Examination of Quantitative Electroencephalographic (QEEG) Biomarkers in Huntington's Disease

The pace of basic science research defining the mechanisms of selective neuronal degeneration in Huntington disease (HD) has far exceeded the pace of translation of this information into clinically effective treatments for the disease. One reason for this bottleneck between bench and bedside is the paucity of available surrogate markers for HD. Identification of surrogate markers is critical for the design of future clinical trials. Such markers could provide a reliable signal of early brain dysfunction in HD and could be used as a biomarker in trials of agents that could prevent onset or delay progression of disease. Frontal-subcortical networks are known to be affected in HD and contribute to the cognitive dysfunction characteristic of the disease. Quantitative EEG (QEEG) can be used to assess the integrity of this circuitry; characteristic QEEG abnormalities long have been known to be present in the early stages of the illness (Bylsma et al., 1994). More recent research has suggested that a comprehensive topographic approach to QEEG analysis may reveal additional changes in brain activity (Bellotti et al., 2004) that may be indicative of subclinical disease (de Tommaso et al., 2003). This proposal aims to determine whether quantitative EEG techniques can be used to identify HD-specific abnormalities and thus serve as surrogate markers of disease. The goals of this pilot project are three-fold. First, we will determine if there are QEEG differences between normal control subjects and those with mild or moderate HD. Second, we will examine associations between severity of HD and the QEEG differences detected and determine if these QEEG differences are present when comparing the least affected HD subjects and normal controls. Third, we will examine associations between QEEG variables of interest and other clinical variables, including age of onset of symptoms, number of CAG repeats, severity of motor and behavioral symptoms as measured by the Unified Huntington Disease Rating Scale (UHDRS) subscores, and severity of cognitive impairment as measured by the cognitive subscore of the UHDRS and Mini-Mental State Examination (MMSE).