Scientific Aspects and Clinical Signs of Muscle Pain—Three Years Later

Abstract

Objectives: Muscle pain is a frequent concomitant symptom in a variety of neuromuscular disease and the most prominent findings in myofascial pain syndrome, as well as in fibromyalgia syndrome.

Findings: Negligible awareness has been focused on pain characteristics in neuromuscular disorders. In the group of inflammatory myopathies, in dermatomyositis, the highest frequency of permanent muscle pain is complained in the shoulder girdle and thigh, and upper arms and legs. Pain quality is reported to be muscle-aching in the majority of patients, but additional different pain characteristics have been documented, including deep, gripping, dull, bright, sharp and superficial. Here small free nerve endings are connected to small blood vessels that show an upregulation of substance P and calcitonine gene related peptide as signs of an increased nociceptive input. Some forms of metabolic myopathies, especially glycogenolytic defects, are characterized by symptoms of stamina, painful contractures with exercise, cramps, and myoglobinuria. Pain expression in McArdle patients with chronic myalgia has frequently the features of functional muscle pain, or fibromyalgia syndrome. Depletion of high-energy phosphates like phosphocreatine and adenosine triphosphate during exercise may contribute to the pathogenesis. In degenerative myopathies, only a few disorders are investigated for pain pattern, but affected patients clearly present with muscle pain in myotonic dystrophies, facioscapulohumeral muscular dystrophy, other rare degenerative myopathies, and the peculiar rippling muscle disease. Most prevalent but still underrecognized as cause of muscle pain is the myofascial pain syndrome.

Conclusion: The pathogenetic background of many type of muscle pain is still uncertain. Free nerve endings, substance P and adenosine triphosphate and tissue acidosis seem to be the player in muscle pain.

KEYWORDS:

• Muscle pain
• degenerative myopathies
• dermatomyositis
• metabolic myopathies
• myofascial pain syndrome