When Fibromyalgia Affects Your Thinking

Fibromyalgia is a condition characterized by widespread pain, fatigue, sleep disturbances, and, often, psychological distress. Of the approximately 10% of Americans who report chronic widespread pain, many of them meet the criteria for fibromyalgia.

Many people with fibromyalgia also report cognitive dysfunction—problems with thinking and memory, which may include “muddy” thinking, poor concentration, short-term memory loss, and other, similar symptoms. These symptoms can occur at any age and can affect all areas of a person’s life, including his job performance and personal relationships. These symptoms may also give rise to fears that the person has developed Alzheimer disease or some other form of dementia. However, there is no evidence that cognitive dysfunction related to fibromyalgia—often called fibro fog—is a sign of Alzheimer disease, nor does fibro fog appear to worsen over time.

Researchers do not yet know what causes cognitive problems to develop in people with fibromyalgia. There may be multiple causes, leading to different patterns of dysfunction. However, research is starting to identify key components that underpin cognitive dysfunction in fibromyalgia.

Defining fibro fog

Fibro fog is an umbrella term that encompasses a number of cognitive problems commonly associated with fibromyalgia. However, while the term has grown in clinical use, it has no authoritative definition that can be quantified in units or demonstrated on an MRI scan or lab test. Because of the lack of agreement as to what fibro fog means, people often fail to distinguish between ordinary memory loss and fibro fog.

Findings from recent research indicate that mental fog, which has been defined and quantified, needs to be built into any definition of fibro fog. Mental fog is a core component of cognitive dysfunction in fibromyalgia and refers to a sense of mental confusion marked by a loss of mental clarity. However, it may be overlooked in people with fibromyalgia because it seems unrelated to their chief complaint of widespread pain. Mental fog and memory loss operate together in the great majority of individuals with fibromyalgia who complain of cognitive deficits. Without high levels of mental fog accompanying memory loss, it is not fibro fog.

Measurement of mental fog is central to an understanding of fibro fog because it transforms subjective impressions into data. The Mental Clutter Scale numerically quantifies the intensity of a person’s mental fog on a scale of 1 to 10 using the following eight features linked to reduced mental clarity:

Individuals are asked to rate how frequently they experienced these problems in the past week on a 10-point scale, with 1 being “not at all” and 10 being “all the time.” Anyone with an average score of 5 or more likely has high levels of mental fog.

Fibro fog refers to the simultaneous presence of memory problems and a high level of mental fog in people diagnosed with fibromyalgia. Once fibro fog is suspected, a neurocognitive examination can be a valuable tool for evaluating a person’s brain function.

Testing for fibro fog

Neurocognitive studies are performed by a trained neuropsychologist and involve a series of cognitive tests. The authors of this article have identified two facets of fibro fog that they believe are pivotal to understanding cognitive dysfunction in fibromyalgia: an accelerated rate of memory loss when a person is distracted, and a slower-than-normal ability to retrieve words from the brain’s memory bank. The neurocognitive tests used in evaluating fibromyalgia should therefore include a test that looks at the effect of distraction on memory, as well as a test for how quickly a person can retrieve words.

Distraction. Distractions that need to be attended to, such as a knock on the door or the timer on the stove, are probably the main cause of forgetfulness in people with fibromyalgia. When distracted, new information fades much more rapidly for individuals with fibromyalgia than for people without the condition. This tendency to forget can be measured by a test called the Auditory Consonant Trigram, which gives a person three letters to remember; then distracts him with another task for 9, 18, or 36 seconds; then asks him to recall the three letters. With a distraction lasting 9 seconds, people with fibromyalgia forget 38% more information than people without it. With a distraction lasting 18 seconds, the difference in the amount forgotten increases to 44%.

Other memory tests may not reveal this problem. The test used most commonly to assess short-term memory is the Wechsler Memory Scale. While this test is no doubt useful in many situations, it assesses short-term memory under test conditions free from distraction. Because people with fibromyalgia largely make new memories at a normal rate under conditions free from distraction, the test makes it seem as though their memory function is normal. Similarly, a medical professional having a conversation with a person who has fibromyalgia may notice no apparent memory problems if there are no distractions during the conversation. But introducing a source of distraction changes things for the person with fibromyalgia and may affect his concentration and memory.

Slow word retrieval. In people with fibromyalgia, the part of the brain known as the lexical memory—or word memory—does not work as fast as other parts of the brain. The mental lexicon is the dictionary of words that a person has acquired during his life and that he stores in his memory. Each time a person speaks, he retrieves words from his mental lexicon. The speed at which a person accesses words from the lexicon is known as his lexical speed. The lexical neural network operates in parallel with multiple other neural networks to transmit a coordinated message within the brain. For reasons that are unclear, the lexical part of the brain in people with fibromyalgia is slower at retrieving linguistic information.

The Stroop Color and Word Test contains a subtest that measures a person’s lexical speed. It is available to most neuropsychologists who administer neurocognitive tests. The Stroop Naming Speed subtest asks people to read words as quickly as they can for 45 seconds. How fast someone names words is a good indicator of his lexical speed. When people with fibromyalgia are asked to name words from a list, they tend to name them more slowly than people who don’t have fibromyalgia. For example, if an individual names one word every 420 milliseconds over 45 seconds, his lexical network is working pretty well. People with fibromyalgia, however, generally name one word every 620 milliseconds over a 45-second period. This indicates that critical information released by the mental lexicon arrives at the brain connections that build neural signals into coherent information 200 milliseconds later in people with fibromyalgia than in people without it.

This slowness may contribute to word retrieval problems, and it can also make it harder for people with fibromyalgia to follow a conversation, because they experience a lag in understanding what the other person or people are talking about.

One possible explanation for this is called the “lexical theory of cognitive dysfunction in fibromyalgia.” According to this theory, the brain is like a bunch of clocks beating in unison to smoothly regulate cognitive operations so that they function normally. Each clock operates in parallel with multiple other neural networks to transmit a coordinated message. A faulty lexical/word-retrieval clock can throw things out of sync, and because the processes are intertwined, disrupt cognition.

We think that the problem with the lexical clock in fibromyalgia is that it has a 200-millisecond delay, going about its neural business over the course of the day one beat behind the other clocks. Since it’s essential for normal brain function that these processes be in sync, a malfunction in lexical circuitry that releases linguistic information out of sync undermines a person’s ability to think and remember.

Treating fibro fog

What can a person do, if anything, about slow word retrieval and difficulty remembering when distracted? One thing that can help is to recognize that the experience is real. People with fibromyalgia can feel frustrated—and possibly doubt their own experience—when others, including some medical professionals, do not take their complaints seriously. So if possible, work with a health-care provider who understands that though you may appear perfectly fine, your fibro fog symptoms are real, and the effect they have on your life is real.

Something that may help those with fibro fog to remember better is a technique called verbalization. When a person says something out loud, it helps him to cement the words or thoughts in his short-term memory. So when meeting someone new or learning a new word, for example, it helps to say the name or word aloud once or twice. You might also consider finding ways to avoid distraction. For example, you could turn the ringer on your phone off when concentrating on a task, or conduct nonurgent business via e-mail instead of on the phone.

Another thing that may help is using the drug methylphenidate (brand name Ritalin), which is approved for treating attention deficit disorder (ADD). Ritalin appears to have short-term benefits for naming speed and cognitive functioning in people with fibromyalgia. In some short clinical trials, Ritalin was able to reduce the time delay in the lexical/word-retrieval clock by approximately 50%, so that word information was back in partial sync with other streams of neural information. This change occurred in tandem with broadly improved cognitive functioning.

Ritalin is a controlled substance and requires a monthly written prescription, which can make using it inconvenient. However, if a person’s fibro fog is bad enough to significantly impair his functioning, he may feel it’s worth the trouble. Other medicines sometimes used for attention deficit disorder, such as Adderall (a combination of amphetamine and dextroamphetamine) and atomoxetine (Strattera), may also be helpful for the cognitive symptoms of fibromyalgia.


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