Mechanomyography: A Novel Adjunct for Treatment of Chronic Entrapment Neuropathy
Saad Javeed, MBBS1; Nathan Birenbaum, MS2; Christopher F Dibble, MD, PhD1; Jacob K Greenberg, MD, MSCI1; Justin K Zhang, BS1; Amir H Faraji, MD, PhD3; Robert J. Spinner, MD4; Wilson Z Ray, MD1
1Washington University School of Medicine, St. Louis, MO; 2Washington University School of Medicine, Saint Louis, MO; 3Houston Methodist Hospital, Houston, TX; 4Department of Physical Medicine and Rehabilitation, Mayo Clinic, Rochester, MN
Introduction: 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 following stimulation of neuromuscular tissue and may indicate underlying nerve dysfunction. This study aimed to assess the role of MMG in evaluating the severity and prognostication of chronic entrapment neuropathy.
Materials and Methods: Twenty-three cubital tunnel syndrome (CuTS) and common peroneal neuropathy (CPN) patients >=18 years of age were enrolled (Fig1). Surgical decompression of entrapped nerves was performed with intra-operative MMG of the hypothenar and tibialis anterior muscles. The MMG stimulus threshold (MMG-st) was defined as lowest nerve electrical stimulation amplitude resulting in consistent motor activity before and after nerve decompression. The MMG-st were correlated with compound muscle action potential (CMAP), motor nerve conduction velocity (M-NCV), baseline functional status (severity), and functional outcomes (prognosis).
Results: Following nerve decompression, MMG-st significantly reducedľ mean reduction of 0.5 mA (95% CI: 0.3-0.7, p<0.001). On bivariate analysis, MMG-st exhibited significant negative correlation with common peroneal nerve CMAP (p<0.05), but no association with ulnar nerve CMAP and M-NCV. On correlation with preoperative electrodiagnosis, the MMG-st was higher in the nerves with axonal loss as compared to the nerves with conduction block (Fig2). MMG-st was negatively correlated with pre-operative hand strength (grip/pinch) and foot dorsiflexion/toe extension strength (p<0.05). At final visit postoperatively, MMG-st significantly correlated with pain, PROMIS-10 physical function (PF), and Oswestry disability index (ODI) (p<0.05). The correlation strength (rs) of pre- and post-decompression MMG-st with motor and clinical function is shown in Fig3 and Fig4, significant spearman's correlations bolded with asterisk.
Conclusion: MMG-st may serve as a marker of axonal integrity in chronic entrapment neuropathies which may aid in clinical decision-making and prognostication of functional outcomes.
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