Visual-motion suppression in congenital pendular nystagmus.

Patients with a congenital pendular nystagmus are known not to experience oscillopsia in a normal visual environment. The data of a 31-year-old female patient suffering from a congenital pendular nystagmus are presented. The aim of the fluorodeoxyglucose positron emission tomography (FDG-PET) experiment was to analyze the regional cerebral glucose metabolism (rCGM) during minimal as well as maximal nystagmus. Video-oculography showed a maximum in frequency of the horizontal pendular nystagmus during gaze to the left, whereas the zone of minimal nystagmus was 10 degrees to the right. Two sessions with an 18F-fluorodeoxyglucose tracer were performed to analyze cerebral blood-glucose utilization when fixating an object in the areas of maximal and of minimal nystagmus. A structural MRI in a clinical 1.5-T scanner was acquired to superimpose the PET results onto the unique anatomy of the patient. By statistical analysis a significant increase in the rCGM in the cerebellar nodulus and a relative decrease in the area of MT/V5 bilaterally during maximal nystagmus were found. When the patient was looking in her null zone, rCGM was increased in V1 and MT/V5 bilaterally. To the best of the authors' knowledge, this is the first proof by means of functional imaging of a suppression of oscillopsia in higher-order visual cortex areas in a patient with a congenital nystagmus.