Deficient prepulse inhibition of blink reflex in migraine and its relation to allodynia.

OBJECTIVE: Prepulse inhibition (PPI) of the blink reflex (BR) is a reduction in BR excitability due to a conditioning stimulus, reflecting sensory gating by brainstem structures. We aimed to analyze PPI changes during a painful episode in chronic or episodic migraine and its relation to allodynia, since abnormal brainstem filtering has been hypothesized in migraine pathophysiology.

METHODS: We included 20 patients with migraine during headache episode, and age- and gender-matched 22 healthy subjects. We recorded BR after unconditioned and conditioned supraorbital stimuli. For conditioned stimuli, we applied preceding subthreshold stimulus to the median nerve at wrist. The presence of PPI was compared between the two groups, as well as the specific BR parameters (latency, amplitude or area of R1 and R2 components) in unconditioned (test) and conditioned (PPI) paradigms.

RESULTS: In the patient group, seven (35%) patients did not have R2-PPI whereas all healthy subjects had R2-PPI (P=0.003). Healthy subjects displayed significantly increased R1 amplitude and reduced R2 amplitude and area after conditioned stimuli. In migraine patients, we observed significant reduction only in R2 amplitude. Logistic regression demonstrated that allodynia was independently related with the presence of PPI (beta: -0.535, P=0.021).

CONCLUSIONS: Our study provides evidence for sensory gating impairment at brainstem level in migraine headache, related to the presence of allodynia.