Why do we need NIRS in migraine?

Migraine patients may present altered values of the parameters related to their cerebral circulation. The non-invasive assessment of the autoregulation of such patients can be helpful in investigating the causes of migraine. We developed a joint analysis protocol based on transcranial Doppler (TCD) and near-infrared spectroscopy (NIRS) for assessing cerebral autoregulation. We tested 30 healthy subjects and 30 patients suffering from migraine without aura. We measured the baseline values of cerebral blood flow velocity (CBFV) in the middle cerebral arteries and the concentration of oxygenated (oxy-Hb) and reduced (deoxy-Hb) haemoglobin in brain tissue. Afterwards, the subjects performed a breath-holding (BH) task. In baseline conditions, we did not find significant difference between the CBFVs of healthy subjects and of migraineurs, even though the latter group showed a greater dispersion of the velocities (healthy: 70.6+/-6.8 cm/s; migraine: 71.5+/-14.4 cm/s). Strong differences in the CBFV were observable during the BH task: migraineurs showed a smaller BH index than controls (0.83+/-0.55% vs. 1.29+/-0.71%; p<0.005) and a reduced increase of the oxy-Hb (migraineurs: 0.033+/-0.019 micromol/l/s; healthy: 0.055+/-0.037 micromol/l/s; p<0.01). Also, we found a different haemoglobin balancing during the BH phase between migraineurs and controls, revealing that migraineurs do not show a marked vasodilation as functional response to the CO(2) increase. We propose this joint analysis protocol to assess cerebral autoregulation of migraine patients, and suggest NIRS as a low-cost, easy, reliable and fast technique to deeply investigate cerebral coupling deregulations.