Experimentally-induced spinal nociceptive sensitization increases with migraine frequency: a single-blind controlled study

The nitric-oxide donor nitroglycerin (NTG) administration induces a facilitation of nociceptive pathways in episodic migraine. This study aims to test the hypothesis that induced spinal sensitization could be more pronounced in patients affected by high frequency migraine (HF-MIG) respect to low frequency migraine (LF-MIG).We enrolled 28 patients with LF-MIG (1-5 migraine days/month), 19 patients with HF-MIG (6-14 migraine days/month) and 21 healthy controls (HC). Spinal sensitization was evaluated with the neurophysiological recording of the temporal summation threshold (TST) of the nociceptive withdrawal reflex at the lower limb. TST was recorded at baseline and 30, 60 and 120 minutes after NTG administration (0.9 mg sublingual).Spinal sensitization was detected in LF-MIG at 60 (p=0.010) and 120 minutes (p=0.001) and in HF-MIG at 30 (p=0.008), 60 (p=0.001) and 120 minutes (p=0.001) after NTG administration. TST did not change in HC (p=0.899). Moreover, TST reduction was more pronounced in HF-MIG respect to LF-MIG (p=0.002).The percentage of patients who developed a migraine-like headache after NTG was comparable in the two migraine groups (LF-MIG: 53.6%, HF-MIG: 52.6%, p=0.284), while no subjects in HC group developed a delayed-specific headache. Notably, the latency of headache onset was significantly shorter in the HF-MIG group when compared to the LF-MIG group (p=0.015).Our data demonstrate a direct relationship between migraine frequency and both neurophysiological and clinical parameters, to suggest an increasing derangement of the nociceptive system control as the disease progresses, probably as a result of the interaction of genetic and environmental factors