What is a multiple sclerosis (MS) attack?

What is a Multiple Sclerosis (MS) Attack?

A multiple sclerosis attack (also called an exacerbation or relapse) is an episode of neurological disturbance caused by inflammatory and demyelinating lesions that must last for at least 24 hours to be classified as a true attack. 1

Definition and Characteristics

• An MS attack refers to an episode of neurological disturbance of the kind seen in MS, with symptoms that are typical of an inflammatory demyelinating event in the central nervous system 2
• To qualify as a true MS attack, symptoms must last at least 24 hours and occur in the absence of fever or infection 1
• Separate attacks must be at least 30 days apart to be considered distinct events 1
• Attacks represent objective clinical evidence of lesions that are disseminated in time and space, which is essential for MS diagnosis 2, 3

Distinguishing True Attacks from Pseudoflares

• A true MS flare represents genuine inflammatory and demyelinating activity, while a pseudoflare is a temporary worsening of existing symptoms without new inflammation 1
• True flares often show evidence of new or enhancing lesions on MRI, which is crucial for distinguishing between flare and pseudoflare 1
• Pseudoflares are commonly triggered by external factors such as increased core body temperature or infection 1
• Misinterpreting the type of flare can lead to inappropriate treatment decisions - either delaying necessary treatment or administering unnecessary steroids 1

Diagnostic Confirmation

• MRI imaging is critical for confirming a true attack, ideally showing new or enhancing lesions 1
• A thorough neurological examination is necessary to determine if symptoms represent new deficits or exacerbation of existing ones 1
• Clinical evidence of attacks depends primarily on objectively determined clinical signs, not just historical accounts of symptoms 2, 3
• In the diagnostic process, attacks provide evidence of dissemination in time when they affect different areas of the central nervous system 3

Clinical Significance

• Attacks are a defining feature of relapsing-remitting MS, which affects approximately 60% of MS patients initially 4
• Up to 40% of severe attacks that render patients nonambulatory may not fully resolve, leading to permanent disability 4
• The frequency and severity of attacks in the first two years may have prognostic value, with fewer attacks potentially indicating a more favorable course 4
• Recognition and proper treatment of attacks is essential as they can contribute to accumulating disability over time 5

Common Pitfalls in Attack Identification

• Mistaking symptom fluctuations due to temperature changes, stress, or fatigue for true attacks 1
• Failing to recognize that MRI findings must be interpreted in clinical context, as some patients with true attacks may not show new MRI activity 1
• Not allowing sufficient time between suspected attacks (minimum 30 days) to classify them as separate events 1
• Relying solely on patient-reported symptoms without objective clinical evidence 2, 3