Oculomotor abnormalities in motor neuron disease.

To determine whether there are oculomotor abnormalities in motor neuron disease (MND), electro-oculographic recordings were performed prospectively in 16 MND patients and the results compared with age-matched healthy controls. Parameters analysed included random and fixed saccades (latency, velocity and accuracy), smooth pursuit (gain, total harmonic distortion and number of saccadic intrusions) and optokinetic nystagmus (maximal and mean slow component velocity). Increased saccadic latencies and decreased smooth pursuit gain were the main alterations in the MND group. Correlation with clinical variables showed a positive relationship between smooth pursuit saccadic intrusions and the bulbar clinical score and the rate of progression and a lower optokinetic nystagmus maximal velocity in patients with pseudobulbar syndrome. Our results demonstrate the presence of subclinical supranuclear abnormalities in MND, and support the notion that MND is not merely a degeneration of the motor system.