Neuromuscular transmission in migraine: A single-fiber EMG study in clinical subgroups

Objective: To search for impairment of neuromuscular transmission by single-fiber electromyography (SFEMG) in patients with common forms of migraine. Background: P/Q Ca²⁺ channels are genetically abnormal in most cases of familial hemiplegic migraine (International Headache Society [IHS] code 1.2.3) and may be involved in other types of migraine. Besides in the brain, these channels are found in motor nerve endings, where they control stimulation-induced acetylcholine release. If they are functionally abnormal, the neuromuscular transmission might be impaired. Methods: Sixty-two migraineurs (18 without aura, IHS code 1.1; 19 with typical aura, IHS code 1.2.1; 10 with prolonged aura, IHS code 1.2.2; 15 with and without aura) and 16 healthy control subjects underwent stimulation SFEMG. Results were expressed as the mean value of consecutive differences (MCD) and percentage of single-fiber abnormalities (abnormal jitter or impulse blocking). Results: Average MCD was comparable in control subjects and migraineurs (17.1 ± 2.6 versus 17.5 ± 4.7 μsec). By contrast, single-fiber abnormalities were found in 17 patients but in none of the control subjects (p = 0.036). Most of these patients had unilateral sensorimotor symptoms and/or aphasia and/or loss of balance during the aura. SFEMG abnormalities were significantly correlated with the occurrence of these clinical features and with a diagnosis of migraine with prolonged aura. Conclusions: Stimulation SFEMG shows mild abnormalities of neuromuscular transmission in a subgroup of migraineurs with aura, characterized by clinical features frequently found in human P/Q Ca²⁺ channelopathies. These abnormalities might thus be due to genetically modified P/Q Ca²⁺ channels.