Differentiation of Sensitivity In Different Tissues and Its Clinical Significance

SUMMARY

This paper focuses on the importance of differentiation of sensitivity in somatic parietal tissues [skin, subcutis and muscle]. Such differentiation helps in achieving a correct differential diagnosis among different forms of musculoskeletal pain. Primary and referred pain are also distinguished.

Materials and Methods: Clinical and instrumental methodologies to detect hypo/hyperalgesia in each tissue are reviewed.

Results: PART I reviews previous studies with electrical stimulation. Evaluation of chronic fatigue syndrome [CFS], fibromyalgia [FMS], myofascial pain syndrome [MPS] and referred pain from viscera employing the technique of pain threshold measurement via electrical stimulation showed that each of these conditions is characterized by a different sensory pattern. In CFS, diffuse hyperalgesia is present only at muscle level; in FMS, hyperalgesia occurs in all three tissues including both painful and nonpainful sites; in MPS, hyperalgesia of all three parietal tissues is present but only in painful areas [i.e., over trigger points and target [referred] zones]. Areas of referred pain from viscera show hyperalgesia in all three tissues, which is maximal in muscles and decreases progressively through subcutis to skin.

PART II contains new data obtained by pressure algometry [PA]. Chronic fatigue syndrome patients presented a significantly lower pressure pain threshold [PPT] over muscles than normal control subjects. The lower PPT was spread diffusely over the entire muscle, i.e., not confined to a specific tender area. A significant linear correlation was found between PPTs and electrical pain thresholds in the same subjects.

The authors recommend PA as the method of choice for evaluation of deep tissue tenderness in clinical practice when repeated measurements are required, as in the follow-up of patients with muscle hyperalgesia.

KEYWORDS:

• Skin
• subcutis
• muscle
• pain thresholds
• musculoskeletal pain