AGE AND STAGE DEPENDENCY OF P300 LATENCY ALTERATIONS IN NONDEMENTED PARKINSONS-DISEASE PATIENTS WITHOUT THERAPY

Acoustic P300 was recorded from Fz, Cz and Fz by means of an 'odd-ball ' paradigm in 44 non-demented de novo-Parkinson's disease patients (PD ) or PD patients under treatment withdrawal, and in 31 age-matched nor mal subjects, to evaluate whether a P300 latency increase was present in PD patients. The influence of age and disease stage on latency was successively verified by subgrouping PD patients according to differen t age ('young' or 'old') and disease stage ('early' or 'advanced'). PD patient data were compared to data of normal subjects subgrouped into 'young' and 'old' or, to eliminate the age-dependent shift of latency , this latter was adjusted to 60 years in all the examined subjects. A significant increase of latency has been found in Fz and Cz in the 'o ld' group of PD patients (n = 23) but not in the 'young' group (n = 21 ) utilising both methods. Moreover, a significant latency increase was also present in Fz and Cz in the group of 'advanced' PD patients (n = 8), but not in the group of 'early' PD patients (n = 36) utilising ag e-adjusted measurements. When the 'early' PD patient group was divided into 'young' (n = 20) and 'old' (n = 16), the 'early old' group displ ayed significantly increased latencies in Fz compared with normal subj ects. Abnormal P300 latencies were observed, at least in one electrode , by analysing the raw data, in 5.0% of the 'early young', 43.7% of th e 'early old' and up to 62.7% of the 'advanced' patients. Fz represent ed the site in which abnormal P300 latencies were most often observed. Moreover, in the total group of PD patients, the P300 delay was signi ficant only on the frontal (Fz) site when compared with normal subject s. The reported findings were interpreted as if PD produces a sort of 'accelerated effect of age' on the cognitive functions, presumably pro duced by a mechanism different from the producing motor impairment sin ce no clear correlation could be detected between P300 latency and mot or score. The frontal impairment of P300 is in line with previous neur opsychological findings obtained in these patients. Considering that a bout 30% of PD patients develop dementia during their disease progress ion, a border-line or abnormal P300 latency observed at disease onset may represent a predictive marker of this evolution. (C) 1998 Elsevier Science Ireland Ltd.