Nociceptive Pain in Patients with Neuromuscular Disorders: A Cross-Sectional Clinical Study

Abstract

Background: Muscle pain is a common symptom in patients with neuromuscular disorders (NMD) and accounts for severely reduced quality of life. OBJECTIVE: This clinical study aimed to observe possible differences in pain prevalence among distinct NMDs and to determine whether the patients' nociceptive pain is influenced by gender, muscle strength and psychological factors and to examine potential pain-associated alterations in muscle properties.

Methods: The cross-sectional study on nociceptive pain in various NMDs involved patient-reported outcomes, muscle strength evaluations (dynamometry and quick motor function test (QMFT)), nociceptive pain evaluations (muscular pressure pain threshold (PPT)), and non-invasive measurement of muscle stiffness, frequency, decrement, relaxation, and creep (myotonometry).

Results: Involving 81 NMD patients and a control group, the study found high variability in pain prevalence among the subgroups. Patients with DM2 and FSHD had significantly higher levels of pain prevalence compared to other examined NMD subgroups and the control group. Female gender, high fatigue levels (representing factors such as depression, anxiety, stress, and impairment of quality of life), and low QMFT scores (representing reduced muscle strength) showed an association with increased sensitivity to pressure pain in the arm and leg region. As assessed by myotonometry, less pain is experienced in neck muscles with a high muscle tone, high stiffness, and a short relaxation time highlighting the importance of intrinsic muscular tone for their pressure pain sensitivity.

Conclusion: Individualized therapeutic concepts including psychological and physical approaches in the pain management of patients with NMDs, especially in women, should be considered. Further research in this field is necessary to gain a more detailed insight into the perception of muscle pain.

Keywords: Nociceptive pain; dynamometry; myotonometry; neuromuscular diseases; pain threshold.

Fig. 1

Pain frequency for all six subgroups in four different locations of the body Four body regions: the head, neck and shoulder region; the arm region (including upper arm, forearm and hands); the spine region (including thoracal and lumbar spine); the leg region (including gluteal region, thigh, knee, calf, shin and feet region); the unit of the scale is percentage of patients experiencing pain.

Fig. 2

Pain body maps for the different subgroups DM1 (picture 1), DM2 (picture 2), LOPD (picture 3), SMA (picture 4), FSHD (picture 5) and the control group (picture 6) indicating the frequency of pain in different colors from a low frequency (blue) to a high frequency (red) in different locations.

Fig. 3

Report of pain. Percentage of subjective pain prevalence in all examined patients and in all examined women. The report of pain was significantly (p = <0.01^**) higher in DM1, DM2, and FSHD patients compared to the control group.