In this study, we evaluated the effect of imprecision in patient repositioning encountered in real life on multiple sclerosis (MS) lesion volumes measured from MRIs. We also evaluated two putative methods for reducing the variability in these lesion volume measurements: first, a reduction of slice thickness (from the conventional 5 mm to 3 mm) and second, the application of a new repositioning technique based on the use of head immobilization shells. We evaluated the errors in lesion volume by scanning 10 patients a total of four times using the two slice thicknesses and two repositioning methods (conventional and using a head immobilization shell). The mean absolute percentage difference between two corresponding scans was 6.8% (range, 1.24 to 11%) using conventional slice thickness and repositioning, 4.1% (range, 0.7 to 5.56%) using conventional slice thickness and head immobilization shells, 2.6% (range, 0.8 to 6.66%) using the conventional repositioning technique and 3-mm slice thickness, and 1.4% (range, 0.2 to 6.14%) using slice thickness of 3 mm and head immobilization shells. These mean absolute differences were significantly different (p = 0.0008). Our results indicate that the effect of repositioning errors of the order of those that can be encountered in the daily life situation of clinical trials affects significantly lesion load measurements in MS and that the combined use of thinner slices and more accurate repositioning techniques can markedly improve the reproducibility of such measurements.

Objectives-To evaluate whether a triple dose of gadolinium-DTPA (Gd-DTPA) or delayed MRI increase the number, size, and conspicuousness of enhancing lesions in patients with benign multiple sclerosis. Methods-Tl weighted brain MRI was carried out on 20 patients with benign multiple sclerosis (expanded disability status scale < 3 with a disease duration > 10 years) in two sessions. In the first session, one scan was obtained before and two scans five to seven minutes and 20-30 minutes after the injection of 0-1 mmollkg Gd-DTPA (standard dose). In the second session, six to 24 hours later, the same procedure was repeated with 0*3 mmol/kg Gd-DTPA (triple dose). Results-Nine enhancing lesions were found in seven patients (35%) using the standard dose of Gd-DTPA. The numbers of enhancing lesions increased to 13 (P = 0.03) and the number of patients with such lesions to eight (40%) on the delayed standard dose scans. On the early triple dose scans, we found 19 enhancing lesions in 10 patients (50%). The number of enhancing lesions was significantly higher (P = 0.01) than that obtained with the early standard dose. The number of enhancing lesions was 18 and the number of "active" patients 11 (55%) on the delayed triple dose scans. The enhancing areas increased progressively from the early standard dose scans to the delayed triple dose scans. The contrast ratios of the lesions detected in the early standard dose scans was lower than those of lesions present in the early (P = 0-01) and delayed (P = 0.04) triple dose scans.Conclusions-More enhancing lesions were detected in patients with benign multiple sclerosis with both delay of MRI and the use of a triple dose of Gd-DTPA suggesting that the amount of inflammation in the lesions of such patients is mild and heterogeneous. (3 Neurol Neurosurg Psychiatry 1996;60:526-530)

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Background: To investigate the mechanisms underlying disability in multiple sclerosis (MS), 40 patients with the relapsing-remitting form of the disease and 13 patients with secondary progressive MS underwent multimodal evoked potential (EP), motor evoked potential (MEP), and spinal motor conduction time evaluation. Clinical disability was evaluated by the expanded disability status scale (EDSS) and functional system scales. In secondary progressive MS patients, magnetic resonance imaging (MRI) was used to obtain a semiquantitative estimate of the total lesion load of the brain. Results: Spinal motor conduction time was significantly longer in secondary progressive MS patients than controls (p < 0.001) and relapsing-remitting MS patients (p < 0.05), but did not differ between relapsing-remitting patients and controls. Spinal motor conduction times also correlated directly with EDSS scores (p < 0.001) and pyramidal functional system scores (p < 0.001). Brain lesion load (4960.3 ± 3719.0 mm 2 ) and the total number of lesions (67.7 ± 37.0) in secondary progressive MS did not correlate with disability scores. For the following EPs, the frequencies of abnormalities were significantly higher in secondary progressive MS patients than relapsing-remitting patients: visual evoked potentials (p < 0.05), somatosensory evoked potentials and upper limb motor evoked potentials (p < 0.01), and brainstem auditory evoked potentials, lower limb somatosensory evoked potentials and lower limb motor evoked potentials (p < 0.001). Conclusions: These findings suggest that disability in secondary progressive MS patients is mainly due to progressive involvement of corticospinal tract in the spinal cord. RESUME: Potentiels evoques moteurs et invalidity dans la sclerose en plaques secondaire progressive. Introduction: Nous avons investigue les mecanismes sous-jacents a 1'invalidite dans la sclerose en plaques (SEP) au moyen des potentiels evoques multimodaux (PE), des potentiels evoques moteurs (PEM) et du temps de conduction moteur spinal chez 40 patients atteints de la forme recurrente-remittente et de 13 patients atteints de SEP secondaire progressive. L'invalidite clinique a ete evaluee au moyen de l'echelle d'invalidite elargie (EIE) et d'echelles des systemes fonctionnels. Dans la SEP secondaire progressive, 1'imagerie par resonance magnetique (RMN) a ete utilisee pour estimer semiquantitativement la charge lesionnelle totale du cerveau. R'esultats: Le temps de conduction moteur spinal etait significativement plus long chez les patients atteints de SEP secondaire progressive que chez les controles (p < 0.001) et les patients atteints de la forme recurrente-remittente (p <0 .05), mais etait semblable chez les patients atteints de la forme recurrente-remittente et les controles. Les temps de conduction moteurs spinaux etaient directement correles avec les scores EIE (p < 0.001) et les scores du systeme pyramidal (p < 0.001). La charge lesionnelle du cerveau (4960.3 ± 3719.0 mm 2 ) et le nombre total de lesions (67.7 ± 37.0) ...