3D analysis of spontaneous upbeat nystagmus in a patient with astrocytoma in cerebellum.

Aims: We report the case of a 58-year-old female patient who consulted our Department complaining of positional vertigo and showing spontaneous upbeat nystagmus (UBN) in darkness.

Method: We analyzed her UBN three-dimensionally. The MRI scan revealed the astrocytoma in the left cerebellum involving the cerebellar vermis.

Result: Three-dimensional analysis showed a spontaneous UBN rotating around the intra-aural axis in the pitch plane.

Conclusion: Since the cerebellar vermis is known to plays an inhibitory role on the central vertical vestibule-ocular reflex (VOR), the present results suggest that the spontaneous UBN in darkness observed in this patient was induced by an imbalance of central vertical VOR tone.