Over a period of several years, a patient with angiographically occult vascular malformation (AOVM) involving the brainstem was longitudinally studied by means of serial Magnetic Resonance Imaging (MRI) and multimodal Evoked Potential (EP) recordings (visual-VEP, brainstem auditory-BAEP, somatosensory--SEP--by stimulating median and peroneal nerves). MRI did contribute to an accurate definition of AOVM features. In particular, it was able to follow over time the AOVM size, and to discriminate between recent and old bleedings. Multimodal EP recordings displayed different pathological BAEP and peroneal SEP values, which documented a transient segmental brainstem involvement (related to the presence of hemorrhage), along with persistent and probably irreversible signs of diffuse brainstem dysfunction. Thus, MRI and EP assessment is useful in monitoring the clinical course of brainstem occult vascular malformations.