Tag: review

Chronic fatigue syndrome: a hypothesis focusing on the autonomic nervous system

Abstract:

Chronic fatigue syndrome is a debilitating illness of unknown aetiology, with estimated levels of prevalence of up to about 8. 7/100 000 in the U.S.A. Like pain fatigue it is a personal, emotionally rich experience, which may originate from peripheral or central sites (or both). The nature of the symptoms is complex and reflects the interaction of the patient with the environment and cultural milieu. Accordingly the common use of the same terminology for different types of fatigue may be misleading.

Autonomic activation is a key component of both real and simulated physical exercise. Alterations in autonomic nervous system activity are a key component of several physiopathological conditions. In chronic fatigue syndrome disturbances in autonomic activity, and in other homoeostatic mechanisms, such as the hormonal and immune systems, have been reported recently.

In this review we followed the hypothesis that in chronic fatigue syndrome the paradoxical condition of disturbing somatic symptoms in the absence of organic evidence of disease might be addressed by focusing on attending functional correlates. In particular we addressed possible alterations in cardiovascular autonomic control, as can be assessed by spectral analysis of R-R interval and systolic arterial pressure variability.

With this approach, in subjects complaining of unexplained fatigue, we obtained data suggesting a condition of prevailing sympathetic modulation of the sino-atrial node at rest, and reduced responsiveness to excitatory stimuli. Far from considering the issue resolved, we propose that in the context of the multiple physiological and psychological interactions involved in the perception and self-reporting of symptoms, attendant changes in physiological equivalents might furnish a convenient assessment independent from subjective components.

Indices of sympathetic modulation could, accordingly, provide quantifiable signs of the interaction between subject’s efforts and environmental demands, independently of self descriptions, which could provide convenient measurable outcomes, both for diagnosis and treatment titration in chronic fatigue syndrome.

Comment in: Long- and short-term blood pressure and RR-interval variability and psychosomatic distress in chronic fatigue syndrome. [Clin Sci (Lond). 1999]

 

Source: Pagani M, Lucini D. Chronic fatigue syndrome: a hypothesis focusing on the autonomic nervous system. Clin Sci (Lond). 1999 Jan;96(1):117-25. http://www.ncbi.nlm.nih.gov/pubmed/9857114

 

Autonomic neuropathies

Abstract:

A limited autonomic neuropathy may underlie some unusual clinical syndromes, including the postural tachycardia syndrome, pseudo-obstruction syndrome, heat intolerance, and perhaps chronic fatigue syndrome. Antibodies to autonomic structures are common in diabetes, but their specificity is unknown. The presence of autonomic failure worsens prognosis in the diabetic state. Some autonomic neuropathies are treatable. Familial amyloid polyneuropathy may respond to liver transplantation. There are anecdotal reports of acute panautonomic neuropathy responding to intravenous gamma globulin. Orthostatic hypotension may respond to erythropoietin or midodrine.

 

Source: Low PA. Autonomic neuropathies. Curr Opin Neurol. 1998 Oct;11(5):531-7. http://www.ncbi.nlm.nih.gov/pubmed/9848003

 

Cognitive behavior therapy for chronic fatigue syndrome: efficacy and implications

Abstract:

Cognitive behavior therapy (CBT) is a form of non-pharmacologic treatment. It is based on a model of chronic fatigue syndrome (CFS) that hypothesizes that certain cognitions and behavior may perpetuate symptoms and disability–that is, act as obstacles to recovery. Treatment emphasizes self-help and aims to help the patient to recover by changing these unhelpful cognitions and behavior.

There is now good evidence from 2 independent randomized clinical trials to support the efficacy of CBT in patients with CFS. The treatment effect is substantial, although few patients are cured. The urgent clinical need is to make this form of treatment available to patients with CFS. One approach is to incorporate the principles of CBT into routine clinical practice. The preliminary evaluation of these simpler forms of CBT are promising, although the results of controlled trials are awaited. At present, intensive individual CBT administered by a skilled therapist remains the treatment of choice for patients with CFS.

 

Source: Sharpe M. Cognitive behavior therapy for chronic fatigue syndrome: efficacy and implications. Am J Med. 1998 Sep 28;105(3A):104S-109S. http://www.ncbi.nlm.nih.gov/pubmed/9790491

 

What we know about chronic fatigue syndrome and its relevance to the practicing physician

Abstract:

A number of recent reports have emphasized laboratory abnormalities, clinical tests, and therapeutic approaches that appear to have great promise in the evaluation and management of chronic fatigue syndrome (CFS). Because of the heterogeneity of CFS, the cost of many of these assays and procedures, and the frequent lack of skilled consultants able to apply relevant sophisticated procedures, the solo healthcare provider is often left with uncertain options in patient management. This article summarizes current approaches to patient management, utilizing available information relevant to CFS.

 

Source: Levine PH. What we know about chronic fatigue syndrome and its relevance to the practicing physician. Am J Med. 1998 Sep 28;105(3A):100S-103S. http://www.ncbi.nlm.nih.gov/pubmed/9790490.

 

Illness from low levels of environmental chemicals: relevance to chronic fatigue syndrome and fibromyalgia

Abstract:

This article summarizes (1) epidemiologic and clinical data on the symptoms of maladies in association with low-level chemicals in the environment, i.e., environmental chemical intolerance (CI), as it may relate to chronic fatigue syndrome (CFS) and fibromyalgia; and (2) the olfactory-limbic neural sensitization model for CI, a neurobehavioral synthesis of basic and clinical research. Severe CI is a characteristic of 20-47% of individuals with apparent CFS and/or fibromyalgia, all patients with multiple chemical sensitivity (MCS), and approximately 4-6% of the general population.

In the general population, 15-30% report at least minor problems with CI. The levels of chemicals reported to trigger CI would normally be considered nontoxic or subtoxic. However, host factors–e.g., individual differences in susceptibility to neurohormonal sensitization (amplification) of endogenous responses–may contribute to generating a disabling intensity to the resultant multisystem dysfunctions in CI.

One site for this amplification may be the limbic system of the brain, which receives input from the olfactory pathways and sends efferents to the hypothalamus and the mesolimbic dopaminergic [reward] pathway. Chemical, biologic, and psychological stimuli can initiate and elicit sensitization. In turn, subsequent activation of the sensitized limbic and mesolimbic pathways can then facilitate dysregulation of behavioral, autonomic, endocrine, and immune system functions.

Research to date has demonstrated the initiation of neurobehavioral sensitization by volatile organic compounds and pesticides in animals, as well as sensitizability of cardiovascular parameters, beta-endorphin levels, resting EEG alpha-wave activity, and divided-attention task performance in persons with CI. The ability of multiple types of widely divergent stimuli to initiate and elicit sensitization offers a new perspective on the search for mechanisms of illness in CFS and fibromyalgia with CI.

 

Source: Bell IR, Baldwin CM, Schwartz GE. Illness from low levels of environmental chemicals: relevance to chronic fatigue syndrome and fibromyalgia. Am J Med. 1998 Sep 28;105(3A):74S-82S. http://www.ncbi.nlm.nih.gov/pubmed/9790486

 

Parallels between post-polio fatigue and chronic fatigue syndrome: a common pathophysiology?

Abstract:

Fatigue is the most commonly reported and most debilitating of post-polio sequelae affecting the >1.8 million North American polio survivors. Post-polio fatigue is characterized by subjective reports of difficulty with attention, cognition, and maintaining wakefulness. These symptoms resemble those reported in nearly 2 dozen outbreaks of post-viral fatigue syndromes (PVFS) that have recurred during this century and that are related clinically, historically, anatomically, or physiologically to poliovirus infections.

This article reviews recent studies that relate the symptoms of post-polio fatigue and chronic fatigue syndrome (CFS) to clinically significant deficits on neuropsychologic tests of attention, histopathologic and neuroradiologic evidence of brain lesions, impaired activation of the hypothalamic-pituitary-adrenal axis, increased prolactin secretion, and electroencephalogram (EEG) slow-wave activity.

A possible common pathophysiology for post-polio fatigue and CFS, based on the Brain Fatigue Generator Model of PVFS, and a possible pharmacotherapy for PVFS based on replacement of depleted brain dopamine, will be described.

 

Source: Bruno RL, Creange SJ, Frick NM. Parallels between post-polio fatigue and chronic fatigue syndrome: a common pathophysiology? Am J Med. 1998 Sep 28;105(3A):66S-73S. http://www.ncbi.nlm.nih.gov/pubmed/9790485

 

Neuroimaging in chronic fatigue syndrome

Abstract:

The diagnosis of chronic fatigue syndrome (CFS) is made difficult by the absence of specific biomedical markers, and depends primarily on determining whether subjective information provided by the patient meets the clinical case definition of this syndrome. Reported cognitive difficulties and/or complaints of headache may instigate referral for brain imaging.

This article will discuss the value of neuroimaging in evaluating CFS, specifically reviewing studies that (1) used static magnetic resonance imaging (MRI) to assess structural abnormalities; and (2) assessed regional cerebral blood flow (rCBF) via detection of Tc-99m hexamethylpropyl-eneamine oxime distribution by single-photon emission computed tomography (SPECT). Future research design considerations are explored including (1) the utilization of positron emission tomography (PET) and other emerging neuroimaging technologies; and (2) methodological concerns, i.e., the influence of psychopathology (such as depression) and neurologic disease (such as multiple sclerosis) as possible confounding factors.

 

Source: Lange G, Wang S, DeLuca J, Natelson BH. Neuroimaging in chronic fatigue syndrome. Am J Med. 1998 Sep 28;105(3A):50S-53S. http://www.ncbi.nlm.nih.gov/pubmed/9790482

 

Stress-associated immune modulation: relevance to viral infections and chronic fatigue syndrome

Abstract:

The frequent association of an active viral infection with the symptoms of CFS led researchers to hypothesize that chronic fatigue syndrome (CFS) is induced by a virus. Results of these studies indicated that despite clinical support for this hypothesis, there were no clear data linking viruses to CFS. In this overview, we will explore the interrelation of the immune, endocrine, and central nervous systems, and the possibility that stress and/or the reactivation/replication of a latent virus (such as Epstein Barr virus) could modulate the immune system to induce CFS. Relevant research conducted in the developing field of psychoneuroimmunology will be reviewed, with a particular focus on cytokine synthesis, natural killer (NK) cell activity, and T-lymphocyte function, as they relate to CFS.

 

Source: Glaser R, Kiecolt-Glaser JK. Stress-associated immune modulation: relevance to viral infections and chronic fatigue syndrome. Am J Med. 1998 Sep 28;105(3A):35S-42S. http://www.ncbi.nlm.nih.gov/pubmed/9790480

 

Natural killer cells and natural killer cell activity in chronic fatigue syndrome

Abstract:

Chronic fatigue syndrome (CFS) is associated with insidious and persistent immunologic abnormalities that have proved difficult to reproduce. The heterogeneity of CFS, the variable quality of immunologic assays and their performance, along with an almost complete absence of longitudinal studies of cellular immune abnormalities in CFS may explain this difficulty. However, in a significant proportion of cases, low levels of natural killer (NK) cell activity have been reported.

This article will explore the mechanisms responsible for low NK cell activity, discuss the relation between levels of NK cell activity and health/disease, describe new findings on NK cell-brain interactions, and put forth a specific hypothesis for the role of NK cells in the pathogenesis of CFS.

 

Source: Whiteside TL, Friberg D. Natural killer cells and natural killer cell activity in chronic fatigue syndrome. Am J Med. 1998 Sep 28;105(3A):27S-34S. http://www.ncbi.nlm.nih.gov/pubmed/9790479

 

Neurally mediated hypotension and chronic fatigue syndrome

Abstract:

 

A substantial body of clinical evidence now supports an association between various forms of hypotension and both idiopathic chronic fatigue and the chronic fatigue syndrome (CFS). Patients with CFS have a high prevalence of neurally mediated hypotension, and open treatment of this autonomic dysfunction has been associated with improvements in CFS symptoms. Randomized trials are now in progress to evaluate the efficacy of treatments directed at neurally mediated hypotension in those with CFS patients, and the results of these trials should help guide more basic inquiries into the mechanisms of orthostatic intolerance in affected individuals.

 

Source: Rowe PC, Calkins H. Neurally mediated hypotension and chronic fatigue syndrome. Am J Med. 1998 Sep 28;105(3A):15S-21S. http://www.ncbi.nlm.nih.gov/pubmed/9790477