MS Flare vs. Pseudoflare: Diagnosis and Treatment

Diagnostic Differences

A true MS flare represents a genuine episode of neurological disturbance caused by inflammatory and demyelinating lesions, and must last for at least 24 hours to be classified as a true attack, according to the American Academy of Neurology 1, 2
A pseudoflare is a temporary worsening of existing MS symptoms without new inflammatory activity, commonly triggered by external factors such as increased core body temperature or infection, as noted by the National Multiple Sclerosis Society 1, 2
True flares often show evidence of new or enhancing lesions on MRI, which is a critical diagnostic tool for distinguishing between flare and pseudoflare, as recommended by the American College of Radiology 3, 4
Separate attacks must be at least 30 days apart to be considered distinct events, as defined by the International Panel on the Diagnosis of Multiple Sclerosis 5, 6

A thorough neurological examination is necessary to determine if symptoms represent new deficits or exacerbation of existing ones, and to assess for potential triggers of pseudoflares, as suggested by the European Federation of Neurological Societies 1, 2
MRI imaging is critical for distinguishing between flare and pseudoflare, and should include standardized protocols such as pre-contrast T1-weighted sequences, dual-echo T2-weighted sequences, post-gadolinium T1-weighted sequences, and fluid-attenuated inversion recovery (FLAIR) sequences, as recommended by the Magnetic Resonance Imaging in Multiple Sclerosis (MAGNIMS) consortium 3
Cerebrospinal fluid analysis may be helpful in atypical presentations, and visual evoked potentials can provide additional support in cases with few MRI abnormalities, as noted by the American Academy of Neurology 1, 2

Misinterpreting a true flare as a pseudoflare may delay appropriate treatment, and conversely, misdiagnosing a pseudoflare as a true relapse can lead to unnecessary steroid treatment with potential side effects, as warned by the National Institute of Neurological Disorders and Stroke 2
MRI findings must be interpreted in clinical context, as some patients with true flares may not show new MRI activity, as noted by the International Society for Magnetic Resonance in Medicine 3, 4