We report a case of olivopontocerebellar atrophy without sleep apnea syndro
me who presented nocturnal polyuria. It is considered that a disturbance in
the circadian rhythm for arginine vasopressin secretion due to degeneratio
n of suprachiasmatic nuclei and marked increase in the secretion of atrial
natriuretic peptide due to abnormal diurnal variation in blood pressure may
be involved in the mechanism of nocturnal polyuria.