P998: Excitability changes at brainstem and cortical levels in patients diagnosed with migraine and cluster headache

Abstract

Question: Previous studies reported altered excitability of the central nervous system (CNS) in patients with primary headaches, however their results are contraversial. The aim of this study was to assess the interictal excitability of motor cortex and trigeminal structures in patients diagnosed with migraine or cluster headache. Methods: Twelve patients with migraine without aura (MoA), 8 migraineurs with aura (MA) and 14 patients with cluster headache (CH) diagnosed according to the criteria of International Headache Society (2004) were included in this study, all patients had lateralized headaches. Paired pulse transcranial magnetic stimulation was delivered bilaterally on primary motor cortex to assess short intracortical inhibition (SICI) and intracortical facilitation (ICF) periods of cortical excitability. Moreover, blink reflex recovery was studied at 200, 300, 500 and 800ms interstimulus intervals (ISIs) to investigate the excitability of trigeminal structures in the patient groups and 16 control subjects. Results: ICF was significantly higher at the symptomatic side only in patients with MA compared to control subjects (p=0.001). There was no significant difference for the SICI between patient and control groups. Furthermore, blink reflex excitability was found to be increased bilaterally in patients with MoA, MA and CH in comparison to controls at different ISIs. Conclusions: Our findings suggested that patients with lateralized primary headaches had bilateral hyperexcitability at the trigeminal level whereas only patients with MA displayed unilateral cortical excitability changes interictally, implicating some common but also diverse pathophysiological mechanisms for these primary headaches.