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Macroscopic and microscopic assessments of disease burden by MRI in multiple sclerosis: relationship to clinical
C Gasperini1, M A Horsfield, J W Thorpe
1Multiple Sclerosis NMR Research Group, National Hospital, London.
Abstract:
We have evaluated macroscopic white matter abnormalities (visible lesions) together with microscopic abnormalities in the normal appearing white matter (NAWM) of patients with multiple sclerosis (MS) to determine their relative contributions to the development of disability. The total visible lesion volume (TLV) was computed as a measure macroscopic changes, whereas both texture analysis and T2 were used as possible indicators of diffuse disease in the NAWM. Dual echo T2-weighted SE images were obtained from 41 patients with definite MS: 10 primary progressive (PP), 11 secondary progressive (SP), 10 benign (BE), 10 early relapsing remitting (ERR), as well as from 10 healthy controls. Calculation of T2 and texture parameters were performed in a region of frontal NAWM of patients and controls. The TLV of each patient was measured using a semiautomated lesion detection program. No significant differences were found between the controls and the patients for all texture parameters examined. However, NAWM T2 was longer in the patients than in the controls (P = .02). Mean TLV was highest for SP and lowest for BE and ERR patients. A significant correlation was found between TLV and EDSS (P < .01) but not between NAWM T2 or texture and expanded disability status score (EDSS). Our study suggest that: (a) diffuse changes are present in NAWM, (b) texture analysis is unable to detect any subtle structure in the NAWM abnormalities, possibly because of the limited image resolution; (c) in the development of disability in MS, macroscopic lesions are more important than microscopic abnormalities in the NAWM.
Insights
Macroscopic white matter lesions, not microscopic changes in normal-appearing white matter, significantly contribute to disability in multiple sclerosis (MS) patients. Visible lesion volume strongly correlates with expanded disability status score (EDSS).
Area of Science:
- Neuroimaging
- Neurology
- Radiology
Background:
- Multiple sclerosis (MS) is characterized by white matter lesions.
- Understanding the contribution of macroscopic lesions versus microscopic abnormalities in normal-appearing white matter (NAWM) to disability is crucial.
Purpose of the Study:
- To evaluate the relative contributions of macroscopic white matter lesions and microscopic abnormalities in NAWM to disability progression in MS patients.
- To compare total lesion volume (TLV) with T2 and texture analysis of NAWM as predictors of disability.
Main Methods:
- Acquired dual echo T2-weighted SE images from 41 MS patients (various subtypes) and 10 controls.
- Measured total visible lesion volume (TLV) using semiautomated detection.
- Analyzed T2 and texture parameters in frontal NAWM.
Main Results:
- NAWM T2 was significantly longer in MS patients than controls (P = .02).
- No significant differences in texture parameters between patients and controls.
- Mean TLV varied by MS subtype, highest in SPMS.
- Significant correlation found between TLV and expanded disability status score (EDSS) (P < .01).
- No significant correlation between NAWM T2 or texture and EDSS.
Conclusions:
- Diffuse microscopic changes exist in MS NAWM, but texture analysis may be limited by image resolution.
- Macroscopic lesions (TLV) are more critical than microscopic NAWM abnormalities in driving MS-related disability.
- Visible lesion volume is a key predictor of disability in multiple sclerosis.