Spinal Cord Diffusion-Tensor Imaging and Motor-evoked Potentials in Multiple Sclerosis Patients: Microstructural and Functional Asymmetry

Purpose: To assess possible association between intrinsic structural damage and clinical disability by correlating spinal cord diffusion-tensor (DT) imaging data with electrophysiological parameters in patients with a diagnosis of multiple sclerosis (MS). Materials and Methods: This study was approved by the local ethical committee according to the declaration of Helsinki and written informed consent was obtained. DT images and T1- and T2-weighted images of the spinal cord were acquired in 28 healthy volunteers and 41 MS patients. Fractional anisotropy (FA) and apparent diffusion coefficients were evaluated in normal-appearing white matter (NAWM) at the cervical level and were correlated with motor-evoked potentials (n = 34). Asymmetry index was calculated for FA values with corresponding left and right regions of interest as percentage of the absolute difference between these values relative to the sum of the respective FA values. Statistical analysis included Spearman rank correlations, Mann-Whitney test, and reliability analysis. Results: Healthy volunteers had low asymmetry index (1.5%-2.2%). In MS patients, structural abnormalities were reflected by asymmetric decrease of FA (asymmetry index: 3.6%; P = .15). Frequently asymmetrically affected among MS patients was left and right central motor conduction time (CMCT) to abductor digiti minimi muscle (ADMM) (asymmetry index, 15%-16%) and tibialis anterior muscle (TAM) (asymmetry index, 9.5%-14.1%). Statistically significant correlations of functional (ie, electrophysiological) and structural (ie, DT imaging) asymmetries were found (P = .005 for CMCT to ADMM; P = .007 for CMCT to TAM) for the cervical lateral funiculi, which comprise the crossed pyramidal tract. Interobserver reliability for DT imaging measurements was excellent (78%-87%). Conclusion: DT imaging revealed asymmetric anatomic changes in spinal cord NAWM, which corresponded to asymmetric electrophysiological deficits for both arms and legs, and reflected a specific structure-function relationship in the human spinal cord. © RSNA, 2013.

Genome-wide search for markers associated with osteochondrosis in Hanoverian warmblood horses

A genome-wide scan was performed to detect quantitative trait loci (QTLs) for osteochondrosis (OC) and osteochondrosis dissecans (OCD) in horses. The marker set comprised 260 microsatellites. We collected data from 211 Hanoverian warmblood horses consisting of 14 paternal half-sib families. Traits used were OC (fetlock and/or hock joints affected), OCD (fetlock and/or hock joints affected), fetlock OC, fetlock OCD, hock OC, and hock OCD. The first genome scan included 172 microsatellite markers. In a second step 88 additional markers were chosen to refine putative QTLs found in the first scan. Genome-wide significant QTLs were located on equine chromosomes 2, 4, 5, and 16. QTLs for fetlock OC and hock OC partly overlapped on the same chromosomes, indicating that these traits may be genetically related. QTLs reached the chromosome-wide significance level on eight different equine chromosomes: 2, 3, 4, 5, 15, 16, 19, and 21. This whole-genome scan was a first step toward the identification of candidate genome regions harboring genes responsible for equine OC. Further investigations are necessary to refine the map positions of the QTLs already identified for OC.

Inappropriate interventions during the long-term follow-up of patients with an implantable defibrillator

QUESTIONS UNDER STUDY: In patients with an implantable defibrillator (ICD), inappropriate ICD interventions alter the quality of life, may cause hospitalisations and limit cost-effectiveness. The aim of the study was to determine the incidence and causes of inappropriate ICD interventions, and to identify patients at risk. METHODS: For this observational longitudinal study, consecutive patients undergoing ICD implantation at the University Hospital of Berne were included in a registry. All stored electrograms of episodes triggering ICD interventions were systematically reviewed and analysed to determine whether ICD interventions were appropriate or inappropriate. Inappropriate ICD interventions were classified according to their cause, and risk factors were sought. RESULTS: 214 consecutive patients were followed during a median time of 2.7 years (3.7 years IQR, 698 patient years). 81 inappropriate ICD interventions occurred in 58 patients (27%). Factors triggering inappropriate ICD interventions included atrial fibrillation and flutter (n = 35, 44%), sinus tachycardia (n = 26, 32%), lead fracture (n = 12), recurrent self-terminating ventricular tachycardia (n = 5), double-counting due to T-wave oversensing (n = 3). The only identifiable risk factor for inappropriate ICD interventions was sustained ventricular tachycardia as index arrhythmia. CONCLUSIONS: An important proportion of ICD patients suffer inappropriate ICD interventions that are most commonly due to supraventricular arrhythmias. Patients with ventricular tachycardia prior to ICD implantation are at higher risk of inappropriate ICD interventions. Interventions aiming at decreasing the risk of inappropriate ICD interventions should be considered in these patients.