Double saccadic pulses and macrosaccadic oscillations from a focal brainstem lesion

Double saccadic pulses (DSP) are saccadic intrusions that consist of an initial saccade away from a fixation followed immediately by a return saccade back to the fixation. DSP have been reported in patients with presumed multiple sclerosis and metabolic encephalopathy. However, DSP have not been described in a circumscribed brain lesion. We report a man who developed almost continuous DSP with intervening macrosaccadic oscillations from a circumscribed lesion in the dorsal pontine tegmentum which extended up to the midbrain level and spared the nucleus raphe interpositus where the pause cells reside. Damage to the projections from the superior colliculus to omnipause neurons and resultant dysfunction of omnipause neuron may be a mechanism of saccadic intrusions and oscillations observed in our patient with a circumscribed brainstem lesion.