Skewering the subthalamic nucleus via a parietal approach.

BACKGROUND/AIMS: A frontal burr hole around the level of the coronal suture is the conventional entry point when performing subthalamic nucleus (STN) deep brain stimulation (DBS). However, alternative approaches may sometimes be necessary. METHODS: We present a report of delayed hardware erosion through the scalp in the left frontal region after successful bilateral STN DBS for Parkinson's disease. The left STN was retargeted via a parietal entry point. RESULTS: Significant improvement in UPDRS motor score (59%) was obtained with bilateral stimulation 6 months after re-operation. The literature was examined for similar approaches and the rationale, risks and benefits of non-frontal entry points in functional neurosurgery were explored. CONCLUSION: Together with a brief review of STN anatomy, this report demonstrates that the parietal approach to the STN remains a viable option in addition to the more traditional frontal access.

Impaired ideomotor limb apraxia in cortical and subcortical dementia: a comparison of Alzheimer's and Huntington's disease.

BACKGROUND: Although ideomotor limb apraxia is often considered to occur only in dementia with cortical involvement like Alzheimer's disease (AD), it is also frequently seen in dementia with subcortical degeneration like Huntington's disease (HD). METHODS: To assess the occurrence of ideomotor limb apraxia, 46 patients with HD (27 men) and 37 patients with AD (16 men), matched for cognitive performance, were assessed with an apraxia test battery containing tests of the imitation of meaningless hand and finger gestures, the performance of meaningful gestures and of pantomimic movements. RESULTS: There was a high frequency of ideomotor limb apraxia in both AD and HD patients. For the assessment of hands' imitation 13.5% of the AD patients and 41.3% of the HD patients were apraxic, for fingers' imitation 21.6% (AD) and 41.3% (HD) were apraxic, for gestures 27.0% (AD) and 32.6% (HD), and for the assessment of pantomimic movements 24.3% (AD) and 52.2% (HD) showed apraxia. In the AD patients, disease severity was related to the occurrence of apraxia. CONCLUSIONS: Ideomotor limb apraxia is a common sign in both groups of patients, occurring in a high percentage. For particular neuropsychological deficits, including ideomotor limb apraxia, a division of dementia in a subcortical and cortical subtype seems to be clinically not meaningful.

Improving targeting in image-guided frame-based deep brain stimulation.

BACKGROUND: Deep brain stimulation (DBS) is commonly used in the treatment of movement disorders such as Parkinson disease (PD), dystonia, and other tremors. OBJECTIVE: To examine systematic errors in image-guided DBS electrode placement and to explore a calibration strategy for stereotactic targeting. METHODS: Pre- and postoperative stereotactic MR images were analyzed in 165 patients. The perpendicular error between planned target coordinates and electrode trajectory was calculated geometrically for all 312 DBS electrodes implanted. Improvement in motor unified PD rating scale III subscore was calculated for those patients with PD with at least 6 months of follow-up after bilateral subthalamic DBS. RESULTS: Mean (standard deviation) scalar error of all electrodes was 1.4(0.9) mm with a significant difference between left and right hemispheres. Targeting error was significantly higher for electrodes with coronal approach angle (ARC) ≥10° (P < .001). Mean vector error was X: -0.6, Y: -0.7, and Z: -0.4 mm (medial, posterior, and superior directions, respectively). Targeting error was significantly improved by using a systematic calibration strategy based on ARC and target hemisphere (mean: 0.6 mm, P < .001) for 47 electrodes implanted in 24 patients. Retrospective theoretical calibration for all 312 electrodes would have reduced the mean (standard deviation) scalar error from 1.4(0.9) mm to 0.9(0.5) mm (36% improvement). With calibration, 97% of all electrodes would be within 2 mm of the intended target as opposed to 81% before calibration. There was no significant correlation between the degree of error and clinical outcome from bilateral subthalamic nucleus DBS (R = 0.07). CONCLUSION: After calibration of a systematic targeting error an MR image-guided stereotactic approach would be expected to deliver 97% of all electrodes to within 2 mm of the intended target point with a single brain pass.

Minimizing brain shift in stereotactic functional neurosurgery.

BACKGROUND: Stereotactic functional neurosurgical interventions depend on precise anatomic targeting before lesioning or deep brain stimulation (DBS) electrode placement. OBJECTIVE: To examine the degree of subcortical brain shift observed when adopting an image-guided approach to stereotactic functional neurosurgery. METHODS: Coordinates for the anterior and posterior commissural points (AC and PC) were recorded on thin-slice stereotactic magnetic resonance imaging (MRI) scans performed before and immediately after DBS electrode implantation in 136 procedures. The changes in length of AC-PC and in stereotactic coordinates for AC and PC were calculated for each intervention. In patients with Parkinson disease undergoing bilateral subthalamic nucleus (STN) DBS with at least 6 months of follow-up, pre- and postoperative scores of the motor part of the Unified Parkinson's Disease Rating Scale (UPDRS-III) were reviewed. RESULTS: Mean (SD) change in AC-PC length (DeltaAC-PC) was 0.6 (0.4) mm. There was no statistically significant difference in DeltaAC-PC between groups when examining anatomic target subgroups (P =.95), age subgroups (P = .63), sex (P = .59), and unilateral versus bilateral implantation (P =.15). The mean (SD) vector changes for the commissural points were: -0.1 (0.3) mm in X, -0.4 (0.6) mm in Y, and -0.1 (0.7) mm in Z for the AC; and -0.1 (0.3) mm in X, -0.2 (0.7) mm in Y, and 0.0 (0.7) mm in Z for the PC. There was a negligible correlation between the magnitude of brain shift and percentage improvement in UPDRS-III off-medication in patients undergoing STN DBS for PD (R <0.01). CONCLUSION: Brain shift has long been considered an issue in stereotactic targeting during DBS procedures. However, with the image-guided approach and surgical technique used in this study, subcortical brain shift was extremely limited and did not appear to adversely affect clinical outcome.

Combating depression in Huntington's disease: effective antidepressive treatment with venlafaxine XR.

Patients with Huntington's disease (HD) often suffer from psychiatric symptoms including affective disorder, psychosis, irritability, and apathy, which may be present in all stages of the disease. However--despite the obvious likelihood that these symptoms may be reduced by antidepressive treatments--to date, the effectiveness of such treatments in HD has only ever been examined in case studies. Twenty-six HD patients (17 men), with a diagnosis of major depression, were studied. The symptoms of HD and depression were systematically measured using the Beck Depression Inventory and the Hamilton Rating Scale for Depression both at baseline and after 4 weeks of treatment with venlafaxine XR. After 4 weeks of venlafaxine XR treatment, the symptoms of depression in HD patients decreased significantly relative to baseline. However, approximately one in five patients developed significant venlafaxine-related side effects (nausea and irritability). Venlafaxine XR is highly effective in the treatment of depression in HD, although it may produce unpleasant side effects. Further studies are required to establish the most suitable treatment for depression in HD.