Tag: EMG

The role of clinical neurophysiology in the definition and assessment of fatigue and fatigability

Highlights:

  • Though a common symptom, fatigue is difficult to define and investigate, and occurs in a wide variety of disorders, with differing pathological causes.
  • This review aims to guide clinicians in how to approach fatigue and to suggest that neurophysiological tests may allow an understanding of its origin and severity.
  • The effectiveness of neurophysiological tests as cost-effective objective biomarkers for the assessment of fatigue has been summarised.

Abstract

Though a common symptom, fatigue is difficult to define and investigate, occurs in a wide variety of neurological and systemic disorders, with differing pathological causes. It is also often accompanied by a psychological component. As a symptom of long-term COVID-19 it has gained more attention.

In this review, we begin by differentiating fatigue, a perception, from fatigability, quantifiable through biomarkers. Central and peripheral nervous system and muscle disorders associated with these are summarised. We provide a comprehensive and objective framework to help identify potential causes of fatigue and fatigability in a given disease condition. It also considers the effectiveness of neurophysiological tests as objective biomarkers for its assessment. Among these, twitch interpolation, motor cortex stimulation, electroencephalography and magnetencephalography, and readiness potentials will be described for the assessment of central fatigability, and surface and needle electromyography (EMG), single fibre EMG and nerve conduction studies for the assessment of peripheral fatigability.

The purpose of this review is to guide clinicians in how to approach fatigue, and fatigability, and to suggest that neurophysiological tests may allow an understanding of their origin and interactions. In this way, their differing types and origins, and hence their possible differing treatments, may also be defined more clearly.

Source: Tankisi H, Versace V, Kuppuswamy A, Cole J. The role of clinical neurophysiology in the definition and assessment of fatigue and fatigability. Clin Neurophysiol Pract. 2023 Dec 18;9:39-50. doi: 10.1016/j.cnp.2023.12.004. PMID: 38274859; PMCID: PMC10808861. https://www.sciencedirect.com/science/article/pii/S2467981X23000367 (Full text)

Post-viral fatigue syndrome: evidence for underlying organic disturbance in the muscle fibre

Abstract:

Ten patients with post-viral fatigue syndrome and abnormal serological, virological, immunological and histological studies were examined by the single-fibre electromyographic (EMG) technique after excluding concurrent problems in the neuromuscular system. No abnormality of fibre density was noted but all patients had abnormal jitter values. Very high jitter values were not associated with impulse or concomitant blocking. The findings confirm the organic nature of the disease. A muscle membrane disorder probably arising from defective myogenic enzymes is the likely mechanism for the fatigue and the single-fibre EMG abnormalities. This muscle membrane defect may be due to the effects of a persistent viral infection.

 

Source: Jamal GA, Hansen S. Post-viral fatigue syndrome: evidence for underlying organic disturbance in the muscle fibre. Eur Neurol. 1989;29(5):273-6.  http://www.ncbi.nlm.nih.gov/pubmed/2792146