Identifying Suspected Volume Conduction Contamination of External Anal Sphincter Motor Evoked Potentials in Lumbosacral Spine Surgery.

PURPOSE: Iatrogenic injury to sacral nerve roots poses significant quality of life issues for patients. Motor evoked potential (MEP) monitoring can be used for intraoperative surveillance of these important structures. We hypothesized that volume conducted depolarizations from gluteus maximus (GM) may contaminate external anal sphincter (EAS) MEP results during lumbosacral spine surgery. METHODS: Motor evoked potential from the EAS and medial GM in 40 patients were prospectively assessed for inter-muscle volume conduction during lumbosacral spine surgeries. Peak latency matching between the EAS and GM MEP recordings conditionally identified volume conduction (VC+) or no volume conduction (VC-). Linear regression and power spectral density analysis of EAS and medial GM MEP amplitudes were performed from VC+ and VC- data pairs to confirm intermuscle electrical cross-talk. RESULTS: Motor evoked potential peak latency matching identified putative VC+ in 9 of 40 patients (22.5%). Mean regression coefficients (r2) from peak-to-peak EAS and medial GM MEP amplitude plots were 0.83 ± 0.04 for VC+ and 0.34 ± 0.06 for VC- MEP (P < 0.001). Power spectral density analysis identified the major frequency component in the MEP responses. The mean frequency difference between VC+ EAS and medial GM MEP responses were 0.4 ± 0.2 Hz compared with 3.5 ± 0.6 Hz for VC- MEP (P < 0.001). CONCLUSIONS: Our data support using peak latency matching between EAS and GM MEP to identify spurious MEP results because of intermuscle volume conduction. Neuromonitorists should be aware of this possible cross-muscle conflict to avoid interpretation errors during lumbosacral procedures using EAS MEP.

Peripheral leg ischemia detected via intraoperative neurophysiological monitoring during a multilevel complex anterior and posterior operation.

Intraoperative neurophysiologic monitoring is a technique utilized during spinal operations to minimize sensory and motor function morbidity. We herein report a case of a 73-year-old female with renal cell carcinoma and metastatic involvement of the cervical and thoracic spine, who underwent a multilevel complex anterior and posterior operation. Neurophysiological monitoring was able to localize the lower limb ischemia utilizing somatosensory evoked potentials. This prompted intraoperative investigation of the peripheral ischemia, and the patient was found to have an Angio-Seal device embolus in the right popliteal artery that dislodged from the right femoral artery.

Deception awareness improves P300-based deception detection in concealed information tests.

We asked if increased awareness of deception enhanced P300-based detection of concealed information with two groups: 1) Control subjects saw a randomized series of either rare probes (subject home towns), frequent irrelevants (other towns), and rare targets, which are irrelevant stimuli but requiring Button 1 responses. Probes and non-target irrelevants required Button 2 responses. Controls were told to be sure they performed target/non-target discrimination correctly, and were so reminded throughout the run. 2) Deception subjects received an identical stimulus series and response instructions, but were also alerted about their deception (pressing a non-recognition button to probes) before and throughout the run. The deception group had significantly greater differences between probe and irrelevant P300s than controls, as well as significantly greater individual detections (10/10) than did controls (5/10), suggesting that the deception awareness manipulation enhances test sensitivity.

Towards the pharmacotherapy of eating disorders.

The purpose of this review is to discuss pharmacological options for the treatment of patients with eating disorders. Sequentially described are pharmacotherapy studies of anorexia nervosa (AN), bulimia nervosa (BN) and binge-eating disorder (BED). The quantity of drug trials performed with AN patients has been very limited. While the majority of studies have failed to show medication efficacy for the acute treatment of AN, there is data which suggests that fluoxetine hydrochloride may play a role in preventing relapse during maintenance therapy. Atypical antipsychotics, most often olanzapine, have shown promise in a number of uncontrolled studies. BN has been most extensively studied, with the majority of pharmacological trials focusing on antidepressants. Fluoxetine, at a dose of 60 mg/day, is FDA-approved for the treatment of BN. Psychotherapy, particularly cognitive behavioural therapy (CBT) is of well-established utility in BN and data suggests that the combination of an antidepressant plus CBT is superior to either treatment alone. Recently, there has been interest in the 5-HT3 antagonist, ondansetron, and the anticonvulsant, topiramate. BED investigators have focused largely on antidepressants, which may reduce symptoms of depression and augment psychotherapy. While sibutramine and topiramate have both been associated with weight loss in controlled trials, the former appears to be fairly well-tolerated and the latter appears to be responsible for the emergence of significant cognitive and peripheral nervous system side effects in some patients. Further pharmacological research with eating disorder patients is needed, particularly in the areas of AN and BED. Also, pharmacological augmentation strategies for those not responding to primary therapies should be explored.