Phase-contrast magnet resonance imaging reveals regional, transmural, and base-to-apex dispersion of mechanical dysfunction in patients with long QT syndrome

BACKGROUND

Regional dispersion of prolonged repolarization is a hallmark of long QT syndrome (LQTS). We have also revealed regional heterogeneities in mechanical dysfunction in transgenic rabbit models of LQTS.

OBJECTIVE

In this clinical pilot study, we investigated whether patients with LQTS exhibit dispersion of mechanical/diastolic dysfunction.

METHODS

Nine pediatric patients with genotyped LQTS (12.2 ± 3.3 years) and 9 age- and sex-matched healthy controls (10.6 ± 1.5 years) were subjected to phase-contrast magnetic resonance imaging to analyze radial (Vr) and longitudinal (Vz) myocardial velocities during systole and diastole in the left ventricle (LV) base, mid, and apex. Twelve-lead electrocardiograms were recorded to assess the heart rate-corrected QT (QTc) interval.

RESULTS

The QTc interval was longer in patients with LQTS than in controls (469.1 ± 39.4 ms vs 417.8 ± 24.4 ms; P < .01). Patients with LQTS demonstrated prolonged radial and longitudinal time-to-diastolic peak velocities (TTP), a marker for prolonged contraction duration, in the LV base, mid, and apex. The longer QTc interval positively correlated with longer time-to-diastolic peak velocities (correlation coefficient 0.63; P < .01). Peak diastolic velocities were reduced in LQTS in the LV mid and apex, indicating impaired diastolic relaxation. In patients with LQTS, regional (TTPmax-min) and transmural (TTPVz-Vr) dispersion of contraction duration was increased in the LV apex (TTPVz_max-min: 38.9 ± 25.5 ms vs 20.2 ± 14.7 ms; P = .07; TTPVz-Vr: -21.7 ± 14.5 ms vs -8.7 ± 11.3 ms; P < .05). The base-to-apex longitudinal relaxation sequence was reversed in patients with LQTS compared with controls (TTPVz_base-apex: 14.4 ± 14.9 ms vs -10.1 ± 12.7 ms; P < .01).

CONCLUSION

Patients with LQTS exhibit diastolic dysfunction with reduced diastolic velocities and prolonged contraction duration. Mechanical dispersion is increased in LQTS with an increased regional and transmural dispersion of contraction duration and altered apicobasal longitudinal relaxation sequence. LQTS is an electromechanical disorder, and phase-contrast magnetic resonance imaging Heterogeneity in mechanical dysfunction enables a detailed assessment of mechanical consequences of LQTS.

Magnetic resonance tissue phase mapping demonstrates altered left ventricular diastolic function in children with chronic kidney disease

BACKGROUND

Echocardiographic examinations have revealed functional cardiac abnormalities in children with chronic kidney disease.

OBJECTIVE

To assess the feasibility of MRI tissue phase mapping in children and to assess regional left ventricular wall movements in children with chronic kidney disease.

MATERIALS AND METHODS

Twenty pediatric patients with chronic kidney disease (before or after renal transplantation) and 12 healthy controls underwent tissue phase mapping (TPM) to quantify regional left ventricular function through myocardial long (Vz) and short-axis (Vr) velocities at all 3 levels of the left ventricle.

RESULTS

Patients and controls (age: 8 years-20 years) were matched for age, height, weight, gender and heart rate. Patients had higher systolic blood pressure. No patient had left ventricular hypertrophy on MRI or diastolic dysfunction on echocardiography. Fifteen patients underwent tissue Doppler echocardiography, with normal z-scores for mitral early diastolic (V_E), late diastolic (V_A) and peak systolic (V_S) velocities. Throughout all left ventricular levels, peak diastolic Vz and Vr (cm/s) were reduced in patients: Vz_base -10.6 ± 1.9 vs. -13.4 ± 2.0 (P < 0.0003), Vz_mid -7.8 ± 1.6 vs. -11 ± 1.5 (P < 0.0001), Vz_apex -3.8 ± 1.6 vs. -5.3 ± 1.6 (P = 0.01), Vr_base -4.2 ± 0.8 vs. -4.9 ± 0.7 (P = 0.01), Vr_mid -4.7 ± 0.7 vs. -5.4 ± 0.7 (P = 0.01), Vr_apex -4.7 ± 1.4 vs. -5.6 ± 1.1 (P = 0.05).

CONCLUSION

Tissue phase mapping is feasible in children and adolescents. Children with chronic kidney disease show significantly reduced peak diastolic long- and short-axis left ventricular wall velocities, reflecting impaired early diastolic filling. Thus, tissue phase mapping detects chronic kidney disease-related functional myocardial changes before overt left ventricular hypertrophy or echocardiographic diastolic dysfunction occurs.

Details of left ventricular radial wall motion supporting the ventricular theory of the third heart sound obtained by cardiac MR

OBJECTIVE

Obtaining new details of radial motion of left ventricular (LV) segments using velocity-encoding cardiac MRI.

METHODS

Cardiac MR examinations were performed on 14 healthy volunteers aged between 19 and 26 years. Cine images for navigator-gated phase contrast velocity mapping were acquired using a black blood segmented κ-space spoiled gradient echo sequence with a temporal resolution of 13.8 ms. Peak systolic and diastolic radial velocities as well as radial velocity curves were obtained for 16 ventricular segments.

RESULTS

Significant differences among peak radial velocities of basal and mid-ventricular segments have been recorded. Particular patterns of segmental radial velocity curves were also noted. An additional wave of outward radial movement during the phase of rapid ventricular filling, corresponding to the expected timing of the third heart sound, appeared of particular interest.

CONCLUSION

The technique has allowed visualization of new details of LV radial wall motion. In particular, higher peak systolic radial velocities of anterior and inferior segments are suggestive of a relatively higher dynamics of anteroposterior vs lateral radial motion in systole. Specific patterns of radial motion of other LV segments may provide additional insights into LV mechanics.

ADVANCES IN KNOWLEDGE

The outward radial movement of LV segments impacted by the blood flow during rapid ventricular filling provides a potential substrate for the third heart sound. A biphasic radial expansion of the basal anteroseptal segment in early diastole is likely to be related to the simultaneous longitudinal LV displacement by the stretched great vessels following repolarization and their close apposition to this segment.

Effects of ventricular insertion sites on rotational motion of left ventricular segments studied by cardiac MR

OBJECTIVE

Obtaining new details for rotational motion of left ventricular (LV) segments using velocity encoding cardiac MR and correlating the regional motion patterns to LV insertion sites.

METHODS

Cardiac MR examinations were performed on 14 healthy volunteers aged between 19 and 26 years. Peak rotational velocities and circumferential velocity curves were obtained for 16 ventricular segments.

RESULTS

Reduced peak clockwise velocities of anteroseptal segments (i.e. Segments 2 and 8) and peak counterclockwise velocities of inferoseptal segments (i.e. Segments 3 and 9) were the most prominent findings. The observations can be attributed to the LV insertion sites into the right ventricle, limiting the clockwise rotation of anteroseptal LV segments and the counterclockwise rotation of inferoseptal segments as viewed from the apex. Relatively lower clockwise velocities of Segment 5 and counterclockwise velocities of Segment 6 were also noted, suggesting a cardiac fixation point between these two segments, which is in close proximity to the lateral LV wall.

CONCLUSION

Apart from showing different rotational patterns of LV base, mid ventricle and apex, the study showed significant differences in the rotational velocities of individual LV segments. Correlating regional wall motion with known orientation of myocardial aggregates has also provided new insights into the mechanisms of LV rotational motions during a cardiac cycle.

ADVANCES IN KNOWLEDGE

LV insertion into the right ventricle limits the clockwise rotation of anteroseptal LV segments and the counterclockwise rotation of inferoseptal segments adjacent to the ventricular insertion sites. The pattern should be differentiated from wall motion abnormalities in cardiac pathology.

Normal values of regional and global myocardial wall motion in young and elderly individuals using navigator gated tissue phase mapping

The purpose of this study was to evaluate normal values for regional and global myocardial wall motion parameters in young and elderly individuals, as detected by navigator gated high temporal resolution tissue phase mapping. Radial, longitudinal and circumferential ventricular wall motion, as well as ventricular torsion and longitudinal strain rates, were assessed in two age groups of volunteers, 23 ± 3 (n = 14) and 66 ± 7 years old (n = 9), respectively. All subjects were healthy, non-smokers without known cardiac disease. An increased global left ventricular (LV) torsion rate (peak systolic torsion rate 20.6 ± 2.0 versus 14.5 ± 1.0°/s/cm, peak diastolic torsion rate -25.2 ± 1.8 versus -14.1 ± 1.3°/s/cm) and a decrease in longitudinal LV motion (peak systolic values at mid-ventricle 5.9 ± 0.5 versus 8.5 ± 0.8 cm/s, peak diastolic values -10.7 ± 0.7 versus -15.2 ± 0.9 cm/s) in the older age group were the most prominent findings. Lower peak diastolic radial velocities with a longer time-to-peak values, most pronounced at the apex, are consistent with reduced diastolic function with ageing. Lower peak clockwise and counter-clockwise velocities at all LV levels revealed limitations in resting LV rotational motions in the older group. Significant changes in the undulating pattern of the rotational motions of the left ventricle were also observed. The results demonstrate distinct changes in regional and global myocardial wall motion in elderly individuals. Increased LV torsion rate and reduced LV longitudinal motion were particularly prominent in the older group. These parameters may have a role in the assessment of global LV contractility and help differentiate age-related changes from cardiac disease.

Influence of eddy current, Maxwell and gradient field corrections on 3D flow visualization of 3D CINE PC-MRI data

PURPOSE

The measurement of velocities based on phase contrast MRI can be subject to different phase offset errors which can affect the accuracy of velocity data. The purpose of this study was to determine the impact of these inaccuracies and to evaluate different correction strategies on three-dimensional visualization.

METHODS

Phase contrast MRI was performed on a 3 T system (Siemens Trio) for in vitro (curved/straight tube models; venc: 0.3 m/s) and in vivo (aorta/intracranial vasculature; venc: 1.5/0.4 m/s) data. For comparison of the impact of different magnetic field gradient designs, in vitro data was additionally acquired on a wide bore 1.5 T system (Siemens Espree). Different correction methods were applied to correct for eddy currents, Maxwell terms, and gradient field inhomogeneities.

RESULTS

The application of phase offset correction methods lead to an improvement of three-dimensional particle trace visualization and count. The most pronounced differences were found for in vivo/in vitro data (68%/82% more particle traces) acquired with a low venc (0.3 m/s/0.4 m/s, respectively). In vivo data acquired with high venc (1.5 m/s) showed noticeable but only minor improvement.

CONCLUSION

This study suggests that the correction of phase offset errors can be important for a more reliable visualization of particle traces but is strongly dependent on the velocity sensitivity, object geometry, and gradient coil design.

Spatial correlation of action potential duration and diastolic dysfunction in transgenic and drug-induced LQT2 rabbits

BACKGROUND

Enhanced dispersion of action potential duration (APD) is a major contributor to long QT syndrome (LQTS)-related arrhythmias.

OBJECTIVE

To investigate spatial correlations of regional heterogeneities in cardiac repolarization and mechanical function in LQTS.

METHODS

Female transgenic LQTS type 2 (LQT2; n = 11) and wild-type littermate control (LMC) rabbits (n = 9 without E4031 and n = 10 with E4031) were subjected to phase contrast magnetic resonance imaging to assess regional myocardial velocities. In the same rabbits' hearts, monophasic APDs were assessed in corresponding segments.

RESULTS

In LQT2 and E4031-treated rabbits, APD was longer in all left ventricular segments (P < .01) and APD dispersion was greater than that in LMC rabbits (P < .01). In diastole, peak radial velocities (Vr) were reduced in LQT2 and E4031-treated compared to LMC rabbits in LV base and mid (LQT2: -3.36 ± 0.4 cm/s, P < .01; E4031-treated: -3.24 ± 0.6 cm/s, P < .0001; LMC: -4.42 ± 0.5 cm/s), indicating an impaired diastolic function. Regionally heterogeneous diastolic Vr correlated with APD (LQT2: correlation coefficient [CC] 0.38, P = .01; E4031-treated: CC 0.42, P < .05). Time-to-diastolic peak Vr were prolonged in LQT2 rabbits (LQT2: 196.8 ± 2.9 ms, P < .001; E4031-treated: 199.5 ± 2.2 ms, P < .0001, LMC 183.1 ± 1.5), indicating a prolonged contraction duration. Moreover, in transgenic LQT2 rabbits, diastolic time-to-diastolic peak Vr correlated with APD (CC 0.47, P = .001). In systole, peak Vr were reduced in LQT2 and E4031-treated rabbits (P < .01) but longitudinal velocities or ejection fraction did not differ. Finally, random forest machine learning algorithms enabled a differentiation between LQT2, E4031-treated, and LMC rabbits solely based on "mechanical" magnetic resonance imaging data.

CONCLUSIONS

The prolongation of APD led to impaired diastolic and systolic function in transgenic and drug-induced LQT2 rabbits. APD correlated with regional diastolic dysfunction, indicating that LQTS is not purely an electrical but an electromechanical disorder.

Improved method for quantification of regional cardiac function in mice using phase-contrast MRI

Phase-contrast magnetic resonance imaging is a technique that allows for characterization of regional cardiac function and for measuring transmural myocardial velocities in human hearts with high temporal and spatial resolution. The application of this technique (also known as tissue phase mapping) to murine hearts has been very limited so far. The aim of our study was to implement and to optimize tissue phase mapping for a comprehensive assessment of murine transmural wall motion. Baseline values for regional motion patterns in mouse hearts, based on the clinically used American Heart Association's 17-segment model, were established, and a detailed motion analysis of mouse heart for the entire cardiac cycle (including epicardial and endocardial motion patterns) is provided. Black-blood contrast was found to be essential to obtain reproducible velocity encoding. Tissue phase mapping of the mouse heart permits the detailed assessment of regional myocardial velocities. While a proof-of-principle application in a murine ischemia-reperfusion model was performed, future studies are warranted to assess its potential for the investigation of systolic and diastolic functions in genetically and surgically manipulated mouse models of human heart disease.

Details of left ventricular remodeling and the mechanism of paradoxical ventricular septal motion after coronary artery bypass graft surgery

OBJECTIVE

The purpose of this study was to obtain new details of three-dimensional left ventricular wall motion related to ventricular remodeling in patients undergoing coronary artery bypass graft (CABG) surgery.

METHODS

Cardiac-gated, phase-contrast measurements using navigator-gated, high temporal resolution, tissue phase mapping were obtained on 19 patients (66 ± 7 years old) before and after CABG. Left ventricular motion patterns and myocardial velocities were recorded for radial, circumferential and longitudinal motion. Radial, circumferential and longitudinal velocity curves were obtained separately for 16 ventricular segments. Ventricular torsion rate and longitudinal strain rate were also derived pre- and post-surgery.

RESULTS

After CABG, there was a significant improvement in apical contraction, with an apparent paradoxical decrease in the radial inward motion of the septal segments at the left ventricular base. Despite improved ventricular contractility during systole, peak longitudinal and rotational velocities decreased or showed no significant changes. An altered pattern of rotational motion with decreased initial counter-clockwise rotation at the beginning of systole and subsequent lower amplitude of reversed motions in diastole was also noted in most left ventricular segments. Lower peak clockwise rotational velocities were recorded in the basal anteroseptal segment with relatively higher values in the rest of the basal segments.

CONCLUSION

Our results suggest that post-operative changes after CABG are limiting ventricular rotational and longitudinal motions, despite an increase in ventricular contractility due to revascularization. At the ventricular base, the restrained rotational motion of basal anteroseptal segment, located proximally to the right ventricular insertion, and higher rotational velocities of the rest of the segments are pushing the septum toward the right ventricle during ventricular twisting. At the ventricular apex, the restrain in rotational motion caused by post-operative adhesions is affecting all apical segments due to a much smaller left ventricular diameter at this level. The rotating apex and the apical septum are similarly displaced toward the right ventricle during ventricular twisting.

Chasing the reflected wave back into the heart: a new hypothesis while the jury is still out

Background:

Arterial stiffness directly influences cardiac function and is independently associated with cardiovascular risk. However, the influence of the aortic reflected pulse pressure wave on left ventricular function has not been well characterized. The aim of this study was to obtain detailed information on regional ventricular wall motion patterns corresponding to the propagation of the reflected aortic wave on ventricular segments.

Methods:

Left ventricular wall motion was investigated in a group of healthy volunteers (n = 14, age 23 ± 3 years), using cardiac magnetic resonance navigator-gated tissue phase mapping. The left ventricle was divided into 16 segments and regional wall motion was studied in high temporal detail.

Results:

Corresponding to the expected timing of the reflected aortic wave reaching the left ventricle, a characteristic “notch” of regional myocardial motion was seen in all radial, circumferential, and longitudinal velocity graphs. This notch was particularly prominent in septal segments adjacent to the left ventricular outflow tract on radial velocity graphs and in anterior and posterior left ventricular segments on circumferential velocity graphs. Similarly, longitudinal velocity graphs demonstrated a brief deceleration in the upward recoil motion of the entire ventricle at the beginning of diastole.

Conclusion:

These results provide new insights into the possible influence of the reflected aortic waves on ventricular segments. Although the association with the reflected wave appears to us to be unambiguous, it represents a novel research concept, and further studies enabling the actual recording of the pulse wave are required.

Uprighting and distalisation of first permanent maxillary molars in patients with undermining resorption: a case report

This case report describes a treatment method for distalisation and uprighting of first permanent maxillary molars with the aim of preventing complications in the presence of undermining resorption of the second deciduous molar. We present a fixed appliance, which is a compliance-independent and effective alternative to the methods used thus far such as removable plates with distal screws or separating ligatures.

Longitudinally and circumferentially directed movements of the left ventricle studied by cardiovascular magnetic resonance phase contrast velocity mapping

OBJECTIVE

Using high resolution cardiovascular magnetic resonance (CMR), we aimed to detect new details of left ventricular (LV) systolic and diastolic function, to explain the twisting and longitudinal movements of the left ventricle.

METHODS

Using CMR phase contrast velocity mapping (also called Tissue Phase Mapping) regional wall motion patterns and longitudinally and circumferentially directed movements of the left ventricle were studied using a high temporal resolution technique in healthy male subjects (n = 14, age 23 +/- 3 years).

RESULTS

Previously undescribed systolic and diastolic motion patterns were obtained for left ventricular segments (based on the AHA segmental) and for basal, mid and apical segments. The summation of segmental motion results in a complex pattern of ventricular twisting and longitudinal motion in the normal human heart which underlies systolic and diastolic function. As viewed from the apex, the entire LV initially rotates in a counter-clockwise direction at the beginning of ventricular systole, followed by opposing clockwise rotation of the base and counter-clockwise rotation at the apex, resulting in ventricular torsion. Simultaneously, as the entire LV moves in an apical direction during systole, the base and apex move towards each other, with little net apical displacement. The reverse of these motion patterns occur in diastole.

CONCLUSION

Left ventricular function may be a consequence of the relative orientations and moments of torque of the sub-epicardial relative to the sub-endocardial myocyte layers, with influence from tethering of the heart to adjacent structures and the directional forces associated with blood flow. Understanding the complex mechanics of the left ventricle is vital to enable these techniques to be used for the evaluation of cardiac pathology.

Rare pattern of aortic arch branching in a patient with operated congenital heart disease

Magnetic resonance imaging (MRI) has become one of the state-of-the-art examinations for the primary diagnostics and follow-up of patients with congenital cardiac defects. The evaluation of the altered cardiovascular system, however, remains a diagnostic challenge. We present MRI findings in a boy with a complex congenital heart defect. To reveal postoperative changes in blood flow dynamics, time-resolved contrast-enhanced 3D MR angiography (CE-MRA) was performed, providing information on altered vessel anatomy and vascular dynamics using spatio-temporal image acceleration. Additionally, an exceptional and rarely described supraaortic vessel variation was detected, consisting of five independent supraaortic arteries. The knowledge of this unusual vessel anomaly detected by CE-MRA might be significant in the case of future therapeutic interventions.

Myocardial Tissue Phase Mapping with Cine Phase-Contrast MR Imaging: Regional Wall Motion Analysis in Healthy Volunteers

PURPOSE

To establish prospectively a database of normal three-dimensional systolic and diastolic endocardial and epicardial velocity values for all myocardial segments in healthy volunteers by using cine phase-contrast velocity magnetic resonance imaging, also called tissue phase mapping (TPM).

MATERIALS AND METHODS

The study was approved by the institutional ethics committee and was conducted according to principles of the Declaration of Helsinki; each subject provided informed written consent. Ninety-six healthy volunteers (57 [59%] men, 39 [41%] women; mean age, 38 years +/- 12 [standard deviation]) underwent cardiac phase-contrast imaging with a black blood segmented k-space gradient-echo sequence for the analysis of three-dimensional myocardial velocity with high spatial resolution at 1.5 T on basal, midventricular, and apical short-axis views. Eighteen consecutive volunteers were imaged twice to determine interstudy reproducibility, and intra- and interobserver variability values were analyzed. Systolic and diastolic velocity curves were analyzed for peak velocity and time to peak velocity in the radial, circumferential, and longitudinal directions, as well as for torsion rate and longitudinal strain rate. Mixed-effects models with a random intercept for volunteers were used to test differences among the three ventricular sections and the transmural, endocardial, and epicardial parameters.

RESULTS

TPM enabled reproducible assessment of myocardial velocity with small intra- and interobserver variability values. Systolic peak radial velocity was lowest at the apical level (P < .001); diastolic peak radial velocity was similar at all three myocardial levels (P = .73). As viewed from the apex, a relative counterclockwise rotation during systole was followed by a relative clockwise rotation of the apex against the base. Diastolic and systolic peak longitudinal velocity values decreased from base to apex (P < .001). A gradient between endocardium and epicardium was observed for radial velocity values, with greater endocardial velocity values (P < .001).

CONCLUSION

TPM is a reproducible comprehensive modality for assessment of regional wall motion, and intra- and interobserver variability values are low.

Sex-specific characteristics of cardiac function, geometry, and mass in young adult elite athletes

PURPOSE

To study young adult elite athletes with age- and sex-matched sedentary controls to assess sex-specific differences for left ventricular (LV) and right ventricular (RV) volumes and mass as well as for LV contraction and relaxation.

MATERIALS AND METHODS

A total of 23 male athletes (mean age 25 +/- 4 years, training 22 +/- 7 hours/week in rowing, swimming, or triathlon) and 20 female athletes (mean age 24 +/- 4 years, training 19 +/- 5 hours/week in rowing, swimming, or triathlon) and age- and sex-matched sedentary controls (21 male/17 female) underwent cardiovascular magnetic resonance (CMR) imaging (1.5 Tesla). Cardiac phase contrast imaging using a black-blood k-space segmented gradient echo sequence was used for analysis of cardiac contraction and relaxation and steady-state free-precession cine images were acquired for determination of cardiac volumes and mass.

RESULTS

Male and female athletes showed similar increases in LV and RV volume and mass indices when compared to controls (ranging between 15% and 42%). No sex-specific differences in training effect on LV and RV volumes, mass indices, and ejection fractions, as well as LV to RV ratios of these volume and mass indices (parameters of balanced LV and RV dilatation and hypertrophy) were observed (all P for interaction >0.05). Similarly, no sex-specific differences in training effect on cardiac contraction and relaxation were found (all P for interaction >0.05).

CONCLUSION

Young adult elite athletes do not show sex-specific adaptive structural and functional changes to exercise training in accordance with the benign nature of the hypertrophy associated with athlete's heart.

Single-breathhold 3D-trueFISP cine cardiac imaging

Cardiac MRI function measurements are typically based on multiple breathhold 2D sequences to acquire images of the entire heart. In the present study, the feasibility of a cine 3D TrueFISP technique in which several complete volumetric measurements may be obtained during a single breathhold is demonstrated. In contrast to 3D FLASH, the TrueFISP sequence offers an excellent contrast between the myocardium and the intraventricular cavity without the use of contrast agent. An ECG-gated 3D cine TrueFISP sequence was implemented with a repetition time of 2.4-2.8 ms, which allows imaging of the complete heart within a single breathhold throughout 20-46 heartbeats with a 3D frame rate of 8-13 volumes per cardiac cycle and a spatial resolution of about 1.5 x 3.5 x 3.5 mm(3). Breathhold volumetric cine imaging with the 3D TrueFISP technique holds promise for rapid and accurate evaluation of the cardiac regional wall motion and the calculation of cardiac volume and ejection fraction.

Multiple sclerosis: etiology and epidemiology

Multiple sclerosis (MS) is a demyelinating, auto-immune disease which affect the central nervous system. The research seems to implicate a small or incomplete slow-growing virus as the causative agent. The measles virus has been suspected because of high titers of measles antibodies in MS patients' serum and cerebrospinal fluid. An immunological deficiency in MS patients may be linked to genetic factors such as HL-A tissue types and histocompatibility antigens. Genetics and socioeconomic conditions may also result in the distinct geographical pattern of MS distribution in the world.