Symptoms of Chronic Fatigue Syndrome/Myalgic Encephalomyelitis (ME/CFS) can involve the central nervous system (cognition, executive function, short-term memory), the peripheral nervous system (muscle weakness, fatigue with exertion), and the autonomic nervous system (heart rate, blood pressure, breathing, digestion). A close analysis of 177 symptom checklists collected from ME/CFS patients over 4.5 years revealed a previously unreported commonality among patients. The majority of patients present with some level of anticholinergic syndrome – a dramatic deficiency of acetylcholine, which could be responsible for symptoms affecting the central, peripheral and autonomic nervous systems. This is the first time that low acetylcholine levels have been suggested as a cause of many disabling symptoms in ME/CFS.
Be sure to see part 2: Answers and Treatment
Prevalence estimates of Chronic Fatigue Syndrome range from 0.5% to 3% in the United States (2-9 million sufferers), and yet effective treatment continues to elude practitioners. A syndrome similar to Chronic Fatigue Syndrome has been described as far back as the mid-18th century, but the medical community struggles for consensus. Indeed, even the name Chronic Fatigue Syndrome is a point of contention. Chronic Fatigue Syndrome may be called systemic exertion intolerance disease (SEID), myalgic encephalomyelitis, chronic fatigue, and immune dysfunction syndrome, among others. Currently, most sources use a combined term, Chronic Fatigue Syndrome/Myalgia Encephalomyelitis (ME/CFS) to describe this disorder.
|Frequency of Symptoms Occurring in Chronic Fatigue Syndrome|
|Symptom||Percent of patients|
|Tender lymph nodes||80|
|Figure 1. Staus, SE, J Infect Dis 1988, 157:405.|
Countless patients are clearly suffering from a constellation of debilitating symptoms, yet there is a frustrating lack of objective biomedical findings. As such, clinicians struggle to even make the diagnosis of ME/CFS, much less provide effective treatment.
There is no typical presentation of ME/CFS, yet there are some features common to many patients with the syndrome. Most patients are highly functioning prior to illness and experience a sudden onset of symptoms, usually after a viral illness, trauma or extreme stress. Excessive physical activity exacerbates fatigue and related symptoms.
Many patients describe certain triggers that bring about or worsen symptoms such as emotional distress, physical trauma, decreased sleep quantity/quality, infection, and standing or sitting up for an extended period.[4, 5, 6] Each of these triggers taxes the patient and is, in one form or another, an exertion. Indeed, post-exertional malaise is often included as a diagnostic criterion. Post-exertional malaise is an exacerbation of some or all of an individual’s ME/CFS symptoms that occurs after physical or cognitive exertion and leads to a reduction in functional ability. Exertion exacerbates fatigue, cognitive symptoms, pain, delayed recovery of muscle function, increased severity and incidence of sleep problems, and inappropriate autonomic responses.[4, 8, 9]
A large number of additional symptoms, beyond fatigue, are present in a majority of ME/CFS sufferers, and often, these symptoms can come and go. These symptoms can include a sore throat, tender lymph nodes, muscle and joint pain, feverishness, insomnia, tachycardia, abdominal pain, and others (see Figure 1). Attempts to locate the underlying cause(s) of such disparate symptoms have been unsuccessful to date. Some of the leading hypotheses are viral infection[3, 10] immune dysfunction, endocrine/metabolic dysfunction,[12, 13]neutrally – mediated hypotension,[14,15] genetic disorders,[16, 17] disordered sleep, and complicated depression.
Clearly, multiple systems of the body are involved simultaneously in ME/CFS. Symptoms of CSF/ME involve the central nervous system (cognition, executive function, short-term memory), the peripheral nervous system (muscle weakness, fatigue with exertion), and the autonomic nervous system (heart rate, blood pressure, breathing, digestion).
The cognitive symptoms of ME/CFS can be every bit as debilitating as the physical symptoms. Patients report phenomena brain fog, confusion, and the inability to concentrate. Short-term memory deficits and slowed information processing are common; the latter may be experienced as a mental fatigue similar to the physical fatigue of the condition.[20, 21]
In ME/CFS, the prevalence of attention deficits may be as high as 93% and 85% for memory disturbances. Three-quarters of patients experience substantial difficulty finding the correct words during verbal tasks. Problems remembering, difficulty expressing thoughts, difficulty paying attention, slowness of thought, absentmindedness, and difficulty understanding are orders of magnitude more common in people with ME/CFS than in healthy volunteers.
The peripheral nervous system (which controls muscles) has been found to affect ME/CFS patients and not uncommonly, patients complain of weakness. Fulcher, et al found that patients with ME/CFS were weaker than sedentary and depressed controls, suggesting that weakness was not psychosomatic or secondary to deconditioning. Their study found that ME/CFS patients had significantly higher submaximal oxygen uptakes during exercise, and multiple regression models suggested that exercise incapacity was directly related to quadriceps muscle weakness.
The autonomic nervous system controls bodily functions such as heart rate, blood pressure, pupil dilation, digestion, and salivation. It coordinates the activity of various organ systems without requiring conscious effort.
Many ME/CFS patients have abnormal autonomic nervous system function. Orthostatic intolerance (the inability to adjust heart rate and blood pressure when changing position) is included in the updated diagnostic criteria for Chronic Fatigue Syndrome. Orthostatic intolerance includes symptoms of lightheadedness, dizziness, faintness, or syncope when vertical. Patients may present with neurally mediated hypotension, extreme pallor, nausea, irritable bowel syndrome, heart palpitations with or without cardiac arrhythmias, urinary frequency and bladder dysfunction, and exertional dyspnea and/or postural orthostatic tachycardia syndrome (POTS).[7, 25]
In order to look for clues to answer this question, between June 2011 and April 2015 Genetic Disease Investigators, LLC collected symptom questionnaires from 192 individuals with ME/CFS, resulting in 177 viable checklists. Each questionnaire contained 156 potential symptoms listed alphabetically.
Not surprisingly, autonomic symptoms were common.
|Percentage of respondents suffering with the following autonomic symptoms included:|
|Symptom||Percent of patients|
|Lack of perspiration||46|
|Decreased blood pressure when standing||78|
|Bradycardia or tachycardia||81|
|Increased body temperature||57|
Central nervous system symptoms were also common.
|Percentage of respondents suffering with the following central nervous system symptoms included:|
|Symptom||Percent of patients|
|Abnormal mood swings – almost bipolar presentation||41|
Peripheral nervous system symptoms were also common and were reported with the following frequency:
|Symptom||Percent of patients|
|Wakeful myoclonic jerks||74|
|Loss of coordination (ataxia)||77|
Additional symptoms not currently regarded as typical for ME/CFS (yet often present in anticholinergic syndrome) were reported with the following frequency:
|Symptom||Percent of patients|
|Seeing periodic flashes of light||63|
|Seeing “dancing lines, spiders or insects”||42|
|Hallucinations – auditory or visual||28|
|Textured surfaces bother you visually||45|
|Warping or waving of surfaces and edges||29|
|Sensitivity to sudden sounds||96|
When viewed as a whole, the above 36 symptoms are the symptoms of Acute Anticholinergic Syndrome. This syndrome must be identified by presentation (not via blood work) because acetylcholine breaks down rapidly. These symptoms suggest but do not prove, that the majority of patients with ME/CFS suffer from symptoms of extremely low levels of acetylcholine.
To understand abnormalities in acetylcholine, one must first understand where and how it acts under normal circumstances. Acetylcholine is the neurotransmitter of neuromuscular junctions, ganglia in the autonomic nervous system, and is present in discrete locations throughout the brain.
In the central nervous system (the brain and spinal cord), acetylcholine is critical for memory formation and recall. For example, there are acetylcholine receptors in the hippocampus, Neil cortex, and amygdala — the main memory forming structures in the brain. Likewise, acetylcholine is the major neurotransmitter in the basal nucleus of Meynert, which degenerates in Alzheimer’s disease.
Acetylcholine is integral to the proper function of the peripheral nervous system and is the main neurotransmitter at every skeletal neuromuscular junction in the body. All conscious muscular movement requires acetylcholine.
Acetylcholine is a major component of the autonomic nervous system and is required for proper vagus nerve function.
As a syndrome, ME/CFS is a constellation of symptoms. It is difficult to envision a single pathological process that gives rise to all of the various symptoms. Nevertheless, abnormalities in the acetylcholine system could explain many, if not most of the symptoms of ME/CFS.
The effects of acetylcholine deficiency are understood primarily because of the actions of atropine. Atropine blocks acetylcholine receptors, thus preventing the neurotransmitter from interacting with postsynaptic neurons. Acetylcholine deficiency (brought on by atropine) causes ventricular fibrillation, tachycardia (rapid heart rate), dizziness, nausea, blurred vision, loss of balance, dilated pupils, photophobia, dry mouth, dry eyes, extreme confusion, dissociative hallucinations, and excitation in addition to unusual symptoms such as visual snow and seeing dancing lines, spiders and insects .[29, 30]
The link between ME/CFS and acetylcholine has been the subject of ongoing research with particular attention to potential autoimmune conditions that could affect acetylcholine receptors. For example, some researchers found autoantibodies against muscarinic cholinergic receptors in over half of the people with ME/CFS.[31,32]
Spence, Khan, and Belch showed that patients with ME/CFS have abnormalities in the acetylcholine (cholinergic) system. The researchers showed the acetylcholinesterase inhibitor, edrophonium, applied to the skin reacts abnormally in patients with chronic fatigue syndrome. The same research group has confirmed the results of their research in several papers.[34, 35, 36, 37]
Yamamoto, et al (2012) used a radioactive agent that specifically binds to muscarinic acetylcholine receptors in the brain. They report decreased levels of receptors in the brain, but normal activity of acetylcholinesterase.
Taken together, these results suggest an interesting possibility that explains the disparate findings of all of these researchers: ME/CFS patients may have abnormally low levels of acetylcholine.
If this hypothesis was true, one could treat many symptoms of chronic fatigue syndrome by increasing acetylcholine levels within the synapse. Indeed, researchers have attempted to do this very thing. Kawamura and co-authors report three cases in which a small dose of oral pyridostigmine, an acetylcholinesterase inhibitor which increases acetylcholine levels in synapses, improved symptoms of chronic fatigue syndrome. Many patients with POTS (Postural Orthostatic Tachycardia Syndrome) have improved gastrointestinal symptoms (gastroparesis, constipation) with the use of pyridostigmine.
But because pyridostigmine does not cross the blood-brain barrier, it cannot boost acetylcholine in the brain and assist with central nervous system symptoms.
Acting on the evidence of low acetylcholine levels as exhibited by symptomology, Genetic Disease Investigators, LLC began to search for a compound that could cross the blood-brain barrier and boost acetylcholine in the central nervous system as well as effectively replace acetylcholine in the autonomic nervous system and the peripheral nervous system.
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