Mechanomyography as a Surgical Adjunct for Treatment of Chronic Entrapment Neuropathy: A Case Series

Abstract

BACKGROUND: Chronic entrapment neuropathy results in a clinical syndrome ranging from mild pain to debilitating atrophy. There remains a lack of objective metrics that quantify nerve dysfunction and guide surgical decision-making. Mechanomyography (MMG) reflects mechanical motor activity after stimulation of neuromuscular tissue and may indicate underlying nerve dysfunction. OBJECTIVE: To evaluate the role of MMG as a surgical adjunct in treating chronic entrapment neuropathies. METHODS: Patients 18 years or older with cubital tunnel syndrome (n = 8) and common peroneal neuropathy (n = 15) were enrolled. Surgical decompression of entrapped nerves was performed with intraoperative MMG of the hypothenar and tibialis anterior muscles. MMG stimulus thresholds (MMG-st) were correlated with compound muscle action potential (CMAP), motor nerve conduction velocity, baseline functional status, and clinical outcomes. RESULTS: After nerve decompression, MMG-st significantly reduced, the mean reduction of 0.5 mA (95% CI: 0.3-0.7, P < .001). On bivariate analysis, MMG-st exhibited significant negative correlation with common peroneal nerve CMAP (P < .05), but no association with ulnar nerve CMAP and motor nerve conduction velocity. On preoperative electrodiagnosis, 60% of nerves had axonal loss and 40% had conduction block. The MMG-st was higher in the nerves with axonal loss as compared with the nerves with conduction block. MMG-st was negatively correlated with preoperative hand strength (grip/pinch) and foot-dorsiflexion/toe-extension strength (P < .05). At the final visit, MMG-st significantly correlated with pain, PROMIS-10 physical function, and Oswestry Disability Index (P < .05). CONCLUSION: MMG-st may serve as a surgical adjunct indicating axonal integrity in chronic entrapment neuropathies which may aid in clinical decision-making and prognostication of functional outcomes.

Commentary: Mechanomyography as a Surgical Adjunct for Treatment of Chronic Entrapment Neuropathy: A Prospective Case Series

“…6 In this study, the authors found that MMG correlated with common peroneal nerve compound muscle action potential. 5 Owing to the limitations of small sample size, heterogenicity of severity in conduction block, and short follow-up time, there were no significant correlations found between MMG stimulus thresholds and nerve conduction velocity nor were there significant correlations with postoperative motor strength. 5 Despite the limitations, this prospective case series was able to demonstrate the utility of MMG as an intraoperative tool to not only quantify the extent of decompression but also possibly provide a basis for prognostication of eventual recovery.…”

“…5 Owing to the limitations of small sample size, heterogenicity of severity in conduction block, and short follow-up time, there were no significant correlations found between MMG stimulus thresholds and nerve conduction velocity nor were there significant correlations with postoperative motor strength. 5 Despite the limitations, this prospective case series was able to demonstrate the utility of MMG as an intraoperative tool to not only quantify the extent of decompression but also possibly provide a basis for prognostication of eventual recovery. Future work investigating MMG alongside current well-known technologies such as triggered EMG and intraoperative action potentials may demonstrate superiority of 1 nerve monitoring technique depending on the extent or location of compression.…”

“…In this study, the authors detail their prospective case series evaluating the use of intraoperative mechanomyography (MMG) as a surgical adjunct in treating chronic entrapment neuropathies. 5 Although a variety of surgical approaches exist, including open vs endoscopic and with or without nerve transposition, the inability to provide objective real-time data limits surgical decisionmaking. 6 Intraoperative nerve monitoring reflects immediate neuronal changes after decompression, such as normalization of nerve stimulation parameters, which can be attributed to intraneuronal pressure relief and improved microcirculation.…”