J Electrodiagn Neuromuscul Dis.  2021 Dec;23(3):82-88. 10.18214/jend.2021.00066.

Trans-Synaptic Degeneration of Peripheral Motor Axons from Metastatic Brain Tumors: Electrophysiological Findings in Two Cases

• Won JH
• Chae HJ
• Kim K
• Hyun SE

• KMID: 2526157
• DOI: http://doi.org/10.18214/jend.2021.00066

Abstract

Denervation potentials obtained during electromyography (EMG) are usually considered as evidence of axonal degeneration in the peripheral nervous system (PNS). However, they may also appear when only central nervous system (CNS) lesions exist. Here, we present trans-synaptic degeneration from CNS lesions in 2 cases with electrophysiologic findings of motor axon degeneration caused not by PNS lesions, but by metastatic tumors involving the corresponding primary motor cortexes. When cancer patients show denervation potentials in needle EMG results, physicians usually consider PNS-related etiologies first, such as drug-induced generalized peripheral polyneuropathy or metastatic lesions (e.g., Pancoast tumor). However, metastatic brain tumors in the motor cortex could cause the same denervation potentials as PNS lesions, such as cervical polyradiculopathies or plexopathies. When PNS-type abnormalities are revealed on EMG in cancer patients, further screening to evaluate CNS lesions involving the corresponding corticospinal tracts should be included to ensure a timely and proper intervention.

Keyword

Brain metastasis; Nervous system; Trans-synaptic degeneration