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

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.

Nociceptive pain in adult patients with 5q-spinal muscular atrophy type 3: a cross-sectional clinical study.

BACKGROUND: Spinal muscular atrophy (SMA) is an autosomal recessive neuromuscular disorder caused by mutations in the SMN gene, leading to progressive muscular weakness, atrophy and so far neglected musculoskeletal pain. This study is the first to characterize nociceptive pain in patients living with SMA type 3 by assessing whether muscle pain is associated with alterations in muscle strength, function, stiffness, frequency, decrement, relaxation, or creep. METHODS: We performed a cross-sectional pilot study on 20 SMA3 patients. We evaluated motor function and muscle strength (dynamometry, quick motor function test and 6-min-walk test), nociceptive pain (pressure algometer evaluating muscular pressure pain threshold (PPT)) and non-invasive measurement of muscle stiffness, frequency, decrement, relaxation, or creep (myotonometry with the MyotonPro®). For statistical analysis, we used t tests, Mann-Whitney U tests and linear regression. RESULTS: Significantly more women than men reported musculoskeletal pain (p = 0.003). A lower score in dynamometry was associated with lower scores in PPT in all extremities reflecting a higher sensitivity of these muscles to pressure. We did not find significant correlations between the PPT values and the MyotonPro values in the corresponding muscles. Assessments of PPT before and after the 6-min walk test did not show clinical meaningful changes. Besides nociceptive pain, fatigue was prevalent in 50% and pain in 55% of the patients. CONCLUSIONS: Muscle pain in SMA3 is associated with muscular weakness in the arms and legs, but not with changes in muscular stiffness, frequency, decrement, relaxation, or creep. This shows that muscle pain in SMA3 is mainly caused by changes in the dysbalanced musculoskeletal system due to muscle weakness.