Postmortem analysis following 71 months of deep brain stimulation of the subthalamic nucleus for Parkinson disease.

Deep brain stimulation (DBS) of the subthalamic nucleus (STN) is a clinically effective neurosurgical treatment for Parkinson disease. Tissue reaction to chronic DBS therapy and the definitive location of active stimulation contacts are best studied on a postmortem basis in patients who have undergone DBS. The authors report the postmortem analysis of STN DBS following 5 years and 11 months of effective chronic stimulation including the histologically verified location of the active contacts associated with bilateral implants. They also describe tissue response to intraoperative test passes with recording microelectrodes and stimulating semimacroelectrodes. The results indicated that 1) the neural tissue surrounding active and nonactive contacts responds similarly, with a thin glial capsule and foreign-body giant cell reaction surrounding the leads as well as piloid gliosis, hemosiderin-laden macrophages, scattered lymphocytes, and Rosenthal fibers; 2) there was evidence of separate tracts in the adjacent tissue for intraoperative microelectrode and semimacroelectrode passes together with reactive gliosis, microcystic degeneration, and scattered hemosiderin deposition; and 3) the active contacts used for approximately 6 years of effective bilateral DBS therapy lie in the zona incerta, just dorsal to the rostral STN. To the authors' knowledge, the period of STN DBS therapy herein described for Parkinson disease and subjected to postmortem analysis is the longest to date.

Intersurgeon variability in the selection of anterior and posterior commissures and its potential effects on target localization.

BACKGROUND: This study reports the intersurgeon variability in manual selection of the anterior and posterior commissures (AC and PC). The study also investigates the effect of this variability on the localization of targets like the subthalamic nucleus, ventralis intermedius nucleus and globus pallidus internus. The additional effect of variation in the selection of the mid-plane on target localization is also evaluated. METHODS: 43 neurosurgeons (38 attendings, 5 residents/ fellows) were asked to select the AC and the PC points (as routinely used for stereotactic neurosurgical planning) on two MRI scans. The corresponding mid-commissural points (MCPs) and target coordinates were calculated. RESULTS: The collected data show that the MCP is more reliable than either the AC or the PC points. These data also show that, even for experienced neurosurgeons, variations in selecting the AC and the PC point result in substantial variations at the target points: 1.15 +/- 0.89 mm, 1.45 +/- 1.25 mm, 1.21 +/- 0.83 for the subthalamic nucleus, ventralis intermedius nucleus, and globus pallidus internus, respectively, for the first MRI volumeand 1.08 +/- 1.37 mm, 1.35 +/- 1.71 mm, 1.12 +/- 1.17 mm for the same structures for the second volume. These variations are larger when residents/fellows are included in the data set. CONCLUSIONS: The data collected in this study highlight the difficulty in establishing a common reference system that can be used to communicate target location across sites. It indicates the need for the development and evaluation of alternative normalization methods that would permit specifying targets directly in image coordinates or the development of improved imaging techniques that would permit direct targeting.

Neuromodulation of the cingulum for neuropathic pain after spinal cord injury. Case report.

The authors present a case in which high-frequency electrical stimulation of the cingulum using standard deep brain stimulation (DBS) technology resulted in pain relief similar to that achieved with cingulotomy and superior to that achieved with periventricular gray matter (PVG) stimulation. This patient had a complete spinal cord injury at the C-4 level and suffered from medically refractory neuropathic pain. He underwent placement of bilateral cingulum and unilateral PVG DBS electrodes and a 1-week blinded stimulation trial prior to permanent implantation of a pulse generator. During the stimulation trial, the patient's pain level was assessed using a visual analog scale, and pain medication usage was recorded. During this period the patient was blinded to stimulation parameters. Stimulation of the cingulum provided better pain control than PVG stimulation or medication alone. The authors believe that cingulum stimulation can benefit patients with severe neuropathic pain that is refractory to other treatments. Advantages over cingulotomy include reversibility and the ability to adjust stimulation parameters for optimum efficacy.

Delayed occurrence of multiple spinal drop metastases from a posterior fossa choroid plexus papilloma. Case report.

Choroid plexus papilloma is a benign central nervous system tumor that occasionally spreads along the subarachnoid space. The authors report the case of a 49-year-old man who presented with back pain 19 years after resection of a posterior fossa choroid plexus papilloma. Magnetic resonance imaging revealed multiple spinal lesions without any residual or recurrent intracranial tumor. All spinal lesions were resected and histologically diagnosed as atypical choroid plexus papilloma. The authors suggest that patients in whom choroid plexus papilloma is diagnosed should undergo total neuraxis imaging at the time of initial diagnosis as well as periodic follow-up examinations after resection to rule out drop metastases.

Work hours restrictions as an ethical dilemma for residents: a descriptive survey of violation types and frequency.

BACKGROUND: The Accreditation Council for Graduate Medical Education (ACGME) implemented requirements regarding allowable duty hours for resident training in the United States in July 2003. In a previous pilot study at Vanderbilt University Medical Center, a significant number of residents reported violation of requirements. In addition, almost half of those individuals admitted under-reporting their hours worked. The authors' goal was to further delineate the type and frequency of violations and under-reporting. METHODS: A survey tool was designed to assess specific types of violations as well as factors that influence the number of hours residents worked and reported. Approval was obtained from the Vanderbilt Institutional Review Board and Office of Graduate Medical Education before enrollment of subjects. The program directors of Pediatrics, Internal Medicine, Medicine-Pediatrics, and General Surgery supported the participation of their residents. A voluntary anonymous survey of these residents was conducted 1 year after the pilot study. RESULTS: Of 263 eligible residents, 175 were surveyed. Of 175 residents, 125 (71%) residents responded. Eighty-five percent of residents reported violation of duty-hour requirements within the preceding 3 months. Residents reported violation of specific requirements as follows: 1 day off in 7, 28%; 80-hour weekly average, 65%; and "24+6" consecutive hours, 85%. Residents were asked to estimate the number of hours by which they exceeded requirements. Hours over the 80-hour weekly requirement were reported as follows: 1 hour, 12%; 2 hours, 15%; 3 hours, 21%; 4 hours, 5%; 5 hours, 14%; and 6 or more hours, 33%. Hours over the "24+6" requirement were reported as follows: 1 hour, 30%; 2 hours, 42%; 3 hours, 18%; 4 hours, 7%; 5 hours, 1%; and 6 or more hours, 2%. Forty-eight percent of respondents admitted under-reporting violations to their program director. CONCLUSIONS: Eighty-five percent of residents reported at least 1 violation, and 48% admitted under-reporting violations. These results support the previous findings of 80% and 49%, respectively. Of the various requirements, the "24+6" rule was most frequently violated. Of those in violation of the "24+6" requirement, the majority (90%) exceeded limits by no more than 3 hours. Of those in violation of the 80-hour weekly average requirement, the majority (57%) exceeded limits by no more than 5 hours. Per the ACGME website, "an RRC may grant exceptions for up to 10% of the 80-hour limit, to individual programs based on a sound educational rationale." Although the overall percent of residents reporting violation remains high, the number of excess hours worked is small relative to established standards (within 10%). The authors propose that systems adaptations could be developed to improve compliance. Special attention is warranted to investigate the activities of residents in the post-call period.

Rod derotation techniques for thoracolumbar spinal deformity.

OBJECTIVE: The operative correction of scoliosis requires multiple intraoperative techniques and tools to achieve an adequate result. Frequently, multiple methods are used to accomplish this, such as rod cantilever techniques, in situ bending, Smith-Petersen and pedicle subtraction osteotomies, closed reduction methods, and rod derotation techniques. Rod derotation techniques will be reviewed and discussed in this article. METHODS: A review of the available literature on anterior and posterior rod derotation is performed with a case example of the authors' experience utilizing this technique. RESULTS: Rod derotation is one technique that can transform a pathological scoliotic curve to normal physiological kyphosis or lordosis by simply rotating a rod intraoperatively. CONCLUSION: In this article, the authors present rod derotation as a valuable technique in the surgical arsenal for the treatment of scoliosis, including a discussion of the technique and its limitations.

Automatic selection of DBS target points using multiple electrophysiological atlases.

In this paper we study and evaluate the influence of the choice of a particular reference volume as the electrophysiological atlas on the accuracy of the automatic predictions of optimal points for deep brain stimulator (DBS) implants. We refer to an electrophysiological atlas as a spatial map of electrophysiological information such as micro electrode recordings (MER), stimulation parameters, final implants positions, etc., which are acquired for each patient and then mapped onto a single reference volume using registration algorithms. An atlas-based prediction of the optimal point for a DBS surgery is made by registering a patient's image volume to that reference volume, that is, by computing a correct coordinate mapping between the two; and then by projecting the optimal point from the atlas to the patient using the transformation from the registration algorithm. Different atlases, as well as different parameterizations of the registration algorithm, lead to different and somewhat independent atlas-based predictions. We show how the use of multiple reference volumes can improve the accuracy of prediction by combining the predictions from the multiple reference volumes weighted by the accuracy of the non-rigid registration between each of the corresponding atlases and the patient volume.