Toshiharu Otaka

Nexframe Frameless Stereotaxy with Multitract Microrecording: Accuracy Evaluated by Frame-Based Stereotactic X-Ray

Objective: The development of image-guided systems rendered it possible to perform frameless stereotactic surgery for deep brain stimulation (DBS). As well as stereotactic targeting, neurophysiological identification of the target is important. Multitract microrecording is an effective technique to identify the best placement of an electrode. This is a report of our experience of using the Nexframe frameless stereotaxy with Ben’s Gun multitract microrecording drive and our study of the accuracy, usefulness and disadvantages of the system. Methods: Five patients scheduled to undergo bilateral subthalamic nucleus (STN) DBS were examined. The Nexframe device was adjusted to the planned target, and electrodes were introduced using a microdrive for multitract microrecording. In addition to the Nexframe frameless system, we adopted the Leksell G frame to the same patients simultaneously to use a stereotactic X-ray system. This system consisted of a movable X-ray camera with a crossbar and was adopted to be always parallel to the frame with the X-ray film cassette. The distance between the expected and actual DBS electrode placements was measured on such a stereotactic X-ray system. In addition, the distance measured with this system was compared with that measured by conventional frame-based stereotaxy in 20 patients (40 sides). Results: The mean deviations from 10 planned targets were 1.3 ± 0.3 mm in the mediolateral (x) direction, 1.0 ± 0.9 mm in the anteroposterior (y) direction and 0.5 ± 0.6 mm in the superoposterior (z) direction. The data from the frame-based stereotaxy in our institute were 1.5 ± 0.9 mm in the mediolateral (x) direction, 1.1 ± 0.7 mm in the anteroposterior (y) direction and 0.8 ± 0.6 mm in the superoposterior (z) direction. Then, differences were not statistically significant in any direction (p > 0.05). The multitract microrecording procedure associated with the Nexframe was performed without any problems in all of the patients. None of these electrodes migrated during and/or after the surgery. However, the disadvantage of the system is the narrow surgical field for multiple electrode insertion. Coagulating the cortex and inserting multiple electrodes under such a narrow visual field were complicated. Conclusion: The Nexframe with multitract microrecording for STN DBS still has some problems that need to be resolved. Thus far, we do not consider that this technology in its present state can replace conventional frame-based stereotactic surgery. The accuracy of the system is similar to that of frame-based stereotaxy. However, the narrow surgical field is a disadvantage for multiple electrode insertion. Improvement on this point will enhance the usefulness of the system.

Thalamic deep brain stimulation for the treatment of action myoclonus caused by perinatal anoxia.

Background: Perinatal anoxia rarely causes myoclonus as the main neurologic abnormality. The exact neuronal mechanism underlying myoclonus induced by perinatal anoxia remains unknown. Some studies have indicated that the development of involuntary movements may be related to the maturation of the thalamus after birth. Objectives and Methods: Here, we describe the first case of a patient who developed action myoclonus after experiencing perinatal anoxia and was successfully treated by chronic deep brain stimulation (DBS) of the thalamus (thalamic DBS). Results andConclusion: The effectiveness of chronic thalamic DBS in this patient supports the concept of involvement of the thalamus in postperinatal anoxic myoclonus.

Corticospinal descending direct wave elicited by subcortical stimulation.

Summary: Recent studies have indicated the importance of subcortical mapping of the corticospinal tract (CT) during tumor resection close to the primary motor area. It is substantial evidence that the corticospinal descending direct wave (D-wave) can be used as a guide for mapping of the primary motor cortex (M1) and for monitoring of the CT functional integrity. In the present study, the authors investigated the feasibility of D-wave recordings after subcortical stimulation. The authors examined 14 patients with brain tumors close to the M1 and/or CT, who exhibited no obvious motor deficit before surgery. Subcortical white matter was electrically stimulated in monopolar or bipolar fashion by recording the descending wave (D-wave) from the spinal epidural space using a catheter-type electrode. Subcortical D-wave was more clearly recorded after monopolar stimulation than after bipolar stimulation. The features of the subcortical D-wave, including its waveform, conduction velocity, and latency, were nearly identical to those of the corticospinal D-wave recorded after M1 stimulation. Subcortical D-wave amplitude was prone to change depending on the distance from the stimulation points to the CT. Changes in parameters of subcortical D-wave may provide valuable information to prevent postoperative motor deficit. Further studies are required to clarify the relationship between the distance from the stimulating point to the CT and the amplitude of the subcortically elicited D-wave.

Effect of Subthalamic Nucleus Deep Brain Stimulation on the Autonomic Nervous System in Parkinson’s Disease Patients Assessed by Spectral Analyses of R-R Interval Variability and Blood Pressure Variability

Objective: Autonomic nervous system impairment is an untoward symptom that is typically observed in advanced Parkinson’s disease (PD) patients. However, details of the effects of subthalamic nucleus deep brain stimulation (STN-DBS) on the autonomic nervous system remain unclear. Methods: Twenty-eight patients with advanced PD (12 males and 16 females) who underwent bilateral STN-DBS and 13 age-matched healthy controls were included in this study. We analyzed the dynamic cardiovascular autonomic function regulating the R-R interval and blood pressure by spectral and transfer function analyses of cardiovascular variability before and after STN-DBS. Results: Vagally mediated arterial-cardiac baroreflex function improved after STN-DBS compared to that before STN-DBS (p < 0.05). However, there were no statistically significant differences in the results of the comparison of vagally mediated arterial-cardiac baroreflex function between on-stimulation and off-stimulation. Conclusions: The vagal component in cardiac autonomic dysfunction associated with PD is expected to improve after STN-DBS. We considered that the patients improved their lifestyle; in particular, increasing the amount of exercise by STN-DBS and the best pharmachological treatment may have positive effects on parasympathetic activities.

Effects of Electrode Implantation Angle on Thalamic Stimulation for Treatment of Tremor

Introduction. Chronic thalamic stimulation has been confirmed as an effective treatment for tremor. The optimal target has been commonly accepted to be situated within the ventral thalamus, but a standard trajectory of the deep brain stimulation (DBS) electrode has not yet been established. Materials and Methods. A 53‐year‐old man with an 11‐year history of essential tremor was treated by DBS of the thalamus. In this patient, we had a chance to compare the effects of different trajectory angles of the DBS electrode on tremor. Results. Intraoperative stimulation with the DBS electrode temporarily inserted at a high angle to the horizontal plane of the anterior commissure–posterior commissure (AC–PC) line to cover only the nucleus ventralis intermedius (Vim) was not effective. In contrast, stimulation with the DBS electrode permanently implanted at a low angle, covering a wide area extending from the nucleus ventralis oralis (Vo) to the Vim, reduced the tremor. Conclusion. We report on the case of a patient who showed different effects on tremor depending on the trajectory angle of the DBS electrode to the AC–PC line. The insertion trajectory of the DBS electrode may be an important factor for the treatment of tremor.

Fatal hemorrhage from AVM after DBS surgery: case report.

Intracranial hemorrhage is a crucial complication of deep brain stimulation (DBS) surgery. The bleeding caused by mechanical tissue injury due to microelectrode and/or DBS electrode lead insertion has been well studied. However, hemorrhage caused by a congenital underlying disease such as vascular malformation has not been examined carefully.

Impact of Subthalamic Nucleus Stimulation on Young-Onset Parkinson's Disease

Objective. To clarify the efficacy of subthalamic nucleus (STN) stimulation in young‐onset Parkinsons disease (PD), we compared the effects of STN stimulation on the motor symptoms between young‐onset PD (YOPD) and late‐onset PD (LOPD). Methods. We analyzed the effects of STN stimulation on motor function and motor fluctuations in 15 patients with YOPD, and 113 patients with LOPD who underwent STN stimulation during the same period. The Unified Parkinsons Disease Rating Scale (UPDRS) was evaluated during the on‐period and off‐period, which are defined as the times at which the motor symptoms are the best and worst during the daily active time with sustaining anti‐parkinsonian drugs. The dyskinesia severity rating scale (DSRS) also was employed to assess the severity of peak‐dose dyskinesia. We analyzed the changes in levodopa equivalent daily dose (LED), motor fluctuations, DSRS, and UPDRS part 3 score after STN stimulation, and compared the changes in each score between the two groups (YOPD vs. LOPD). Results. The LED was reduced, and the on‐off motor fluctuation index, dyskinesia rating scale score (on‐period), and UPDRS part 3 score (on‐ and off‐periods) were improved in both the YOPD and LOPD groups. The improvement rates of the UPDRS part 3 scores in both the on‐ and off‐periods in the YOPD group were superior to those in the LOPD group. The results of multivariate logistic regression analysis demonstrated that YOPD itself is the best responder to STN stimulation. Conclusions. STN stimulation can reduce the LED and improve motor fluctuations in patients with YOPD. The effects of STN stimulation on the motor symptoms of YOPD patients are superior to those in LOPD. The present findings suggest that YOPD patients suffering from several problems related to pharmacological therapy are probably good candidates for STN stimulation.

Simulation to locate burr hole sites in a patient for deep brain stimulation surgery and clipping of intracranial aneurysm.

Background and Objective:  Deep brain stimulation (DBS) candidates with neurologic diseases such as unruptured aneurysm present additional challenges to neurosurgeons when craniotomy must precede DBS surgery. Such craniotomy may potentially overlap with intended burr hole sites for the later insertion of DBS electrodes, and the skin incision for craniotomy may lie very close to or intersect with that for the burr holes. We report here a case of forehead craniotomy prior to DBS surgery in which we employed a neuronavigation system to simulate locations for the craniotomy and burr holes.

S28-3 D-wave monitoring in brain tumor surgery

through: (1) Somatosensory evoked potential phase reversal technique; (2) DCS with a short train of 5 7 monopolar stimuli (0.5ms duration, ISI 4.1, intensity up to 20mA) at 1 2Hz. To monitor motor pathways during tumor removal, MEPs are recorded from controlateral limb muscles after either DCS and/or transcranial electrical stimulation. When approaching tumor borders, MEP monitoring is combined with periodical direct subcortical stimulation (DSS) to localize the corticospinal tract (CT) and guide resection.A more than 75% drop in transcranial MEP amplitude at the end of surgery, and a DSS thresholds lower than 3 4mA are associated to post-operative neurological worsening. However these two neurophysiological warning signs are not significantly related and do not necessarily identify the same patients, suggesting that continuous MEP monitoring and periodical subcortical mapping should be combined to minimize risks. Recently, thanks to the introduction of diffusion tensor imaging and neuronavigation, there has been an increasing interest for the correlation of fiber tractography with subcortical stimulation. This work is providing some degree of reliability in the assessment of subcortical current spreading. Preliminary data suggest that 1mA = 1mm may be an acceptable practical parameter to judge on the distance from the CT, when using subcortical mapping.

72. Neuronal activity of the globus pallidus in dystonia

To test the effect of motor imagery as compared to voluntary muscle contraction on the excitability of the anterior horn cells, we studied F-wave persistence and amplitude, monitoring the force by a transducer. F-waves were recorded from the first dorsal interosseus muscle at rest and under a battery of motor tasks which comprised mental imagery and mild to moderate abduction of the index finger in 10 increments up to 30% of the maximal force. During each step lasting for 20 s, 20 stimuli were applied to the ulnar nerve at the wrist at the rate of one per second. In 12 healthy subjects, F-wave persistence (mean ± SD) significantly (p < 0.05) increased from 32.5 ± 11.9% at rest to 58.3 ± 15.2% during motor imagery and to 87–91% during voluntary contraction. Similarly, F-wave amplitude significantly (p < 0.05) increased from 41.3 ± 77.1 lV at rest to 91.2 ± 142.7 lV during motor imagery and to 183–274 lV during voluntary contraction. In contrast, F-wave latency changed little regardless of motor tasks. Motor imagery, though to a lesser degree than muscle contraction, effectively enhances the excitability of the anterior horn cells, thereby increasing F-wave persistence and amplitude above the baseline.