Correlation of outcome to neurosurgical lesions: confirmation of a new method using data after microelectrode-guided pallidotomy.

The purpose of this study was the development of a new method to correlate functional surgery with outcome measures. Lesions following microelectrode guided globus pallidus internus (GPi) pallidotomy for Parkinson's disease are presented to demonstrate this new method in regard to clinical outcome. A clinical series of 26 patients with extensive neurological and neuropsychological data were studied. Three-month postoperative MRI lesion borders at the AC-PC plane were scaled to a standard size, and the lesions were stored in a virtual array with a cell size of one voxel. The average outcome measure for each voxel is presented graphically. Unified Parkinson's disease rating scale (UPDRS) motor scores improved more with posterolateral and centrally located GPi lesions than with anteromedial lesions. A correlation of lesion location to outcome was also visible for subscales of the UPDRS. The distributions were similar for the left and right sides, as well as for ipsi- and contralateral measurements. In general, verbal fluency decreased after lesioning the dominant hemisphere, and posterolateral lesions caused less impairment. This method enables associative analyses between brain area and outcome down to the size of a few voxels. This may be particularly helpful for planning and validating neurosurgical targets for various disorders.

Bilateral thalamic deep brain stimulation: midline tremor control.

OBJECTIVES: To determine the efficacy of bilateral deep brain stimulation (DBS) for management of midline tremor (head, voice, tongue, trunk) in patients with essential tremor. DESIGN: Prospective assessment of tremor at baseline (presurgical), and postoperatively at 1, 3, and 12 months, and annually thereafter. METHODS: A clinical series of 22 individuals undergoing staged, bilateral DBS for treatment of essential tremor. The tremor rating scale was the primary outcome measure. RESULTS: Midline tremor showed significant improvement with stimulation "on" at nearly every postoperative interval when compared with stimulation "off" and with baseline tremor. Bilateral stimulation was associated with a significant incremental improvement in midline tremor control compared with unilateral stimulation: average "stimulation on" percentage change in midline tremor from the unilateral to bilateral period was 81%. Head and voice tremor showed the most consistent improvement. Among those requiring a change in stimulation parameters because of side effects, dysarthria, disequilibrium, motor disturbances, and paraesthesiae were the most common. Dysarthria was more common with bilateral (n = 6; 27%) than with unilateral (n = 0) stimulation. Stimulation parameters remained largely unchanged after the first three months. Nine of 44 leads placed (20%) required subsequent repositioning or replacement. CONCLUSIONS: Unilateral thalamic stimulation significantly improves midline tremor, and subsequent bilateral thalamic stimulation offers an additional incremental improvement in midline tremor control.

Thalamic deep brain stimulation for essential tremor: recommendations for long-term outcome analysis.

OBJECTIVES: Determine the efficacy of thalamic deep brain stimulation (DBS) for tremor control among individuals with essential tremor (ET). METHODS: A clinical series of 52 consecutive individuals undergoing placement of a DBS system for treatment of ET completed an unblinded battery of subjective and objective measures at postoperative intervals of one, three, and 12 months, and annually thereafter up to three years. The assessment battery included measures of tremor and activities of daily living. RESULTS: Both subjective and objective measures showed that stimulation was associated with significant improvement at nearly every postoperative interval as compared to pre-operative and stimulation 'off' ratings of activities of daily living functioning, midline tremor, contralateral upper extremity tremor, and contralateral lower extremity tremor. Ipsilateral tremor showed some improvement with stimulation, but only within the first three months. Trend analysis showed stable tremor control. Stimulation settings remained largely unchanged after the first three months. Dysarthria was more common among those with bilateral stimulation. A range of missing data estimation methods were performed, and subsequent analyses corroborated the main findings of the study. CONCLUSION: Thalamic DBS is generally a well-tolerated and effective treatment for ET. Methodological and analytical recommendations are provided for the evaluation of long-term outcome.

Quantitative and qualitative outcome measures after thalamic deep brain stimulation to treat disabling tremors.

OBJECTIVE: We studied outcome measures after unilateral and bilateral thalamic stimulation to treat disabling tremor resulting from essential tremor and Parkinson's disease. The surgical technique, qualitative and quantitative tremor assessments, stimulation parameters, locations of active electrodes, complications, and side effects are described and analyzed. METHODS: Forty-one patients with essential tremor or Parkinson's disease underwent implantation of 56 thalamic stimulators. Preoperative qualitative and quantitative tremor measurements were compared with those obtained after unilateral and bilateral surgery, with activated and deactivated stimulators. Stimulation parameters and stimulation-related side effects were recorded, and outcome measures were statistically analyzed. RESULTS: Qualitative measurements demonstrated significant improvement of contralateral upper-limb (P < 0.001), lower-limb (P < 0.01), and midline (P < 0.001) tremors after unilateral surgery. Ipsilateral arm tremor also improved (P < 0.01). No differences were observed with the Purdue pegboard task. Quantitative accelerometer measurements were correlated with qualitative assessments and confirmed improvements in contralateral resting (P < 0.001) and postural (P < 0.01) tremors and ipsilateral postural tremor (P < 0.05). Activities of daily living improved after unilateral surgery (P < 0.001) and additionally after bilateral surgery (P < 0.05). Adjustments of the pulse generator were required more frequently for tremor control than for amelioration of side effects. Bilateral thalamic stimulation caused more dysarthria and dysequilibrium than did unilateral stimulation. Stimulation-related side effects were reversible for all patients. Stimulation parameters did not change significantly with time. A significantly lower voltage and greater pulse width were used for patients with bilateral implants. CONCLUSION: Unilateral thalamic stimulation and bilateral thalamic stimulation are safe and effective procedures that produce qualitative and quantitative improvements in resting, postural, and kinetic tremor. Thalamic stimulation-related side effects are mild and reversible.

Simultaneous thalamic deep brain stimulation and implantable cardioverter-defibrillator.

Thalamic deep brain stimulation is becoming increasingly popular for the control of drug-refractory tremor. Implantable cardiac pacemakers and defibrillators are commonly used therapeutic modalities. Concerns exist about the potential interactions between these 2 devices in the same patient, but no experience has been reported previously. We describe a patient with essential tremor who had a deep brain stimulator implanted into the left ventral intermediate nucleus of thalamus, who subsequently needed an implantable cardioverter-defibrillator. Despite concerns about possible interactions between the 2 types of implanted electrical devices (i.e., a situation similar to drug-drug interactions), the deep brain stimulator and the implanted pacemaker-defibrillator functioned appropriately, and no interaction occurred in our patient.

Predictors of neuropsychological outcome in patients following microelectrode-guided pallidotomy for Parkinson's disease.

OBJECT: The authors studied neuropsychological performance following microelectrode-guided posteroventral pallidotomy in patients with Parkinson's disease (PD) and evaluated correlations with presurgical and surgical factors. METHODS: Neuropsychological changes 3 months (43 patients) and 12 months (27 patients) after microelectrode-guided pallidotomy for PD are reported in a series of 44 consecutive patients with the disease, who improved neurologically, as measured by the Unified Parkinson's Disease Rating Scale (UPDRS) in both the "off' (p<0.001) and best "on" (p<0.001) states. Findings of the vocabulary subtest of the Wechsler Adult Intelligence Scale-Revised (p<0.01), Letter Fluency (p<0.001), Verbal Fluency for semantic categories (p<0.001), and the Wisconsin Card Sorting Test (p<0.01) showed a significant decline in neuropsychological performance in patients 3 months after undergoing left-sided pallidotomy. Impairment in the language domain (semantic fluency) persisted at the 12-month follow-up examination (p<0.01). Visual memory improved after right-sided pallidotomies (p<0.01 after 3 months), with a nonsignificant trend toward persistent improvement 1 year postsurgery (p<0.02 after 12 months). Preoperative semantic fluency was influenced by patient age (p<0.001) and by the width of the third ventricle (p<0.05), as measured by magnetic resonance imaging. A regression model revealed that semantic fluency 3 months postoperatively was significantly affected by the baseline score (p<0.001), side of surgery (p<0.001), handedness (p<0.01), and patient age (p<0.05). However, postoperative lesion volume, lesion location, number of tracks, number of lesions, distance from anatomical landmarks, or UPDRS score did not significantly contribute to neuropsychological outcome. CONCLUSIONS: Neuropsychological changes in a cohort of patients with PD who underwent pallidotomy and experienced excellent clinical benefits and minimum postoperative complications, emphasize the importance of neuropsychological examinations and further investigation of predictive factors.

Computer-assisted neurosurgery by using a noninvasive vacuum-affixed dental cast that acts as a reference base: another step toward a unified approach in the treatment of brain tumors.

OBJECT: The purpose of the study was to evaluate the use of the Vogele-Bale-Hohner (VBH) mouthpiece, which is attached to the patient's upper jaw by negative pressure, for patient-image registration and for tracking the patient's head during image-guided neurosurgery. METHODS: A dynamic reference frame (DRF) is reproducibly mounted on the mouthpiece. Reference points, optimally distributed and attached to the mouthpiece, are used for registration in the patient's absence on the day before surgery. In the operating room, the mouthpiece and DRF are precisely repositioned using a vacuum, and the patient's anatomical structures are automatically registered to corresponding ones on the image. Experimental studies and clinical experiences in 10 patients confirmed repeated (rigid body) localization accuracy in the range of 0 to 2 mm, throughout the entire surgery despite movements by the patient. CONCLUSIONS: Because of its noninvasive, rigid, reliable, and reproducible connection to the patient's head, the VBH vacuum-affixed mouthpiece grants the registration device an accuracy comparable to invasive fiducial markers.

Thalamic stimulation for the treatment of midline tremors in essential tremor patients.

The authors prospectively collected unblinded data from 27 consecutive patients following thalamic stimulation. A significant reduction of midline tremor was achieved after unilateral surgery, but a staged contralateral surgery had an additional effect. A subgroup analysis showed significant beneficial effects for head, voice, tongue, and face tremor. The most frequent reversible side effects were disequilibrium, dysarthria, and paresthesias. We observed more pulse generator adjustments for speech problems in the bilaterally implanted group.