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Biomedical subjects

Douglas Labar

Publications and source records attributed to Douglas Labar.

8 recordsLinked to original sources
PubMed2005

Frameless stereotactic placement of depth electrodes in epilepsy surgery.

OBJECT: Depth electrodes are useful in the identification of deep epileptogenic foci. Computerized tomography-magnetic resonance (CT/MR)- and angiography-guided frame-based techniques are safe and accurate but require four-point skull fixation that limits cranial access for the placement of additional grids and strips. The authors investigated the viability and accuracy of placing depth electrodes by using a commercially available frameless system. METHODS: A slotted, custom-designed adapter was built to interface with the StealthStation Guide Frame-DT and 960-525 StealthFighter. The Cranial Navigation software was used to plan the trajectory and entry site based on preoperative spoiled gradient MR imaging studies. Forty-one depth electrodes were placed in 51 targets in 20 patients. Thirty-one of these electrodes were inserted through the temporal neocortex following craniotomy and placement of subdural grids, whereas 10 were placed through burr holes. All electrodes had contact either within (71%) or touching (29%) the target, 50 of which (98%) provided adequate recordings. Although the mean distance of the distal electrode contact from the intended target was 3.1 +/- 0.5 mm, the mean distance to the edge of the anatomical structure was 0.4 +/- 0.9 mm. Placement via the laterotemporal approach was significantly (p < 0.001) more accurate than that via the occipitotemporal approach. No complication occurred. CONCLUSIONS: Depth electrodes can be placed safely and accurately by using a commercially available frameless stereotactic navigation system and a custom-made adapter. Depth electrode placement to record ictal onsets during epilepsy surgery only requires the contacts to touch rather than to reside within the intended structure. The laterotemporal approach is a more accurate method of placing electrodes than is the occipitotemporal one, likely due to the increased distance from the entry point to the target.

Adolescent↗
PubMed2004

Vagus nerve stimulation for 1 year in 269 patients on unchanged antiepileptic drugs.

PURPOSE: To study, in patients on unchanged antiepileptic drugs (AEDs): (1) seizure rates after 3 and 12 months of vagus nerve stimulation (VNS); (2) effects of VNS parameters; (3) patient characteristics versus VNS responsiveness. METHODS: We located in the VNS registry 269 patients treated for 1 year with no changes in AEDs. Seizure rates were calculated at 3 and 12 months. We analyzed: (1) 3 months versus 12 months seizure rates; (2) effects of changing duty cycles between 3 and 12 months; (3) effects of output current; (4) seizure rate changes associated with patient characteristics. RESULTS: Seizure rates improved between 3 months (median = -45%) and 12 months (median = -58%) (P < 0.0001). There were no differences between patients who stayed on standard or rapid cycling, or changed from standard to rapid. Stimulation parameters did not affect seizure rates. VNS responsiveness was associated with older age (P = 0.016), longer duration epilepsy (P = 0.033), and syndromes other than Lennox-Gastaut (P = 0.003). CONCLUSIONS: This was an analysis of treatment outcomes, not a prospective clinical trial. Nonetheless, our results suggest: (1) seizure rates decline with increasing VNS duration; (2) this decline occurs without AED changes; (3) this decline is not due to changes in stimulation parameters; (4) patient characteristics predictive of VNS responsiveness remain elusive.

Adolescent↗
PubMed2004

Affective tasks elicit material-specific memory effects in temporal lobectomy patients.

Eighteen patients who had undergone a right (9) or left (9) temporal lobectomy (RTL, LTL) including removal of the amygdala and hippocampus were evaluated. Sixteen male and sixteen female undergraduate subjects were evaluated for normative comparison. All subjects were administered Verbal (words) and Visual (faces) paired associates tasks. The present study sought to evaluate material-specific memory after temporal lobectomy, and to compare affective versus neutral memory as well. Thus, there were 4 tasks: Verbal Affective, Verbal Neutral, Visual Affective, and Visual Neutral. The material-specific effects of better Verbal memory performance by the RTL subjects compared to the LTL subjects and better Visual memory performance by the LTL subjects than the RTL subjects were only significant for the Affective tasks, and not the Neutral tasks. Perhaps adding an affective dimension to the material-specific memory tasks engaged the amygdala in addition to the other structures known to be important in memory. A strong interpretaion of the present data is made difficult by task differences and the low average IQ and possible reorganization of function that may have occurred in the patient sample.

Adult↗
PubMed2003

Observations on the use of vagus nerve stimulation earlier in the course of pharmacoresistant epilepsy: patients with seizures for six years or less.

BACKGROUND: This study retrospectively compared the effectiveness of vagus nerve stimulation (VNS) therapy among a constant cohort of patients in the patient outcome registry, which systematically monitors outcomes of patients receiving VNS therapy. Patients in the study had pharmacoresistant seizures for 6 years or less (early treatment group) or more than 6 years (late treatment group) before initiation of VNS therapy, and results are provided after both 3 and 12 months. REVIEW SUMMARY: Of 405 patients, 51 were in the early and 354 in the late treatment groups. Median age at onset of seizures was 7 years in the early and 4.5 years in the late treatment group. Seizure reduction of 100% was reported in 7.8% (early) and 3.7% (late) patients at 3 months and 11.8% (early) and 4.5% (late) at 12 months (P = 0.033). Reductions in seizure frequency greater than or equal to 90% for early and late treatment groups were similar: 11.8% (early) and 11.0% (late) at 3 months and 23.5% (early) and 17.0% (late) at 12 months. CONCLUSIONS: Patients treated earlier with VNS therapy were twice as likely to report no seizures as patients who had seizures for more than 6 years before they received VNS therapy. The effectiveness of VNS therapy should be assessed among other patients with pharmacoresistant seizures and lesser cumulative seizure loads.

Adolescent↗
PubMed2002

Neurostimulation therapy for epilepsy.

Neurostimulation therapy for epilepsy is growing in popularity. By appropriate targeting of applied electrical activation at selected nervous system sites, antiseizure effects may be achieved without the common sedative side effects of antiepileptic medications. Risks of neurostimulation therapy are those associated with the device implantation surgical procedures. Vagus nerve stimulation (VNS) reduces seizures by 45% and has been employed in over 13,000 patients worldwide. New reports suggest VNS is particularly beneficial for patients with Lennox-Gastuat syndome. VNS also reduces sudden unexpected death in epilepsy. New publications describing small, uncontrolled case series also suggest deep brain stimulation and transcranial magnetic stimulation may develop into effective antiepileptic therapies in the future.

Brain Diseases↗
PubMed2002

Global affective memory for faces in patients with temporal lobe epilepsy.

Eighteen (9 left, 9 right) epileptic patients with unilateral temporal lobe epilepsy (TLE) and 20 control participants were evaluated. Participants were instructed to make global affective judgments of likeability in a face memory task or to make neutral piecemeal judgments of nose size during the encoding phase of the task. A main effect of better memory after using a global affective versus a neutral piecemeal encoding strategy was found. Patients with right sided abnormality performed more poorly in the global affective encoding condition than patients with left-sided abnormality or than the control participants. No differences were seen among groups for the neutral piecemeal condition. Further, unlike the left TLE patients and the control participants, the right TLE patients did not show better performance when using the global affective encoding strategy over the neutral piecemeal strategy. This is discussed in relation to the literature suggesting an important role for the right hemisphere in global affective processing and memory, as well as the literature indicating an important role for the amygdala in affective memory.

Adolescent↗