MRI criteria for multiple sclerosis in patients presenting with clinically isolated syndromes: a multicentre retrospective study

Summary

Background

The 2001 and 2005 McDonald criteria allow MRI evidence for dissemination in space (DIS) and dissemination in time (DIT) to be used to diagnose multiple sclerosis in patients who present with clinically isolated syndromes (CIS). In 2006, new criteria were proposed in which DIS requires at least one T2 lesion in at least two of four locations (juxtacortical, periventricular, infratentorial, and spinal-cord) and DIT requires a new T2 lesion on a follow-up scan. We applied all three criteria in a large cohort of CIS patients to assess their performance by use of conversion to clinically definite multiple sclerosis (CDMS) as the outcome.

Methods

Patients who had two MRI scans within 12 months of CIS onset were identified in four centres in the Magnims European research network. The specificity and sensitivity of MRI criteria for CDMS after 3 years was assessed in 208 patients. A Cox proportional hazards model was applied in a larger cohort of 282 patients that included all patients irrespective of length of follow-up.

Findings

The specificity of all criteria for CDMS was high (2001 McDonald, 91%; 2005 McDonald, 88%; new, 87%). Sensitivity of the new (72%) and 2005 McDonald (60%) criteria were higher than the 2001 McDonald criteria (47%). The Cox proportional hazards model showed a higher conversion risk for all three criteria in those with both DIS and DIT than those with either DIS or DIT alone. When all three criteria were included in the model, only the new criteria had an independent significant effect on conversion risk.

Interpretation

The new criteria are simpler than the McDonald criteria without compromising specificity and accuracy. The presence of both DIS and DIT from two MRI scans has a higher specificity and risk for CDMS than either DIS or DIT alone.

Introduction

Clinically silent MRI lesions suggestive of demyelination are found in 50–70% of patients who present with a clinically isolated syndrome (CIS) suggestive of multiple sclerosis.1, 2, 3 Clinically definite multiple sclerosis (CDMS) develops after prolonged (7–14 years) follow-up in 56–88% of patients with abnormal MRI and in approximately 20% with normal MRI.4, 5, 6, 7

Brain MRI criteria for dissemination in space (DIS) have been developed to improve prediction of CDMS.8, 9, 10 These criteria have focused on the number, activity (presence of gadolinium enhancement), and location of lesions, and include lesions in three regions that are defined as characteristic for demyelination: juxtacortical, infratentorial, and periventricular.

The 2001 McDonald diagnostic criteria for multiple sclerosis include MRI evidence of DIS and dissemination in time (DIT), which allow a diagnosis of multiple sclerosis to be made in CIS patients.¹¹ The DIS criteria were those developed for brain MRI by Barkhof and colleagues⁹ and Tintore and colleagues,¹⁰ in addition to allowing one spinal-cord lesion to substitute for a brain lesion. Evidence for DIT requires either a gadolinium-enhancing lesion after at least 3 months from CIS onset, or a new T2 lesion developing on a scan subsequent to a reference scan obtained at least 3 months after CIS onset.

When retrospectively applied to two CIS cohorts who had been recruited into prospective serial MRI and clinical follow-up studies, the 2001 McDonald criteria had a high specificity for CDMS.12, 13 However, the requirement for a gadolinium-enhancing lesion for DIT on a 3 month follow-up scan resulted in low sensitivity at this timepoint (ie, many cases who develop CDMS do not fulfil the criteria after 3 months).¹² When a new T2 lesion on follow-up scanning was allowed as evidence for DIT if the reference scan was obtained within 3 months of CIS onset, the criteria became more sensitive and remained highly specific.¹⁴

In 2005, the McDonald criteria were revised. Changes in imaging criteria included (1) a greater role for spinal-cord lesions as evidence for DIS while retaining essentially the same Barkhof-Tintore DIS findings for brain abnormalities, and (2) allowing a new T2 lesion that had occurred any time after 30 days from CIS onset as evidence of DIT.¹⁵ The performance of these criteria in predicting CDMS has not been reported.

In 2006, a single-centre study of CIS patients proposed new imaging criteria for multiple sclerosis.¹⁶ DIS was achieved with at least one T2 lesion in at least two of four locations defined as characteristic for multiple sclerosis in the McDonald criteria: juxtacortical, periventricular, infratentorial, and spinal-cord. DIT required a new T2 lesion on a follow-up scan irrespective of the timing of a baseline scan. These criteria are based on the findings of T2-weighted images alone and do not require gadolinium enhancement. Compared with the 2001 McDonald criteria, the new criteria were similarly (highly) specific for CDMS and more sensitive.¹⁶

Within the Magnims European multicentre collaborative research network, which studies MRI in multiple sclerosis, data were collected on 282 CIS patients from four centres (Barcelona, Amsterdam, Milan, and London), who had two MRI scans within 12 months of CIS onset and were followed up clinically. Some of the patients from one centre were included in previous reports that assessed the diagnostic criteria.12, 16 Our aim was to investigate the performance of the two McDonald (2001 and 2005) criteria and the new MRI diagnostic criteria with respect to development of CDMS.