EEG patterns in each phase of hemiplegic migraine: a systematic review and pooled prevalence meta-analysis

Hemiplegic migraine (HM) is a rare subtype of migraine with aura, and its pathophysiology is similar to that of migraine with aura, primarily involving cortical spreading depression. Electroencephalography (EEG) may serve as a valuable tool for investigating brain function in patients with hemiplegic migraine. Therefore, this study aims to synthesize available evidence through a systematic review and pooled prevalence meta-analysis to assess the types of EEG abnormalities observed in each migraine phase in patients with hemiplegic migraine and to estimate the prevalence of EEG abnormalities during the interictal period.

We searched PubMed, Scopus, and Cochrane up to January 2025 and included articles, including case reports, case series, and retrospective studies that reported EEG abnormalities in hemiplegic migraine. The prevalence of abnormal EEG during the interictal phase was analyzed through pooled data analysis.

A total of 40 articles involving 65 patients were included in the analysis. The most common EEG abnormality During the aura phase was low-amplitude activity affecting the hemisphere contralateral to the hemiparesis, observed in 71.4% (5/7) of cases. Similarly, During the headache and post-headache phases, the most frequently observed EEG abnormality was medium- to high-amplitude slowing, particularly in the hemisphere contralateral to the hemiparesis, occurring in 54.9% (28/51) and 37.5% (9/24) of cases, respectively. Meanwhile, 78.8% (26/33) of patients' EEG recordings during the interictal phase were normal.

This study found that the most common EEG abnormality during the aura phase was low-amplitude activity in the hemisphere contralateral to the hemiparesis, while during the headache and post-headache phases, medium- to high-amplitude focal slowing was frequently observed in the same hemisphere. EEGs during the interictal phase were mostly normal. These findings provide an overview of characteristic EEG patterns in each phase of hemiplegic migraine and may support the hypothesis that widespread cortical spreading depression precedes subcortical propagation.