Electrodiagnostic Findings Using Radial Motor Segmental Conduction Study and Inching Test in Patients With Radial Neuropathy.

Objectives: The aims of this study were to characterize the electrodiagnostic findings of radial neuropathy using motor segmental conduction study and to determine the utility of subsequent inching test in precise lesion localization.

Design: Twenty-three patients with radial neuropathy were evaluated using radial neuropathy using motor segmental conduction study with three-point stimulation. The pathomechanism of the lesions according to the radial neuropathy using motor segmental conduction study was classified into three groups: conduction block, mixed lesion (combination of conduction block and axonal degeneration), and axonal degeneration. Inching test was performed in patients with conduction block to localize the lesion site, and needle electromyography identified the most proximal radial nerve-innervated muscles affected.

Results: Out of 23 cases, the radial neuropathy using motor segmental conduction study demonstrated probable partial conduction block in 10, mixed lesions in 2, and axonal degeneration in 10. One case could not be categorized with radial neuropathy using motor segmental conduction study alone. As determined by radial neuropathy using motor segmental conduction study and inching test, the most common cause of conduction block was compression, while the most common cause of axonal degeneration was iatrogenic. In the conduction block group, the lesion locations identified by radial neuropathy using motor segmental conduction study and inching test were consistent with needle electromyography localization.

Conclusions: The combined radial neuropathy using motor segmental conduction study and inching test technique can precisely localize radial motor nerve injuries and provide detailed information on electrodiagnostic characteristics of radial mononeuropathy.