Tag: review

Muscle biochemistry and pathophysiology in postviral fatigue syndrome

Abstract:

Patients with postviral fatigue syndrome (PVFS) usually complain of the skeletal muscle-related symptoms of fatigue and myalgia. It is not surprising therefore that the muscles have recently been the object of intensive studies which have used a variety of biochemical and physiological techniques. The aim of this chapter is to review these findings, and to discuss their significance or otherwise to the presenting symptoms and course of the condition.

 

Source: Edwards RH, Newham DJ, Peters TJ. Muscle biochemistry and pathophysiology in postviral fatigue syndrome. Br Med Bull. 1991 Oct;47(4):826-37. http://www.ncbi.nlm.nih.gov/pubmed/1794087

 

Neurophysiology of postviral fatigue syndrome

Abstract:

The exact pathophysiology of excessive fatigue in patients with postviral fatigue syndrome (PVFS) remains uncertain in spite of increasing investigation. One objective abnormality of neuromuscular function is the increased jitter on single fibre EMG studies. While this is a sensitive technique which indicates a disturbance in the peripheral part of the motor unit, it is non-specific and its role in the pathophysiology remains unclear.

Impaired muscular activation with added force in response to superimposed electrical stimulation suggests an extra-muscular and/or central component of fatigue. Conventional neurophysiological studies and those of strength and endurance have shown no objective abnormality in patients compared with controls. The previous reports of disturbed muscle metabolism on NMR spectroscopy have not been confirmed in more recent studies and no consistent abnormality of excitation-contraction coupling has so far emerged.

Finally, unlike patients with depression, cognitive evoked potential studies suggest impaired attention, memory and stimulus evaluation in postviral fatigue syndrome. In future studies, the importance of utilising approved clinical criteria for patient inclusion cannot be overemphasized. Control groups should include sedentary or deconditioned as well as depressed subjects to help standardise these important variables.

 

Source: Jamal GA, Miller RG. Neurophysiology of postviral fatigue syndrome. Br Med Bull. 1991 Oct;47(4):815-25. http://www.ncbi.nlm.nih.gov/pubmed/1794086

 

Clinical spectrum of postviral fatigue syndrome

Abstract:

Many different neurological and psychiatric syndromes follow viral infections, but their clinical pictures and pathogeneses are poorly understood. The syndromes include acute disseminated encephalomyelitis (post-infectious encephalomyelitis), the Guillain-Barre syndrome (post-infectious neuritis) and Reye’s syndrome.

Recently, attention has been focused on another common postviral neurological syndrome, i.e. the postviral fatigue syndrome (PVFS)–termed myalgic encephalomyelitis (ME) and a host of other designations. PVFS occurs both sporadically and in epidemics, with cases being reported from all over Europe, the United States, Australasia and South Africa.

It is difficult to make the diagnosis and this has meant, in the past, that it is not until an epidemic has occurred that random cases which presented in the preceding years are realised to represent the same condition. With renewed interest in the syndrome and greater attention from physicians, however, diagnosis of sporadic cases is now becoming more common.

 

Source: Behan PO, Bakheit AM. Clinical spectrum of postviral fatigue syndrome. Br Med Bull. 1991 Oct;47(4):793-808. http://www.ncbi.nlm.nih.gov/pubmed/1794085

 

Immunology of postviral fatigue syndrome

Abstract:

Postviral fatigue syndrome is associated with persistent infection by a virus. The patient with the condition has failed to eliminate the virus in the usual time. There is little evidence of a deficient immune response by the patient as the explanation for the viral persistence, and it must be assumed that most of the explanation lies in down-regulation of virus expression in infected cells. The general symptomatology of postinfectious syndromes may be mediated by cytokines liberated as part of the infection. Part of the syndrome may also be due to local effects of virus infection in muscles or the central nervous system (CNS).

 

Source: Mowbray JF, Yousef GE. Immunology of postviral fatigue syndrome. Br Med Bull. 1991 Oct;47(4):886-94. http://www.ncbi.nlm.nih.gov/pubmed/1724405

 

Amplification and identification of enteroviral sequences in the postviral fatigue syndrome

Abstract:

Evidence from several sources has long suggested that enteroviruses might play a role in the postviral fatigue syndrome (PVFS).

We used the most sensitive molecular virological method available at present, the polymerase chain reaction (PCR) amplification technique, to look for enteroviral copies in peripheral blood leucocytes and muscle from a well-defined group of patients. We demonstrated that our PCR method amplified a sequence common to a wide range of enteroviral serotypes. A highly significant number of the muscle biopsies (53%: P = less than 0.001) from the patients were positive for enteroviral sequences. With regard to the leucocyte samples, 16% in both patient and control were positive.

The PCR results on the peripheral blood leucocytes were in keeping with serological findings, in showing that the level of exposure to enteroviruses seemed to be the same in patients and controls: it was therefore of the greatest interest that patients were 6.7 times more likely to have enteroviral genome in their muscle.

We conclude that persistent enteroviral infection plays a role in the pathogenesis of PVFS, also providing preliminary evidence that severe mitochondrial injury is one of the mechanisms involved.

 

Source: Gow JW, Behan WM. Amplification and identification of enteroviral sequences in the postviral fatigue syndrome. Br Med Bull. 1991 Oct;47(4):872-85. http://www.ncbi.nlm.nih.gov/pubmed/1665380

 

The chronic fatigue syndrome

Abstract:

The chronic fatigue syndrome (CFS) was formally defined in 1988 to describe disabling fatigue of at least 6 months’ duration of uncertain etiology. Reports of CFS have emerged from the United States, Canada, the United Kingdom, Australia, New Zealand, Israel, Spain, and France. The disease primarily affects individuals between 20 and 50 years of age, and there is a preponderance of females.

Although a triggering infectious illness is reported by most patients with CFS, there is no convincing evidence causally linking any currently recognized infectious agent to CFS. Multiple minor immunologic aberrations are frequent but inconsistent and of uncertain significance. There is no consistent evidence for myopathy or physical deconditioning.

Depression is found in approximately 50% of CFS patients, with depression preceding the physical symptoms in half of the cases. No therapy has been proved effective in controlled clinical trials with prolonged follow-up, although antidepressants have not been formally evaluated.

The long-term prognosis of patients with CFS has not been well studied, but CFS appears to be a disease of prolonged duration with considerable morbidity but no mortality. Further research into the pathogenesis and treatment of CFS is necessary.

 

Source: Shafran SD. The chronic fatigue syndrome. Am J Med. 1991 Jun;90(6):730-9. http://www.ncbi.nlm.nih.gov/pubmed/2042689

 

Human herpesvirus-6 (HHV-6) (short review)

Abstract:

Human Herpesvirus-6 is the etiological agent of Roseola infantum and approximately 12% of heterophile antibody negative infectious mononucleosis. HHV-6 is T-lymphotropic, and readily infects and lyses CD4+ cells. The prevalence rate of HHV-6 in the general population is about 80% (as measured by IFA) with an IgG antibody titer of 1:80. A lower prevalence, however, is observed in some countries.

HHV-6 is reactivated in various malignant and non-malignant diseases as well as in Chronic Fatigue Syndrome and transplant patients. Furthermore, elevated antibody titers were also observed in lymphoproliferative disorders, auto-immune diseases and HIV-1 positive AIDS patients. There appears to be some strain variability in HHV-6 isolates.

The GS isolates of HHV-6 (prototype) was resistant to Acyclovir, Gancyclovir, but its replication was inhibited by Phosphonoacetic acid and Phosphoformic acid. HHV-7 isolated from healthy individuals showed, by restriction analysis, that 6 out of 11 probes derived from two strains of HHV-6, cross-hybridized with DNA fragments, derived from HHV-7.

 

Source: Ablashi DV, Salahuddin SZ, Josephs SF, Balachandran N, Krueger GR, Gallo RC. Human herpesvirus-6 (HHV-6) (short review). In Vivo. 1991 May-Jun;5(3):193-9. http://www.ncbi.nlm.nih.gov/pubmed/1654146

 

Fibromyalgia, chronic fatigue syndrome, and myofascial pain syndrome

Abstract:

There continues to be an emerging body of literature related to fibromyalgia and the related conditions chronic fatigue syndrome and myofascial pain.

During the past year, the most notable contributions included a large multicenter study providing new diagnostic criteria for the classification of fibromyalgia and clinical studies describing the overlap of fibromyalgia, chronic fatigue syndrome, and myofascial pain.

Pathophysiologic studies were often preliminary and uncontrolled but the focus of these studies on abnormal nociception, neurohormones, and muscle metabolism provides an exciting hypothesis to unify pain, fatigue, and sleep disturbances, the primary symptoms of fibromyalgia. Unfortunately, new therapeutic trials were neither innovative nor especially encouraging.

 

Source: Goldenberg DL. Fibromyalgia, chronic fatigue syndrome, and myofascial pain syndrome. Curr Opin Rheumatol. 1991 Apr;3(2):247-58. http://www.ncbi.nlm.nih.gov/pubmed/2064904

 

Physiologic measurement of exercise and fatigue with special reference to chronic fatigue syndrome

Abstract:

Oxidative metabolism is the major source of energy for muscle activity, and maximal oxygen uptake (VO2max), the product of maximal cardiac output and maximal arteriovenous oxygen difference, indicates individual capacity for oxidative metabolism and performance of exercise by the large muscles.

Strength, a function of muscle cross-sectional area, motor-unit recruitment, and neuromuscular coordination, is the ability to develop force in a single, brief, maximal-effort voluntary contraction of rested muscle. Weakness is a diminished ability of rested muscle to exert maximal force. Fatigue is a loss of maximal force-generating capacity that develops during muscular activity, likely originates within muscle itself, and persists until muscle is fully recovered. Individual perception of motor effort can be determined with standardized rating scales.

These concepts are discussed in detail, their relevance to the pathophysiology of exercise in chronic fatigue syndrome is analyzed, and a general strategy of exercise evaluation pertinent to chronic fatigue syndrome is presented.

 

Source: Lewis SF, Haller RG. Physiologic measurement of exercise and fatigue with special reference to chronic fatigue syndrome. Rev Infect Dis. 1991 Jan-Feb;13 Suppl 1:S98-108. http://www.ncbi.nlm.nih.gov/pubmed/2020810

 

Validation of biologic markers for use in research on chronic fatigue syndrome

Abstract:

Unresolved aspects of chronic fatigue syndrome can be addressed by research involving biologic markers. These may be any molecular, biochemical, physiological, or other biologic parameter obtainable from biologic specimens. The use of biologic markers in research requires their validation as dependent or independent variables. Additionally, other characteristics of markers such as reliability of assays, background level, confounding factors, interpretations, and legal and ethical implications should be considered before the use of markers in research. A checklist is provided for evaluating a biologic marker before its inclusion in research.

 

Source: Schulte PA. Validation of biologic markers for use in research on chronic fatigue syndrome. Rev Infect Dis. 1991 Jan-Feb;13 Suppl 1:S87-9. http://www.ncbi.nlm.nih.gov/pubmed/2020808