Exploring Divergent Electrodiagnostic and Sonographic Findings in Patients With Suspected Carpal Tunnel Syndrome: Role of Median Nerve Cross-Sectional Area.

OBJECTIVES: Evaluate electrophysiologic and sonographic findings in patients with suspected carpal tunnel syndrome (CTS) that had divergent electrodiagnostic (EDX) and ultrasound imaging (USI) diagnoses of CTS.

METHODS: Retrospective analysis of 665 limbs from patients who underwent EDX testing and USI. MANOVA, Chi Square, and correlations were used to analyze electrophysiologic and sonographic variables in limbs with divergent findings. CTS diagnosis was determined using EDX- and USI-based classification systems, stratified by median nerve cross-sectional area (CSA) cutoff values producing large conclusive or small questionable shifts in diagnostic probability.

RESULTS: The proportion of limbs with a USI diagnosis of CTS but normal electrophysiologic findings was 17% and 35% when considering CSA cutoff values producing large conclusive and small questionable shifts in diagnostic probability, respectively. These limbs had significantly slower median sensory and motor latencies and larger distal and delta CSA compared to limbs with concordant findings. Conversely, the proportion of limbs with an EDX diagnosis of CTS but normal sonographic findings was 6% and 35% when considering CSA cutoff values producing large conclusive and small questionable shifts in diagnostic probability, respectively. These limbs had faster median motor latency, larger proximal and smaller distal and delta CSA compared to limbs with concordant findings.

CONCLUSIONS: Median nerve CSA proved to be the most reliable and clinically meaningful factor in limbs with divergent EDX and USI diagnoses of CTS regardless of diagnostic accuracy threshold. These results underscore the importance of integrating EDX testing and USI in patients with suspected CTS, particularly in cases with inconclusive or conflicting findings.