Normalizing motor-related brain activity: subthalamic nucleus stimulation in Parkinson disease

OBJECTIVE

To test whether therapeutic unilateral deep brain stimulation (DBS) of the subthalamic nucleus (STN) in patients with Parkinson disease (PD) leads to normalization in the pattern of brain activation during movement execution and control of movement extent.

METHODS

Six patients with PD were imaged off medication by PET during performance of a visually guided tracking task with the DBS voltage programmed for therapeutic (effective) or subtherapeutic (ineffective) stimulation. Data from patients with PD during ineffective stimulation were compared with a group of 13 age-matched control subjects to identify sites with abnormal patterns of activation. Conjunction analysis was used to identify those areas in patients with PD where activity normalized when they were treated with effective stimulation.

RESULTS

For movement execution, effective DBS caused an increase of activation in the supplementary motor area (SMA), superior parietal cortex, and cerebellum toward a more normal pattern. At rest, effective stimulation reduced overactivity of SMA. Therapeutic stimulation also induced reductions of movement related "overactivity" compared with healthy subjects in prefrontal, temporal lobe, and basal ganglia circuits, consistent with the notion that many areas are recruited to compensate for ineffective motor initiation. Normalization of activity related to the control of movement extent was associated with reductions of activity in primary motor cortex, SMA, and basal ganglia.

CONCLUSIONS

Effective subthalamic nucleus stimulation leads to task-specific modifications with appropriate recruitment of motor areas as well as widespread, nonspecific reductions of compensatory or competing cortical activity.

From the Oklahoma State Department of Health. CDC recommendations for diagnosis and initial management of hepatitis C virus infection

Hepatitis C is a growing public health concern in the United States. All physicians should be aware of who should be tested for HCV, based upon risk factors for infection, as well as how to manage persons found to have positive screening tests. The following recommendations focus primarily on the role of the primary care physician in the initial evaluation and management of persons who test positive for HCV and are excerpted from the Centers for Disease Control document "Recommendations for Prevention and Control of Hepatitis C Virus (HCV) Infection and HCV-Related Chronic Disease," Oct. 16, 1998/47(RR19); 1-39.