Category: Cognitive Dysfunction

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

 

Sensory and cognitive event-related potentials in myalgic encephalomyelitis

Abstract:

Myalgic Encephalomyelitis (ME) is a form of post viral fatigue syndrome resulting in myalgia and fluctuating fatiguability. Symptoms reflecting central nervous system dysfunction are common and include muscle weakness, headache, sensory disturbances, poor short term memory and impairment of concentration.

In view of the fact that sensory and cognitive disturbances are experienced by many patients objective evidence was sought with multi-modality sensory evoked potentials and auditory event-related cognitive potentials in a group of ME patients both with and without the enteroviral antigen, VP1 test positive.

The auditory brainstem, median nerve somatosensory and pattern reversal checkerboard visual potentials were normal for all 37 patients tested. In contrast to the sensory potentials significant differences in the mean latencies of the cognitive potential N2 and P3 were found. Reaction times were also significantly prolonged but the performance in terms of error was not significantly affected. No significant difference emerged in any of the parameters for the VP1 test. P3 was abnormal in latency or amplitude in 36% of the VP1 positive patients for the frequency discrimination task and 48% for the more difficult duration discrimination task.

The abnormalities indicate attentional deficits in some patients and slower speed of information processing in others. The prolonged latencies observed in these patients have not been observed in patients with depression in many other studies.

 

Source: Prasher D, Smith A, Findley L. Sensory and cognitive event-related potentials in myalgic encephalomyelitis. J Neurol Neurosurg Psychiatry. 1990 Mar;53(3):247-53. http://www.ncbi.nlm.nih.gov/pubmed/2324756

Note: You can read the full article here: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1014138/

 

The neuropsychological dimensions of postinfectious neuromyasthenia (chronic fatigue syndrome): a preliminary report

Abstract:

Postinfectious neuromyasthenia (PIN) is a clinical syndrome of protracted and incomplete recovery after an apparent viral-like illness. Medical investigation yields few abnormalities which might account for the symptomatology. A substantial number of PIN patients complain of cognitive changes.

Specific complaints include impaired attention, concentration and abstraction skills. This study was designed to systematically investigate whether the aforementioned subjective complaints could be quantified objectively using standard neuropsychological instruments. Results indicated that on all tests but one, the subjects’ performances were significantly higher than those of their age matched groups in the normative data.

Specifically, PIN patients scored significantly better than their age matched norms on tests of concentration, attention and abstraction. What is most striking is the discrepancy between the subjective complaints of cognitive impairment and the objective results of the subjects’ performances on all tests.

These findings suggest that psychological factors may play an important role in the cognitive functioning of individuals diagnosed with postinfectious neuromyasthenia.

 

Source: Altay HT, Toner BB, Brooker H, Abbey SE, Salit IE, Garfinkel PE. The neuropsychological dimensions of postinfectious neuromyasthenia (chronic fatigue syndrome): a preliminary report. http://www.ncbi.nlm.nih.gov/pubmed/2394541

 

Immune Markers in Cerebrospinal Fluid Provide Insights Into the Basis for Symptoms Like “Brain Fog”

Press Release: Mailman School of Public Health, March 30, 2015. Scientists at Columbia University’s Mailman School of Public Health have identified a unique pattern of immune molecules in the cerebrospinal fluid of people with myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) that provides insights into the basis for cognitive dysfunction—frequently described by patients as “brain fog”—as well as new hope for improvements in diagnosis and treatment.

In the study published in Molecular Psychiatry, Mady Hornig, MD, and colleagues used immunoassay testing methods to measure levels of 51 immune biomarkers called cytokines in the cerebrospinal fluid of 32 people with ME/CFS for an average of seven years, 40 with multiple sclerosis, and 19 non-diseased controls. The researchers found that levels of most cytokines, including the inflammatory immune molecule interleukin 1, were depressed in individuals with ME/CFS compared with the other two groups, matching what was seen in a blood study in patients who had the disease for more than three years. One cytokine—eotaxin—was elevated in the ME/CFS and MS groups, but not in the control group.

“We now know that the same changes to the immune system that we recently reported in the blood of people with ME/CFS with long-standing disease are also present in the central nervous system,” says Dr. Hornig, professor of Epidemiology and director of translational research at the Center for Infection and Immunity at the Mailman School. “These immune differences may contribute to symptoms in both the peripheral parts of the body and the brain, from muscle weakness to brain fog.”

Implications for Diagnosis and Treatment

“Diagnosis of ME/CFS is now based on clinical criteria. Our findings offer the hope of objective diagnostic tests for disease as well as the potential for therapies that correct the imbalance in cytokine levels seen in people with ME/CFS at different stages of their disease,” adds W. Ian Lipkin, MD, John Snow Professor of Epidemiology and director of the Center for Infection and Immunity.

There is precedent for use of human monoclonal antibodies that regulate the immune response in a wide range of disorders from rheumatoid arthritis to multiple sclerosis. However, the researchers note, additional work will be needed to assess the safety and efficacy of this approach.

The study was supported by a grant from the Chronic Fatigue Initiative of the Hutchins Family Foundation and the Edward P. Evans Foundation.

Additional authors include Andrew F. Schultz, Meredith L. Eddy and Xiaoyu Che at the Mailman School; C. Gunnar Gottschalk and Daniel L. Peterson at Sierra Internal Medicine in Incline Village, NV; and Konstance K. Knox at Coppe Health Care Solutions in Waukesha, WI, and Simmaron Research in Incline Village, NV.

Journal Reference: M Hornig, G Gottschalk, D L Peterson, K K Knox, A F Schultz, M L Eddy, X Che, W I Lipkin. Cytokine network analysis of cerebrospinal fluid in myalgic encephalomyelitis/chronic fatigue syndrome. Molecular Psychiatry, 2015; DOI: 10.1038/mp.2015.29

 

Reduced gait automaticity in female patients with chronic fatigue syndrome: Case-control study

Abstract:

Patients with chronic fatigue syndrome (CFS) report difficulties walking for a prolonged period of time. This study compares gait automaticity between women with CFS and nondisabled controls.

The “stops walking with eyes closed with secondary cognitive task” test is based on the classic “stops walking while talking” test but compares walking with eyes closed while performing a secondary cognitive task in a female CFS population (n = 34) and in female nondisabled controls (n = 38).

When initiating gate, 23.5% of patients with CFS looked toward the ground compared with only 2.6% of nondisabled controls. After 7 m, subjects were asked to close their eyes, and after another 7 m, they were asked, “How much is 100 minus 7?” Of the patients with CFS, 55.9% stopped walking compared with 5.3% of nondisabled controls. Less automated walking was observed in patients with CFS than in nondisabled controls (p < 0.001). The test-retest reliability is moderate for global stopping.

This simple test observed reduced gait automaticity in patients with CFS for the first time. Dual tasking could be helpful to address the functional limitations found in this particular study.

 

Source: Jan b Eyskens, Jo Nijs, Kristien Wouters, Greta Moorkens. Reduced gait automaticity in female patients with chronic fatigue syndrome: Case-control study. Journal of Rehabilitation Research & Development (JRRD), Volume 52 Number 7, 2015, Pages 805 — 814.
Note: You can read the full study HERE.