Twenty patients with RRMS and twenty healthy subjects as controls were enrolled in the study. The average TCD examination interval was 192 days before Fingolimod treatment and 421 days after Fingolimod treatment. We performed TCD recordings from the M1-segments of both middle cerebral arteries simultaneously during breath holding. The cerebrovascular reactivity was defined as a relative increase of the blood flow velocities and reactivity index was determined as the relative increase of the blood flow velocities per second during breath holding.

The Doppler data of the left and right side were quite similar, and therefore all data on both sides were combined. The cerebrovascular reactivity to breath holding was significantly lower at pre-treatment period (41%) and post-treatment period (40%) in patients with RRMS comparing to the controls (48%, p<0.017). Similar results were obtained at reaction indexes. RRMS patients have lower reaction indexes (pre 3.2%/sec and post 3.4%/sec) in patients comparing than those of controls (5.2%/sec, p<0.001).

To our best knowledge the present study is the first study examining cerebrovascular reactivity in patients with RRMS before and after Fingolimod treatment using the transcranial Doppler. Our results suggest the cerebrovascular reactivity was impaired in patients with MS, however, it has not been influenced by Fingolimod treatment.