Magnetization Transfer Ratio in Peripheral Nerve Tissue: Does It Depend on Age or Location?

BACKGROUND AND PURPOSE: Magnetization transfer contrast imaging provides indirect information on the concentration of "bound" water protons and their interactions with "free" water molecules. The purpose of this study is to analyze location- and age-dependent changes in the magnetization transfer ratio (MTR) of lower extremity nerves. MATERIALS AND METHODS: Ten younger (20-32 years) and 5 older (50-63 years) healthy volunteers underwent magnetization transfer contrast imaging at 3 Tesla Two 3-dimensional gradient echo sequences with and without an off-resonance saturation pulse (repetition time: 58 milliseconds; echo time: 2.46 milliseconds; band width: 530 Hz/Px; flip angle: α = 7°) were acquired at 3 different locations covering the proximal thigh to the distal lower leg in the group of younger volunteers and at 2 different locations covering the proximal to distal thigh in the group of older volunteers. Sciatic and tibial nerve regions of interest (ROIs) were manually drawn and additional ROIs were placed in predetermined muscles. Magnetization transfer ratios were extracted from respective ROIs and calculated for each individual and location. RESULTS: In young volunteers, mean values of nerve and muscle MTR were not different between the proximal thigh (nerve: 20.34 ± 0.91; muscle: 31.71 ± 0.29), distal thigh (nerve: 19.90 ± 0.98; P = 0.76; muscle: 31.53 ± 0.69; P = 0.87), and lower leg (nerve: 20.82 ± 1.07; P = 0.73; muscle: 32.44 ± 1.11; P = 0.51). An age-dependent decrease of sciatic nerve MTR was observed in the group of older volunteers (16.95 ± 1.2) compared with the group of younger volunteers (20.12 ± 0.65; P = 0.019). Differences in muscle MTR were not significant between older (31.01 ± 0.49) and younger (31.62 ± 0.37; P = 0.20) volunteers. CONCLUSION: The MTR of lower extremity nerves shows no proximal-to-distal gradient in young healthy volunteers but decreases with age. For future studies using MTR in peripheral nerve disorders, these findings suggest that referencing magnetization transfer contrast values in terms of age, but not anatomical nerve location is required.

High-resolution dental magnetic resonance imaging for planning palatal graft surgery-a clinical pilot study.

AIM: To evaluate whether high-resolution, non-contrast-enhanced dental magnetic resonance imaging (MRI) can be used for accurate determination of palatal masticatory mucosa thickness (PMMT) and to locate the greater palatal artery (GPA). MATERIALS AND METHODS: In five volunteers (four males, one female; mean age 30.2 ± 0.4 years), two independent raters measured PMMT by use of dental MRI in 180 positions. For comparison, clinical bone sounding was performed. The GPA was identified in time-of-flight (TOF) angiography and MSVAT-SPACE-prototype sequence. Intra- and inter-observer agreement for MRI measurements, agreement between MRI and bone sounding were analysed by intra-class correlation coefficient (ICC) and Cohen's kappa (κ). RESULTS: Reliability of dental MRI measurements was high (intra-observer-ICC 0.962; inter-observer ICC 0.959). Agreement of MRI measurements with bone sounding was moderate (ICC 0.744), and the GPA could be identified in 60% of measurement points using the TOF-angiography alone and in 85% with additional information of the MSVAT-SPACE. Good intra-observer agreement was observed for GPA identification (κ: 0.778). CONCLUSION: Palatal masticatory mucosa thickness measured by high-resolution, non-contrast enhanced dental MRI is comparable with that obtained by bone sounding. Dental MRI enables reliable, non-invasive and radiation-free planning of palatal tissue harvesting and can also be used for location of the GPA at 85% of measurement points, which might help reduce complications during surgery.

Oxytocin and reduction of social threat hypersensitivity in women with borderline personality disorder.

OBJECTIVE: Patients with borderline personality disorder are characterized by emotional hyperarousal with increased stress levels, anger proneness, and hostile, impulsive behaviors. They tend to ascribe anger to ambiguous facial expressions and exhibit enhanced and prolonged reactions in response to threatening social cues, associated with enhanced and prolonged amygdala responses. Because the intranasal administration of the neuropeptide oxytocin has been shown to improve facial recognition and to shift attention away from negative social information, the authors investigated whether borderline patients would benefit from oxytocin administration. METHOD: In a randomized placebo-controlled double-blind group design, 40 nonmedicated, adult female patients with a current DSM-IV diagnosis of borderline personality disorder (two patients were excluded based on hormonal analyses) and 41 healthy women, matched on age, education, and IQ, took part in an emotion classification task 45 minutes after intranasal administration of 26 IU of oxytocin or placebo. Dependent variables were latencies and number or initial reflexive eye movements measured by eye tracking, manual response latencies, and blood-oxygen-level-dependent responses of the amygdala to angry and fearful compared with happy facial expressions. RESULTS: Borderline patients exhibited more and faster initial fixation changes to the eyes of angry faces combined with increased amygdala activation in response to angry faces compared with the control group. These abnormal behavioral and neural patterns were normalized after oxytocin administration. CONCLUSIONS: Borderline patients exhibit a hypersensitivity to social threat in early, reflexive stages of information processing. Oxytocin may decrease social threat hypersensitivity and thus reduce anger and aggressive behavior in borderline personality disorder or other psychiatric disorders with enhanced threat-driven reactive aggression.