lacking respect to baseline (p = 0.01) and to that of HV (p = 0.02) like in episodic migraine, while the IDAP slope significantly flattened (p < 0.0001). GON-B-induced reduction in headache days positively correlated with IDAP slope decrease (rho = 0.51, p = 0.03).ConclusionsGON-B may be effective in the treatment of CM, with or without MOH. The pre-treatment IDAP increase is compatible with a weak central serotonergic tone, which is strengthened after GON-B, suggesting that serotonergic mechanisms may play a role in CM and its reversion to episodic migraine. Since the degree of post-treatment IDAP decrease is correlated with clinical improvement, IDAP might be potentially useful as an early predictor of GON-B efficacy.

Treating Chronic Migraine With Neuromodulation: The Role of Neurophysiological Abnormalities and Maladaptive Plasticity

“…The number of attacks is the main risk factor for chronification itself (Buchgreitz et al, 2006). In CM, outside an attack, the neurophysiological response to repeated stimuli is similar to the pattern found in episodic form during an attack: hyperexcitability, central sensitization and normal habituation (Ayzenberg et al, 2006; Chen et al, 2011, 2012; Mathew, 2011; Schoenen, 2011; Viganò et al, 2018). Interestingly, when patients are successfully treated and return to episodic migraine, the low preactivation and the lacking habituation reappear (Chen et al, 2011, 2012).…”

“…As neurotransmitter, serotonin seems to be directly involved. In a recent paper of our group, we investigated electrophysiological patterns associated to transition from CM to EM after GON anesthetic block (Viganò et al, 2018). We found that during the recovery from chronic to episodic migraine, an early increase of the serotonin firing (within the 1st week after GON block) was found in patients who had clinical improvement in the following weeks.…”

“…On the other hand in case of response the exact neurophysiological mechanism remains only speculative. Moreover some recent trial showed that neurophysiological modifications could also precede the clinical improvement suggesting how it is achieved (Viganò et al, 2018).…”

Consensus of the Brazilian Headache Society on the treatment of chronic migraine

“…Not many trials have been conducted to investigate the efficacy of cephalic segment peripheral nerve blocks in the management of chronic migraine. The heterogeneity of study cohorts, designs and techniques do not allow consistent conclusions 111,112,113,114 . However, it is worth mentioning a doubleblind RCT in which 44 participants were submitted to weekly bilateral greater occipital nerve blockades for one month, with 0.5% bupivacaine or saline solution (1.5 mL).…”

The fifth cranial nerve in headaches

“…A recent neurophysiological study investigating the serotonergic tone, found a low baseline serotonergic tone in chronic migraineurs with MOH, but it recovers after a week following anaesthetic block of the greater occipital nerve. Moreover, the size of the recover positively correlated with the clinical benefit after a month [103].…”