Evaluation of Normal Appearing White Matter by Proton Magnetic Resonance Spectroscopy in Multiple Sclerosis

Nihal IŞIK1, Fatma CANDAN1, Alp DİNÇER2, Zahide YILMAZ1

1SSK Göztepe Eğitim Hastanesi Nöroloji Kliniği, İSTANBUL
2Bakırköy Radyotom ve Radyomar Görüntüleme Merkezi, İSTANBUL

Keywords: Multiple sclerosis, normal appearing white matter, axonal damage, proton magnetic resonance spectroscopy

Abstract

Background: Recent pathological and Proton Magnetic Resonance Spectroscopy (P-MRS) studies have indicated that presence of axonal damage in normal appearing white matter (NAWM) may be an important cause of disability in multiple sclerosis (MS).
Objectives: To investigate the axonal damage in NAWM of MS patients by using P-MRS which determines the biochemical metobolites and in addition, to find the relationships between axonal damage and clinical parameters of relapsing remitting (RR) MS patients. Patients and Methods: 57 MS patients (41 relapsing-remitting, 8 primary progressive; PP, and 8 secondary progressive, SP), and 10 healthy subjects as a control group, underwent cranial MR imaging (MRI) and single voxel P-MRS study. The metabolic ratios of N-acetylaspartate (NAA)I creatine (cr), choline (Cho)/cr and myoinositol (ml)/cr in the NAWM of MS patients and in the normal white matter (NWM) of control group were determined. For the RR-MS patients, the associations between the NAA/cr ratios of NAWM, and clinical disability (EDSS) and disease duration were investigated.
Results: There were a significant decrease (p<0.01) in NAA/cr ratios in both NAWM of MS patients as a general group and subgroups, than control group, but no significant differences were found for the other metabolite ratios. The lowest NAA/cr ratio was detected respectively in PP­MS, SP-MS and RR-MS patients. The NAA/cr ratios of RR-MS patients were significantly negatively correlated (r =-0.29, p<0.05) with the EOSS, but not with the duration of disease. The NAA/cr ratios in both patients who had duration of disease ?5 five years and more than 5 years, were found significantly lower than control group (p<0.05).
Conclusion In this study axonal damage, as assessed by decreased NAA/Cr ratios, found in NAWM of MS patients, supported the axonal damage in MS is not only confined to lesions and occurs even in the white matter which appears normal on cranial MRI. In addition to this, results of the RR-MS patients studied here, indicated that axonal damage in NAWM may be associated with dısability.