44. Features of laser evoked potentials in pre-symptomatic Huntington disease patients

We evaluated pain perception and evoked responses by laser stimuli (LEPs) in presymptomatic Huntington disease (HD) patients. We recorded mismatch negativity (MMN) and P3a also to esplorate attention in HD subjects. 6 Presymptomatic gene mutation carriers (pHDs) 7 subjects at risk and 10 healthy controls were compared with 10 symptomatic HDs subjects. LEPs were obtained by four scalp electrodes, (Fz, Cz, referred to the nasion; T3, T4, referred to Fz), stimulating the dorsum of both hands. The MMN was measured in the difference waveshapes of deviant minus standard The P3a was the most positive peak between 300 and 500 ms. A delay in nociceptive input processing emerged in pHDs with CAG replication suggesting a forthcoming onset of the disease, in absence of clinical evidence of abnormalities in pain perception or attention delay. Neurophysiological measurements, such as event-related potentials (ERPs), have been suggested to provide a biological substrate for some aspects of cognitive disturbance. This experimental model is interesting for the evaluation of attention to salient stimuli, potentially relevant for a motor response, studying also the cognitive mechanisms able to compensate the reduced function of the motor cortex in these patients.