Biomedical subjects

Shearwood McClelland

Publications and source records attributed to Shearwood McClelland.

8 recordsLinked to original sources

PubMed2006

A technique for minimally altering anatomically based subthalamic electrode targeting by microelectrode recording.

OBJECT: Implantation of a subthalamic nucleus (STN) deep brain stimulation (DBS) electrode is increasingly recognized as an effective treatment for advanced Parkinson disease (PD). Despite widespread use of microelectrode recording (MER) to delineate the boundaries of the STN prior to stimulator implantation, it remains unclear to what extent MER improves the clinical efficacy of this procedure. In this report, the authors analyze a series of patients who were treated at one surgical center to determine to what degree final electrode placement was altered, based on readings obtained with MER, from the calculated anatomical target. METHODS: Subthalamic DBS devices were placed bilaterally in nine patients with advanced PD. Frame-based volumetric magnetic resonance images were acquired and then transferred to a stereotactic workstation to determine the anterior and posterior commissure coordinates and plane. The initial anatomical target was 4 mm anterior, 4 mm deep, and 12 mm lateral to the midcommissural point. The MERs defined the STN boundaries along one or more parallel tracks, refining the final electrode placement by comparison of results with illustrations in a stereotactic atlas. In eight of 18 electrodes, the MER results did not prompt an alteration in the anatomically derived target. In another eight placements, MER altered the target by less than 1 mm and two of 18 electrode positions differed by less than 2 mm. The anterior-posterior difference was 0.53 +/- 0.65 mm, whereas the medial-lateral direction differed by 0.25 +/- 0.43 mm. The ventral boundary of the STN defined by MER was 2 +/- 0.72 mm below the calculated target (all values are the means +/- standard deviation). All patients attained clinical improvement, similar to previous reports. CONCLUSIONS: In this series of patients, microelectrode mapping of the STN altered the anatomically based target only slightly. Because it is not clear whether such minor adjustments improve clinical efficacy, a prospective clinical comparison of MER-refined and anatomical targeting may be warranted.

Brain Mapping↗

PubMed2006

Carcinomatous meningitis from urachal carcinoma: the first reported case.

Carcinomatous meningitis (CM) occurs in less than 10% of cancer patients. Although patients frequently present with a focal complaint, multifocal signs are often found following careful neurological examination. The gold standard for diagnosis remains the demonstration of neoplastic cells in the cerebrospinal fluid. Despite the discouraging prognosis, palliative treatment may improve quality of life and lengthen lifespan. We report a patient with known primary carcinoma of the urachus who presented with headaches, nausea, vomiting and ataxia 1 week following resection of a nodular arachnoidal metastasis (indenting the cerebellum). Lumbar cerebrospinal fluid subsequently confirmed carcinomatous meningitis. This is the first reported case of carcinomatous meningitis resulting from metastatic urachal carcinoma.

Adenocarcinoma↗

PubMed2006

Facial emotion recognition after curative nondominant temporal lobectomy in patients with mesial temporal sclerosis.

PURPOSE: The right (nondominant) amygdala is crucial for processing facial emotion recognition (FER). Patients with temporal lobe epilepsy (TLE) associated with mesial temporal sclerosis (MTS) often incur right amygdalar damage, resulting in impaired FER if TLE onset occurred before age 6 years. Consequently, early right mesiotemporal insult has been hypothesized to impair plasticity, resulting in FER deficits, whereas damage after age 5 years results in no deficit. The authors performed this study to test this hypothesis in a uniformly seizure-free postsurgical population. METHODS: Controls (n=10), early-onset patients (n=7), and late-onset patients (n=5) were recruited. All patients had nondominant anteromedial temporal lobectomy (AMTL), Wada-confirmed left-hemisphere language dominance and memory support, MTS on both preoperative MRI and biopsy, and were Engel class I 5 years postoperatively. By using a standardized (Ekman and Friesen) human face series, subjects were asked to match the affect of one of two faces to that of a simultaneously presented target face. Target faces expressed fear, anger, or happiness. RESULTS: Statistical analysis revealed that the early-onset group had significantly impaired FER (measured by percentage of faces correct) for fear (p=0.036), whereas the FER of the late-onset group for fear was comparable to that of controls. FER for anger and happiness was comparable across all three groups. CONCLUSIONS: Despite seizure control/freedom after AMTL, early TLE onset continues to impair FER for frightened expressions (but not for angry or happy expression), whereas late TLE onset does not impair FER, with no indication that AMTL resulted in FER impairment. These results indicate that proper development of the right amygdala is necessary for optimal fear recognition, with other neural processes unable to compensate for early amygdalar damage.

Adolescent↗

PubMed2005

Subthalamic stimulation for Parkinson disease: determination of electrode location necessary for clinical efficacy.

OBJECT: Deep brain stimulation (DBS) of the subthalamic nucleus (STN) performed using intraoperative microelectrode recording (MER) to adjust electrode placement has become a widely used treatment for patients with advanced Parkinson disease (PD). Few studies have been conducted to examine the location of implanted electrodes relative to the intended target, and even fewer have been undertaken to investigate the degree to which variations in the location of these electrodes impacts their clinical efficacy. This study was performed to examine these issues. METHODS: The authors located 52 bilaterally implanted DBS electrode tips on postoperative magnetic resonance (MR) images obtained in 26 consecutive patients. Postoperative and preoperative planning MR images were merged to determine the DBS electrode tip coordinates relative to the midcommissural point. Surgical records listed the intended target coordinates for each DBS electrode tip. Clinical outcome assessment included the Unified PD Rating Scale (UPDRS) motor score at 1 year, standardized questionnaires, and routine follow-up visits. The mean difference between electrode tip location and intended target for all 52 electrodes was less than 2 mm in all axes. Only one electrode was farther than 3 mm from the intended target, and this was the only electrode that had to be replaced due to lack of clinical efficacy (lack of tremor suppression); its reimplantation 4 mm more medially provided excellent tremor control. High correlation coefficients indicate that the MR imaging analysis accurately determined the anatomical location of the electrode tips. Blinded videotape reviews of UPDRS motor scores comparing effects of stimulation in patients who were "on" and "off" medication identified subgroups in whom there was minimal and maximal stimulation response. Patients in these subgroups had no differences between the MR imaging-determined actual electrode tip location and its intended location. Similarly, improvements of dyskinesias and severity of symptoms encountered during the wearing-off period for the drug did not correlate with variations of electrode tip location. CONCLUSIONS: The findings in this study lead the authors to suggest that a DBS electrode placed anywhere within a 6-mm-diameter cylinder centered at the presumed middle of the STN (based on stereotactic atlas coordinates) provides similar clinical efficacy. Future studies may be warranted to evaluate prospectively the degree to which MER modification of the anatomically and/or image-determined target improves clinical efficacy of DBS electrodes.

Adult↗

PubMed2005

Microelectrode recording-determined subthalamic nucleus length not predictive of stimulation-induced side effects.

OBJECT: Deep brain stimulation (DBS) of the subthalamic nucleus (STN) has become a popular treatment for patients with medically refractory Parkinson disease. Many surgeons believe that microelectrode recording (MER) during DBS electrode implantation is needed to optimize placement, whereas stimulation-induced side effects such as paresthesias, dystonic contractions, dyskinesias, and ocular motor signs that become apparent postoperatively may be an indicator of the proximity of the electrode to various boundaries of the STN. This study was performed to evaluate the relationship between mapping of the STN by using MER and postoperative stimulation-induced side effects. METHODS: Eighty-two electrodes implanted in 75 patients between March 1999 and March 2003 were retrospectively examined to evaluate the length of the STN defined by MER, and the number of and threshold for postoperative stimulation-induced side effects. Electrodes were typically tested with increasing stimulation amplitudes (maximum 6 V) by using a monopolar array. The 82 electrodes were associated with 97 stimulation-induced side effects. The mean time between surgery and testing stimulation-induced side effects was 3.9 months. Statistical analysis (two-tailed t-test) revealed no significant difference in the number of stimulation-induced side effects (or the mean threshold for paresthesias, the most common side effect) for electrodes associated with an STN length less than 4.5 mm (13 electrodes) compared with those associated with an STN greater than or equal to 4.5 mm (69 electrodes, p = 0.616). For every electrode, the target adjustment based on MER results was within 2 mm of the image-planned target (usually 1 mm anterior). In the x axis (medial-lateral orientation), there was no systematic difference in adjustments made for the electrodes associated with the shorter compared with the longer STN lengths. In the y axis (anterior-posterior orientation), there was a very small statistically significant difference in the mean adjustment (0.4 mm) between the two groups. CONCLUSIONS: Analysis of these results suggests that a shorter MER-determined STN length alone does not reliably predict the incidence of stimulation-induced side effects.

Chi-Square Distribution↗

PubMed2005

Unusual findings in brain biopsies of two patients with acute magnetic resonance imaging lesions associated with focal seizures.

PURPOSE: Patients with focal seizures often have magnetic resonance imaging (MRI) abnormalities in the brain region of their presumed seizure focus. Neoplasms, ischemic infarctions, inflammatory processes, and other specific pathologic entities have been diagnosed by biopsies of such MRI abnormalities. Two patients with this presentation had brain lesion biopsies with a leading presumptive diagnosis of glial neoplasm but were found to have indistinct histopathology. METHODS: Each patient was initially seen with focal seizures (right parietal region, right hippocampus) corresponding with focally increased T2 signal on MRI. In both patients, the preoperative clinical suspicion was for neoplastic or inflammatory processes. RESULTS: Several weeks after seizure onset, craniotomy in patient 1 and stereotactic needle biopsy in patient 2 revealed mild gliosis with reactive vascular changes and perivascular hemosiderin deposition, not diagnostic of but compatible with venous congestion (or possibly venous thrombosis). Postoperatively, patient 1 had brief sensory seizures that stopped 5 months after surgery, whereas subsequent seizures did not develop in patient 2. Both patients had normalization of their MRI (except for postoperative changes) and have remained seizure free. CONCLUSIONS: We describe two patients who had brain biopsies of striking focal increased T2 signal MRI abnormalities associated with seizures. Pathologic findings contradicted our preoperative suspicions (neoplasm or inflammatory process), compatible with (but not conclusive for) subacute venous congestion/thrombosis. These findings indicate that patients with seizures may have an associated discrete intraaxial MRI lesion that is not neoplastic. To our knowledge, this is the first report of focal seizure-associated MRI lesions with biopsy findings compatible with venous congestion/thrombosis.

Adult↗

PubMed2005

The transformation of pediatric gliomatosis cerebri to cerebellar glioblastoma multiforme presenting as supra- and infratentorial acute disseminated encephalomyelitis. Case report.

Cerebellar glioblastoma multiforme (GBM) is a rare entity in adults and an extremely rare entity in children. Approximately 30 cases have been reported in the literature. The authors report the case of a histologically confirmed cerebellar GBM presenting initially as supra- and infratentorial gliomatosis cerebri. Acute disseminated encephalomyelitis had been diagnosed in the patient and that diagnosis remained until near the end of his treatment. This case underscores the need for recognizing the clinical presentation of gliomatosis cerebri and multifocal GBM in the pediatric subpopulation thought to harbor demyelinating disease.

Cerebellar Neoplasms↗

PubMed2004

Implantation of bilateral deep brain stimulators in patients with Parkinson disease and preexisting cardiac pacemakers. Report of two cases.

Deep brain stimulation (DBS) has become an important modality in the treatment of refractory Parkinson disease (PD). In patients with comorbid arrhythmias requiring cardiac pacemakers, DBS therapy is complicated by concerns over a possible electrical interaction between the devices (or with device programming) and the inability to use magnetic resonance imaging guidance for implantation. The authors report two cases of PD in which patients with preexisting cardiac pacemakers underwent successful implantation of bilateral DBS electrodes in the subthalamic nucleus (STN). Each patient underwent computerized tomography-guided stereotactic frame-based placement of DBS electrodes with microelectrode recording. Both extension wires were passed from the right side of the head and neck (contralateral to the pacemaker) to place the cranial pulse generators subcutaneously in the left and right abdomen. The cranial pulse generators were placed farther than 6 in from the cardiac pacemaker and from each other to decrease the chance of interference between the devices during telemetry reprogramming. Postoperative management involved brain stimulator programming sessions with simultaneous cardiological monitoring of pacemaker function and cardiac rhythm. No interference was noted at any time, and proper pacemaker function was maintained throughout the follow-up period. With bilateral STN stimulation, both patients experienced a dramatic improvement in their PD symptoms, including elimination of dyskinesias, reduction of "off" severity, and increase of "on" duration. With some modifications of implantation strategy, two patients with cardiac pacemakers were successfully treated with bilateral DBS STN therapy for refractory PD. To our knowledge, this is the first report on patients with cardiac pacemakers undergoing brain stimulator implantation.

Aged↗