BACKGROUND: Bickerstaff's brainstem encephalitis (BBE) is a very rare disease of the central nervous system. Aetiology of the disease is auto-immunological. However, it is not entirely understood. Clinically BBE manifests in progressive ophthalmoplegia, ataxia and consciousness disturbances. Clinical symptoms are usually preceded by an unidentified infection of the upper respiratory tract. Usually, the disease has one phase, but individual relapses have also been described. Despite quite severe clinical symptoms, the prognosis is usually good. CASE REPORT: The article presents a case of a patient with relapsing-remitting severe BBE. The case is presented due to the relapsing-remitting clinical course of the disease that resulted in patient's death, rarely described in the literature. We also present the results of subsequent MR scans in the course of the disease, so far described only in individual reports. It is also the first report in the world's literature presenting the results of series of MR spectroscopy (MRS) examinations in the course of BBE. CONCLUSIONS: MR examination is an important component in BBE diagnostics, allowing to differentiate atypical cases and place them under special supervision due to the possibility of the severe clinical course. MR also facilitates differentiation between Miller-Fisher Syndrome (MFS) and BBE in cases of diagnostic doubts. Adding MRS and MRI to the protocol allows us to define the nature of morphological changes more accurately in patients with suspected or diagnosed BBE.