OBJECTIVE: To detect an alteration in central nervous system function using KDT and VCS by demonstrating a difference during a migraine attack compared to the inter-ictal (between attack) phase.
BACKGROUND: Migraine is characterized by head pain and other symptoms such as photophobia, cognitive dysfunction and alterations in visual contrast during attacks. The KDT is a timed rapid number naming test that evaluates saccadic eye movements, attention, information processing, and is highly sensitive to altered cerebral function. For VCS, participants are asked to read rows of letters of varying size on an iPAD with low contrast level to the background. KDT and VCS have been shown to correlate with neurologic dysfunction in various neurological diseases.
DESIGN/METHODS: We included adult subjects with episodic or chronic migraine with or without aura (less than 25 headache days/month). We enrolled on-site Mayo employees, and the KDT and VCS were performed by the same examiner to minimize bias. For each participant, we performed KDT and VCS testing during headache phase of migraine attack, and inter-ictal non-headache phases. Power analysis suggests a sample size of 26 subjects is needed to detect an effect size of 0.8 for both KDT and VCS, with an 80% power and a significance level at 0.05. Subjects served as their own controls.
RESULTS: We collected data on 28 subjects. There was a statistically significant difference in the performance of KDT during a migraine attack compared to the interictal baseline. On average, the KDT score was 6.3 seconds longer during the migraine attack compared to the interictal baseline performance. For VCS (both 100% and 2.5% contrast sensitivity), there was no significant difference between the migraine attack and the interictal baseline.
CONCLUSIONS: This study provides objective quantitative data demonstrating altered cerebral function during migraine attacks. Saccadic eye movements may serve as a biomarker for a migraine attack. The KDT could be an effective tool to understand migraine pathophysiology, document the true interictal state, as well as to characterize migraine associated disability during and between attacks.
Summary Points:
- Migraine patients demonstrated a significant 6.3 second worsening in K-D Test performance from baseline during migraine attack
- This study provides objective quantitative data demonstrating altered cerebral function during migraine attacks
- The K-D test serves as a migraine biomarker and may predict the premonitory phase and onset of migraine attack providing an opportunity for earlier therapeutic intervention to improve patient outcomes