Partanen Juhani V, Lajunen Hanna-Reetta, Liljander Sara K
Department of Clinical Neurophysiology, Helsinki University Central Hospital, Espoo, Finland.
Department of Neuroscience and Biomedical Engineering, Aalto University School of Science, Espoo, Finland.
BMJ Neurol Open. 2023 Jun 15;5(1):e000420. doi: 10.1136/bmjno-2023-000420. eCollection 2023.
Muscle membranes have a sensation of pain, but within the muscle tissue, the origin of pain is unclear. We present a hypothesis that the pain receptors of the muscle tissue are situated principally in the muscle spindles. A recent report reintroduced that 'end plate spikes' in needle electromyography (EMG) are fusimotor unit potentials of the intrafusal muscle fibres, and thus represent a marker of muscle spindles.
We studied four relaxed muscles with 50 EMG needle insertions in each and mapped the appearance of pain and spontaneous EMG activity.
Only 4.0% of the needle insertions in muscle tissue elicited pain. However, needle insertions in local active points showing 'end plate spikes' and, thus, fusimotor unit potentials of the muscle spindles elicited pain in 86% of the insertions, whereas needle insertions in points without 'end plate spikes' elicited pain in only 1.0% of the insertions (p<0.001).
Muscle spindles have pain receptors. The extrafusal muscle tissue is practically pain-free for the needle insertions. This demonstrates a scarcity of extrafusal pain receptors. How this observation is put into perspective with the muscle pain syndromes was discussed.
肌膜有痛觉，但在肌肉组织内，疼痛的起源尚不清楚。我们提出一个假说，即肌肉组织的痛觉感受器主要位于肌梭。最近一份报告再次提出，针极肌电图（EMG）中的“终板棘波”是梭内肌纤维的融合运动单位电位，因此是肌梭的一个标志物。
我们研究了四块放松的肌肉，每块肌肉进行50次针极插入，并绘制疼痛出现情况和自发肌电图活动。
肌肉组织中只有4.0%的针极插入引发疼痛。然而，在显示“终板棘波”、即肌梭融合运动单位电位的局部活性点进行针极插入时，86%的插入引发疼痛，而在无“终板棘波”的点进行针极插入时，只有1.0%的插入引发疼痛（p<0.001）。
肌梭有痛觉感受器。对于针极插入，梭外肌组织实际上无痛觉。这表明梭外痛觉感受器稀少。讨论了如何将这一观察结果与肌肉疼痛综合征联系起来。
