Deep brain stimulation lead-contact heating during 3T MRI: single- versus dual-channel pulse generator configurations.

BACKGROUND: Magnetic resonance imaging (MRI) after deep brain stimulation (DBS) carries the risk of heating at the lead-contacts within the brain. OBJECTIVE/HYPOTHESIS: To compare the effect of single- and dual-channel DBS implantable pulse generator (IPG) configurations on brain lead-contact heating during 3T MRI. METHODS: A phantom with bilateral brain leads and extensions connected to two single-channel IPGs or a dual-channel right or left IPG was utilized. Using a transmit/receive head coil, seven scan sequences were conducted yielding a range of head-specific absorption rates (SAR-H). Temperature changes (ΔT) at the bilateral 0 and 3 lead-contacts were recorded, and normalized temperatures (ΔT/SAR-H) and slopes defining the ΔT/SAR-H over the SAR-H range were compared. RESULTS: Greater heating was strongly correlated with higher SAR-H in all configurations. For each scan sequence, the ΔT/SAR-H of single-channel left lead-contacts was significantly greater than the ΔT/SAR-H of either dual-channel configuration. The slope defining the relationship between ΔT and SAR-H for the single-channel left lead (1.68°C/SAR-H) was significantly greater (p < 0.0001) than the ΔT/SAR-H slope for the single-channel right lead (0.97°C/SAR-H), both of which were significantly greater (p < 0.0001) than the ΔT/SAR-H slopes of left or right leads (range 0.68 to 0.70°C/SAR-H) in the dual-channel configurations. There were no significant differences in ΔT/SAR-H slope values between the dual-channel configurations. CONCLUSION: DBS hardware configuration using bilateral single-channel versus unilateral dual-channel IPGs significantly affects DBS lead-contact heating during 3T MRI brain scanning.

Nontraumatic spontaneous acute subdural hematoma in identical teenage twins 1 year apart.

OBJECTIVES: Acute subdural hematoma (ASDH) is a life-threatening injury with a high mortality rate. Most ASDH cases are a result of trauma; nontraumatic causes are relatively rare with an incidence rate of 3% to 5%. We report an unusual series of 2 patients, identical twins, who had nontraumatic subdural hematomas 1 year apart, one at age 15 and the other at age 16. METHODS (CASE PRESENTATIONS): Identical twin brothers presented 1 year and 10 days apart to an academic medical center after incurring confusion, decreased mental functioning, and a subsequent comatose state. The injuries occurred while the patients were playing football, but there was no evidence of traumatic blow to the head in either brother. RESULTS: Both patients had computed tomographic scans and both underwent emergency surgery for hematoma evacuation. Both patients recovered full neurological function and remained healthy 12 years after surgery. CONCLUSIONS: Acute spontaneous subdural hematoma is an emergent medical condition that may result in rapid neurological decline and must be addressed in a timely fashion. After evacuation of the hematoma, intracranial pressure decreases and cerebral perfusion pressure increases, which may allow normal perfusion of the brain. Consequently, prompt recognition and evacuation of an ASDH can drastically improve prognosis. Rarely, subdural hematoma can occur without head injury and should be in the differential diagnosis of athletes who rapidly become comatose.

Effect of deep brain stimulation of the subthalamic nucleus upon the contralateral subthalamic nucleus in Parkinson disease.

High frequency stimulation (HFS) of the subthalamic nucleus (STN) is an effective treatment of idiopathic Parkinson disease (PD). Exactly how HFS works remains unclear. Although HFS of the STN is most effective in improving contralateral motor functions, clinical studies have shown bilateral beneficial effects suggesting that unilateral STN HFS affects both ipsilateral and contralateral basal ganglia networks. In this study we evaluated the effect of STN HFS upon the contralateral STN in 14 PD subjects. The neural recordings were done during stereotaxic neurosurgery for implantation of deep brain stimulation electrodes in the second STN. Neuronal activity of the STN was analyzed before and during two minutes of HFS. There was a significant increase in the multiunit spiking activity of the STN during HFS in the contralateral STN. Our study provides direct electrophysiological evidence that the STN HFS is associated with increased activity of the contralateral STN. These findings suggest that increased STN output underlies therapeutic mechanisms of action of HFS.