ABSTRACT
OBJECTIVES: Deep brain stimulation (DBS) of the subthalamic nucleus (STN) can be a highly effective treatment for Parkinson's disease. However, therapeutic efficacy can be limited by inconsistent targeting of this nucleus. It was shown previously that an increase in local field potential (LFP) power over the beta frequency band may provide intraoperative confirmation of STN targeting. Whether the depth of this focal increase also helps predict the depth and voltage chosen for chronic stimulation is tested here. METHODS: LFPs were recorded from the contacts of 57 DBS electrodes as the latter were advanced in 2 mm steps from above to below the intended surgical target point in STN. RESULTS: A spectral peak in the bipolar LFP was recorded in the 11-35 Hz band at the lowest contact pair that underwent a steep but focal change during electrode descent in all but three sides. The depth of the initial intraoperative step increase in beta correlated with the depth of the contact independently chosen for chronic DBS (Spearman's rho=0.35, p=0.01). In addition, the absolute difference between the depths of the initial increase in beta and the contact chosen for chronic DBS correlated with the voltage used for chronic stimulation (rho=0.322, p=0.017). Thus more voltage had to be employed if a depth was selected for chronic stimulation that differed from that of the beta generator. CONCLUSIONS: Online spectral analysis of LFPs recorded from the DBS electrode may help identify the optimal therapeutic target in the STN region for DBS.
Subject(s)
Deep Brain Stimulation , Evoked Potentials/physiology , Parkinson Disease/therapy , Subthalamic Nucleus/physiology , Adult , Aged , Beta Rhythm , Electric Stimulation , Electrodes, Implanted , Electrophysiological Phenomena , Female , Humans , Intraoperative Period , Male , Middle Aged , Prospective Studies , Software , Stereotaxic TechniquesABSTRACT
BACKGROUND/AIMS: Deep brain stimulation (DBS) is widely used to treat motor symptoms in patients with advanced Parkinson's disease. The aim of this study was to investigate the anatomical aspects of the electric field in relation to effects on speech and movement during DBS in the subthalamic nucleus. METHODS: Patient-specific finite element models of DBS were developed for simulation of the electric field in 10 patients. In each patient, speech intelligibility and movement were assessed during 2 electrical settings, i.e. 4 V (high) and 2 V (low). The electric field was simulated for each electrical setting. RESULTS: Movement was improved in all patients for both high and low electrical settings. In general, high-amplitude stimulation was more consistent in improving the motor scores than low-amplitude stimulation. In 6 cases, speech intelligibility was impaired during high-amplitude electrical settings. Stimulation of part of the fasciculus cerebellothalamicus from electrodes positioned medial and/or posterior to the center of the subthalamic nucleus was recognized as a possible cause of the stimulation-induced dysarthria. CONCLUSION: Special attention to stimulation-induced speech impairments should be taken in cases when active electrodes are positioned medial and/or posterior to the center of the subthalamic nucleus.
Subject(s)
Deep Brain Stimulation , Movement/physiology , Parkinson Disease/therapy , Speech Intelligibility/physiology , Subthalamic Nucleus/physiopathology , Aged , Brain Mapping , Electrodes, Implanted , Female , Humans , Male , Middle Aged , Models, Neurological , Stereotaxic Techniques , Subthalamic Nucleus/surgeryABSTRACT
Deep brain stimulation (DBS) is an established treatment for Parkinson's disease. Success of DBS is highly dependent on electrode location and electrical parameter settings. The aim of this study was to develop a general method for setting up patient-specific 3D computer models of DBS, based on magnetic resonance images, and to demonstrate the use of such models for assessing the position of the electrode contacts and the distribution of the electric field in relation to individual patient anatomy. A software tool was developed for creating finite element DBS-models. The electric field generated by DBS was simulated in one patient and the result was visualized with isolevels and glyphs. The result was evaluated and it corresponded well with reported effects and side effects of stimulation. It was demonstrated that patient-specific finite element models and simulations of DBS can be useful for increasing the understanding of the clinical outcome of DBS.
Subject(s)
Deep Brain Stimulation/methods , Models, Neurological , Parkinson Disease/therapy , Brain Mapping/methods , Electrodes, Implanted , Finite Element Analysis , Humans , Magnetic Resonance Imaging/methods , Parkinson Disease/physiopathologyABSTRACT
The authors report two cases of neurological deterioration following long commercial flights. Both individuals harbored intracranial space-occupying lesions. The authors assert that preexisting reduced intracranial compliance diminishes an individual's reserve to accommodate the physiological changes resulting from a commercial flight. Airline passengers are exposed to a mild degree of hypercapnia as well as conditions that simulate those of high-altitude ascents. High-altitude cerebral edema following an ascent to great heights is one facet of acute mountain sickness and can be life threatening in conditions similar to those present on commercial flights. Comparable reports documenting neurological deterioration at high altitudes in patients with coexisting space-occupying lesions were also reviewed.
Subject(s)
Aircraft , Brain Edema/diagnosis , Brain Neoplasms/diagnosis , Choroid Plexus , Granuloma/diagnosis , Hydrocephalus/diagnosis , Travel , Xanthomatosis/diagnosis , Atmospheric Pressure , Cerebral Aqueduct/pathology , Choroid Plexus/pathology , Diagnosis, Differential , Disease Progression , Fatal Outcome , Female , Humans , Hypoxia, Brain/complications , Hypoxia, Brain/diagnosis , Magnetic Resonance Imaging , Middle Aged , Risk Factors , Tomography, X-Ray ComputedABSTRACT
Deep brain stimulation (DBS) of the subthalamic nucleus (STN) can be a highly effective treatment for Parkinson's disease (PD). However, therapeutic efficacy is limited by difficulties in consistently and correctly targeting this nucleus. Increasing evidence suggests that there is abnormal synchronization of beta frequency band activity (approximately 20 Hz) in the STN of PD patients, as reflected in the oscillatory nature of the local field potential (LFP). We hypothesized that an increase in the power of the LFP beta activity may provide intra-operative confirmation of STN targeting in patients undergoing STN implantation for the treatment of advanced PD. Accordingly, we recorded LFPs from the four contacts of DBS electrodes as the latter were advanced in 2 mm steps from a point 4-6 mm above the intended surgical target point in the STN, to a point 4 mm below this. Contacts were configured to give three bipolar recordings of LFPs. These were analyzed on 16 sides in 9 patients. The power in the 13-35 Hz band recorded at the lowest contact pair underwent a steep but focal increase during electrode descent. The depth of the peak beta activity showed excellent agreement with the level of the intra-operative clinical stun effect (k coefficient = 0.792). The depth of peak beta activity also showed 100% specificity and 100% sensitivity for placement within STN in comparison to pre- and Post-operative stereotactic MRI. Functional physiological localization of STN by the on-line spectral analysis of LFPs is quick to perform and may provide information directly relevant to the position of the electrode contact actually used for DBS.
