Evaluation of cognitive function for Amyotrophic Lateral Sclerosis with Event-related potentials

The purpose of this preliminary study is to determine the profile of amyotrophic lateral sclerosis (ALS) is characterized by systemic neuropsychological test batteries and event-related potential (ERP) measures. We examined 11 cases diagnosed as the sporadic form of ALS according to the El Escorial criteria; 4 patients had a spinal, 7 had a bulbar onset of the disease. We compared ALS patients with normal controls (NC) that were matched sex, age, and education. Neuropsychological signature was assessed by the mini-mental state examination (MMSE) and the New Modified Wisconsin card sorting test (WCST). We also performed correlative studies with respiratory test, arterial blood gas analysis, clinical acuity (using "revised ALS functional rating scale"), and duration of morbidity. The auditory "oddball" stimulation was presented and recorded from 20 channels and global field power (GFP) and peak latency of GFP were determined. MMSE score, resulted in more than 24, revealed obvious dementia of all patients. However, the preservative errors of WCST supposed to increase among bulbar-onset patients. In ERP study, the prolongation of P3 GFP latency compared with NC was recognized. N2 GFP peak amplitude positively correlated with PaO2 level and negatively correlated with PaCO2 level. In addition, we found negative correlation between vital capacity and N1 GFP amplitude, and between vital capacity and P3 GFP latency. According to the advance of clinical acuity, P3 latency was prolonged. Our findings supported that a reduction of prefrontal function exists in the bulbar-onset patients, although hypoxia and hypercapnia may also influence to cognition indicated by abnormalities of ERP components regardless of ALS subtype. Combination ERP measurement and the detailed neuropsychological and clinical acuity assessments clarified many factors influence to cognitive function of sporadic ALS patients.