Objective To investigate the clinical manifestations and diagnosis of patients with abnormal signal of bilateral pontine brachium on magnetic resonance imaging (MRI),in order to improve the understanding of diseases involving bilateral middle cerebellar peduncles.Methods Combined with auxiliary examination,we compared the clinical manifestations of five patients and analyzed the characteristics of diseases involving bilateral middle cerebellar peduncles.Results MRI was similar in all five patients.Symmetrical T2-weighted,FLAIR-weighted images of bilateral middle cerebellar peduncles were seen on MRI,with corresponding hypointensity on T1 WI of all five patients.No obvious enhancement has been showed.But there were different clinical manifestations and diagnosis of them.The first patient manifested as dizziness,visual rotation,slurred speech and inactivity of right limb.She was diagnosed with acute cerebral infarction.The second patient only manifested as dizziness.Combined with the history of cerebral infarction,he was diagnosed as Wallerian degeneration.The third patient manifested as blindness in the left eye,vision blurred in right eye and numbness of limbs.She was diagnosed with neuromyelitis optica.The forth patient manifested as lisp,walking instability,talk rubbish and hyperspaamia.She took heroin for dozens of times,and was diagnosed with heroin encephalopathy finally.The final patient manifested as ataxia,slurred speech,choking,dysphagia,less facial expression and urinary retention.He was diagnosed with olivopontocerebellar atrophy.Conclusions The etiology of bilateral pontine brachium lesion is complex.Cerebrovascular diseases,demyelinating diseases,infectious and toxic diseases,and neurodegenerative diseases can be involved.The mechanism of bilateral pontine brachium lesions is not very clear and needs to be further explored.