Multiple Sclerosis Attacks
Defining an MS attack, and what it means for prognosis.
One of the hallmark features of MS are “attacks” (also called relapses or exacerbations). This characteristic of the illness defines the disease for most people, at least in the early stages, and most of the medicines used specifically for MS have been approved based on their ability to prevent attacks. Despite this, in my experience many patients with MS who have experienced an attack have a poor understanding of what an attack actually is and what it means for the prognosis of their disease.
So, what does this scary-sounding word mean? Fortunately, a formal definition of an attack exists. I have included the criteria for an attack from a 2010 position paper on the diagnosis of MS entitled: Diagnostic criteria for multiple sclerosis: 2010 Revisions to the McDonald criteria:
What Is An Attack?
- Neurological disturbance of kind seen in MS
- Subjective report or objective observation
- At least 24 hours duration in absence of fever or infection
- Excludes pseudoattacks, single paroxysmal symptoms (multiple episodes of paroxysmal symptoms occurring over 24 hours or more are acceptable as evidence)
- Some historical events with symptoms and pattern typical for MS can provide reasonable evidence of previous demyelinating event(s), even in the absence of objective findings
Determining Time Between Attacks
- 30 days between onset of event 1 and onset of event 2
Let me clarify some important points in the above definition, based on conversations I have had with patients who are confused by this admittedly confusing topic.
First of all, attacks have to last at least 24 hours, although usually they last at least several days in my experience. I have met many worried patients who believe they have had numerous attacks after experiencing a transient neurological symptom lasting for only a few minutes. These events are not considered attacks.
Also, an attack cannot occur in the setting of a fever or infection. When the symptoms of an attack occur during a fever or infection it is termed a pseudorelapse. During a pseudorelapse, patients can feel certainly feel worse, but this is due to the reemergence of old, partially healed symptoms during a time of stress on the body. To understand why, consider the scenario of a broken bone. Though a bone may heal, it might not return to its full strength. If it is stressed again, it is more likely to break in the same location.
The same is true in MS, and for the nervous system, fevers, infections, or metabolic derangements can cause old symptoms that incompletely healed to return. This is why many doctors will inquire about symptoms of an infection and check a urine analysis to look for signs of a urinary tract infection prior to treating patients for an attack. It is important that patients tell their doctor about any symptoms of an infection if they feel they are experiencing a relapse
Finally, to be considered an attack, the symptom usually, though not always, has to be something new. Many patients recover well from attacks, though incompletely.
Symptoms may come and go for reasons that are not entirely clear, and include:
- double vision
These fluctuations of existing symptoms are not considered to be attacks. Admittedly, it is often not possible to tell if a patient is having an attack, or a recurrence of an old symptom.