What test is ordered annually to monitor disease activity in patients with multiple sclerosis?

Annual MRI Monitoring for Multiple Sclerosis

Brain MRI should be performed at least annually in patients with established multiple sclerosis to monitor disease activity and treatment response. 1

Standard Annual Monitoring Protocol

The MAGNIMS consensus guidelines, published in Nature Reviews Neurology, establish that follow-up brain MRI scans should be conducted at minimum once yearly for routine MS monitoring. 1 This recommendation applies to patients with stable disease on treatment who do not require enhanced surveillance.

Core MRI Sequences Required

For annual monitoring, the following sequences provide sufficient information about disease activity:

• T2-weighted and T2-FLAIR sequences to detect new or enlarging lesions, which indicate ongoing disease activity even in clinically stable patients 1
• Proton density sequences as an alternative or complement to T2-FLAIR for lesion detection 1
• Contrast-enhanced T1-weighted sequences can be omitted in stable patients, as new or enlarging T2 lesions provide adequate evidence of subclinical disease progression 1, 2

When Contrast Is Still Necessary

Gadolinium-enhanced imaging remains essential in specific scenarios:

• Unexpected clinical presentations or atypical symptoms 1, 2
• Suspected treatment-related complications, particularly opportunistic infections like progressive multifocal leukoencephalopathy (PML) 1
• Initial diagnostic workup to establish baseline inflammatory activity 2
• When determining lesion acuity would change management decisions 2

Intensified Monitoring Schedules

Certain high-risk situations require more frequent MRI surveillance beyond the annual standard:

Every 3-4 Months Monitoring

• Natalizumab-treated patients at high PML risk (JCV seropositive, treatment duration ≥18 months) require brain MRI every 3-4 months with FLAIR, T2-weighted, and diffusion-weighted imaging 1
• Patients switching disease-modifying therapies need enhanced pharmacovigilance with MRI every 3-4 months for up to 12 months, particularly when transitioning from natalizumab to fingolimod, alemtuzumab, or dimethyl fumarate 1
• Early disease or radiologically isolated syndrome may warrant MRI every 3-6 months in the first year, then annually if stable 2

Every 6-12 Months Monitoring

• Low PML risk patients (JCV seronegative on natalizumab) require annual brain MRI assessment 1
• Patients with documented disease activity may need MRI every 6 months during the first 1-2 years of treatment 3

Technical Standardization Requirements

To ensure accurate comparison across serial scans:

• Use the same MRI scanner and identical imaging protocols as the baseline/reference scan whenever possible 1
• Maintain consistent pulse sequences and spatial resolution to detect subtle changes reliably 1
• Minimum lesion size of 3 mm (≥3 pixels) should be used to maintain reproducibility 2
• MRI subtraction techniques can facilitate detection of new lesions but automated subtraction should be used cautiously 1

Role of Spinal Cord Imaging

Routine spinal cord MRI is not recommended for annual monitoring in most MS patients. 1 Brain MRI is more sensitive for detecting disease activity, and spinal cord imaging adds limited value because:

• Most spinal cord lesions are clinically symptomatic 1
• Strong correlation exists between new brain and spinal cord lesions 1
• Technical challenges with spinal cord imaging reduce standardization 1

Spinal cord imaging remains essential for initial diagnostic workup and complete dissemination in space assessment, but not for routine follow-up. 2

Complementary Monitoring: Optical Coherence Tomography

OCT should be integrated alongside annual MRI monitoring as a complementary tool. 4 The National Institute of Neurological Disorders and Stroke recommends OCT provides high-resolution imaging that complements MRI, with repeat examinations every 6-12 months for early MS or radiologically isolated syndrome. 4 However, OCT should never replace MRI monitoring or clinical disability assessments. 4

Critical Pitfalls to Avoid

• Age-related white matter changes (periventricular capping, small vessel disease) can mimic MS lesions and require careful morphological assessment 2
• Comorbidities like migraine can produce white matter lesions; attention to lesion morphology and distribution is essential 2
• Delaying treatment decisions while waiting for contrast enhancement is inappropriate, as non-enhancing lesions still represent disease progression 3
• Assuming clinical stability equals radiological stability is dangerous, as substantial subclinical MRI activity occurs in clinically stable patients 5, 6

Treatment Decision Thresholds

Current practice demonstrates that clinicians increasingly use low thresholds for treatment modification:

• One new T2 lesion prompts treatment change in 26.9% of cases 6
• Six new T2 lesions lead to treatment change in 50.2% of cases 6
• Contrast-enhancing lesions are 2.43 times more likely to trigger treatment change compared to new T2 lesions alone 6

This reflects a shift toward "no evidence of disease activity" (NEDA-3) treatment goals since high-efficacy therapies became available. 6