THE AUDITORY STARTLE RESPONSE IN PROGRESSIVE SUPRANUCLEAR PALSY

The EMG characteristics of the normal auditory startle response in man are compatible with an origin in the pontine reticular formation and with conduction down the spinal cord in a slowly conducting, possibly reticulo-spinal pathway. The startle was reduced or absent in patients with progressive psupranuclear palsy, consistent with loss of neurone s in the lower pontine reticular formation. In contrast, the startle w as present and of normal form in patients with Parkinson's disease. Ho wever, it was delayed in onset. This result was not influenced by trea tment with L-dopa. The late auditory startle in Parkinson's disease mi ght be related to withdrawal of facilitatory input to brainstem centre s from the basal ganglia.