Akshay Gupte

Selection of optimal programming contacts based on local field potential recordings from subthalamic nucleus in patients with Parkinson's disease.

BACKGROUNDIn the United States, the most commonly used surgical treatment for patients with Parkinsons disease is the implantation of deep brain stimulation (DBS) electrodes within the subthalamic nucleus. However, DBS device programming remains difficult and is a possible source of decreased efficacy. OBJECTIVEWe investigated the relationship between local field potential (LFP) activities in the subthalamic nucleus and the therapeutic response to programming. METHODSWe recorded LFPs with macroelectrodes placed unilaterally for DBS in 4 PD patients, 3 weeks after implantation, before the start of log-term DBS. Power-frequency spectra were calculated for each of 7 possible electrode contacts or contact pairs, over multiple 5- to 10-minute quiet waking epochs and over 30-second epochs during hand movements. Subsequently, DBS devices were programmed, with testing to determine which electrode contacts or contact pairs demonstrated optimal therapeutic efficacy. RESULTSFor each patient, the contact pair found to provide optimal efficacy was associated with the highest energy in the β (13–32 Hz) and γ (48–220 Hz) bands during postoperative LFP recordings at rest and during hand movements. Activities in other frequency bands did not show significant correlations between LFP power and optimal electrode contacts. CONCLUSIONPostoperative subband analysis of LFP recordings in β and γ frequency ranges may be used to select optimal electrode contacts. These results indicate that LFP recordings from implanted DBS electrodes can provide important clues to guide the optimization of DBS therapy in individual patients.

MRI-related heating near deep brain stimulation electrodes: more data are needed.

Magnetic resonance imaging (MRI) of patients with implanted deep brain stimulation (DBS) devices poses a challenge for healthcare providers. As a consequence of safety concerns about magnetic field interactions with the device, induced electrical currents and thermal damage due to radiofrequency heating, a number of stringent guidelines have been proposed by the device manufacturer. Very few detailed investigations of these safety issues have been published to date, and the stringent manufacturer guidelines have gone unchallenged, leading some hospitals and imaging centers around the world to ban or restrict the use of MRI in DBS patients. The purpose of this review is to stimulate research towards defining appropriate guidelines for the use of MRI in patients with DBS. Additionally, this review is intended to help healthcare providers and researchers make sound clinical judgments about the use of MRI in the setting of implanted DBS devices.

Effect of the extracranial deep brain stimulation lead on radiofrequency heating at 9.4 Tesla (400.2 MHz)

To study the effect of the extracranial portion of a deep brain stimulation (DBS) lead on radiofrequency (RF) heating with a transmit and receive 9.4 Tesla head coil.

Impulsive behavior and associated clinical variables in Parkinson's disease.

BACKGROUND Parkinsons disease (PD) is a degenerative brain disorder accompanied by the loss of dopaminergic neurons and the presence of motor and non-motor symptoms. OBJECTIVE We performed a cross-sectional, questionnaire-based analysis of impulsive behavior in our PD clinic population to assess prevalence and associated characteristics. RESULTS We found a higher prevalence of impulsive behavior (29.7%) than previously reported, and found multiple, concurrent impulsive behaviors in 26% of subjects reporting impulsive behavior. CONCLUSIONS Our findings contribute to the growing awareness of impulsive behavior in PD, and support the need for longitudinal studies to assess changes in impulsive behaviors in Parkinsons patients.

Bowstringing as a complication of deep brain stimulation: case report.

OBJECTIVEThis retrospective case series describes bowstringing as a complication of deep brain stimulator implantation for Parkinsons disease, defined as abnormal tethering of leads between the pulse generator and stimulating electrode, associated with contracture of the patients neck over the extension cable. There are no previous reports of this specific complication, which presumably has been more broadly classified under hardware-related complications. CLINICAL PRESENTATIONBowstringing may result in discomfort, restriction of movements, and/or equipment malfunction. Patients were identified by postoperative surveillance in clinic and by review of our database of Parkinsons disease patients who had undergone subthalamic nucleus deep brain stimulator placement. The incidence of this complication was 2.6% (6/228) in our overall clinic population, composed of 0% (0/181) of patients who received a Soletra pulse generator and 12.7% (6/47) of patients who received a Kinetra pulse generator. INTERVENTIONThe proportion of patients with bowstringing requiring operative revision was 83% (5/6), with 60% (3/5) patients undergoing conversion to single-channel pulse generators and 40% (2/5) undergoing revision of the original dual-channel pulse generator. CONCLUSIONFactors associated with bowstringing include the use of dual-channel pulse generators and scar lysis complicated by seroma or infection. The mean time from implantation to bowstringing was 8.6 months with a range of 0.5 to 22 months. Bowstringing is a rare but potentially serious complication, and further study is needed to accurately predict and avoid this problem.

Local field potentials of subthalamic nucleus contain electrophysiological footprints of motor subtypes of Parkinson’s disease

Significance Despite the fact that deep-brain stimulation (DBS) of the subthalamic nucleus (STN) has emerged as an effective surgical treatment for Parkinson’s disease (PD), there is no available neurobiomarker providing information about the symptoms of PD subtypes in STN. In this paper, we report the finding of neural correlates of two motor phenotypes of PD in the territories of STN. Despite advances in imaging, microelectrode recording continues to be best practice and the dominant method for STN localization during DBS surgery [Abosch A, et al. (2013) Stereotact Funct Neurosurg 91:1–11]. Hence, we anticipate our findings will provide possibilities for the intraoperative interpretation of oscillatory dynamics of STN and that these well-localized patterns can be used as objective tools for future neuromodulation technologies. Although motor subtypes of Parkinson’s disease (PD), such as tremor dominant (TD) and postural instability and gait difficulty (PIGD), have been defined based on symptoms since the mid-1990s, no underlying neural correlates of these clinical subtypes have yet been identified. Very limited data exist regarding the electrophysiological abnormalities within the subthalamic nucleus (STN) that likely accompany the symptom severity or the phenotype of PD. Here, we show that activity in subbands of local field potentials (LFPs) recorded with multiple microelectrodes from subterritories of STN provide distinguishing neurophysiological information about the motor subtypes of PD. We studied 24 patients with PD and found distinct patterns between TD (n = 13) and PIGD (n = 11) groups in high-frequency oscillations (HFOs) and their nonlinear interactions with beta band in the superior and inferior regions of the STN. Particularly, in the superior region of STN, the power of the slow HFO (sHFO) (200–260 Hz) and the coupling of its amplitude with beta-band phase were significantly stronger in the TD group. The inferior region of STN exhibited fast HFOs (fHFOs) (260–450 Hz), which have a significantly higher center frequency in the PIGD group. The cross-frequency coupling between fHFOs and beta band in the inferior region of STN was significantly stronger in the PIGD group. Our results indicate that the spatiospectral dynamics of STN-LFPs can be used as an objective method to distinguish these two motor subtypes of PD. These observations might lead to the development of sensing and stimulation strategies targeting the subterritories of STN for the personalization of deep-brain stimulation (DBS).