Increased CBF velocity during word fluency in Huntington's disease patients

1. This study examined the effects of word fluency and reading on cerebral blood flow in Huntington's disease (HD) patients. 2. Changes in cerebral flow velocity in the anterior (ACA) and middle (MCA) cerebral arteries were measured with functional transcranial Doppler ultrasonography (fTCD) in 13 normal controls and 9 gene positive HD patients. To control for motor effects of word fluency, two "control" conditions, including silent word fluency and a reading test, were also administered to all subjects. 3. Cerebral blood flow velocity was increased during the out loud word fluency test in the ACA, but not MCA, in the HD group compared to controls. This increase was due to motor components of the test, as during silent word fluency the HD group had a decrease in cerebral blood flow relative to controls. Significant correlations between blood flow in the ACA and word fluency test scores were found. Cerebral blood flow velocity during testing also was able to predict group assignment (i.e., control vs. mild HD vs. moderate HD). 4. These findings add to a growing body of literature suggesting that CBF velocity in HD is abnormal during cognitive and motor tasks. Although previous work reported that CBF velocity in HD is decreased during hand use on a maze test, the current experiment finds that speech production increases cerebral blood flow velocity in HD patients. Collectively, these results point to a fundamental disturbance in the regulation of CBF in HD. Mechanisms that could account for these findings, including the potential involvement of nitric oxide, are discussed.