The prevalence and frequency of interictal microembolic signals (MES) are higher in migraineurs with higher cortical dysfunction (HCD) during aura, compared with migraineurs without HCD during aura and with healthy controls, according to a study published online ahead of print September 29 in Cephalalgia.
Jasna Zidverc-Trajkovi´c, MD, a neurologist at the Neurology Clinic of the Clinical Center of Serbia in Belgrade, and her colleagues used transcranial Doppler ultrasound to test their hypothesis that the complexity of migraine aura depends on hypoperfusion caused by microemboli that occur in different regions of the brain. The goal was to evaluate the prevalence and clinical impact of interictal MES in migraineurs with HCD during aura.
The investigators enrolled 34 individuals with migraine who experienced language and memory impairment during aura (HCD group), 31 patients who had migraine with only visual or visual and somatosensory symptoms during aura (control group I), and 34 healthy individuals (control group II). A Doppler instrument was used to detect microemboli, and the researchers also compared demographic data, disease features, and the detection of MES between these groups, as well as the predictors of HCD during the aura.
MES Predicted HCD
The duration of aura (34.71 ±18.05 minutes vs 23.87 ±13.64 minutes) was significantly longer, and the frequency of aura per year (16.29 ±14.21 vs 10.10 ±11.00) was significantly higher in the HCD group, compared with control group I. The presence of somatosensory symptoms during the aura was significantly higher in the HCD group as well.
A binary logistic regression analysis identified three independent predictors of HCD occurrence in patients with migraine aura. These predictors were longer duration of the aura, presence of somatosensory symptoms during the aura, and positive MES detection.
MES were interictally detected in 29% of patients with migraine who experienced migraines with HCD during the aura, but in only 3% of participants with visual or somatosensory aura. In addition, the number of detected MES in a single patient was as high as 85 among patients in the HCD group, compared with eight that were detected in other examined patients and healthy controls.
Stroke-Risk Stratification
The detection of MES and investigation of the origin of microembolism could be a valuable tool for screening individuals with migraine with aura for ischemic stroke risk, as well as investigating links between migraine with aura and ischemic stroke, said Dr. Zidverc-Trajkovi´c.
The investigators speculated that in patients who have memory and language impairment during migraine aura, the cerebral cortex may be affected by cortical spreading depression in regions beyond the occipital lobe, and microemboli may trigger cortical spreading depression. This sequence of events, in turn, might contribute to the pathophysiology of migraine aura.
“Further research should include analysis of the influence of microemboli on the neuron–glial interaction or the network modulation and pathophysiology of cortical spreading depression,” the investigators said.
MES Was Recorded Outside Migraine Attacks
“Cortical spreading depression has been shown to occur in humans in ischemic stroke, severe traumatic brain lesions, and following hypoxia, and the scientifically relevant question is how spreading depression is triggered in patients who suffer from migraines with aura,” said Hans-Christoph Diener, MD, PhD, Chair of the Department of Neurology at the University of Duisburg-Essen in Germany, in an accompanying editorial. “The current study proposes that microemboli are a potential trigger.
“Microembolic signals, or MES, were detected in 29.4% of patients with higher cortical aura, which was much higher than in the other two groups,” he added. “But what does this finding implicate? The nature of MES is unknown in patients without atherosclerotic plaques, and one assumed mechanism is right–left shunt either through a patent foramen ovale or through pulmonary shunts. Patent foramen ovale is associated with a higher prevalence of migraine with aura.
“The major shortcoming of the study is the recording of MES outside migraine attacks. It is difficult to understand how MES occurring outside migraine attacks should play a role in the rare events of complex auras, and many of the assumptions and implications of the authors in the discussion are not supported by scientific evidence,” said Dr. Diener.
“In summary, this is an interesting observation with very limited relationship to the pathophysiology of migraine aura, and further research is needed,” Dr. Diener concluded.
—Roxanne Nelson