Ulnar-evoked motor activity recorded over the abductor pollicis brevis region in carpal tunnel syndrome: a preliminary case series.

OBJECTIVE: To describe a brief and easily applicable electroneurographic (ENG) maneuver that can reveal ulnar-evoked motor activity detectable over the abducto'r pollicis brevis (APB) region in selected carpal tunnel syndrome (CTS) cases. The aim is to illustrate how targeted ulnar stimulation may complement routine CTS evaluation, rather than to redefine severity grading or clinical decision making. METHODS: Routine upper-limb nerve conduction studies were supplemented with targeted motor stimulation of the ulnar nerve at the wrist, elbow, and above the elbow while recording over the APB region. From a larger CTS cohort, three illustrative cases with distinct electrophysiological patterns were retrospectively selected to demonstrate ulnar-evoked activity detectable at the APB recording site across selected CTS severity categories. RESULTS: In all three cases, ulnar nerve stimulation elicited reproducible compound muscle action potentials recorded over the APB region, including situations where median-evoked APB responses were markedly reduced or absent. Latency characteristics and proximodistal consistency were compatible with known patterns of median-ulnar motor communication and demonstrated how ulnar-evoked activity detectable at the APB site may appear across the chosen CTS severity categories. CONCLUSION: This preliminary case series shows that targeted ulnar stimulation can reveal ulnar-evoked motor activity detectable over the APB recording site in selected CTS patients. These descriptive findings raise the hypothesis that median motor parameters alone may not fully reflect the pattern of motor activity measurable at the APB region in all individuals. SIGNIFICANCE: The maneuver is simple and quick, and may provide supplementary neurophysiological information in CTS-particularly in cases with reduced or absent median-evoked APB responses. Larger studies are required to determine its reproducibility, prevalence, and clinical relevance.