ObjectiveTo study the dynamic changes of facial nerve F wave in patients with brainstem infarction，and to explore its value in diagnosis and prognosis evaluation of acute brainstem infarction. MethodsFifty-three patients with brainstem infarction were enrolled in our hospital. Electrophysiological examinations were performed on the 3rd，7th，14th，1st and 3rd days of onset，including the occurrence rate and latency of facial nerve F wave，and compared with the healthy side. Three months after onset，the patients were divided into good prognosis group（mRS≤2） and poor prognosis group（mRS>2） according to mRS neurological function score，and 10 healthy adults were included as control group with the same detection method. The incidence and latency of facial nerve F wave at different time points were compared. Results53 patients with brainstem infarction showed a decrease in the occurrence rate of f wave and an extension in the latency period on the 3rd，7th and 14th days of onset respectively，with a statistically significant difference compared with the healthy side（P<0.05）. However，the incubation period recovered at 3 months after onset，with no significant difference compared with the healthy side（P>0.05），while the occurrence rate was still statistically significant compared with the healthy side（P<0.05）. In patients with different types of brainstem infarction，the occurrence rate and incubation period of f wave in each group decreased to different degrees on the 3rd and 7th day，and the difference was not statistically significant（P>0.05）. The occurrence rate and incubation period of f wave in Raymond-Cestan syndrome group first recovered from the 14th day，with significant difference compared with other groups（P<0.05）. The occurrence rate and incubation period of f wave in Millard-Gubber syndrome group were higher than those in other groups at the 1st and 3rd month of onset，the difference was statistically significant（P<0.05）. On the 3rd and 7th day of onset，the incubation period and occurrence rate of f wave in the two groups increased and decreased，with no significant difference（P>0.05）. From the 14th day on，the incubation period and f wave occurrence in the group with good prognosis first recovered in the group with poor prognosis，with significant difference（P<0.05）. At the 3rd month of onset，the occurrence rate of F wave in the group with good prognosis was significantly higher than that in the group with poor prognosis，and the difference was statistically significant. However，the incubation period of the two groups had obvious recovery，and the difference was not statistically significant（P>0.05）. ConclusionThe changes of facial nerve F wave and latency can occur in patients with brainstem infarction in the early stage，but there is no differential diagnosis value for different types of cerebral infarction in the acute stage，which can provide valuable objective basis for prognosis evaluation after the acute stage.